Welcome everyone
Thanks for braving the light clouds and the crowded hall
We've never had so many attendees at an event
so unfortunately
We don't have seats for more than 150 people but this is great that so many people are enthusiastic about space science and astronomy
So thank you all for coming. I'm Dr. Cameron Hummels. I'm a research scientist here who also does
organizes these public education events, so
Just a few quick announcements before I introduce our speaker
At the door you may have seen we have our schedule for the next six months of events on the front side
We have seven public lectures followed by stargazing not all of them have a lunar eclipse, unfortunately
but we do have telescopes to view
whatever awesome astronomical objects are in the sky
So I encourage you to grab one of those on your way out on the back side is our schedule for
astronomy on tap for the next six months. Astronomy on tap is
a series of informal talks that are given at a bar in Old Town Pasadena
So you can have a beer and hear about
Space and the cosmos and it's all free
There's also a pub quiz accompanying it so I encourage you to check that out as well.
In addition, we're having our first foreign language astronomy on tap. It's astronomy on tap in Spanish in February
So I encourage those of you who are Spanish speakers to attend that
So as you may have seen there have been a lot of clouds today
Unfortunately, we get like 300 nights of clear weather in Southern California and tonight hasn't been ideal.
However, you can see for those of you on this side of the room looking out
You can still see the moon so the clouds are to some degree clearing
Hopefully they will continue to clear and we'll have decent views of the moon when it starts to eclipse in about
30 minutes, but don't worry about the timing. The eclipse is not a short event like "oh I missed it!"
It takes it takes a couple of hours to occur. The partial part of the eclipse will start at about 7:30
where the moon starts entering the the shadow of the earth and so it'll start getting darker like a
like somebody took a big bite out of it and it will continue and that bite will get larger until at about
8:43 it'll enter the total stage of the eclipse where the moon starts to turn red and some of the headlines calling this a
Blood Moon
Because it turns red, but don't worry. There's nothing bad about that and that will last about an hour and then
The partial phase will begin again and last another hour hour and a half
But we'll only stick around till 10:00 because it's Sunday and people need to sleep.
So anyway, so the layout for tonight is after I stop yapping, I will introduce our speaker for the night
We'll have a roughly 30-minute talk
Bye bye, Jamie
And then I'll give a five-minute
presentation on what to expect with the eclipse, a little bit more in depth than what I just did and
Then and then we'll have the telescope's set up and hopefully.we'll have viewing. We'll also have a panel Q&A here for about two hours
that you can go in and out of here if you get tired of
waiting to see the eclipse, you can come in here and we'll have a panel of experts from the
astrophysics and astronomy department here to answer any question you might have about space science or physics or astronomy
So I encourage you to check that out. Anyway, okay, so our speaker tonight is Dr. Jamison Rollins
He did his undergrad at Michigan
he did his PhD with me actually at Columbia University and
finished eight years ago and has been here since then as a staff scientist working on the LIGO project that was awarded the Nobel Prize
in 2017 in physics.
I mean, he wasn't awarded it
His team
his team was awarded it but he's an indispensable member of that team and and so I encourage you guys to
To enjoy his talk, so please welcome. Dr. Jameson Rollins
Thank you
It's very cool to see so many people here
All right, so as Cameron said I work for LIGO and
It's been very exciting last couple of years for us and for astronomy because of us, I think.
So let me give you guys an introduction to LIGO and what we've been doing and how
We're kind of revolutionising astronomy right now
Alright
Okay, this is a gravitational wave.
So gravitational waves were
predicted by Einstein in his general theory of relativity which he published in
1916 and so one of the very interesting thing is his theory of gravity, the general theory of relativity and
He predicts that there are these waves of gravity. So this is an example of just like a tube with a gravitational wave
Traveling down the axis of the tube. So it's to give you a sense of what the wave looks like as it travels
So
Back after he made this prediction
People didn't really initially believe that it would be
possible to see these waves because they're really really small and I'll talk about that later. But um
back in
1993
these two guys
got the Nobel Prize for showing that a binary system, which in this case
it was two neutron stars where one of them was a
a pulsar, which emits these pulses of radio waves--
--their orbit was speeding up and
what they showed was that the rate at which the orbit was speeding up was
exactly matching the prediction you would get from Einstein's general theory of relativity
for if this system was emitting gravitational waves
So that was--it was not a direct detection of gravitational waves
but it was our first real evidence that these waves were a real phenomenon that existed and
So what's what you're seeing in the background here is the curvature of space-time. That is the cause of
That the curvature is being caused by these two neutron stars orbiting around each other
And the ripples you see are the gravitational waves
All right, so here's here's one a cross-section of that ring, right
so what you can see here is as
the wave passes through it causes the ring to squash in one dimension and expand and the other and
and then, you knowm as the wave oscillates through it
changes the axis in which the squashing and expanding are happening, and we call this a strain
So what the gravitational wave is producing is a strain in space-time
and
This device, so that...people tried to start looking for gravitational waves by seeing if they could
pick up the vibrations with large masses that would ring like a bell and
those were called
bard detectors
but they didn't have any success with those and then
In the 70s a couple people had this idea to use light to see if we could measure
the strain caused by these gravitational waves passing through the earth. And so this is a device called a Michelson interferometer
where you have a laser beam that shoots and hits a
beam splitter mirror, splits into two arms
goes down and hits mirrors at the ends of the arms
and then the laser beams come back together and recombine at this beam splitter.
But what you can see happens is if the arm lengths change relative to each other, then you get either
light coming out this this port here, which we call the dark port because there's no light going there
but if the mirrors move a little bit, then you get some light coming out, and that's kind of the principle of how these Michelson interferometers work.
All right
So what they had was this brilliant idea, which was well, maybe we can just use these Michelson interferometers
to hear these gravitational waves
Basically the way that the gravitational wave, the way that the interferometer, you know
responds to the stretching of the arms is basically the exact same thing that happens when a gravitational wave passes by
Right. So this is the this is the cross section of the tube
squashing and expanding, and you can see if you attach the end mirrors of the Michelson interferometer
onto the ring
then the mirrors move and you get light alternatively coming out and not coming out of that dark board
and so potentially these interferometers are detectors of these waves
So then after many years of research and development and trying to make these interferometers more and more and more sensitive
the people that originally made these experiments went to the National Science Foundation and said hey
we'd like a bunch of money to make a really big version of this
because we know that if their gravitational waves coming and they're hitting the earth, they're really really weak and
It's gonna be really hard to hear them, and we need a really big Michelson interferometer to be able to detect them
so they made a compelling enough case that the National Science Foundation gave the money
to make in fact two of these detectors, because we argued that we wouldn't be able to determine
definitively that we had heard a signal from outer space if we only had one detector.
Because if we had one detector we might have just been hearing a glitch or some earthquake rumble or something like that
But if we have two detectors that are far away from each other and don't talk to each other
then if we hear a signal in both detectors at the same time
then that's a really good indication that the signal came from outer space
So this is LIGO. T This one's in Washington state in Eastern Washington, and this one's in
Livingston, Louisiana, which is northwest of New Orleans
and you can see it's a desert here and it's basically a swamp here, and these arms are four kilometers long
So this is two and a half mile long arms
And this is it's basically it's the it's a Michelson interferometer
Like I just described
Except it's more complicated because it's doing all these tricks with the light to try to--
we put in a lot of laser light and we try to bounce it around to sort of amplify the signal, but basically the laser
and the beam splitter are in this building. And then there's a mirror here, and a mirror down at the other end of the other arm
we shoot the light through, itbounces down these arms. Come comes back together, and we detect that
little bit of light that leaks out of the port on the other side
So this is what it looks like in the in that big central building
So you can see, here's a person for scale
So these are big chambers that hold the mirrors. So instead of having little mirrors, we've got big mirrors that are--
well here, I'll show you a picture right here. This is all, by the way, a vacuum system
so we're trying to make this interferometer
as sensitive to motion as we possibly can, so we've got to shield it from everything else in
the universe, and so basically we put it in this big vacuum system
so there's not even any air molecules that are banging around in there at all
So this is what the mirrors look like. And so this here is the mirror
It's actually got a cover on it to protect it right now. But this is the mirror.
It's hanging from this big suspension system
This is actually hanging by these little tiny fibers from this mirror here, which is hanging by fibers from more stuff up here
It's all hanging from the ceiling, which is not actually the ceiling;
it's a big table, which is a big seismic isolation table
The whole point of this whole structure here is to isolate
this mirror from any of the motion of the ground
So if the ground moves, this mirror does not move, that's the goal
Here's another picture I really like which is at the end station
So here is the end mirror, and down this tube here, two-and-a-half miles down
that way is the beam splitter, the vertex. And then this is a contraption that
takes the little bit of light that leaks through this mirror--
remember most of the light comes down here and then bounces back, but a tiny little bit leaks through, and then that
gets shot up to this
optical table up here, where we can read out some diagnostic information
All right, so the important thing to emphasize about LIGO is that it is really a transducer
This is sort of a technical description. It's a transducer
transducer of differential space-time strain into electrical signals
So that differential space-time strain, that's the effect that the gravitational wave has as it passes through space
So really what LIGO is, it's a microphone for space-time
so to me, I really love this analogy, because basically
what we're doing with LIGO, is that for the entire history of astronomy
all we've been able to do is look at the sky with telescopes
I won't say all because we've been able to do a lot of stuff by looking at the sky with telescopes
or listening to it with radio antennae or X-ray telescopes
but all of those telescopes are looking at the
electromagnetic signals that come from
distant objects, but gravitational waves are completely different
physical phenomenon; it's not electromagnetism
It comes from much different kinds of
you know, motion of matter on a bulk scale
and so it causes--when you have a lot of matter moving around, it causes these ripples in space-time,
these waves, and we hear these waves with LIGO
So I really like to talk about, instead of seeing with LIGO,
hearing with LIGO, because it really complements the way that we see with telescopes with
you know, having these microphones for listening to outer space. So it's a completely new thing
It's like we have been completely unable to hear what's going on in the universe until now, so it's really a very big
paradigm shift in what we can do with astronomy
All right. So this is the one technical graph
I'm going to show, because it's really in some sense, it's our most fundamental graph
and I think it's really kind of informative to see. So this is if you take
what you call a spectrum of the signal that comes out of LIGO. So imagine you've got a microphone
that's sitting in an empty room, and you turn up--
there's no sound in the room at all, and you turn the volume up really really loud
Probably everybody can imagine what you're gonna hear is like a hiss, right? Just like a background hiss. Well, what do you hear it?
What is that hiss exactly?
That hiss is probably coming from the
electronics in the microphone. The microphone, maybe just you know
residually
moving around because of the air molecules
that are not being caused by other sounds, but just because the the air molecules are just moving because of thermal motion
because they're not at Absolute Zero, or the electronics in the microphone itself or in the amplifier may cause some noise
So this this is the spectrum of
that
same thing, that same hiss for LIGO. So this is our ultimate sensitivity,
that hiss determines
how
how
faint of a signal you can hear. If you've got a microphone that's got a loud hiss on it
then you're not going to be able to hear any signals that are smaller than that hiss
that aren't louder than that hiss
The hiss is gonna mask that signal
So this is that same hiss for LIGO
and so we measure this all the time because this tells us how good we're doing.
The y-axis is amplitude and the x axis is frequency
For a microphone, you know, what's the frequency that we can hear with our ears?
It's about a hundred Hertz to a kilohertz to 10 kilohertz
So interestingly,
This is 10 Hertz here. This is a hundred Hertz. And this is a thousand Hertz. So very interestingly,
the frequency band that we hear with LIGO is exactly the same frequency band that we can hear with our ears
Totally coincidentally, that's not done on purpose
that's just that the things that limit our sensitivity happened to be the
things that limit it to this audio band.
