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Title: Gravitational wave astronomy -- opening a new window on the Universe | Martin Hendry | TEDxGlasgow
Published: 2014-07-23
Source: https://www.youtube.com/watch?v=LfYloEifk2o
there's a classic urban myth which says that if everyone in China jumps up in the air altogether then the airflow be roped off its axis but believe me I've done the calculations and I can see that the air Sox's barefoot we see if although as someone who grew up in Britain in the nineteen eighties the warts Michael freshman harder keen to spring to mind nevertheless even
a single person if we jump up in the air time so to speak meet the F. move the trouble is you don't look at me very much so I suppose we couldn't make a measurement not so much of a jumping sign to shaking the Arabs but a measurement so precise but I could tell us something about the change in the shape of space itself produced by
an exploding star half way across the galaxy not really does sound like science fiction but in fact such a machine already exists it's called a Weezer interferometer and it's one of the most sophisticated scientific instruments we've ever built I'm in a few years time we're confident it's going to open up for as a whole new we of looking at the universe called gravitational we've stormy the
gravitational waves are not the same thing as white they're not part of the spectrum of light that we call the electromagnetic spectrum stretching all the way from review weaves to Dahmer race we've already got lots of different types of light and over the last sixty years or so we've got really rather goods but proving the universe with all those different kinds of light whether it's building
a giant radio telescope on the surface our pitching a gamma ray observatory I can speak we've used these different windows in the because moss to tell us some quite amazing things about how our universe works we've pulled the box from the death of stars we've explored the hearts of galaxies we've even started to find planets lately yeah going right and other stars but the gravitational we've
spectrum will be completely different it will give us a window in the universe into some of the most violent and energetic events in the course moss exploding stars awaiting what calms maybe even the Big Bang itself no what will we wear from the gravitational wave Wendell on the universe well maybe the most exciting thing is the things we don't know about yet a so called on
the one on notice the things that we don't even know we don't know yet it's going to take a few more years but we're almost there the before we talk about gravitational waves let's have a think about gravity that's another urban mass which I'm sure everyone has heard all of the one about the apple falling on ice at Houston's hate no I'm not really sure if
there was any genuine friends involved in the hot spot where ever he got his inspiration for all you can come up with a very clever idea because he wore tight but he could use the same physical law to describe both from apple falling from a tree or the moon orbiting the F. I'm too cold desi's universal law of gravity and it basically says that everything in
the cosmos trucks everything else it's a beautiful Phoebe and it's also very practically useful that laces do all sorts of useful things in our modern world and high stone for more than three hundred years it license fly aircraft tough we during the world it laces fly a rocket to the moon and back but there is a problem with Newton's law of gravity philosophical problem but a
very fundamental level it doesn't really make sense because Newton says there's a force between the air from the menu see well how does the moon knoll that supports to orbit the air I just the force actually get from the earth to the moon this was a problem which no less than Albert Einstein puzzled over in the early years of the twentieth century and Einstein came up
with a truly remarkable on Sir no the Einstein was probably before celebrity selling fifth even though he died in nineteen fifty five in nineteen ninety nine the editors of time magazine voted him the person of the twentieth century although I should mention that there was a public vote on the website and the wait for Elvis Presley now I'm as big a fine of the the king's
music is anyone but I still have to go with the editors decision here in fact I even have my own I'm action figure of a study in the university so what exactly did Einstein do if he was the person of the twentieth century well forty did was make us rethink what gravity really yes and then spends picture gravity isn't so much a force between the air
from the moon or opposing trees instead it was a carving or a bending of space and time themselves so good metaphor here is to think of the air sitting on a straight sheet of rubber a trampoline the mass of the year the very great mass of the air McBain bought rubber sheet what and then you don't really needs to have the moon anymore feeling a force
reaching out from here the moon just follows the not true cars and beings of speech and tying a reindeer invite Einstein also said that we should no longer really think of speech in parliament separate things so you hear people talk about the fabric of space time what Einstein said wars but gravity these are carving a bending of space time orders another physicist John Wheeler printed rather
neatly speech tie and tails mocked her home to move I'm Martha tell speech tying her to carve no all my savings very Grindin fundamental about the nature of the universe but it's got a lot of practical applications as well thirty feet on the Arabs in the air as Phoebe gravity that's a very remarkable protection of Einstein speedy which you probably have never noticed before did you
know for example that clocks run more slowly on the surface of the year then high above the air because the gravitational field is stronger you might remember that scene in the movie mission impossible ghost protocol when tall cruise is stealing the Peugeot Khalifa the world's tallest building but even when he was eight hundred meters above the grains tomes watching she was too busy to notice but
tomes watch would only be running a few billionths of a second faster than it would have done third grade level so what's a few billionths of a second between friends well that's actually enough to make a difference through the global positioning system the GPS satellites there detox because to be adjusted for trains running faster at the altitude of the soft lights and also for pink fourteen
microseconds a D. no the radio signals and microwave signals from the satellites controllable obtain Paloma terse in forty microseconds so just think provides your site Nov would be it was only good to ten kilometers we don't get lost pretty damn quick so I was staying speedy of gravity his general theory of relativity really does Harv everyday practical effects on our daily lives but it's a very
