Science

Black hole Science

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Somewhere in our galaxy at some time in the future the spacecraft from Earth will encounter the most dangerous object in the universe this is an object that is not made from ordinary matter it’s not made for antimatter it doesn’t matter that have matter at all it’s made out of a pure warpage of space and time nothing comes out of things only go into it it’s that one-way nature which probably upsets people most caused us to be really disturbed in fact causes many scientists to be disturbed Matt Reich was quite surprising when astronomers found that there was really good reason to suspect that the universe should be full of these extraordinary objects at some time in the future a spacecraft from Earth will encounter an extraordinary universe full of black holes everybody has heard of black holes no one has really seen them the spacecraft of our dreams has reached not a solid object but the boundary to a region of space where gravity has gone mad waiting below as a black hole in space this is where a mighty star has died and left a bottomless pit from which there is no escape welcome to the edge of the universe and to the end of space and time phil charles not only dreams black holes he hunts them down for a living he’s found the strongest evidence yet for a black hole lurking in our own galactic backyard searching for these things is the most wonderful way of going to the frontiers of modern physics the most exciting thing that the modern scientists can do by day Phil Charles lectures on Astrophysical theory at Oxford University by night gears at the forefront of the hunt for Astrophysical facts to be a successful black hole hunter you have to have ready access to the largest ground-based telescopes we have to go all over the world to the Palmer and Hawaii in the northern hemisphere to South Africa Chile and Australia and southern hemisphere around the globe Phil Charles and his fellow astronomers call upon the world’s most sophisticated astronomical arsenal to probe the depths of space for these mystery objects from x-rays satellites and Hubble Space Telescope in orbit to the finest radio and optical telescopes on the ground today’s destination is La Palma in the Canary Islands Nepal is definitely one of my favourite places I’ve been studying black holes on La Palma for over seven years now the very nature of black holes makes them in lucid quarry by definition if they can’t be seen and material is falling into it’s only in the 1990s as mainstream science come to a consensus that black holes might actually exist theory tells us the deep inside black holes everything we know about the universe will come to an end to the real universe but the mathematics is unequivocal when a massive star dies it will have no choice but to form a black for astronomers like Phil Charles black holes remain the big game of the universe but how do you catch a small invisible nothing that maybe hundreds of thousands of light-years away across the noisy ocean of space with more stars in the heavens than all the grains of sand on all the world’s beaches how do you hunt for that one dark star that swallows right rather than shines like a beacon astronomers must hunt not for black holes themselves but for the effects they generate in space around them Phil Charles looks for visible stars that black holes might have trapped in orbit but even they can be hard to find when you are looking for needle in a haystack we need the needle to shout out that they were here that we do through in fact that in the late 1980s the Japanese launched an x-ray satellite called Ginga which had what we call an all-sky monitor on it for detecting x-rays from anywhere in the sky it’s the x-rays that alert us to the presence of this needle the needle in the haystack that were searching for while sweeping the heavens in 1989 the Ginga satellite reported a mysterious burst of x-rays in our own galactic neighborhood the source of the radiation was an invisible object three thousand light-years away around which a faint star seemed to be circling the star had the catalog name V 404 Sydney it was just the star-filled Charles have been looking for Phil Charles prying weapon in the search for black holes is the massive William Herschel telescope perched on the rim of an extinct volcano two and a half kilometres above the Atlantic Ocean okay really the gratings loaded said to go for the last seven years Charles has pointed the telescope towards the star V 404 trying to work out just what sort of highly compact object the star must be circling the most likely candidate is a stellar mass black hole the most common kind according to the theory such a black hole should weigh ten times as much as a star like our Sun but would only be about the diameter of central London less common is a second type of black hole supermassive heavyweights believed to lurk in the heart of galaxies but to understand any black oh you must begin with gravity for within this darkness gravity is in total control our modern quest to understand gravity and ultimately black holes was born in this room on Christmas Day 1642 but it was a shaky start the great Isaac Newton was premature and only just survived his first day of life showing little promise as a farmer the young Isaac Newton was sent up to Cambridge University as an academic you who would formulate laws of physics which still form the basis of modern science fate played its part in 1665 the plague swept across England Cambridge was closed to help contain the spread of the contagion Anoop who was forced to flee he sought refuge back at Woolsthorpe manor over the next 18 months here he was to discover the mathematics of calculus