What you see here is
this black dashed line is
what our theoretical goal was
for how low we were going to make the hiss, the background hiss, in LIGO
And it's limited basically by this green curve here, this blue curve, and this red curve
The dashed lines.  And those are all
fundamental physical limitations in the detector itself. The green is the
residual seismic noise, so we try to get rid of any motion of the ground by having those suspension systems and seismic isolation platforms
but we still have a little bit of that residual motion, gets down to the bottom of the test mass and that
makes this green curve here
the mirrors are not at Absolute Zero. They're not at absolute zero temperature. They have some residual temperature
in fact, they're at regular room temperature and
what makes temperature is
molecules moving
That's what makes something warm to the touch, is the fact that the molecules are moving around a lot more than something that's cool to the touch.
So because the molecules in the mirror are moving around
that limits how small of a motion we can see with that mirror
So you guys can maybe start to get a sense of how small of a motion we're
actually looking for with these detectors, because we're now worried about the
residual motion of the molecules in the mirrors because they're not at Absolute Zero temperature
So we're getting really small
Okay. Now this blue curve is interesting because that's what we call quantum noise
So because we've made these detectors so sensitive
we're sensitive to quantum mechanical in the detector
So the primary one is that the laser beam is a quantum mechanical thing
the light is made up of individual photons, individual quanta of light
and those little photons, those little bits of packets of light, don't all hit the mirror at the same time. They hit the mirror like rain
and each time one of those packets of light hits the mirror
it pushes the mirror just a little bit, and so the rain all bouncing on the mirror causes the mirror to fluctuate
And that's a quantum mechanical noise that adds a hiss that we can hear in this in this region over here
and so you put all these together and you get this theoretical limit
as to how sensitive we can make the detectors, how small we can make the hiss in the detector
These more noisy curves you see up here, that's how well we're actually doing
So this is how well we are, how well we're doing as of this past October
We've gotten a little bit better than this
But basically this is where we're at now, and these these gray curves in the background
This is the this gray curve here, is where we were doing back in O1,
back in September 2015, and this light gray one in the background is what we were doing back in 2009,
when we finished our first
construction of the detector, and before we took it all apart to make it better. And so you can see we've improved a lot and
We're still not at this, what we call this design sensitivity yet, but we're trying to get there
We're working hard on improving that right now in fact. So there's something I want to point out. So here's the strain, right?
That's that thing I was talking about that we measure of the space time.
Over here is the displacement. So what this is, it's a little bit different measure
But this is saying, how much actual motion do we see in meters
in the interferometer. Remember I was saying that the Michelson interferometer is two arms
We're measuring a differential motion of the arms. Well, how big of a motion do we actually detect with these detectors?
At this point
It's hard to even
You know, understand what these numbers are, but right here basically we're less than 10 to the minus 20 meters
10 to the minus 20 meters
This still boggles my mind to think about it. How big is a micron?
How big is a millimeter? That's 10 to the minus 3 meters
How big is a micron, which is like less than the size of your hair? That's 10 to the minus 6 meters
A nanometer is 10 to the minus 9 meters. The size of an atom is 10 to the minus 10 meters
That's 10 orders of magnitude bigger than this
So the size from a meter (I'm roughly 2 meters tall) to an atom
That's 10 orders of magnitude
You have to go another 10 orders of magnitude to get to the
distances that we can measure with these detectors
I've been doing this for basically 20 years and it still blows my mind every time I say this
This is a
cartoon of an atom. It's a hydrogen atom. That's the electron zooming around
We're zooming in to the proton at the middle of the atom
That is the motion that we can see. This is like the edge of the proton
It's crazy, I acknowledge that
But it works! We do it. All right. So LIGO
Advanced LIGO. Like I said there was an initial LIGO that started construction back in like 2000.
We built it up. We we took data for a while. We didn't see anything
We got some money to do this big upgrade, and we were going to start our first observing run on September 18, 2015
and then on
September 14th, while we were in what we call an engineering run
well
We where we were
like
preparing to start our
official run, and we were still messing around, but then we would leave it quiet at night and let it take data
We saw our first event. So it was like before we had even really
fully turned it on, we saw this signal, and it was really loud. Loud for us, right?
I mean that's moving like a proton size.
But this is what we saw. So this is the raw data. It's been filtered a little bit,
so it's not exactly the raw data, but you can start to see these these interesting squiggles in it
And this is the the Washington detector. This is the Louisiana detector
this here is a
numerical simulation of two black holes colliding together
a numerical simulation of the gravitational wave that would pass through Earth of two black holes colliding together
If you take this signal, subtract this signal,
then you're just left with noise. You're left with nothing
So the point is, is that what we detected is
basically matches to the
precision that we can measure it, exactly
the signals that we predict by general relativity from two black holes colliding
So this was, this is not how we do the detection, for what it's worth. But this is just an example of
to sort of demonstrate what we're seeing
This is a spectrogram of that signal. So you can see that this is time going on along
and this is 0.3 seconds, and this is 0.4 or 0.5 seconds
So this is only a hundred and fifty milliseconds long here, and these are the different frequencies
like there were on the x-axis of that other graph. So here's 30 Hertz
128 Hertz, 512 Hertz, and you can see that this chirp signal where you get the frequency
the pitch goes up with time and the amplitude goes up so it's a (chirp sound)
That's the signal! It's very short though
So in actuality if you listen to it in full speed
it just sounds like a little click. But if you slow it down
You get to hear the full chirp.
And so this is another simulation of the same two black holes that we think we observed, and in this case
what it is is imagining if you're pretty close to the black holes and watching them
Sort of against the night sky in the background
And you can see all of this, all of this crazy stuff happening that you're seeing is the space-time
being warped by the black hole's orbiting around each other and
it's causing the light from the stars behind it to bend
Alright, so we took data for a whole year and we ended up hearing three black holes
And I say three with the star because we definitely heard--
--we heard three black hole mergers, which is actually, depends how you want to count it,
you have two black holes that merge into a new one.
And so these three mergers, and then we had one merger that was a little bit quiet
so we weren't totally sure that it was from outer space, and it could have been, you know, just a glitch in our detector
we were pretty confident, but we still put an asterisk by it
So then fast forward to 2017, we've improved the detectors more
We've spent a lot of time trying to make them even more sensitive, try to work out all the kinks
try to make that hiss even quieter and
we start another, we do another observing run.
Later in that observing run our European counterpart, called Virgo, comes online
Virgo is near Pisa in Italy and it's very similar design to the LIGO detectors
And then
right after they come online, we hear another gravitational wave
and interestingly, we get a little bit of a blip in the Virgo detector
so it's kind of proof that the Virgo detector can hear gravitational waves as well, which is great because
What we ultimately want to do
I mean there's a couple things that we want to do. We obviously want to hear as many of these signals as we can
but what we can do with LIGO or
specifically with a network of LIGO, with many LIGOs around the globe is
to try to identify where in space the signal came from
These gravitational wave detectors are pretty much omnidirectional
They can hear gravitational waves coming from anywhere in space
If you've got two of them
Then you can start to
triangulate where in space that came from, because the wave will hit one detector before it hits the other. If you've got three
then you can make a even better estimation of where it came from in the sky
so if you can say
with certainty that the gravitational wave came from a very particular point in the sky
then you can tell telescopes to go look over there to see if they see anything
Wouldn't that be cool, if we saw something that happened, like an explosion
around the same time that we heard gravitational waves? And so this is an indication of what we call the sky localization
So if you just have the two LIGO detectors
What you get is these big bands,
swaths across the sky of where we think the gravitational wave came from
These bands, they kind of looked small in this
in this, you know, all-sky picture, but this is actually a lot of area
I mean there's billions of galaxies and stuff in these areas. So we can't tell people
to just go look all over the place for an explosion
It's too big of an area, but you can see here
once we got the Virgo detector in, the sky localization starts to get much smaller
which is very encouraging
Alright.  Then, in August of 2017, we heard a very interesting signal, one that we have been waiting for for a long time
So everything that we've heard up till now are these binary black holes
The black holes are about ten to twenty, thirty times the mass of the Sun
They're very very massive, but they're black holes. And what do we know about black holes?
No light comes out of a black hole!
Smash two black holes together,
still no light comes out; you just get a bigger black hole
all right, but what we were hoping to see
were the collision of two neutron stars
So neutron stars are made of matter
that is not quite as exotic as black hole matter. We don't actually know what's inside of a black hole
We just know that nothing is coming out of it
That's why it makes it really hard to know what's going on inside
But neutron stars are made up of neutrons, and we know a lot about neutrons
and we speculate that if you smash two giant balls of neutrons together
it's going to make a really big explosion in electromagnetic light that we should be able to see with telescopes
So in August 2017,
we heard a very interesting signal
that was much longer than the other signals.  Remember the other signal was just a fraction of a second long
And this is six seconds here, right? This is just the last six seconds of this signal
It's much longer
Right after the end of our signal, less than two seconds later,
a gamma-ray observatory saw a gamma-ray flash
So that's very interesting, those two signals are very close together
So that made us really really really excited that maybe something interesting was going on
So here's an example of how long that signal was. These are the other signals we detected; they're really short.
And then this is this new one that came in
Almost a minute long. We heard it for over a minute, basically
So these signals right? This is one second. So these other binary black hole signals are much shorter
and that's a indicator that this new signal we saw was very different than the other ones
and in fact, the masses that we predicted from this
new signal was the masses we predict that neutron stars are, which is about one and a half times the mass of the Sun
So this is again that that sky localization map like I showed before
But here's the new signal, and you can see that's a really small
relatively small area, and it's small enough that we could tell people with telescopes
hey, maybe you could just go scan around in that area and see if you see something interesting
And of course astronomers are much more clever and they've got much more sophisticated ways
to go and see if there is a new star
in a particular region of space, and so
After we made this detection we told astronomers like hey, there's something interesting going on over there,
you might want to look. And these are all telescopes across the Earth that
then went and took pictures of that point in the sky, and then a bunch of space-based ones too, like Hubble took pictures and
probably it's safe to say that in the weeks after this
pretty much every telescope on the planet probably pointed at this point in the sky
because what we saw was a totally new thing. So here again is the localization
and I'm focusing on this because this is the thing that is really the game-changer in astronomy right now
Right. So this is Fermi
It's a space satellite that saw that gamma-ray burst
But they didn't really know where it was coming from; they have this really big area on the sky
Then they localized it with another detector
Then you had the two LIGO and Virgo detectors that make a much smaller point in the sky
These are all the galaxies that are in that region
zoom in on this one
And then watch out for it, so this is a galaxy here
So here's another zoom in; that's the Milky Way
This is the region that we localized it to
And you can see there's a lot of stuff going on here, right? There's a lot of stuff in the sky
so it's an interesting challenge still, even with this reduced area that we've given them, to find something
that has something interesting going on
and so here zooming into the
zooming into the galaxy
And then notice
Right here
That's what we saw
And it seems incredible that we would be able to find that needle in the haystack
but we have a lot of tricks up our sleeves nowadays, because for instance we...
LIGO had a prediction
Because we suspect that this is from neutron stars, we can make these numerical
simulations about what the waveforms look like, how far away they are, and we can basically
give you an estimate of how far away it is.
