In the center of every galaxy is a supermassive black hole a black hole that can be
millions or billions of times the mass of our Sun that a kind of the most extreme object in the universe and
Sometimes they collide with each other
this is something unfortunately you'll never be able to see directly because they don't give out light that black holes, but
You can see them through the gravitational waves that they give out and in 2034
We'll be launching a spacecraft into space which will be a giant gravitational wave detector
It's called Lisa the laser
Interferometric space antenna and the facts around this mission are so cool and the stuff we'll be able to discover incredibly cool
So I wanted to do a video about it
You probably remember a few years ago
We had the very first detection of gravitational waves which science has got very excited about and with good reason
everything we know about the universe so far comes from light going from
Radio waves through visible light through to gamma rays. That's everything we know about space
gravitational waves opened up a new way to look at space and they saw
Mergers between black holes and other black holes of black holes and neutron stars, and I've done a video about that detection of gravitational
Waves which you can see here, but the brief summary is there are two detectors in the u.s
Called LIGO and one in Italy called Virgo by combining them all together they can make
Detection z' and see the direction that gravitational waves come through their interferometers, which means there are an L shape
They send lasers and bounce them off mirrors, and then they check
What happens when those lasers interfere with each other if there's a change in?
Dimension of one of the arms they can detect changes in size ten thousand times smaller than a proton
Which is just insane
also since they've been turned on they've done a bunch of
Detection runs and in the last run they were seeing a gravitational wave
Signal on average about once every 5 days, which means that black holes are merging
Incredibly frequently far more frequently than we really expected before we started doing those measurements
So for a long time people have wanted to put a gravitational wave detector into space
There's good reasons for like you can make it huge. So at least it's gonna have a 2.5 million
Kilometer arm length, which is about six times the distance from the earth to the moon and also in space
It's quieter on earth ground-based detectors are susceptible to wobbling around because of seismic
Vibrations or a truck driving past or someone sneezing, which you don't tend to get in space
So that's why they wanted to send it. There trouble is space missions are obviously very expensive and prone to
Failure, so they have to make sure that it works really really really well
Lisa is a European Space Agency mission run in collaboration with NASA
Because it will be so big Lisa will be able to see things that we just can't see with the earth-based detectors
You can actually see a different frequency range
So Lisa will be able to see one frequency range ground-based detectors another and because they see different frequency bands
They're kind of a complement to each other. So Lisa will be able to see the kinds of signals that LIGO and Virgo see
Years and years before they actually do the final merger
But the final merger will actually detect with the ground-based detectors
the coolest thing that Lisa will be able to see is the merger of supermassive black holes because supermassive black holes are the cause of
Galaxies they'll probably be surrounded by gas. So if we detect gravitational waves that look like a supermassive black hole merger
We can look to see if there are any x-rays coming from the same event
Which we will do in the future with the Athena x-ray Observatory
Lisa can tell us the direction of sources to an accuracy of about a square degree
This observation would be cool because it might explain the high energy Jets
We see coming from the cause of certain galaxies
We might even be able to see one of these Jets turn on which would be very
exciting and Lisa will also be able to see the absolute distance to things which is very useful to
calibrate other distance measures that we use like Cepheid variables or
supernovae Lisa will be able to make an independent measurement of the Hubble constant more accurately than any current technique and
Be able to measure it in an epoch of cosmic history where other measurements aren't available
The Hubble constant is a fan datian of our model of the universe and how it's expanding
So it's a very important thing to measure accurately
Also gravitational waves don't really get absorbed by anything as they travel through space
So if they're a signal strong enough Lisa will be able to see out to the very edge of the observable
Universe and as you're looking further away into deep space, you're also looking further back through time
So Lisa will allow us to study the history of how galaxies form from the early universe through to today and Lisa
Theoretically will be able to see
tiny amount of time after the Big Bang so something like a billionth of a second or even
shorter after the Big Bang and
We don't know what we'll see there, but it could lead to new physics
It could lead to us understanding how the forces of nature emerged. Maybe we'll detect some signal of new forces of nature or
Test theories that we have like cosmic super strings
Which is something no other current technique can do and it'll also be able to see orbiting white dwarf stars in our own galaxy
Now, how does Lisa work
well
It's made of three spacecraft arranged in a triangle and the spacecraft of flying informations that they stay exactly
The same distance away from each other
Each one has two gold platinum cubes in the middle
Which a test message which are essentially mirrors which bounce the lasers back and forth from the other spacecraft
and those test masses are protected from radiation and particles from the outside space by the
Surrounding spacecraft which has got micronewton thrusters
So it whatever it gets a bump from somewhere it it moves back so that inside the spacecraft. It's completely undisturbed
So it's really exciting that we're going to be able to use this
Detector to probe into areas of physics that we've never had access to before
And it's going to launch in 2030 for which it's quite a long time in the future
But they've already launched a mission to test some of the technology
It's called Lisa Pathfinder and it ran from March 2016 to June
2017 and the critical part were these
- 2 kilogram test masses which they tested to see if they could just have
freely falling through space
Protected by that external spacecraft they characterize the different sources of noise in space things like gas
particles within the actual spacecraft
You're the big part of the mission are the optics of the laser beams
They tested the optics and found that it's a hundred times better than what they need
So now that they know the technology is gonna work. They're building Delisa probe and although we have to wait until
2034 I think it's going to be worth the wait because I think this technology has got the
It's going to be as a revolutionary something like the Hubble Space Telescope
The big thanks to the European Space Agency for letting me use a load of their cool animations in this video and a special
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