Hey Crazies.
Astronomical scales are so big, they can often
be difficult to imagine.
Things like planets are huge,
but then the distances between them are even
bigger.
So much bigger, in fact, it’s almost always
impossible to show the sizes
and distances to-scale at the same time.
On top of that, the human brain can sometimes
resist the reality of these numbers.
The Earth is a little under 25,000 miles around,
but, standing on the ground, you can only
see a max of about 3 miles,
which is 0.00001% of the Earth surface.
That perspective makes the Earth look flat
even though it isn’t.
There’s photographic and video evidence!
But let’s step away from the Earth to the
next closest thing: the Moon.
We’re going to need some non-scientists
for this.
Let’s ask some people on the street!
As your attorney, I’d recommend against
this.
Really?
You’d have to get everyone’s written permission.
It’s messy.
Man! Hmmmm
I’ve got it!!!
Let’s send interview clone to ask my parents.
I've got a basketball here and what I want you to imagine is that this is the Earth.
OK.
OK, so we're scaling the Earth down a little bit and we're imagining the Earth is this basketball.
OK.
First question, how big do you think the Moon is if this is the size of the Earth?
You can show it with your hands or whatever.
I would say... this big.
About that big? OK.
What do you think, Dad?
A baseball.
Baseball? OK.
There's the Moon.
Oh, so we were close!
Close. It's a little smaller than you thought, but that's OK.
A lot of people think that the Moon is bigger than it actually is and that's OK.
Alright, just to clarify, we’re using
a 
basketball and a tennis ball as scale models.
The Earth has a diameter of about 7918 miles
and a basketball has a diameter of about
9 and a half inches.
That’s a scale of 52.8 million to 1.
The Moon has a diameter of 2159 miles
making it 3.67 times smaller than Earth.
A tennis ball has a diameter of a little over
2 and a half inches.
A near-perfect match to our scale.
Ok, back to my parents.
If this is the Earth and this is the Moon,
how far away is the Moon from the Earth?
I'm going to say... over here.
Over there? OK. What do you think, Dad?
Hmmm to the scale?
Yeah yeah, to the scale.
Right about there?
Yep.
These are very typical answers from people
who have never seen the numbers.
I can’t wait to see their reactions to the truth.
[Maniacal Laughter]
You want to know how far away it actually is?
Yes.
24 feet.
Are you... OK, so where is that?
You got it?
Uh huh.
Good.
Wow.
Right about there.
Wow!
It's a lot farther away than it looks.
It is!
24 feet!
Because I know that's the closest thing to the Earth, so everything else is so much farther.
The international space station they say is floating up in the sky, right??
Uh huh.
Right about there.
Seriously?! Wow!
This is why it took, you know, 4 days to get to the Moon
when they went on the Apollo mission.
Amazing!
It's, like, way over there!
That’s right. People think the Earth and
the Moon look like this,
when in reality, they look like this.
I always make a point in my videos to draw
the Earth-Moon system to scale.
Because it’s one of the few astronomical
distances I can actually do that with.
To put this in perspective though,
the distance from the center of the Earth
to the center of the Moon,
is 30 Earths.
Surface to surface, you can fit 29.5 Earths
in-between the Earth and the Moon.
Hey! As long as you line them up on their side, you can fit all the other 7 planets in there together.
It’s crazy!
We can actually measure how far away the Moon
is using the delay of a reflected laser.
There are mirrors that NASA astronauts put
on the moon to reflect a laser back to Earth.
and the round-trip takes about 2 and half
seconds.
OK, so the Moon is a lot farther away than
it looks.
But, just for fun, let’s say the Earth and
the Moon were this close.
What would that look like in the sky?
For this, we need something called “angular
size” measured in degrees or radians, rather than something like miles or meters.
It’s the angle the object takes up in your
field of view.
For the real moon, that’s a little over
half a degree.
The real moon doesn’t take up much sky,
but if it were closer.
Say, this close.
Instead of looking normal like this, it would
look like this!
spanning almost 14 degrees in your field of view.
Absolutely terrifying!
Thankfully, it’s much farther than that,
but let’s take one more step away from the Earth.
The Sun is over 864,000 miles across and about
93 million miles away.
In our scale model, that makes the Sun 86
and half feet across,
which looks like this sitting on an American
football field.
I’d like to remind you the Earth is still
a basketball on this scale.
Thankfully, it’s not this close to the Sun.
To scale, the distance between them is about
1.8 miles.
The Sun is barely visible and the basketball
Earth is far too small to see.
Other stars are too far away to even place
on this scale.
The universe is vast, cold, and empty and
we are so small and insignificant.
The only hope we ever have of being important
is to other people.
So, did this video leave you in a
pit of despair or does it motivate you to
be less of jerk?
I’d like to know in the comments.
Thanks for liking and sharing this video.
Don’t forget to subscribe if you'd like to
keep up with us.
And until next time, remember,
it’s OK to be a little crazy.
In the last video, we took a small look at
light inside materials.
Comment response time!
A Thrasher and others pointed out that my
answer lacked the detail that you would usually
find in a Science Asylum video.
and, honestly, I don’t disagree with you.
But there are a few things going on here I
should clarify.
One! The video was originally longer, but
I cut a few sections out at the last minute.
I did this mainly because I suck at animating
wave interference and I just couldn’t animate
those sections.
There are more details about that in my most
recent vlog.
Two! I purposefully left out a discussion
about group vs phase velocity.
Lukas Fires brought it up in a comment thread
if you’re interested.
I just felt like it was going to over complicate
the conversation.
Light waves inside materials are unimaginably
complicated!
I tried to simplify things a little by having
only two atoms in the picture.
You get light wherever the wave-fronts overlap.
In hindsight, it might have been over-simplified.
And three! The video wasn’t about why it
slows down.
The title was “does light slow down in glass?”
It was never meant to go into any real depth.
As Krishna CoC pointed out, I was trying to
connect it to the video before it about math
and language.
That being said,
you clearly prefer more detailed videos
since that’s something that separates this
channel from other science channels.
I will keep that in mind moving forward.
Navrit kaur asked about how the refractive
index factors into all this.
Wave interference is really complicated, so we'd like to avoid it if at all possible.
The refractive index is our way to do that.
Theoretically, it contains a bunch of
information:
Mainly, how far apart the atoms are,
how well their electron clouds respond to
the light, and what the wavelength of the
light is.
Yes, the refractive index does slightly depend on wavelength.
That’s why you can get things like rainbows.
Anyway, the delay between when the original
light passes through an atom
and when that atom sends out its own light…
can affect how those waves combine inside the glass.
Like I said, it’s super complicated.
Ibrahim went to the dark place and brought
up quantum mechanics.
Theoretically speaking, the photon takes all
possible paths simultaneously
allowing it to have wave interference with itself.
What?!?!?
I also purposefully avoided this because if you intend on using quantum mechanics to explain something
you better be prepared to interpret quantum mechanics.
I was not and I’m not sure any of you would
have been either.
Alright Crazies, you’re all amazing and
thanks again to all my patrons on Patreon.
You’re making this mad scientist’s crazy
life a little more manageable.
See you all next time and thanks for watching.