So in fact this galaxy is right at the distance at which we suspected that the signal came from
And so here is a bunch of other astronomical
pictures that were taken with other telescopes, and you can see--here's the galaxy, and here's this new little
dot in the galaxy here
It doesn't really look like much in these pictures, but I can guarantee you that
astronomers lost their minds over this
They were really incredibly excited
because this is the first time we have ever been able to observe a signal like this
Here's another example
So what was interesting about this signal is that
It is
Here's the signal as it's fading away
So this is the wavelength, the color, and this is to how bright it ism and you can see it gets redder as time goes on
You know, the peak of the wavelength starts to move up. That means basically it's cooling down over time
So this is all evidence that what we actually saw here was the explosion that was associated with that gravitational wave that we saw
all right, so
this is a
plot of gamma-ray bursts that we've seen
Okay, so we've seen a lot of gamma-ray bursts, but we weren't exactly sure where they came from
We've seen two kinds of gamma-ray bursts. We've seen these long GRBs and these short GRBs
We've always speculated that these short GRBs come from the collision of two neutron stars
to make these big explosions, but we've never actually
been able to observe the
optical afterglow of these gamma-ray bursts, because we've never been able to localize in the sky
well enough to be able to point telescopes at them
We just basically have these gamma ray detectors which are just listening to the whole sky and then they
they feel a burst go bym but they're not exactly sure where it comes from
But LIGO
because it heard that neutron star for a minute before it collided,
was able to give us a very good indication on the sky of where it was
And so what we were able to see was this gamma-ray burst that was a lot weaker than anything that we had seen before and
had
we were able to then take pictures of it with telescopes
So this was basically a completely new thing that astronomers had never done before, and of course
I mean just detecting gravitational waves from this was completely new, but the fact that we could tell astronomers where to look was also
really new and
one of the things that we think we're learning from this event
is that a lot of the heavy metals, the stuff that's lower down in the periodic table
is probably actually created in these neutron star mergers. It's not created in stars. When stars explode,
they're not energetic enough to make these really heavy elements, but these neutron star mergers probably are
Just to summarize, this is now all of the events that we have seen with LIGO. So these are all the black hole mergers
We've now heard 10 black hole mergers and we've still only heard that one binary neutron star merger, which is down here
So these are the two neutron stars
And this is whatever the remnant was, which we're not sure of. Was it a black hole?
Was it a neutron star? Interestingly, you can see that there's kind of a gap here
These are other black holes that we've detected with x-rays. So we've never seen any neutron stars or black holes in this region
So we're really curious about what's going on in that region
Last thing I want to say is that what we're trying to do is increase this network of gravitational wave detectors
We've got the two in the US, the two LIGO detectors
We've partnered with India to build another identical detector in India.
This is the Virgo detector, which is--I'm sorry, this is old. This is not under construction. They actually obviously detected an event with us
There's a much weaker
detector in Germany
But is still an interesting sort of research and development thing. And then the Japanese are building a detector
So the goal of this is that if we get this network, that we can really pinpoint in the sky where these events are coming from,
and we've already seen one binary neutron star collision
and we expect that
as we keep increasing the sensitivity of the detectors, that we should be able to see a lot more
So probably, hopefully in our next year of observation, which will start in April, we may be able to see
like five of these.  And again, these are totally new things. They're telling us totally new stuff
So this this is now what we call multi messenger astronomy
because we've got two messengers, which in this case are gravitational waves and
electromagnetic waves, that are coming from the same thing in the sky and
by putting the two together
we learn a lot more than even the two individually about what's going on in those explosions
So just last slide
We're trying to figure out how we can make these
detectors even more sensitive, to hear these events even further away. And so we've got a lot of
things that we're working on, we're trying to improve the detectors we have right now
We're talking about building what we call our next generation of detectors, that would have more light power
We would do these crazy things called light squeezing to make the quantum noise be lower
We're gonna try to make them cryogenic, cool them down to 100 degrees below zero
Have better seismic isolation. The real thing we want though is to make the arms longer. Remember our arms right now are four kilometers long
we'd like to make them 10 or
40 kilometers long
Because then we could hear even further and there's already projects
there's a project called LISA that's trying to put one of these in space, and have
three satellites that are shooting laser beams between each other
and the length of those arms is a million kilometers
and those can hear
whole different kinds of gravitational waves, like from black holes falling into supermassive black holes in the center of the galaxy
a whole bunch of interesting stuff
So in our lifetime, if we can make these next generation of detectors, we should hope to hear binary star mergers
potentially years before they collide. So LISA, the space-based one, should be able to tell us
in a year from now, go look over there and you'll see an explosion.
It'll give us lots of time to prepare. And if we make these really long armed ones in
on the ground, we can potentially hear basically every black hole merger in the universe
Because the distance at which we'll be able to hear
these black holes will basically be the horizon of the universe
So it's basically to the edge of the universe, and then we're hoping to hear stuff that we didn't even expect
That'll be even more exciting. So there's a pretty bright future ahead. Thank you
Five minutes
Okay, so I went a little bit long but I'll hang around for the panel
But I'll still take a couple questions right now. If we I think we can take like two or three questions
Yeah
Well I could but it would take a really long time
Yeah, maybe for the Q&A panel
I mean
That's basically you're out you're basically asking about all of the tricks we do in
the detector to amplify the signal and it's not at all a trade secret, but it would take a long time to
explain it, but basically yeah, we're looking for tiny phase shifts in the light and
We we have a lot of tricks that we can make that make it more sensitive
Yeah
Mm-hm
Right
Yeah, that's a very good question so she the question was um, do the gravitational waves always precede the light and
We're not it's not exactly sure
Possibly the the gravitational waves travel at the speed of light so they should travel at the same speed
that the light travels
However the light
They're produced by different things, right the gravitational waves come from the bulk
motion of the two black holes or the two neutron stars
Moving around each other and so for instance when we say that we're going to hear neutron star mergers a year ahead of time
That's we're hearing it long before the neutron stars merged together and make an explosion in light
But we still think that even even with the events that we're detecting, you know
We still the the neutron star merger that we observed
We still heard it for almost a minute before the actual explosion would have happened
Of course, there's some light is starting to come out in that time
but it's not as if the gravitational waves and the light are basically admitted at the exact same time and
You know one of them gets to us before the other they should travel at the same time, but the light comes from more complicated
Dynamics and chemistry of the matter that's you know burning up in the explosion
Alright, I understand a lot of you are very anxious to go outside and see the Eclipse, so we'll take more questions after
During the Q&A panel, but please thank our speaker. Dr. Jamison Rollins
All right
For those of you who stuck around?
The first thing that I'm going to do is I didn't have time to put together a presentation
So I'm going to show this super-awesome NASA
Astrophysics thing that was done as part of the lunar reconnaissance mission
That is a very
quick and dirty
explanation of what's going on during an eclipse and then show you a video that was taken from a number of images of
Previous lunar eclipses to show you kind of what to expect and what's actually going on. So this is only two minutes long, so
Like clockwork the full moon appears every month in our sky a sight so familiar that we often take it for granted
But about twice a year over the course of a few hours the full moon sports a decidedly different
look
What causes this sudden change a lunar eclipse occurs when the moon passes through the Earth's shadow?
Just as a solar eclipse occurs when part of the Earth passes through the moon shadow
But the moon circles the earth every month as it cycles through its phases lining up at both full moon and new moon
So why don't eclipses happen twice a month?
The reason is that the moon's orbit around the Earth is tilted relative to the Earth's orbit around the Sun
Although the earth and the moon always cast long shadows, they rarely shade each other. Thanks to the moon's orbital tilt
But if that's the case, why do eclipses happen at all?
Throughout the year the moon's orbital tilt remains fixed with respect to the Stars meaning that it changes with respect to the Sun
About twice a year this puts the moon in just the right position to pass through the Earth's shadow
causing a lunar eclipse as
The moon passes into the central part of the Earth's shadow called the Umbra it darkens dramatically
Once it's entirely within the Umbra the moon appears a dim red due to sunlight scattered through the Earth's atmosphere
in fact
If you watch the Eclipse from the surface of the Moon you'd see the Sun set behind the entire Earth
Bathing you in a warm red glow
Back home. You'll have to stay up late to watch a lunar eclipse
But if you do you'll see the moon in rare form and you'll catch a brief glimpse of our own planets long shadow
All right, so I think that's a pretty good explanation but I really like this in terms of
Visualizing what to actually expect over the course of the night
So as the Eclipse begins as the the moon starts to pass into the Earth's shadow
Its front edge will start to get darker and darker. This is the stage of the Eclipse that we're in right now
And as it continues to go into this total shadow called the Umbra
It just looks like there's a big bite taken out of the moon until it finally covers it and you start to see this red
Phase which is when the only light that's actually reaching the the moon is
Passing through the atmosphere of the earth and being refracted and having all of the blue light scattered out
much like you see when you look at the sunset and
Eventually, we get through that phase that phase will last from about 841 to 943 or so
and then
It starts the partial phase again when it starts
escaping from the the Umbra the dark shadow and
There's a additional visualization here with actually showing the Umbra but you get the idea
So that's what's happening tonight lunar eclipses tend to happen
Somewhere on the earth every six months or so
This is the last one that'll happen
That's visible from North America for the next two years or so, but it's no big deal and lunar eclipses
Lunar eclipse has happened as I said pretty frequently and they're visible from a very very large swath of the earth
Whereas solar eclipses like the one that happened a year and a half ago
The the well
Raise your hand if you if you saw the total eclipse if you went to totality the region of totality it was pretty awesome
You saw it on YouTube? Okay, that's fair enough
so that's a very very small region of the earth where you have the the moon shadow casting that that
Region as opposed to right now
Everywhere that can see the moon right now. It appears red or will appear red
You can see the lunar eclipse, but with the solar eclipse, it's only a small region where you actually get that total show
And the next total solar eclipse is occurring this year in but it won't be visible from here
It'll be visible from Chile and Argentina and the southern part of South America
So I encourage you to fly there if you have the means because it's awesome
Ok, are there any questions about the moon or the Eclipse or moon phases or anything like that?
Sure, so when the
Right you understand so the Sun is here
The earth is here and the moon is here and when they're all lined up than any
light that would normally go directly to illuminate the moon is being
goodness
Is
Being is being totally blocked by the earth
The earth is in the way of light that would normally go and hit the moon and light it up
The only light that is actually able to reach the moon is
passing around the
the edge of the earth because you know, we have the
Earth
Which is mostly earth, you know rock and dirt and all of that and along the edge
there's the small layer of the atmosphere and that
Atmosphere is able the light can hit it and it can refract and Bend
and so what what would normally not even reach the the moon is able to refract and Bend around it and in doing
So that light the blue light gets scattered out which is why when we look up and then in the day sky it appears blue
And only the red light is able to make it through and hit the the moon and light it up only with the red light
Which then reflects back to us on the night side looking up at the moon. Does that roughly make sense?
You'd see a ring around the Earth from the light that's
Refracting through the atmosphere all around the edge of the earth at that moment and scattering out the blue light
Yeah, scattering out the blue light because short wavelengths of light
Are much more effectively scatter against
The the molecules in our atmosphere, but the red light is able to kind of make it through that
Yeah, and the only light that's able to make it there would be red light so the whole surface of the Moon just appears red
Yeah, of course
If we had no atmosphere then it would be totally dark
It's the fact that we have an atmosphere that's able to refract the light
Around it and scatter out that blue that blue light. But yeah if we didn't have an atmosphere
No light would make it and it would just be a dark dark spot
Any other questions? Yes
That is because so the question is if if
I'm watching some other video here. I don't even know what this is
The question is why is there a period that this the moon appears white and isn't red the entire time and that is because ah
It's because
That's a good question. The reason it goes dark without being read there is
preferentially red
but it's that the illuminated side is so so much brighter than the
shaded region that it just outshines that that
Yeah, the moon gets considerably darker when it's this doesn't really represent that that well
It's on the order of
500 times darker although to Ri Ri doesn't estimate it as 500 times because our eye operates on a logarithmic scale
But but yeah
If you can even if for those of you on the edge here you can look out and see the moon and it's about half
Eaten up right now
Yeah, so we'll set up the Q&A panel here in the next five minutes and you guys are encouraged to stick around and ask whatever
Astrophysical questions you have either about gravitational waves or the or
Aliens, I don't know whatever you want, but we'll be here until til
We'll be here until 9 o'clock maybe later
And then that the telescope's will be set up till 10. So thank you all for coming. Yeah, Oh
Totality begins at 8:41 and lasts until
943 so you've still got
35 minutes until totality begins as I said, we only about halfway through the partial phase where where the moon appears half
Half bitten out of right now
All right, so we'll get started with the panel, QA
our our expert panel tonight consists of
graduate students and a postdoc
From the astronomy and from the physics departments. We've got Ron so
Who is happy to answer questions about black holes, gravitational waves and general relativity. We've got Keisha la day
who is happy to answer questions about telescopes and
How
How stars died excellent a little morbid
Mia de los. Reyes will answer questions about galaxies. How stars are born a little more positive?
ly Rosenthal will answer questions about planets and novi which are
short period bursts on the surface of stars
and I'm Cameron and I'm happy to talk about a bunch of stuff but the stuff I wrote here is the moon because well
everyone's excited about the moon and
And simulations and galaxies and such. So do we have any questions from the audience?
