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00:00Somewhere in our galaxy, at some time in the future, a spacecraft from Earth will encounter
00:20the most dangerous object in the universe.
00:23This is an object that is not made from ordinary matter, it's not made from anti-matter, it
00:33isn't made of matter at all, it's made out of a pure warpage of space and time.
00:39Nothing comes out of it, things only go into it.
00:43It's that one-way nature which probably upsets people most, causes them to be really disturbed,
00:51and in fact causes many scientists to be disturbed.
00:58That's why it was quite surprising when astronomers found that there was really good reason to
01:03suspect that the universe should be full of these extraordinary objects.
01:10At some time in the future, a spacecraft from Earth will encounter an extraordinary universe
01:21full of black holes.
01:23Everybody has heard of black holes.
01:44Everybody has heard of black holes.
01:46No one has really seen them.
01:51The spacecraft of our dreams has reached not a solid object, but the boundary to a region
02:01of space where gravity has gone mad.
02:10Everything below is a black hole in space.
02:14This is where a mighty star has died and left a bottomless pit from which there is no escape.
02:22Welcome to the edge of the universe and to the end of space and time.
02:36Little Charles not only dreams black holes, he hunts them down for a living.
02:42He's found the strongest evidence yet for a black hole lurking in our own galactic backyard.
02:49Searching for these things is the most wonderful way of going to the frontiers of modern physics.
02:55The most exciting thing that a modern scientist can do.
03:10By day, Phil Charles lectures on astrophysical theory at Oxford University.
03:20By night, he is at the forefront of the hunt for astrophysical facts.
03:23To be a successful black hole hunter, you have to have ready access to the largest ground-based telescopes.
03:40We have to go all over the world, to La Palma and Hawaii in the Northern Hemisphere,
03:46to South Africa, Chile and Australia and the Southern Hemisphere.
03:52Around the globe, Phil Charles and his fellow astronomers call upon the world's most sophisticated astronomical arsenal
03:59to probe the depths of space for these mystery objects.
04:07From X-ray satellites and the Hubble Space Telescope in orbit,
04:11to the finest radio and optical telescopes on the ground.
04:18Today's destination is La Palma in the Canary Islands.
04:22La Palma is definitely one of my favourite places.
04:27I've been studying black holes on La Palma for over seven years now.
04:32The very nature of black holes makes them elusive quarry.
04:37By definition, they can't be seen.
04:41If you imagine you have a black hole and material is falling into it...
04:45Only in the 1990s has mainstream science come to a consensus
04:49that black holes might actually exist.
04:55Theory tells us that deep inside black holes,
04:58everything we know about the universe will come to an end.
05:02I was concerned about whether this would ever have any relevance to the real universe.
05:08But the mathematics is unequivocal.
05:11When a massive star dies, it will have no choice but to form a black hole.
05:19For astronomers like Phil Charles, black holes remain the big game of the universe.
05:29For astronomers like Phil Charles, black holes remain the big game of the Universe.