to formulate laws for the motion of the planets and to unravel the spectral nature of light and one day a falling Apple interrupted his thoughts and led him to ponder gravity itself Newton was the first person to give us a really detailed mathematical understanding of one of the basic forces of nature and of course it was the first great triumph of mathematical physics he told us that the force which holds us down here on the earth and which allows an apple to fall is the same force which holds the moon in its orbit around the Earth and makes the planets move in their courses Nutan reason that all matter in the universe has gravity that it’s a force that reaches out from one body to another and pulls everything in words the more mass an object has the more gravity the stronger this inwards for the first person to combine this notion of the inward pull of gravity with knowledge that the speed of light was finite was John Mitchell as rector of Thornhill church in Yorkshire and one of the 18th centuries great forgotten scientists Mitchell took newton’s view of gravity to its ultimate dark conclusion Mitchell’s giant leap was to imagine a ray of light leaving a star in the same way we think today of a rocket leaving planet to escape the Earth’s gravitational pull entirely and travel into space a rocket needs to push itself upwards at 11 kilometers a second faster than gravity tries to pull it back down Mitchell knew nothing of rockets to the moon but he did know that in theory a massive star could have so much gravity that it would pull back into its clutches even rays of light traveling at 300,000 kilometers per second John Mitchell worked out that if you had a body weighing about a hundred million times as much the Sun light couldn’t even escape from it and he then went on to say that for that reason maybe the most massive objects in the universe might be invisible to us Mitchell had explained how gravity could turn a star black but not how he could turn it into a whole a complete understanding of the life and death of stars awaited the nuclear age every star we see in the heavens has a giant nuclear reaction raging at its core it’s what makes a star like our own Sun shine so hot and bright only the nuclear reaction holds gravity at bay the energy pushing outwards stopping the Sun from being pulled tighter smaller and more dense it’s a precarious balance that gravity will always win in the end when the Sun runs out of nuclear fuel its own gravity will crush it into a tiny ball the size of the earth but a hundred thousand times more dense but our Sun has too little mass and therefore too little gravity to become a black hole instead astronomers call such a feeble ember a white dwarf but when a giant star switches off it goes with a bang while we see the outward explosion as a supernova this masks the implosion going on inside the call has been given a gravity bear so extreme that all the atoms have been squeezed into a ball of super dense subatomic particles called neutrons it has become a neutron star a mere 20 kilometers or so in diameter we know that ordinary stars like the Sun will become white doors we know that there are neutron stars which are just a little bit heavier and the question is what is do you have beyond that and we believe it’s black holes theory suggests that when a neutron star is more than three times as heavy as our Sun even the neutrons cannot resist gravity the collapse is irrevocable the density of mass becomes so great in the center that gravity overwhelms space itself distorting it so horribly but it and tying with it begins to wrench off from the outside universe her darkness forms at the heart of the collapsing star and moves relentlessly outwards as the star’s brilliance is sucked in as the star dies a black hole is born Computers mask find out what you can about it we judge that’s a little about black holes exceda they’re stars that have collapsed in on themselves they not only Bend light actually swallowed the forces inside a black Sun are inconceivable they capable of anything they can bend space even time turn both inside out just how a black hole can manifest itself so powerfully in the emptiness of space is something that weighs heavily on professor Stephen Hawking born exactly 300 years after Isaac Newton Hawking now holds Newton’s old job at Cambridge University Hawking’s mind roams free not in Newton’s universe but in the universe of Albert Einstein towards the earth but rules the earth towards the Sun brilliant idea that gravity could be caused by space and time being curved Einstein realized that nothing can exist at a point in space without existing at a particular time as well space and time seemed to be woven together to form the flexible four-dimensional fabric of the universe so-called space-time spacetime is almost impossible to contemplate because our entire sensory existence is limited to the three dimensions of everyday experience the easiest way for us to enter in Stein’s universe is to imagine space and time to be like a sheet of rubber this curvature is einstein’s concept of gravity the more mass a star or planet has the more steeply it bends space-time around it and so the more gravity it has throw something extremely heavy like a collapsing star onto the sheet and you soon end up with a universe full of holes watch it Coney oops as some acid start cools and shrinks that will curb the space-time around it more whore eventually when it shrinks to a certain critical size that will quite literally create a black hole in space-time things can fall into a black hole but nothing can cut out so much I don’t know about astrophysics I wish I read that book by that wheelchair guy the most terrifying concept in astrophysics lurks