Yeah
So the question was why was the Nobel Prize in Physics awarded just to three individuals Kip Thorne
Barry Barry what
Rainer Weiss and Barry bearish
Yeah, and Barry and Kip are both here. So why was it a route awarded to them and not the entire experimental team?
perhaps others can add to this but I just know that with the Nobel Prize they have a
stipulation for the award that it can only go to a maximum number of three people and that's I mean because the Nobel Prize
Started in the early 20th or late 19th century when science was primarily done by
Individuals as opposed to large teams and today so much science is done by you know
Teams of hundreds or in some cases thousands of members and it's just not
kept in line with the the Nobel Prize award committee, but
Just for context. I mean I can remember it was either
2012 or 2013 when the Nobel Prize was given for their discovery of the Higgs boson
It's kind of a similar case where there's a huge team of people and I went to three the three theorists
so
Maybe it's just how they decide like giving to just people who come up with the idea upon which the discovery goes based
And plus it's only like a million dollars and you just put that a thousand ways then
Is it oh, it's ten million, okay
well
it's on the order of a million or a few million dollars and if you split it a thousand or ten thousand ways it
Here's a hundred bucks to you and a hundred bucks to UNICEF
There's a very long history of the Nobel Prize being awarded
somewhat unfairly
so
Professors have been known to take credit for the work that their grad students actually did and this more often happens when the grad students
Or junior scientists are women just putting that out there
Jocelyn Bell Jocelyn Bell is a very good example for the discovery of pulsars
Any other questions, we have lots of time to answer questions, so
The witch press the Brecht, I'll prize Oh breakthrough prize is a bit more fair. Sure. That's fair
My
Okay, this is how our antenna questions being asked is that
Sort of when something moves very fast time gets dilated
So he's talking about you know, you have a rapid expansion the universe during the Big Bang. There's inflation a
Part of the universe and then we are expanding more and more right now, I guess
so
Yeah, yeah, that's a lot of things about measuring like
velocities like this, you know
It's like it's it's a little bit tricky to do it on like honest like honest on this type of scale
just because like everything's relative to one another but one other thing about the expansion is like rather than think of it as just like
Rather than just like it's accelerating away. It's really just a increase of entropy. This order is just increasing
So that's kind of like a better terminology to assign to it and also during the inflation
There's like a description of how like it
inflated like
Faster than speed of light or something. There's an explanation. I completely forgot. I don't know
Okay, so if you think about the one when he says that everything is relative and measuring time and space are both relative if a
car drives by you
You think that you're not moving in the car is moving
The car thinks that you're the one that's moving like whoever's sitting in the car. They're just sitting in the car
They're not moving. You're the one that's moving by them. Does that make sense?
So in general things are located like things like the earth or the entire Milky Way
Our galaxy are located out of specific place
Like a specific coordinate in space and when we say that space itself is expanding if you think of like a grid of points
The points are just moving farther apart
But the space itself is the thing that's moving not us
So yeah, the point is it's okay when we say the Big Bang
It's partly because we don't know what happens and because you can't be outside the singularity. That's yeah, we don't know what happens
Exactly at the point of the Big Bang. I
Just expand on something that that ron alluded to which is that measuring distances and speeds on a time on
scales outside the galaxy is tricky and the reason for that is because
light has a finite speed right 3 times 10 to the 8th meters per second, which means that I
mean the whole concept of measuring distance in lightyears is that
It's the distance that light travels in a year
So the light that you are seeing from the Sun is eight minutes old
It was emitted eight minutes ago the light that you are seeing from
galaxies the galaxies that you actually use to do these measurements of like how fast our
Galaxy is moving at a certain distance away from us. That light is billions of years old
so the catch is although the universe is accelerating and you can measure that by basically like fitting a physical model to
To these observations you make it's counterintuitive because as you look further out you're looking for they're back in time
so so the light that you're observing is from galaxies that
Based on the light that you're observing are moving slower and also they're younger
so
Your intuition for a distance in time just kind of breaks down
with relativity once you go to certain distance scales or certain speeds, so I I
Wouldn't stress about it too much. This is the
summary
Yes, so I mean for as long as humans existed basically the earth has been being was being bombarded by
Okay, I'll repeat the question question is um
Before Lego was built like did we live in a been a calm?
Okay
It depends on the the sensitivity of the detectors
Because there like every observation run it's being his sensitivity
He's like, you know is going down in a way
So it's we're sort of like able to detect more sense of it like the detectives more sensitive
So we're able to detect more signals like maybe smaller mass systems or even you know sources that are further away
So in the next on observation run the sensitivity is gonna be dropped a lot more
I mean, it's gonna it's gonna be more sensitive. Yeah, it's gonna be more it's more sensitive
So we expect to have like, you know, people are predicting
You know tens to hundreds of detection x' to to start occurring during the third observation run
Yeah, so it's really just depends on you know, the detector sensitivity and how we're improving detectors every observation run
Right, so yes, so if you just look at the things that LIGO can detect it is true that
If LIGO is not seeing it then it's probably true that there are other events that are happening out there
But it's just sub-threshold that we don't detect them
But what you also have to remember is that if you remember the plot that was shown in the talk
which is this sensitivity curve of LIGO where you see the kind of frequencies that like we're sensitive to
so LIGO is sensitive to a very limited range of frequencies, but
gravitational waves actually span an
Enormously larger range of frequencies so future emissions which are still being planned and implemented, you know, things like Lisa
so Lisa is laser interferometric space and
and tonight
Yeah, antenna. Yes
Right. So Lisa will is a proposed mission which will fly in the 2030s and
Which is sensitive to a completely different range of frequencies
and
There are things out there which are so loud in gravitational waves that the tail Lisa turns on
They're expected to be like in a thousand times
more thousand times louder than that's most weakest the signals that like Lisa can detect so
So when you think of gravitational waves LIGO is seeing only a very small fraction of things out there. There are things like
Very close white or binary. So wide walls are extremely dense stars
and so the Sun at the end of its life will turn into a white dwarf and
You can have two white dwarfs orbiting each other held together by the gravitational pull which also emit extremely strong gravitational waves
but they're completely out of the range of
LIGO
Yes
Yes, exactly, yes, so there are other instruments that will be sensitive to those kind of gravitational waves
And even right now as you speak we are being bombarded with all of those gravitational waves
It's a set
We don't have the right instruments to detect them and on the other side of the spectrum that is extremely low-frequency gravitational waves
which are emitted by
supermassive black holes, so these are
Orbiting supermassive black holes at the Centers of galaxies and those kinds of vibrational waves will are detected. Well, not directly
Those are indirect detection through things
That are known as pulsatile it is so it's basically another method of detecting gravitational waves where you look at
nearby rapidly rotating stars to see
Anomalies in the in that in the in the way they are rotating and those tell you about how space is being warped by these?
Extremely low frequency gravitational waves. So that's the other side of the switch and these are extremely low frequency gravitational waves
Yes
I
Think I'll have to see the picture
Okay, can I see it I wasn't in here during the talk
Got a new phone now
I
think that's just the help how far away it's sensitive l to like, you know within like what what
So
talking about the sensitivity strain
There's a plot right here and it shows like a LIGO s6 measured which is on one of the scientific runs
Oh one measured is the observation. Um
Run and I think there's like pre. Oh three measurement, which is I guess right now and the design sensitivity. I
Believe I'll stay like looking till I think it's like out too. But what range is sensitive to are something like that possibly
Yeah, that doesn't really make sense because there's a lag 0:01 measured and has 75 megaparsecs because they're the ones measured in
Oh one were oh it's like 410 mega parsecs the first event
yeah, actually, I don't I don't know too much about the noise curves to really
You see what these distance measures really?
The spikes those are just some there's a look just random noises and like, you know, I'm like well
We actually don't really don't know what they are
Yeah, yeah these big spikes that pop up like that
It's just it's just noise in the detectors that hasn't been characterized or subtracted out
I mean there's this people expect like there's like there's some like
Resident going on and some of the dependent dependent just so that the supporting detectors that cause these little spikes in the noise
But yeah
Yeah, there's people who speculate that those could be pulsars
Just just individual pulsars to the with a pulsar if it's um if it's a symmetric in a way
It'll be generating gravitational ways because the whole idea behind gender gravitational waves is you gotta have a clump of mass being accelerated
So you have the two binary black holes that are just two clumps of mass and they're just like, you know
Like the you know, that's generating gravitational waves in this case. You have a symmetric pulsar. So you think it like a
Pulsar, which is rapidly rotating neutron star and then you would have like maybe, you know, there's different ways of how it could be
They could be like a bump or something, you know on the like you sar would have like a small mountain or a hill
Whatever you want to call it and that decla mass is being rotated because it's spinning very rapidly
And that's that's that's emitting at one particular frequency and the frequency with which the gravitation was being a minute. That won't evolve very rapidly
Because if the evolution of its frequency depends on how rapidly the neutron star is rotating
So it'll depend on it like whether it spins down or spins up in a you know
so there's a like some people's neon dad that you know, they like play around be like oh
you know those spice could actually just be continuous waves from a pulsar that's out there but
For the most part these they call continuous waves
um
All all runs currently have not detected any continuous gravitational waves
Because those since they're ringing at one particular fixed frequency
They have to do it like their integration over like six months like to get observed data for about six months
Yeah, that's a great question, so the question was in the presentation that was earlier they talked about the
presenter Jamison Jamison
talked about how
Heavy elements. So heavier than iron and around the weight of gold are produced in neutron star mergers
And so the question was are there other?
Extreme elements like an infinite number of elements that are much heavier that are being produced in these extreme environments, which is a great question
And in part because we don't know the answer is yes in theory
If you have enough energy you can make whatever you want you can
In creep adding neutrons and protons to the elements that are already existing
This is what happens in a neutron star merger, and you can produce anything
Part of the problem with that is we don't think there are that many
Really really extreme environments where you get these ridiculous amounts of neutrons and protons
so it's not really you can't really make an infinite number and
even if you do make something much heavier than the elements that we know about it would be so unstable that we probably wouldn't be
able to detect it because it'll decay very very quickly like in less than a nanosecond maybe and
So that we're already reaching those limits with a lot of the elements the heaviest elements on the known periodic table
So these are the elements that we make here on earth in labs and they already decay
Faster than is useful for anyone
Does that answer your question where else? All right, thank you. Yeah
Yeah
So, right, so the question was in a normal non rotating black hole
We expect the singularity singularity to be a point in a rotating black hole
We expect the singularity to be more like a ring
So what is in the center of that ring and to answer that? I will turn it over to my friend frog?