05:38game of the universe but how do you catch a small invisible nothing that
05:46may be hundreds or thousands of light years away across the noisy ocean of
05:51space with more stars in the heavens than all the grains of sand on all the
05:59world's beaches how do you hunt for that one dark star that swallows light rather
06:06than shines like a beacon
06:15astronomers must hunt not for black holes themselves but for the effects they
06:20generate in space around them Phil Charles looks for visible stars that
06:25black holes might have trapped in orbit but even they can be hard to find when
06:34you are looking for a needle in a haystack we need the needle to shout out and say
06:38we're here that we do through the fact that in the late 1980s the Japanese
06:44launched an x-ray satellite called Ginga which had what we call an all-sky monitor
06:49on it for detecting x-rays from anywhere in the sky it's the x-rays that alert us
06:58to the presence of this needle the needle in the haystack that we're searching for
07:02while sweeping the heavens in 1989 the Ginga satellite reported a mysterious burst of x-rays in
07:10our own galactic neighborhood the source of the radiation was an invisible object 3,000 light
07:17years away around which a faint star seemed to be circling the star had the catalog name v404 Sydney
07:26it was just the star Phil Charles had been looking for
07:47Phil Charles prime weapon in the search for black holes is the massive William Herschel telescope
07:59perched on the rim of an extinct volcano two and a half kilometers above the Atlantic Ocean
08:17okay ready the grating's loaded so we're all set to go for the last seven years Charles has pointed
08:34the telescope towards the star v404 trying to work out just what sort of highly compact object the star
08:41must be circling the most likely candidate is a stellar mass black hole the most common kind according
08:54to the theory such a black hole should weigh ten times as much as a star like our Sun but would
08:59only be about the diameter of central London less common is a second type of black hole supermassive
09:08heavyweights believed to lurk in the heart of galaxies but to understand any black hole you must begin
09:17with gravity for within this darkness gravity is in total control
09:22our 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
09:52showing little promise as a farmer the young Isaac Newton was sent up to Cambridge University
10:04as an academic Newton would formulate laws of physics which still form the basis of modern science
10:17fate played its part in 1665 the plague swept across England Cambridge was closed to help contain the spread of
10:37the contagion
10:38Newton was forced to flee
10:44he sought refuge back at Wolsthorpe Manor
10:50over 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
11:02and to unravel the spectral nature of light
11:09and one day a falling apple interrupted his thoughts and led him to ponder gravity itself
11:17Newton was the first person to give us a really detailed mathematical understanding of one of the basic forces of nature
11:25and of course it was the first great triumph of mathematical physics
11:34he told us that the force which holds us down here on the earth and which allows an apple to fall
11:40is the same force which holds the moon in its orbit around the earth and makes the planets move in their courses
11:46Newton's reasoned that all matter in the universe has gravity
12:14that it's a force that reaches out from one body to another and pulls everything inwards
12:25the more mass an object has the more gravity the stronger this inwards pull
12:30the first person to combine this notion of the inward pull of gravity with knowledge that the speed of light was finite was John Mitchell
12:45as Rector of Thornhill Church in Yorkshire and one of the 18th century's great forgotten scientists
12:52Mitchell took Newton's view of gravity to its ultimate dark conclusion
13:03Mitchell's giant leap was to imagine a ray of light leaving a star in the same way we think today of a rocket leaving a planet
13:11to escape the earth's gravitational pull entirely and travel into space
13:18to escape the earth's gravitational pull entirely and travel into space
13:23a rocket needs to push itself upwards at 11 kilometers a second
13:27faster than gravity tries to pull it back down
13:30Mitchell 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
13:49John Mitchell worked out that if you had a body weight about a hundred million times as much as the Sun light couldn't even escape from it
14:02and he then went on to say that for that reason maybe the most massive objects in the universe might be invisible to us
14:10Mitchell had explained how gravity could turn a star black but not how it could turn it into a hole
14:17a complete understanding of the life and death of stars awaited the nuclear age
14:24every star we see in the heavens has a giant nuclear reaction raging at its core
14:51it's what makes a star like our own Sun shine so hot and bright
15:00only the nuclear reaction holds gravity at bay
15:04the energy pushing out would stopping the Sun from being pulled tighter smaller and more dense
15:10it's a precarious balance that gravity will always win in the end
15:15when the Sun runs out of nuclear fuel its own gravity will crush it into a tiny ball the size of the earth
15:30but a hundred thousand times more dense
15:33but our Sun has too little mass and therefore too little gravity to become a black hole
15:45instead astronomers call such a feeble ember a white dwarf
15:50but when a giant star switches off it goes with a bang
15:59while we see the outward explosion as a supernova this masks the implosion going on inside
16:10the core has been given a gravity bear hook so extreme that all the atoms have been squeezed into a ball of super dense subatomic particles called neutrons
16:25it has become a neutron star a mere 20 kilometers or so in diameter
16:32we know that ordinary stars like the Sun will become white dwarfs
16:37we know that there are neutron stars which are just a little bit heavier
16:43and the question is what do you have beyond that we believe it's black holes
16:49theory suggests that when a neutron star is more than three times as heavy as our Sun
16:59even the neutrons cannot resist gravity the collapse is irrevocable
17:06the density of mass becomes so great in the center that gravity overwhelms space itself
17:12distorting it so horribly that it and time with it begins to wrench off from the outside
17:18universe a darkness forms at the heart of the collapsing star and moves relentlessly outwards as the star's brilliance is sucked in
17:31as the star dies a black hole is born
17:37as like you said
17:39in its power
17:42a black hole
17:44we're being pulled into a black hole
17:48Anna?
