If you’ve been around the more science-y corners of the internet lately, you’ve probably
seen a lot of people talking about a big announcement that was made today.
There were simultaneous press conferences all over the world, and what they announced
was, indeed, a huge deal:
For the first time ever, we’ve detected gravitational waves!
The idea that gravitational waves should exist comes from Einstein’s Theory of General
Relativity, which he published in 1915.
He proposed that any kind of mass distorts the shape of the universe, as well as time,
aka spacetime.
And when a mass moves through the universe, it creates what are basically ripples in spacetime,
which he called gravitational waves.
We can predict what those gravitational waves would look like, using Einstein’s equations
and supercomputers.
Problem is, the simulations show that the ripples are almost always ridiculously tiny,
which has made them incredibly difficult to detect.
And it’s been a bumpy road, with some major setbacks.
But now, we have found them.
The signal was detected on September 14, 2015, by the LIGO observatories in both Washington
State and Louisiana.
The observatories are set up to detect ripples in spacetime, based on the positions of mirrors,
with beams of laser-generated light bouncing off of them, to measure their distance.
And in September, the mirrors appeared to move a tiny bit. But in fact, the mirrors
themselves didn’t move -- the space between them, and all around them, moved!
It was a sign that spacetime was being compressed and stretched by gravitational waves.
For the last five months, researchers around the world have been checking and re-checking
the data, to make sure that what we’re seeing really is the result of gravitational waves
-- as opposed to some kind of glitch, or a misread signal.
And now, they’re as sure as they’ll ever be: the signal came from gravitational waves.
Specifically, it came from two black holes, 1.3 billion light-years from Earth.
These black holes -- each about 150 kilometers in diameter, and about 30 times the mass of
our sun -- crashed into each other.
Black holes tend to do everything in extremes, and in this case, their collision created
ripples in spacetime so strong that we were able to detect them here on Earth.
Even those ripples were tiny -- we’re talking a scale about a thousandth the size of a proton.
But the LIGO observatories are precise enough to detect that change.
So, we’ve officially discovered gravitational waves, which not only helps prove that another
aspect of general relativity is right -- it’s also going to open up a whole new field of
discoveries.
Because once we get good at detecting gravitational waves, we can use them to work backwards,
and figure out what sort of events out there in the universe would have created any particular
set of ripples.
In fact, some of the scientists at the press conference in DC were comparing this discovery
to the invention of the telescope, in terms of how much more we’re going to be able
to learn about the universe.
There’s a lot more we want to talk about with this discovery, and Hank is going to
go into those things in a special, in-depth video on Thursday next week.
But in the meantime, scientists -- and science enthusiasts -- everywhere are cracking open
the champagne. The really nice bottles that they’ve had sitting in a cabinet waiting
for the right moment.
This is that moment.
In the words of David Reitze, the executive director of LIGO:
“We did it!”
Thanks for watching this breaking-news episode of SciShow Space, and thanks especially to
our patrons on Patreon who help make this show possible.