at the bottom of a black hole the singularity everything that has ever fallen into the hole is destroyed at the singularity crushed into a pinpoint of infinite density and infinite smallness even space and time are squelched out of existence all that remains in the outside universe is a perfect sphere of absolute darkness the gravitational ghost of the star that died this fear is called the event horizon and it marks the edge of the abyss this event horizon is not made of matter it’s in some sense almost not even made of a warp each of space-time it’s just a location it is that unique location where gravity is become so strong and just inside there that nothing can escape while the event horizon may be only a few kilometers in diameter the immense gravity of the singularity will have sucked a hole inside it that is impossibly deep to measure in the center there is the so called singularity which is a place where according to Einstein’s theory everything goes infinite where if you do calculations as it were the smoke pours out of the computer and something goes wrong and what that means is that deep inside black hole we have black holes we have a signal that we need some fundamentally new physics to understand what is going on girl slit astronomer Phil Charles thinks he has proved that such intangible objects are to be found in the real universe the giveaway signal was the sudden burst of unexplained x-rays which alerted Phil to V 404 a faint star trapped in orbit around an invisible compact object these are signatures of a star not much different from the Sun and it represents all more than 80% of the light here that we can follow and use the the speeds that we measured to determine the mass of the object we cannot see an excellent analogy is that of a big strong man in a very small light woman as they swing each other around the man hardly moves and the woman despite the balance of their weights moves much more calculations show that V 404 orbits a heavy a mysterious partner once every six and a half days to achieve speeds like these the partner must be very heavy indeed the mass that we measure by this process is 12 solar masses twelve times the mass of the Sun that means it is substantially heavier than what we think is that the largest mass of a neutron star we are virtually certain it’s a black hole the black hole has embraced V 404 in a deadly dance ripping gas from the hapless star and feeding it into a great disc of cannibalized matter as this material spirals towards the hole it heats up and sends a last desperate x-ray signal to the outside world nearly a dozen similar objects have now had their presence betrayed to astronomers in the same way by x-ray signals one of the first was Cygnus x1 I had a bet with Stephen Hawking as to whether Cygnus x1 a particular object from which one saw x-rays coming off it was a black hole Stephen Hawking met that it wasn’t rather it was because I wanted an insurance policy I had done a lot of work on black holes and it would all have been wasted if it had turned out that black holes didn’t exist but at least I would have had a consolation of winning with a pet when Hawking and thorne made the bet in 1974 the evidence was thin but as the years rolled on and the evidence mounted Hawking felt it was safe to concede the wager in 1990 Stephen Hawking happened to be visiting Los Angeles he broke into my office and thumb printed off on this bet his wife discussed this handwritten bet has come to symbolize the first real acknowledgement by the scientific establishment that black holes are really out there all ready robot spacecraft have explored the planets someday we may send an intelligent probe to a black hole in the depths of space beyond our mothership travels fast enough to insert into a safe orbit around the hole a different fate awaits the probe as I approach the black hole I will start to feel a gravitational tug on myself it’s a different kind of a gravitational tug or pull and you’re accustomed to normally you think you’re just pulled down as I sit here in this chair my head is farther away from the center of the earth than my chest and so my head is pull less strongly than my chest is so in fact there’s a difference in the pull my head is being pulled less stronger than my chest I’m actually being slightly stretched apart by gravity did you approach a black hole that difference in pull becomes large or larger as you get closer to the center gravity will get more extreme you would be squeezed and distorted spaghettification is the name something for use for this experience spaghettification is an experience nothing can survive the fragments streak down into the blackness of the home you or I falling into the black hole get will get stretched and our bodies will get too mutilated before we even reach the horizon it’s no good we can’t break free he’s accelerating something else strange happens well before the event horizon is crossed not only space is being stretched so his time the closer the probe gets to the event horizon the harder light from it struggles to escape the mothership sees the probes slow down until it seems to stop time doesn’t change for the probe because gravity is stretching its whole existence but from the motherships perspective the probe has become frozen in time it is both destroyed in an instant and hovering for eternity depending on your point of view nevertheless if you are inside that spaceship looking back at me you can wave you can see me you may think I can see you but I can’t and you go inside the event horizon you can still see out you still see me on the outside right up to the point that you die you can still see me on the outside you’ll have to jump he’s the king what happened well we hit a