James called us from
Twitter asks what are some of the most
exciting astrophysics discoveries we've
made in 2015
oh well the new Horizons flyby of Pluto
Pluto rock in the whole year Dawn's
Wi-Fi of Ceres and Charles: On September 14, 2015,
there was a gravitational wave that came through earth.
Eugene: So what's a gravitational wave?
Neil: So, Einstein showed that
gravity is not best thought
of as a force the way Newton did, but
you are good to think of it as a
deformation in the fabric of space and
time. And if there is a disturbance in
that gravity, in that object, in the mass
of that object, it will send a ripple,
through the fabric of space and time
moving at the speed of light. And in
order to detect such a ripple you need a
very specially designed telescope. It
uses things like interferometers and
lasers and all manner of
things so that when that wave washes
over you you can detect a slight change
in the distance between two points, which
would come about because there's
this, what word did they use Charles?
It's not a shearing effect, it's a...
there's a word they use for so it.
It's a stretching and shrinking of the fabric
of space, and if you measure the distance
between two points extremely accurately
you will notice when this wave passes
across you. Now how accurately? A fraction
the diameter of an atomic nucleus.
That is how accurate you have to be, and
that's why it was 30 years
technologically in the making to make
that discovery on September 14.
Charles: September 14th is when the 
event occurred and the detection
happened then but it took months for the
scientists involved with what's called
the advanced LIGO project to confirm
that indeed it was a gravitational wave
that resulted from the collision of two
black holes more than one billion
light-years away from Earth and its
remnant energy through space-time
rippled through the earth in a fraction
of a second. Neil: Right, oh and it happened
more than a billion years ago only
just hitting us now. So yes, that happened
in September so that was good this is
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