Yes, so still is a singularity like it's like a true singularity as we call it inside the black hole
But that I believe that ring singularity. I got a review some of my textbooks on this
I believe that ring singularity is just a coordinate singularity
It depends on what type of coordinate system you use
So like we have those up that pop up
It's really just like, you know, what type of math were using to describe that environment, you know
And there's some singularities that you can get that you can just change to a different coordinate system
So for example, you have like a coordinate system, that's like the world we live in you know
You have a x y&z the three dimensions that we're in you can you can sort of like go to another coordinate system?
Where you can use what we call like a spherical coordinates where you can describe, you know
How a sphere looks by just like the radius and some angular primer. That's rather than using XY and Z
So that's like at an example from going one from one corner to another coordinates
So in with with a black hole dug inside the black hole
There are a chord and said there are singularities that occur that I just coordinate effects
But there are there are true singularities that do exist in there. Yeah, I
Know a lot less about the Sun rod, but one other thing that I remember is I mean
Did these so I think what you're referring to is like
So that that idea of a rotating black hole has a ring singularity
This is one of those cases. Where a
Different coordinate systems which means basically just like different ways of describing which
where you where you are in space like you could say I'm
Five feet forward one foot up and two feet to the side or you can say I'm looking 30 degrees up
I'm looking 60 degrees to the side and six feet of what six feet away
That affects it
Like what these things look like?
it's also the case that we don't actually really know what's happening inside a black hole like we I mean
There's an event horizon we can sort of
They're actually there's actually a really cool radio telescope project that's working to actually like observe the boundaries of a black
hole's event horizon right now, but
The whole idea of a singularity is that physics actually breaks down there so I
Think we don't we can't say for certain what it's what it's like at least not with our current ideas of how black holes work
So, yeah, so
Most of these Sinclair's that you're talking about also exists inside this horizon
They there are some situations where they can exist outside the horizon
But usually that that's what we call like naked singularities that they're exposed to the universe and they can be observed in a way
So for the most part people don't believe those type of singularities to exist like they've got to be covered by some horizon
that doesn't allow their information to be like
Exposed to us to observe
So the question was what do people mean when they say photon doesn't age
I'd be curious to hear the context in which is it said but my first guess is
The I
mean we're talking a little bit about relativity before right which is the core idea of relativity is that
You're the actual physics that you experience is different
Depending on how fast you're moving with respect to your surroundings
it's not a great way to phrase that but basically basically
the closer you get to the fat the closer you get to the speed of light the weirder things get
So like if I was running at half the speed of light towards you you would appear to be like kind of pancaked and moving
More slow like would be like running in slow motion. Also, I'd be dead because of radiation, but it's fine
But the point is if a photon if if the faster you are if the closer you are to the speed of light
The slower time progresses then if you are moving at the speed of light time does not progress
so a photon is moving by definition at the speed of light so
If you were riding a photon then time, do you would you wouldn't see?
Kind of all of everything in front of you and also all of time would kind of be clap would be sort of collapse
This is again what I mean when I said before that intuition just sort of breaks down
Went the faster you're moving or the the bigger things get
We're happy to keep answering questions, but
Totality will also be going for a while so if you want it
Anyway, so are there any other questions? Well, we're out here. Yeah
Yes, so the question was are there any planets so when when
planets form around a star in general they forming a plane around the
Spinning of the star. Does that make sense?
but the question is are there any planets that were stars that we know of where that is not the case and there are some
In our own solar system. So for instance Neptune has a really tilted orbit
Relative to everything and Pluto also has a tilted orbit relative to everything else and we think this is mostly because of impacts
And we think this is a combination of impacts and also what's called chaotic dynamics, so even in
like a pretty simple
even if you only consider gravity
You can still get weird cases where the interaction of multiple objects can lead to things getting ejected can lead to things getting tilted
could lead to things getting
Really weird orbits shapes. So that happens in our own solar system
and I mean another way to answer that question is I mean that was a great answer at all faxes stuff there also plenty of
Eccentric eccentric orbits, so nope. Neptune is tilted
It also has a relatively eccentric orbit Pluto dwarf planet has a pretty eccentric orbit
and
One of the things that people who study planets outside the solar system right now want to learn is how
Like what is the distribution of eccentricity that?
An orbit, I'm sorry. I should have said
Eccentricity here means basically deviation from a circular orbit
So like as opposed to the earth
which has almost a
Completely circular orbit around the Sun you could have a situation where the planet kind of goes far out and then comes back in
Really close to Soaring goes far out and comes back in
And yeah, so this is kind of dependent this basically could tell you about different formation scenarios for how solar systems form
Do you mean hot Jupiters? So the
Question was have we observed planets that are closer to their host star than they should be?
I guess there are a couple of different ways to answer that but
Most of them they're a bunch of ways where the answer is. Yes. So one of them is
There's this whole class of planets
That astronomers have found that we label hot Jupiters, which means a there they're massive. They're as massive as Jupiter or more massive
And they're hot because they're really close to the the star
around which they've been detected there's a
Important thing note is there is a huge
Depending on the detection method you're using there's a huge
observational bias towards seeing these things as opposed to less massive or
planets or planets that are further from the host star because for example
the Kepler telescope
Which you know detects planets by seeing basically observing a patch of sky
measuring the brightness of all the stars in that patch a bunch of times and then seeing if there are dips and a dip would
Mean that a planet passes in front of the host star because it blocked it's like an eclipse, right?
It blocks a part of the it blocks a part of the light
You're really biased towards short
Clip towards planets that are close to their host star and you're really biased towards big planets because the closer you are to the host
Star the more likely it is that
you the close of the planet is the host star the more likely it is that's gonna pass between the star and our line of
Sight because if a plant is really far out then like what are the odds that its orbit is?
aligned
with ours
Right like it could be
There's this whole they could be occupying a much larger swath of space
So it's they got away from your question a bit, but instead of like how have we found?
Planets that are closer to a star than they should be is. Yeah, we've actually detected a couple of planets both
jupiter-sized and actually earth size and measured to be
Rock to have rocky density that are close enough that it seemed like their atmosphere and outer layers actually have probably been stripped away
And the only thing left is the core
Yeah
Are there planets that don't have a host star?
The short answer is we don't know probably not but there are brown what
Yes, we think there are
We think they're pretty rare
We think that what might have happened is that could have been ejected from their host star by one of these weird dynamical events
or maybe there was an impact and it got so something hit it and it just
Left its system and we detect these using what's called micro lensing. So
basically, the mass of something can be used to bend light and
Planets are pretty small in the grand scheme of things
It's they're tiny compared to stars and compared to galaxies
But they do still bend light a little bit and if they're close enough and in just the right configuration
We can actually measure that bending of the light and so we know a planet is there
Even if we can't see it directly with our own eyes or with, you know other methods like the one we talked about
Yes, we think so are there any other questions yes
What makes us excited to be young astronomers young astronomers I feel like
You have a long career ahead of you
I guess what one one possible answer to that is like what research do you see ahead of you? That's exciting
and so I mean I actually only started working on Planet stuff relatively recently like earlier earlier this
Mid middle of 2018 and it's cool
Learning about the state of the field where you know, we found all these planets with Kepler
and you know a lot of massive planets a lot of close orbiting planets, but seeing the slate of
Instruments that are planning on that people are planning to build over the next even five or ten years
That basically I get like
One of the exciting things for me at least is seeing the path towards finding more earth-like planets
like it's really really hard to do but
Instruments are being designed that I could conceivably in five or ten years
I could be giving someone else will be giving this talk and they'll be talking about like the recent Earth
2j7 whatever that they that they found
All right
so I've studied galaxies and I think the thing that makes me really excited to be an astronomer studying galaxies is
Because really recently, alright so up until very recently. We've sort of had this picture of galaxies as being stable
Because we can really when we look back in
Things far away at galaxies far away. We tend to see we just see images. We can't really see things happening on the timescale of
Galaxies so we don't see galaxies actually interacting. We just see snapshots
It's like looking at a bunch of baby pictures and piecing together the life of something based on, you know, all of their Facebook photos
But what's really exciting is now we're being able to see how galaxies form and change in real time
So with new missions like the Gaia mission
Which has been able to measure the positions and the velocities of a billion stars in our galaxy
So over a billion stars
You can actually see how the stars have been moving in our own galaxy and we can realized that galaxies are
Changing systems, which is really exciting to me and I think in the few
We'll be able to do this not just for the Milky Way, but for other galaxies, too
And we'll start to get a handle on how our Milky Way actually came to be
Right, so as you can see I
work on
How stars die so a lot of deaths especially the ones that are really massive
About 10 times more massive than the Sun
they die in explosions and
These explosions are extremely bright. We can see them in galaxies that are billions of light years away. So that in itself
I find that quite remarkable that you can actually see individual stars exploding in galaxies that are billions of light years away and
Apart from that the reason they're interesting is because they actually tell us
how everything around us was actually phone because
We know that the universe started off with a bunch of hydrogen and helium
that's pretty much all there was but today around you you see quite a large variety of stuff, you know this wood and
metals and iron and all this stuff all this stuff was formed inside stars and inside the
exploding stars primarily and
By looking at these explosions, we can actually piece out, you know
What kind of explosions formed what kind of elements and what the dust that does that tell us about?
how the universe has come to this stage and how it's going to
Eventually evolve so I think
Today because of the technological developments with telescopes and computing and everything
We are really getting into an era where we are. You know, we are finding and understanding
thousands of supernovae each and every year and that
in itself really opens up this, you know entire field of you know, trying to systematically understand what
Relates to what because even today even you know when you actually use real physics
It's very difficult to get a star to explode when you you know with the physics that we understand today
So I think you know that is quite exciting for the you know, the era of time domain astronomy in the near future
Can you repeat the question I I forgot
What what well I'm excited about
Okay. Um, so I'll actually do like more physics astrophysics, so I don't really do much astronomy observations
So but I think I think for me my very small area of work
I work on testing general relativity and
In previously. All I've mostly done is like solar system based tests and things like that and like LIGO was just like
You know something that could or could not have like, you know observed binary black holes
which is like the most the strongest in the most dynamical regime that we're able to test general relativity and
A lot of these things like, you know, like I'm working in the collaboration right now where it's like, you know
It's it's a completely new field
You can like I could I could you know
Depending on how hard I work
I could go to my office right now and in six months I could maybe come up with some weird theory
Or some way to observe it and then like yeah, and it'll be tossed into the you know
Like a analysis pipeline for LIGO like it's just like how rapidly things can be turned around depending on how much I work
Of course, but it's like yeah, so that's that's exciting
But it's also just like the whole future of it
Like I could theoretically do that and you know get stuff that can be observed right now
Or I could you know think more about the future. There's some projects. I'm working on or like things
They're not gonna happen until 2030s and things like that
But that's you know not had that option to kind of
Go where I want do what I want and plus the data is there I want to do anything with the data
So all of that's really it's really exciting. I think for the most part and
like LIGO made this detection like in
September of 2015 and I started grad school in July of 2015 here
So it was like I showed up and as I go that's exciting
One more thing space is so cool. It's so cool. I'm excited all the time about it. Okay
We had a question up here. That was waiting
So that's that's a great question the question was I think as telescopes become more sensitive and we're looking at
and we're and we're looking at more distant objects or let's say an object that I'm
Looking at objects while their gravitational waves being emitted. Well gravitational waves distort the mirror
Is that telescopes used to reflect and concentrate light? The answer is no because
gravitational waves
have
Distorts based on such a minut scale I
I don't I can't I don't know the numbers in my head
But but this is the reason why LIGO is one of the most precise
instruments on on the on the planet they what it was statistic like you have to be like
Oh is precise enough to measure like the width of a hair?
