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Exactly 100 years ago, in 1916, Albert Einstein
predicted the existence of gravitational waves, ripples
in the fabric of spacetime that are produced
by cataclysmic astrophysical events,
such as the collision of two black holes.
As they travel across the universe,
gravitational waves stretch and squeeze space and time.
One and a half billion years ago, two black holes that
were 30 to 40 times the size of the sun collided and they bent
spacetime around themselves.
This created waves that propagated,
traveled through the universe at the speed of light.
And on September 14, 2015, they've reached Earth
and we were ready to catch them.
We were able to do so thanks to a facility
called LIGO, the Laser Interferometer
Gravitational-Wave Observatory.
In Louisiana and in Washington state
there are two almost identical L-shaped detectors
that use lasers to measure the change in distance
between mirrors that are two and a half miles apart.
We're talking about changes in distance that are one
and 10,000th the size of a proton because that's how small
the effects of gravitational wave is on Earth.
When gravitational waves hits LIGO
they stretched and squeezed its arms.
And by doing so, they conveyed the message of something that
happened 1.5 billion years ago.
Within three minutes, we were alerted of this signal
and it was perfect, just as theory predicted it would be.
Within fractions of a second, the frequency and the amplitude
of the vibration increased with the unmistakable chirp pattern
that is expected for colliding black holes.
This is a groundbreaking discovery
that will open a new field of gravitational wave astronomy
where gravitational waves will be a new probe to explore
the mysteries of the universe.
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