little snag when the universe sort of collapsed on itself we don’t really know exactly what would happen deep inside a black hole if you were to fall directly in it could be that something even stranger happens to space under these conditions something like what happens to be any of the universe and indeed some people have speculated that in general it may be possible to avoid the complete singularity and emerge somewhere else some say that if you pass through a rotating black hole you end up in a new universe a new dimension we’ve entered I recall a movie in which at the end of the film the spaceship goes inside the black hole and comes out the other side into another universe that don’t happen it just doesn’t happen at all the fundamental laws of physics say that at the center of the black hole there is a singularity a region where a base and time or infinitely warped a region where when matter flows into it matter gets destroyed but does this have to be so this is the worst place yet speculation that tamed black holes may provide a way of cheating the laws of physics have become a hallmark of science fiction physicist Igor Novikov likes to speculate on what would happen if you join two black holes together to make a wormhole we can imagine a wormhole as two holes and some kind of a tunnel between them but this tunnel is not in our space and it is in some kind of hyperspace outside of our dimensions first employee to make such a wormhole we would have to engineer space-time first bend it until it begins to form a black hole but not so much that a singularity is born then join the bottom of this gravity tunnel to the bottom of a second tunnel to make two holes connected by a continuous tube through hyperspace step two would be to move one hole to wherever it was you wanted to travel one of them can be near our earth in our in in our galaxy but this tunnel can be extremely short say a few meters the tunnel would also be very fragile prone to collapse as soon as a traveler attempted to pass through it but if we could develop the technology to tame the ferocious forces at work we would have opened an interstellar shortcut he can travel from one galaxy to another galaxy only during well let’s say a few seconds we’re a black hole is a one-way street with a dead end of the singularity a wormhole be a freeway to the stars I have to say these are driven by sort of romantic science fiction ideas which is fine I mean a lot of science has driven that way and you and you do good things there’s nothing against that directly it’s just that it seems to me the scientific evidence is just that this is not going to happen it’s just not possible Oxford University’s Roger Penrose pushes the mathematics of black holes in a different direction he’s formulated a way to extract enormous quantities of energy from the way black hole’s spin at the same time as sending enormous quantities of garbage to oblivion in the real universe most black holes should spin because the stars that form them would have been spinning as they collapsed their massive gravity swirling the fabric of space around them like water around a world Penh roses energy extraction process would require building a power station at a safe distance around the spinning hole you could imagine firing a lot of particles or bodies into the neighbourhood of the spinning hole in the right direction the forces of spaghettification will rip these particles apart one particle carries negative energy into the hole and that means that the partner has more energy than the one that fell into it so you can actually extract energy from a black hole through this process the particles could be any old rubbish you never wanted to see again half would disappear into the hole half would be flung outwards with a slingshot of gravitational energy that could be used to drive a turbine the source of that energy is affect the slowing down of the black hole’s rotation because as these particles keep falling into the hole they gradually slow it down but since there’s usually an enormous amount of rotational energy in a rotating black hole this would be an extraordinarily efficient way of extracting energy but there is a long way to go before observational science catches up with the wildest speculations of black hole theory another country another telescope the hunt takes fill Charles to Australia Australia has access to the southern hemisphere of the sky and there we can see the Magellanic Clouds then the Large Magellanic Cloud is our nearest neighboring galaxy and there are about half a dozen very interesting compact objects that we want to study from here we need to get maybe 20 or 30 so that you can really see the the population of black holes that we’re looking at do they all have similar mites are there spread of mass do they all come from the same kinds of original stars we could start to work that out once we can get enough time while Phil Charles turns his sights on the stars of our neighboring galaxy other astronomers are probing galaxies further afield here they are finding objects of staggering intensity formed not from the death of a single star but from the collapse of enough matter to make millions such objects astronomers now believe are supermassive black holes ever since radio telescopes began eavesdropping on the heavens the strongest and most puzzling signals have come from the hearts of distant galaxies astronomers now suspect these radio signals are generated by central supermassive black holes mighty Jets of energized particles are blasted into space from an invisible engine that drives these so-called radio galaxies like great wheels through the heavens nameless stars are ripped apart by an immense gravity to feed central disks of white-hot