Like a foot. I don't know like the distance of many countries to the precision of the width of a hair or something like that
No, I can't Ron. He's not saying yes or no
But the the point is that like the
you use you're just not worried about those those distance scales when you're making the mirror of a telescope like
Current one of the sort of cutting edge cutting edges of current instrumentation right now is adaptive optics
Where you actually deform the mirror of your telescope to compensate for the blurriness that the atmosphere introduces into images
But right so so so the thing about that is, you know, if you're already deforming your mirror actively
You're past the point. You're not you're not gonna have to worry about
Uncertainty the width of a proton your you've your your bottom limb for uncertainty is way above that anyway
Good question, though
Candidate well, not technically candidate grad student grad student. Yes. We're all got students that Cameron left
So the question was regarding Goldilocks planets, which is a term for a planet which is in
Not to like it's close enough to its hosts are but not too close. So that water could form in its surface basically
It's sort of like if you're too close then water will evaporate because the it'll be heated away
If you're too far it'll all be ice. So the question was if there plans to observe
local celestial bodies to
determine whether or not
Certain stellar events affect those planets. So I have a follow-up question. What do you mean by local celestial bodies?
You mean like in our solar system or do you mean around nearby stars? Oh
So so when you say affects on a planet you mean like whether it would impact the habitability of a planet
So I guess the short answer to that is
Kind of not not really so there there are a lot of studies being planned, right?
There's a lot of work being done right now to characterize atmospheres of planets. One thing because when a
Wedding group. I was talking for about transiting planets planets that passed between us and the star that they hosts
so on a planet transits you can actually take a take a spectrum like take the light and put it through a prism and
use that to infer the properties of the planet's atmosphere because the star's light is passing through the
Through the planet's atmosphere and so you can see absorption lines for all the molecules
And so like that there's a mission being planned right now called the James Webb Space Telescope
That will be a telescope in space that we'll be able to do sort of
atmosphere atmospheric characterization on a really unprecedented level but as for
as for weather
affecting
Whether it would affect the planet's habitability. It's kind of nebulous. So I was actually sitting with a recently with a professor who
specializes in this work Heather Knutson who does a lot of atmosphere
characterization and she was saying that
the
She is skeptical of any attempts to characterize like actual detection of life or detection of potential life
Through atmospheres like you can learn about planets atmospheric composition, but the error bars on some of these
qualities like
abundance of nitrogen or abundance of oxygen or whatever the error bars are just gonna be so high because the data is so messy that
It won't tell you whether they're like bio signatures of life. It won't tell you
Yeah, so
That was an answer to a slightly different question. I suppose but the other answer is that
Getting to any other exoplanets. I
It's it would take a long time
To sort of answer part of your question we do actually study the ways that the host star can affect the planet
So for instance, there are these stars called M dwarfs
Which we think might host quite a lot of planets and these are very dim
Stars that we think have a lot of variability and may even produce a lot of you know
X-ray flares and other things and we do think that that would negatively impact the habitability
How much as Lisa it's really hard to say, but it is a thing that people do think about
It's hard to measure
All right, do we have any other questions, okay
So what happened
Was it was clear?
It was like beautifully clear and then within like about ten minutes before it was supposed to reach totality
like basically a fog formed right in front of the moon and
clouded up and right now it's like totally cloudy and you can't see anything but
We're gonna keep stay here until 10:00. So if it clears again
Then you'll be able to see it. But otherwise
No days
You are all getting a taste of what it feels like to actually be a professional astronomer
Taking data only to find out that there's a cloud over your telescope in Hawaii
So congratulations your all your all astronomers now
It's true that's jail
That's also true
You can ask us like what's it like to be a grad student or why is the sky blue or
What God look what causes the speed of light to change so
So it depends so it depends on the medium through which light is traveling
So the catch is that the speed of light is constant in a vacuum, right?
But so light is an electromagnetic wave right? It's a wave in
Sort of the field of electromagnetism which is all around us
The if light if that wave is passing through a medium of a certain density
Like water or glass or air?
Its speed depends on that density
Someone probably has a better answer than me
You can think of it as if there's a lot of stuff between you and the light then the light will get scattered
By the stuff that's in the way
It'll get like absorbed and then emitted and then reabsorbed and remitted or it'll just scatter its way
Through the medium and that slows it down
So even though yes those Lisa in a vacuum, the speed of light is constant
What's physically happening is that stuff is just getting in the way of the light
Which slows it down?
One cool side effect of this is something called Cherenkov radiation
Where light that is traveling in a vacuum?
Like in space, you know pretty good vacuum. Well
and
it's like enter the Earth's atmosphere which has nonzero density and so it slows down and there's actually a
Shockwave effect where you know the light, you know as it's entered once it enters the Earth's atmosphere
technically
For a split moment is traveling faster than the speed of light in that medium
And so you get high you got high energy radiation scattered from that you can actually measure that using high-energy detectors on the ground
They are heat
So the question was do photons get affected by heat so
As we mentioned photons are if heat is a form of photons heat is infrared radiation, which is just another form of light
So heat itself is made of photons if photons get near other photons they can
Nominally interact you can get scattering effects. Usually do you remember any more basic particle physics than me?
Right so photons can interact with each other there is
This beautiful principle in physics called interference where photons interact with each other
So photons do interact with it with each other two interference where the idea is that so
So photons have this dual behavior. They are at the same time particles as well as waves. So there's this wave particle duality
That's a real concept in physics where the idea is that?
photon light is both a particle and a wave and
When you when two waves they get together at the same space at the same time
they can cancel each other or reinforce each other and that's called interference and
That's one of the one of the most beautiful principles in physics, which is actually quite widely used in astronomy
for various kinds of detection techniques
so yes photons can interact in those ways, but for the most part at least
You know the kind of photons we see around us
They will never interfere with it each other because they don't they don't know about each other. So there's this thing called
coherence, which is which is the idea that
Okay, yeah, okay never mind so okay so this so the idea is that
Because you know, if you imagine these different light bulbs they don't know about each other so so
only light that
Has a certain
Relationship to the only photons that have a certain relationship each other with each other are able to you know
Interfere and produce the kind of interference things that I've been talking about. So yes, I
Mean if they're from the same source then maybe but like
you know if I switch on the light bulb here and switch on a light bulb there and expect that something will happen in the
Middle. No, it's not gonna happen because that light bulb doesn't know about this light bulb and
You
Can get interference from infrared photons if they're from the same source
So so if for instance you ever go to my favorite place in the world, which is the Exploratorium in San Francisco
They have this really nice thing where you can focus infrared photons and it's sort of a nice demonstration of yeah
how you can have coherent interference between
infrared photons
Which person may be the person in the front how not the question first, yeah
So I I meant that to be two separate things so the question is what is what is moon simulation
But III was prepared to answer questions about the moon or about simulations or about moon simulations
perhaps
there are in fact
simulations that people will do to understand how the moon formed and
And how it has evolved since it formed to to be the way we see it today
Primarily the the most popular theory for the formation of the moon right now. That seems to match most of the evidence is that
Early on about four-and-a-half billion years ago. The the solar system was a slightly different place
There was a lot more stuff going on. There are a lot of rocks and such flying around and
The there was no moon yet. The earth was just hanging out and it got hit by a big small
You know a small planet s mole that was about the size of Mars
So I guess a pretty big planet decimal
and
that the word the name that we give this even though no one thought because it happened four-and-a-half billion years ago is a is theá--
So thais struck the proto-earth and in doing so it flung all of this material off of the surface of the earth
Which made kind of a ring because it was rotating
It made a ring around the earth and then eventually it coalesced into a single object and cooled
So then you've got the moon hanging out there and over the last four and a half billion years
It's been struck by a number of other smaller objects
Which give it some of the craters and and the sees?
The moiré that you see when you look up those are the dark regions on it. They aren't actual seas
That's what Einstein thought. All right, son
That's what Galileo thought when he first looked up it at this he called them seas, but they they're there's no liquid on the surface
no liquid water on the surface of the Moon so
That was a long response to your question
but
What was your most difficult and favorite course that you've taken as a student I
Think for me it was probably I the question was wait everybody Cameron just said it. Um
Probably the interstellar medium, which is so there's
That was the most difficult
It is the interstellar medium is what it sounds like it's you know the stuff between stars
So you study the chemical composition of nebulae and dust which is actually really important for learning about stars
It's a hard subject. It was also taught by a professor who is
Who these lectures are recorded so he's not going to say who taught the class
My favorite class is galaxies because I love galaxies and I think they're great. My least favorite class was cosmology because
I'm going to pass the mic now
Okay. All right. It was mostly because honestly, I don't find it that incredibly interesting. It's just not fun for me
Cosmology. Yeah
But it's like okay. It's like the boring math part of the universe
I think there's a lot of really interesting physics that can be learned without having to do all this really boring mouth
Use this crappy notation that whatever. Okay, it's fine
I think so. I think the least favorite was I think I'm pretty it was the same as Mia which is cosmology
Yeah, it says yeah, it's just too much math for me basically so
Favorite I probably have a couple
one was high energy astrophysics because I really like high energy astrophysics and
other was the
instrumentation class which I really liked because I also like instrumentation so
Oh, yeah, so my favorite class so far actually was not cosmology
As a general it's um, it's general relativity, which I guess is like a more descriptive form of cosmology
And I really enjoy that for the most part. It was fun class. That's area. I work in and everything
And there's a continuation that onto gravitational waves, which I really like. I took that class twice actually
Just cuz I really enjoyed the teaching style of it
Um actually did take cosmology, but I think I dropped it after three weeks
Actually, I think I was thinking the class with you for about three weeks
yeah, I dropped it though and my my heartis my hardest one I think was um
I'll probably say quantum insider quantum field theory or
statistical physics
Mostly because I did the quantum field theory class
So they I left with it and I was just like I don't even know what I just did
I just did a lot of integrals and I have no
Intuition in that field at all
Yeah
You have a question
Okay, we have the question is
Why is it called a Blood Moon and how does it get that color?
So it's called a Blood Moon because it appears red
Unsurprisingly and it gets that color
Because what's happening is you've got the Sun here. I'm gonna draw a picture. Oh
Yeah, we can we can act this out actually do you want to come down and you can be in this as well
Okay. Okay, you get to be the Sun?
She gets to be the moon
I'm the earth
Okay here well we'll go in front of the table join us, what's your name?
Okay, okay come up here so you get to be the moon
So I'm the earth and what does the moon do?
Does it orbit around the Earth or does the Earth orbit around it or do you know?
In the moon's frame, yes, so that's close
So what happens generally is that the earth stays in one place and the moon goes around it? Okay
So I'm the earth and you're the moon so you go around me so you want
Your redefining physics, okay
So you're the moon
Yeah
Your mo you're the moon and I'm the earth. So you get you go around me. Will you do that?
Okay, so you're the earth and I'm the moon. Okay, so you're the you're the earth and I'm the moon and
I go around you
Okay, and
An Mia is the Sun. Okay, so what happens is?
As I the moon I'm traveling around you the earth
at one point I get in the way and I block the light from
the oh
No, I just did a solar eclipse
Okay
So if I'm over here as the moon
The light that would normally be hitting me and lighting me up and causing you to see a bright moon in the sky
Now I'm hiding behind you and I don't get any light from Mia. I'm blocked. I'm in your shadow
And so I I turn dark right?
That's what starts to happen during the lunar eclipse. Did you see any of the lunar eclipse?
Just now no, okay
Only a bit
But what happens is you have a cloud of gas that's surrounding you call
it called an atmosphere and that's that's what we're breathing right now on the earth and
it turns out that the light is able to refract through that atmosphere and
Hit the moon even when I'm in your shadow. Oh
Yeah
uh, what does refract mean it means that the light travels through and it gets bent as it travels through the
The gas and the atmosphere and it bends around you and in doing so
It filters out the blue light
So only the red light is able to get to me
The moon and then it reflects back to you and you only see me as a blood-red moon
during that period but
Within about an hour I keep moving and then I'm not in your shadow anymore
And then I'm lit up by the Sun again, and then I'm not red anymore
Does that make sense?