deep space where you really see it to the Max in fact if gravity is all about bending speech tighten we can do a kind of thought experiment we can imagine well if you could put enough mock terror into a small enough speech eventually he would bend spacetime so much but even white couldn't escape the clutches of gravity you've got yourself a black hole no black holes
would imagine to reading the type of Einstein in fact in nineteen sixteen just after unstated published his theory the was a wonderful paper written by a young scientist who was out the front in the first World War at the time Carl sports show and it's six eight feet of a black hole the black holes really do say things as if they belong in the realms of
science fiction but we do think that black holes actually test and that for even light to escape from a black hole truly would be mission impossible we find what because in the remnants of exploded stars we even seem to find them and super masa form in the hearts of virtually every galaxy in the universe now imagine you could take a black hole and music close to
the speed of light but would she cupped speech prime a lot like dropping a con in bold or not fabric of a trampoline send ripple spreading aids and those ripples of what we call gravitational waves so gravitational waves would be produced by things like black holes or they're slightly less extreme gravitational cousins called neutron stars and if you could get two of them to Kuwait together
close to the speed of light that would really make some waves that's what we're looking for as we embark on this new field of gravitational we've astronomy if only it was not easy that's the plan but to do it is tough because even though the gravitational we shakeup speech time colossal we wear the black holes are just like ripples in a point if the spread of
through the universe the get weaker and weaker by the time we arrive at the yeah shaking of space time that we're trying to measure is roughly speaking about a million million million for the meter that's pretty tough to measure so how did you do that well at the risk of sounding like one of those Las Vegas Mudgett shoes it's all done with matters and leaves arse
what you do is you take a lease a bit shame that laser beam at a minority splits into two beans that going right triangles teach other banks from all four matter recombined them and then have a look at what you've got now if the two beams of troubled exactly the same distance then what you get by is the beams and perfect state with each other there
liked we've just the cold was other forms of white so the we've trains will be much stop but if they've traveled a different distance we'll be out of step with each other the interfere with each other we call this phenomenon interference so that's why these things are cold Huizar interferometers so I leave an interferometer it's a cool thing to house if you want to try and
catch a gravitational wave but remember they're incredibly minute signals so it's going to be a huge engineering challenge to build one join Stein said that when a gravitational wave goes by that restrictions squeeze the space time in our vicinity but by this incredibly tiny amount so we're trying to use the laser beam and it's an interference pattern detail as if a gravitational wave has gone past
but you've really got to scale up the experiment uncool large I'm not as we are l'aigle comes and Michael stands for lease are interferometer gravitational we've observatory and it's the most ambitious and sophisticated scientific projects ever undertaken by the National Science Foundation in the US in fact it up to my goose there's one in Louisiana and there's another one in Washington state and together with two
other interferometers one called geo in Germany and vertical and actually this is our ereli warning system for gravitational waves nope the building quite remote locations like what I think the locals don't really get what they're for one of my Weigel colleagues was flying over the living since I had a family passengers on the flight was looking down at the detector and says I have a CD
what lots for its actually a secret government pardon machine but he wasn't quite sure how to respond but well he sort of said looking than fly that they'll shape she said abi have to come back again they tell you saw who really is science fiction but finding gravitational leaves we very much hope in a few years time will be science fact noticed tough all of those
tiny tiny effects were trying to measure could be swamped by the local effects of disturbances from shaking the ground not because of right there in the universe because a very much more Mundine phenomena human acts so what you've gotta do is pick your matters on very complex suspension systems push against the limits of my TV was technology and even the buffeting of that era and the
laser beam could swamper signal so we have to send the Weezer's back and forth and the most ultrahigh vacuum system in the return air only one trillions of the atmospheric pressure that we briefing here today so put all that together spend a few hundred million dollars and hopefully what you're going to find some gravitational waves but it takes a lot of scientists to do it so
I glossed over part of the why go scientific cooperation more than nine hundred scientists and engineers around the world looking for gravitational waves no we haven't found any yet but having multiple detectors is not just a buy one get one free this because if you detect a signal in both detectors Borth why go detectors but helps to convention you've really got something and if you see
it in Virgo when she was well all the better so very soon we're going to have a global network of advanced detectors because the light was on quake sensitive enough to do the job yet but we're giving them more heavy matters more powerful lasers better suspension systems and we expect by about twenty sixteen that will have a network of advanced gravitational we've interferometers looking for gravitational
waves now how long will we have to wait to get a signal we don't really know but based on what we do know what we don't think it should be more than a few months in fact at a conference last year a group of us and pulling try to come up with a figure a date when we expect to see one there are times when a
little bit in her cheeks will be protected the date of January first twenty seventeen I did point type there probably wouldn't be very many people out walking law school that day however gravitational waves are coming we stand on the brink of opening this new window in the universe and it's a very exciting time to be an astrophysicist you very much