matter shining a hundred times more brightly than a whole galaxy of stars like our Milky Way powering everything is the hidden central object as small as our solar system but we’re enough matter to make millions or even billions of stars has undergone a titanic gravitational collapse tonight we’re looking at the radio galaxy m87 m87 is a nearby giant galaxy which is very unusual in having a large powerful jet coming out of it m87 s jet is like an enormous death ray of charged particles moving close to the speed of light and six thousand light-years in length the jet is a signature of the way the black hole is swirling matter and space around it astronomers use the speed of the swirling matter to calculate the black hole’s mass well we’re talking about a black hole which is a billion solar masses or more which is therefore it’s much larger than anything we are used to seeing in our own galaxy but it’s fairly typical of what we think many radio galaxies have in their nucleus astronomers suspect radio galaxies are those galaxies with plenty of matter left from the black hole to eat if a galaxy appears quiet it’s probably because the black hole has run out of food if we look in the center of almost any galaxy there should be lurking a dark mass of millions of solar masses at least which may be the remnant of some past activity in that galaxy and in the last few years has been growing evidence that these dark masses actually do exist but seeing them is still beyond us even the latest high-resolution Hubble images can show only the bright central disc the Jets of energized particles but not the black speck in the middle we will never be able to appreciate the full majesty of a supermassive black hole from Earth time for our spacecraft to make another journey if one was to take a journey starting in the outer part of a galaxy and moving in sea very hot blowing gas filling the galaxy which is being heated by some mysterious powerful central source and find gas orbiting in the disk swirling at nearly the speed of light and getting very hot and getting so hot that it radiates not just visible light but very energetic radiation like x-rays it is one of the great cosmological contradictions that the larger the black hole the weaker the gravitational forces near the event horizon this time there is no spaghetti as we approach the event horizon the intense gravitational curvature wrenches the light from the universe to a bright point directly overhead we have reached the point of no return we are now inside the black hole but where is the singularity if you are falling into a black hole and the singularity you knew from your calculations that the singularity was out there and you’re heading for it you look at it you don’t see it it’s like a singularity that you’re heading for in the future and you don’t actually see it the singularity is where science ends and speculation begins space and time have ceased to exist replaced by a seething chaotic mass we can call quantum foam into this bizarre conjecture has disappeared all the mass and energy that has ever fallen inside the event horizon this is where Einsteins laws fail this is where the laws of quantum mechanics fail this is where the secrets of the universe are hidden the singularity is an object at the core of a black hole that is governed not by the ordinary laws of physics that were familiar with but by the laws of quantum gravity which we only are beginning to glimpse and understand if the probe was strong enough it would fall towards the singularity for perhaps an hour until it blindly met its future at the end of space and time you would then experience the final crunch in the center learning in your final moments that new physics prevailing at those times perhaps but you’ll be able to send no signal to the external world of the interior region what really happens to it at the end is is as unknown as what happened before the Big Bang is it’s the other end of that story we do expect to find singularities in the Big Bang well of course that was the first one we and to worry about black holes and in the Big Crunch affair is one is about the virial temperature the electrons may be rather cool but we have of course is two tornadoes orbiting inside a larger tornado and coming the other and colliding and coalescing the world’s leading cosmological minds can now gather to talk with facts and figures about what was not long ago dismissed as flights of fancy showing of course is observational it can’t be it seems our understanding of the nature of the universe is accelerating homers day by day these are the facts it seems that most nearby galaxies and perhaps therefore most galaxies Harbor a central black hole our galaxy would seem rather underprivileged if it didn’t have one as well the evidence has come only in the last few months that makes this a compelling case astronomers are virtually certain that hidden behind the dust in the center of our own Milky Way galaxy there is a black hole weighing three million times the mass of the Sun even as little as five years ago people thought that we could get away with not having to have black holes in our own galaxy we could explain almost everything that we see by neutron stars no theorists now believes that we’re dealing with ordinary neutron stars and more there are things out there that they have to be compact and they have to be explained and I think that’s an extremely exciting prospect everybody has trouble coming to terms with black holes locked within these prisons of light are the secrets of the universe where did it come from and where is it going to we may never answer these questions but for once we know where the answers you

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