No, okay
Thank you for joining us Sarah
That was a challenging question
Any any other questions, yeah, that's okay
Good question
so the
the question is will the rings on Saturn ever become a big moon in the same way that I described our moon formed out of
Kind of a ring or a series of like a disc II like structure around the earth
the
Rings on Saturn aren't just if if you've seen pictures or actually seen the Rings it's not just a pure disk. There are individual
Ring-like structures. And in fact, there are gaps between those rings those gaps are usually
Occupied by things called shepherd moons
so essentially you'll have a
You'll have a ring and then you'll have a moon just a little bit farther out and it's essentially clearing that space
so the stuff that was
potentially in that region either formed into the moon or
Fell into the ring in interior to it or exterior to it in that ring. So you have a number of different
Shepherd moons in between the rings that are usually pretty small will they ever form like a single structure?
I think they're dynamically pretty stable
Maybe if there were a big
There were a nearby planet that came close to it
And and perturbed those it might
coalesce into larger
objects, but for the most part
In its current state it's pretty dynamically stable and should remain
For the indefinite future the same is true. All of the gas giants have some ring system. They're just much much fainter
we can't see them readily with our eyes or even with with telescopes small telescopes and so on and so forth, but
Jupiter
Neptune Uranus all have some rings structure around them
Why why was that why is the Saturn ring structure stable? Whereas the one that formed the moon around the earth?
Unstable that it formed it coalesced into a into the moon. Is that your question? I
Don't know the answer to that question it I
Think the impact wasn't enough to kick out the material to a large enough distance
Because the ring structure I mean when you see pictures of Saturn those rings go out on the order of the radius of the planet
Right. They're very very very large. Whereas the
No, because the moon is the moon's even further up than that to I I don't have a good I'll think about it
I don't have a good explanation for that but perhaps
I think this is it, which is that the Shepherd moons actually play a role in maintaining the ring structure
So the rate the rocks that you see in the ring in Saturn, they're not
Constant all the time. They're continuously being replenished by new rocks that are being formed by you know
new smaller pieces of rock that are being formed by
Collisions among amongst those rocks as well as with the moons that are sitting inside those rings
So in that sense, there is a continuous new supply of material that is going into those rings
Around Saturn especially because you know Saturn has you know some hundred moons or something
So there is a continuous supply of rocks that is going in there because of collisions
Did you hear that so they were talking about how the earth does not continue to replenish its supply of mini moons
Our moon is also
Our moon is also large enough that it's spherical and can actually and has cleared most of its own orbit around the earth
Whereas the moon the little moonlets around Saturn are not spherical and not as not nearly as massive
Yeah, the ring stuff is not as there's not as much material in the Rings as there is an oven yeah, that's a great question
Yeah
Is there a question why is there a reason why the gas giants have rings?
Right, so is there a reason why the gas giants have rings but the rocky planets inner rocky planets don't
Yeah, I could be do to them
Yeah, that's a yeah, yeah Nikita in the back has made a great point Nikki does another Astra grad student
Yeah, so she was saying that has to do with the sublimation radius of so Lee was talking earlier about how they're different radii away
From the star within which you could have
solid ice liquid ice or all the
Solid ice liquid water or or all of the water has his basically vapor, right?
So Saturn is far enough out that most of the stuff in its rings is ice and dust
I
was just I was not raising that point which is that they're earth-like planets that are
Close to that that are much
Closer to their their host stars than the earth is and they're earth-like planets that are further away. So
Okay, I saw word
Yeah, so - did you understand what what Mia and and Nikita had pointed out okay
Yeah, so in as to say to basically give the voice - Nikita who's in the back answering all of these questions
generously
In the interior all of the material that would go towards a ring, which is primarily Isis and such
those those are
vaporized and and kicked into the outer solar system where they can cool and coalesce into
The structures that would be able to form rings. Did I did I say that correctly, roughly?
Okay, it passes muster with the expert in the back Oh
More conversation
Some of it is mass mass of the system
so lower mass objects aren't able to hold things in their orbits as effectively and all of the
The rocky planets in the interior are much less massive than the gas giants
Which it probably will
Will curtail this because I don't want to keep people indefinitely either
maybe three more questions and then we'll kind of
expire
Yeah, who was that who was the next in the back
So I didn't understand
So the question was I think you were talking specifically
in the context of the Saturn conversation
We were just happening having yeah, so so the the question was suppose that there rocks. There's like a rock just behind the moon
Or how would the moon clear it out of orbit? Because they're moving at the same rate
I don't I don't know off the top of my head. I think it has to do with
gravitational
instabilities in the orbit like it's some combination of
Collisions with objects because I mean those rings like nice and ticular now
but they might not they weren't always that way that way I mean objects were moving with different inclinations and
Would scatter off of each other or gravitationally influence each other. So I think
the answer is that
Magar potential instability combined with combined with collisions
So the question is what is the importance of measuring these gravitational waves or sounds
So for the most part it points out that there's a separate type of radiation that exists because and also it's giving us information that
We could we could not detect before information about the universe
because all of astronomy all the way since
You know optical telescopes of a thousand years ago or however long they were at they're around
All of it has been based. All of a Shami has been based on electromagnetic radiation
generated by excited electrons
That emit photons or you know across like all the way from infrared to gamma rays
gravitational radiation is
the gravitational analogue of that
You know to electromagnetic radiation and so gravitational waves ours into the gravitational radiation
So it's allowing us a new different type of information, you know to get did you get from the universe?
One of the most direct examples of this one that we've seen so far is
There's been a lot of talk about LIGO and black holes
Black holes by definition don't emit radiation
So you can't if a black hole merger isn't happening with any gas around it or anything?
That would be affected and emit light you can't see it happening with light
But a black black holes when they emerge emit gravitational
Waves and so gravitational waves are the only ways to study
black holes in a vacuum so that so that that's why I mean
That's why the no but that's why that's why there was a Nobel Prize for this because it's just a way to study
I mean, it's it's proof. It's proof of general relativity. It's it's another
There, you know Einstein's theory has been proven multiple times in multiple ways. But this is a particularly important one because
gravitational waves have been predicted by theory since the sixties for a very long time, but
There's no way to observe it until now another way is you know
by hearing black hole mergers or hearing white dwarf mergers
You can learn about population of black holes in the galaxy, right?
You can learn about sort of the distribution of masses for these things
Which could tell you about this distribution of masses of the stars that you know preceded them?
So it's basically a whole new avenue for learning about the universe and it opens up doors a lot of doors that were closed
Using only traditional telescopes does that answer your question
Yeah, and when you're hearing you basically they're a thing that there are objects in space that you can hear and gravitational waves
But you can't see with light
Do you mean so the question was what are we learning from the unknown? So do you mean about gravitational waves in particular?
Oh, you mean practical applications, so
Okay, so the question was yeah
What are what are practical applications what we're doing I can I give a quick answer
I think everyone everyone has a different answer to this question. I'm gonna steal one from a
Particle physicist and a documentary that was named. Sorry. I like which is there are two answers to this question. There's the there's the
answer that's like
Practical and what actually you know, it's it's true and will lead to avenues for science
We don't know and then there's the answer which is the reason why everyone's actually doing it. So the first answer is in
Developed, you know, you heard probably during the talk. I wasn't there but about the technological marvel marvel
That is like oh right developing these intricate systems in in the course of developing the technology
You need to see the most distant galaxies to hear black holes or for particle physics, you know to discover the Higgs boson
You have to develop all these secondary technologies and those have immense practical benefits
so for example, I mentioned before that one of the current vanguards of
work in
instrumentation for big telescopes is adaptive optics where a mirror
Basically, you know atmospheres between you and stars and galaxies atmosphere makes things really blurry
You can basically have a smart mirror that will
you shoot you basically shoot a laser into the sky or use a star a bright star as a reference and
Do a bunch of math to tell a mirror
Like Pistons on the back of a mirror how to deform it in such a way that suddenly you get a clear image
That's really great for astronomy because it gives you in detailed image. This is where before you had blobs that's currently being used
There there are a lot of Defense applications but in in like
Medical research that that kind of the algorithms used to develop that and the technologies are used to like look into people's blood streams
Apparently this is like a super cool thing for like using infrared light to look into someone's skin to make a diagnosis
The development of the LHC a Large Hadron Collider led to
Dick the most powerful magnets ever developed and those have I forget what but those are their practical applications for that. So
Oh, yeah, that's a good one the internet the internet was developed. That's you know, debate the pros and cons but overall
It's pretty useful thing
So basically in astronomy in particular
I was a field where the end result isn't really practical there have been a
Ton of spin-off technologies both actual hardware and data processing but then there's the other so that was the answer which you tell them
Yeah what but no, they're something like
There's a other practical applications, but then everyone actually just does it cuz it's really cool and we like to learn stuff
And
Another aspect of it although none of us work explicitly on this but being able to detect
Near-earth objects that potentially could impact the earth
Asteroids and comets and so on and so forth is potentially one of the most important
contributions we can make if we can save civilization from a
Deep impact slash Armageddon like future impact that could wipe out, you know a city or something like that
Oh
So the question is has anyone
seen where two of the mergers of black holes from a gravitational wave event and
Two and another two merger that those two merger merged together
No that hasn't occurred and I don't think we ever
anticipate being able to discover that in our time scale in the the time scale that we're detecting these because black holes as
We understand that black holes shouldn't be so
High a density that you have a lot together
That could potentially merge on under those those kind of timescales. But I mean, I guess it's possible Ron do you guys do you
Have like like, you know inside like near the center of our galaxy
There's a lot of black holes being flung around around at the major potential supermassive black hole that
Exists at you know the center of most galaxies you
Could have situations where you get maybe a triple system if they're close enough
Yeah, like one inner binary system and one out of it binary system
So it's possible for those two sort of occur on human civilities and timescales. But within our lifetime not likely
So oh
You're talking about them being in binaries to begin with okay?
So
for the most part all the binaries we observed so far are stars that have
Existed together since their beginning like yeah these binary stars they they form together
They form as binaries they exist as binaries and eventually both of them die out in some process, you know
Where one one one one star dies and it causes the other one to die and so on and so forth
so towards the end you have two stars that essentially
You know have like lived entire lives together and they're still in orbit as dead as dead stars
Which are what black holes and neutron stars are and eventually they will
You know merge together - what - one final black hole
so that's the primary, you know formation channel that we sort of assume right now and there's other there's other methods as
Dynamical captures like at the center of a galaxy and things like that. That's another way that can you know form these binaries
Does that answer your question
For the most part
uh, he's sort of saying like
you know solving the gravity problem in a way sort of getting information outside the
inside of a black hole at the singularity in order to you know, uh,
you know what the gravity problem is like altogether like to
Okay, yes, I haven't really heard much about that
But for my from just like trying to understand the interior black holes like you
You're you're dealing with an area where you will eventually see the breakdown of
general relativity
Mostly just because general relativity is a classical theory in a way it treats
You know what? We call the graviton the particle analog that
Causes interactions, you know
With gravity, I guess
is that you like the gravitation waves that we detect and
you know for the most part is the bulk motion of these gravitons you have like
Ten to eighteen or ten to the twenty gravitons that are like moving in bulk motion
So it still it's classical form so near a black hole, ur inside of a black hole
it's is theoretically possible that you're gonna start to see the actual breakdown general relativity and you'll start to get um,
no real good data on like maybe what a quantum theory of gravity might be like
altogether, it's just you can be seeing effects that are beyond general relativity because the current the current consensus right now is general relativity is
Not the complete theory that it'll eventually break down. We just don't know when
It's possible it could occur like you know, the interior black holes
Those are both great questions first one for personal challenges in grad school. I think everyone will have a difference to this question
For me at least for the first few years. It was a
orienting yourself a bunch of among a bunch of people who are all
Brilliant and you immediately feel that nothing you do can live up to you know
The people around you who are incredibly accomplished and you know, there's a term for this is called impostor syndrome
most people get it in grad school
but also
Learning how to pick what you want to work on I think can be can be tricky
And thankfully and grant in most scribe programs and here also you get a chance like you you do first-year project you think about what?
No
See if that works. If not, you try something else, but I think like that transition can be tricky
so if you if you decide to go down at the grad school path
Don't expect a lot of people in their applications
Which this is kind of what you're supposed to do you apply and you say like I'm gonna work on
Galaxy formation at this like four galaxies this particular redshift and I'm gonna solve this exact problem and like that's good
You're supposed to write a detailed application, but when you get to grad school
It's good to keep an open mind to different challenges that you might want to work on cuz you know
What is who's available to work on what can change?
What your interests will change and I think it's important to just kind of be open to that
To be open to the fluidity of that experience
As for flat-earthers, you can fly a plane around the earth
So I think one of the agree with Lee that one of the biggest challenges is a sort of transition from taking classes where there
Are correct answers to doing research where there are?
No one knows what the answers are no one knows if the project you're gonna try works at all
Or if it's going to fail and that can be really difficult to adjust you. I also
Would like to add that
Challenges in grad school are often compounded. If you do not look like the stereotypical image of an astronomer, which is a white, dude and
that can be
Tough to deal with I think I didn't realize how difficult it was going to be until I got to undergrad and grad school
So that was hard
I think
reef flat earthers
At the last international Flat Earth conference
they said that there would be
prominent flat-earthers from around the world
coming to attend
And I think that really just speaks for itself
For the record Mia is one of the people that I am
Intimidated by and him convinced so that there are a bunch of brilliant people at this tables what I'm trying to say
It's because I would win in a fight
Right, I think Lee and me have mostly covered challenges
I would have thought of as a grad student
But there's probably something Addison. That's probably specific to the field. I work in which is I work in time-domain astronomy
so the idea of kind of in astronomy is that we try to understand how stars die and they die in these incredible explosions and
Part of the problem is that these explosions are short-lived? Well short lived on human timescales, you know the star explodes
You can see the explosion for like a few weeks and then it fades away
but a lot of interesting science can be done if you're very alert and you
decide to follow up on
explosions very early
And that's what part of the problem comes because explosions don't think of no, when is the weekend or when is it 2:00 a.m
In California, so, you know at oftentimes we get texts or even phone calls, you know, oh wait
There's a GRB that went off at 3:00 in the morning and I have to wake up to make sure that a telescope observes this
event and
That's part of the job is that I'm doing astronomer
That these explosions don't care about weekends. They don't care about public holidays or anything else
So that's part of the well, I would say it's an interesting experience to adjust to this. I was definitely a bit
Shocked initially, but I was like, yes fine. It's I can do this. Yeah. So yeah, that is oh
Yeah, so I guess like one of the things was challenges you mentioned
I would say um
Yeah course isn't this imposter syndrome there zone this isolation in a way
I
Feel like you know a lot of times I just get your head so bogged down in your work and you don't really interact with
Many people or you interact with only a handful of people and you could start to feel very isolated in a way
Like I've gone through like, you know, maybe an entire week where I think the only words I've said were like
you know ordering coffee or something from some, you know, some Bruce they're out there or something and
yeah, so that does happen as well as it's really just like because I work in a more theoretical field sometimes you
work on a problem for months and even even a year and
Everything fall doesn't go through properly
You start to realize that the idea you had it's not gonna work out so I get just like oh, okay
I guess I just wasted that that year of my life and then well
I guess it's not really wasted because you know down the road that you shouldn't go down in the future
There's that and also sometimes you you know
Sort of like think that your ideas like really great and really awesome and then it turns out not to be you know
Like it's either
You know not accepted to the journal that you want
Maybe it's like rejected in a way
Or maybe it just doesn't pick up much momentum as you would expect it to and you're just like, okay
Well, I kind of gauge that wrong
So yeah. Those are those are different challenges and
as far as like flat-earthers and those type of people I
I kind of just I have my time then to talk to them or try to debate these things
I
Went to graduate school, I'm a product of graduate school
Challenges to graduate school
staying focused on a particular topic
It's really easy to jump around to lots of different topics and projects and so on and so forth, but ultimately
The thing that you're graded on within the academic realm is the papers that you get out
And if you're just doing a little thing here that's unrelated
You know doesn't go towards a paper it it isn't good for your career
So really staying focused on the things that count which is to say single first author papers for yourself
It can be yeah, try not to get distracted by all the other cool stuff whether it's academic related or not academic related
I went to graduate school in New York City at Columbia. And there's a lot of non-academic
distractions in New York City
So sometimes it was challenging to stay focused on that in terms of the flat earth
or how to deal with flat earthers one thing that you can point out is
That a lot of people if you if you watch a if you sit and watch a sailboat go over the horizon
the last thing and even the ancient greek mariners
Figured this out
The last thing that you see is it goes over the horizon are the top part of the sail
Because it's the curvature of the earth as it goes farther and farther away. It's getting lower and lower on the horizon
so you only are able to see the top part as opposed to at all just fading out uniformly if it were flat and
Of course. Yeah asking them to go to the sea and stand there and watch
For an hour or two as a boat goes over the horizon maybe too much
But it is an experiment that they could actually conduct if they really cared and it would demonstrate the curvature of the earth
But I find that a lot of father Arthur's I mean skepticism is very important. Not just
Taking for granted what someone else tells you on authority that that's the truth being?
skeptical and deciding to test something for yourself is important and so at some level the idea of
flat earthers like
Going bucking the trend and not not just taking it for granted that whatever is in a they read in a book is is correct
I agree with that but there are some very very simple demonstrations that they themselves can do to demonstrate that the earth is not flat
Or even logical things like we pointed out that we have
Airplanes that go around the earth and don't just fly off the edge, so
There there are some simple demonstrations. So I think most of it is not about the science
It's just about trying to be different and trying to disagree with you know
Everybody else. That's my interpretation of it
Well, wait, there's still a couple more questions, I don't know I I don't want to keep people here
It's pretty late, but if people have questions you have fun, okay?
Okay, how many more questions raise your hand
If you still have a question, I see two three four Oh a young gentleman in the back
okay, so we'll take those four questions and then
then we'll
Disband so sir
Okay, so the question is the consensus was that MIT throws the best parties in Cambridge, Massachusetts
by far
How does Caltech
compare I
Don't think the parties are very good here. I
think
Grad student life and undergrad life is somewhat separated. But I've heard that they build large several story structures for parties
So that's pretty cool
Yeah
Also drives into the desert and then explodes massive kegs of things. We don't endorse this also
But yeah, that's undergrad life good yeah in the back
What happens when you go inside a black hole
This is a great question. So I think we should talk maybe about the parts of a black hole
There's what's called the event horizon, which is the point of no return of the black hole
Which defines what we call the ergosphere of the black hole and then at the inside of black hole?
There's something called a singularity. We don't actually know what happens when you get
to the singularity because
Yeah, as a lot of people I mentioned we don't we just don't know what happens when you get there but on your way there
Many things will happen to you and none of them are good. So
First the gravity is so strong. Okay, so you get ripped apart by what are called tidal forces
so basically the gravity is so strong and coming from such a dense part of
Space that your feet will get pulled much more heavily much like much stronger than your head
And so you'll effectively be ripped apart like spaghetti. So we call the spaghettification
that's the actual technical term and
Then you'd you're at that point. I don't think you really care about anything else. I
Mean, I think I think that's pretty much it for you
Yeah, yeah
So being being ripped apart like that
That's due to the tidal forces that occurs with smaller black holes, like if it's only a few solar masses, for example
Your body will be will be ripped apart and everything you won't be able to go inside the black hole
But if you're if you fall into you like a supermassive black hole for example millions or billions of times
You know the mass of our Sun the curvature, you know
It's not it's not extreme as much much of an extreme curvature as smaller black holes
So when you're falling in is essentially a big flat plane similar to you like here on earth, you know
you don't really experience the curvature of Earth only over long distances and
also the how the curvature you know
Depending on how the degree of the curvature that will also affect the type of tidal forces of your experience
So when you go into a supermassive black hole you actually can go past the horizon
So you start to fall in and what happens is that you sorta get closer and closer to this massive black hole and
Pretty soon like the entire area around you starts to turn black like, you know, it comes up like up to the horizon
But that doesn't mean that you've gone through the horizon yet because what happens is that light it gets B gets bent
Around massive objects. This happens with black holes as well
You fall deeper and deeper and the black, you know
the blackness of the black hole will just start to income so late like encapsulate you all around you and
What you start to see the most the last thing you see before you enter the black hole is that you start to see?
This big like circular thing and that's the that's the light of all those entire universe
Being gravitationally lends around so you observe the entire observable universe right there
And that would be the last thing that you see before you fall in
Did you fall in and we actually don't know what happens when you fall into the black hole a lot of crazy stuff happens
but eventually you will get to where the singularity is and
Nothing can sort of escape, you know, the forces of that because it's like it's like a point, you know
So it has extreme curvature there
So where curvature blows up so adapt when you get there, that's when again you would get like, you know torn apart. So
So it's not recommended to to go into one
Yeah, so yeah, they they fall off the amplitude of the wave form falls off as one over the distance oh
you want to know um
how do
gravitational waves diminish with distance and also
If you like what like would we feel if you were a close closer?
Yeah, so yes, they do did he do - with distance less well over the distance from from the observer to the source
And if you are actually very close to a source generating black holes
We'll take an example being um binary black holes in this case. Is that
you
go through this in small phase and towards when they merge you have this big burst of you know to merge the merger signal the
Burst of gravitational waves that gets emitted if you're too close
what happens is because it's it's literally like space and time that's being fluctuated and
That you know that fluctuation can actually eventually like if you're too close to it it can overcome, you know
The the binding of like, you know tommix scale the binding energy on atomic scale
So it'll literally rip your atoms apart of your body and you can't reconstruct it from there
So I just sort of like ripped apart on like an atomic scale
And there's actually an interesting thing
I think I like we spoke with with Kip once about was that if you could hear the gravitational wave
Like your eardrums resonate a specific frequency
And are you able to hear that before you get?
Blowing to blow into your atoms that we couldn't really find an answer to that but it was something interesting that we're talking about
You're talking like you have like two entangled particles and then you sort of
Okay
Okay, yeah, actually I'm not really familiar on their the quantum side of gravity
So in sort of coming with an idea of quantum gravity, there's sort of two approaches people who work on the more
Classical side, you know what gr. And stuff like that and try to you know, see any deviations in gr
that's kind of where I work and
there's other people who work purely from like a like the quantum aspect quantum field aspect and try to derive like
fundamental like
the
equations that are like in gravity like, you know, like
like Newtonian gravity
for example people try to work from from like quantum field theory and stuff like that to
Reconstruct some of the phenomena in classical gr. So yeah. Sorry. I don't really know
I'm like, yeah, I don't really read much into siskins work or anything
Thanks everyone for coming and staying so late
Again, we have these once a month we actually have to in
In March one is a visiting professor. Who's a
Astrophysical theorist from Berkeley who's going to be talking but yeah
So we have six more in the next six months
I encourage you to grab a schedule out front we'll have telescopes set up after each one in this Q&A panel
We unfortunately won't have a lunar eclipse for each one
But we also have astronomy on tap once a month for the next six months. Our next one is next Monday
So thanks everybody for come