17:49compute its mass
17:50find out what you can about it
17:52not a weird chance
17:54i know so little about black holes
17:56except that there's stars that have collapsed in on themselves
17:59they not only bend light they actually swallow it the forces inside a black sun are inconceivable
18:06they're capable of anything they can bend space even time turn both inside out
18:11just how a black hole can manifest itself so powerfully in the emptiness of space is something
18:25that weighs heavily on professor Stephen Hawking born exactly 300 years after Isaac Newton Hawking
18:32now holds Newton's old job at Cambridge University Hawking's mind roams freely not in Newton's
18:43universe but in the universe of Albert Einstein we are used to thinking of gravity as a force that
18:51pulls bodies towards the earth and pulls the earth towards the Sun but Einstein had the brilliant
18:58idea that gravity could be caused by space and time being curved rather than flat
19:04Einstein realized that nothing can exist at a point in space without existing at a particular time as
19:14well space and time seem to be woven together to form the flexible four-dimensional fabric of the
19:21universe so-called space-time space-time is almost impossible to contemplate because our entire
19:35sensory existence is limited to the three dimensions of everyday experience the easiest way for us to
19:46enter Einstein's universe is to imagine space and time to be like a sheet of rubber
19:51if space-time were empty the sheet would be flat but massive bodies like the earth and Sun will bend the feet and cause it to be curved
20:05this curvature is Einstein's concept of gravity the more mass a star or planet has the more steeply it bends
20:15space-time around it and so the more gravity it has throw something extremely heavy like a collapsing star
20:25onto the sheet and you soon end up with a universe full of holes oh watch it Cody yeah yeah oops
20:40as some massive star pools and strings that will curve the space-time around it more and more
20:48eventually when it shrinks to a certain critical size that will quite literally create a black hole in
20:58space-time things can fall into a black hole but nothing can get out
21:05there's so much I don't know about astrophysics I wish I read that book by that wheelchair guy
21:13the most terrifying concept in astrophysics lurks at the bottom of a black hole the singularity
21:26everything that has ever fallen into the hole is destroyed at the singularity crushed into a
21:33pinpoint of infinite density and infinite smallness even space and time are squelched out of existence
21:41all that remains in the outside universe is a perfect sphere of absolute darkness a gravitational ghost of
21:54the star that died this sphere is called the event horizon and it marks the edge of the abyss
22:02this event horizon is not made of matter it's a in some sense almost not even made of a warpage of
22:11space-time it's just a location it is that unique location where gravity is become so strong just inside
22:20there that nothing can escape while the event horizon may be only a few kilometers in diameter the immense
22:33gravity of the singularity will have sucked a hole inside it that is impossibly deep to measure in the center
22:41there is the so-called singularity which is a place where according to Einstein's theory
22:47everything goes infinite where if you do calculations as it were the smoke pours out of the computer and something
22:54goes wrong and what that means is that deep inside black hole we have black holes we have a signal that we need some
23:03fundamentally new physics to understand what is going on
23:12you're on the slit astronomer Phil Charles thinks he has proof that such intangible objects are to be found in the
23:21real universe
23:28the giveaway signal was the sudden burst of unexplained x-rays which alerted Phil to V 404
23:33a faint star trapped in orbit around an invisible compact object
23:40we have to wait for that x-ray outburst to die away so that we can see that faint cool star that's orbiting the compact object
23:48we need to follow its motion now once the outburst has died away we can see this you're talking about very faint stars
23:57below 17th many below 20th magnitude that's more than a million times fainter than the faintest star you can see with the naked eye
24:05and that means you have to come to places like this to use telescopes like that
24:10the massive William Herschel telescope concentrates the feeble light from V 404 and feeds it into a spectrum analyzer
24:23these are signatures of a star not much different from the Sun and it represents all more than 80% of the light
24:30here that we can follow and use the the speeds that we measured to determine the mass of the object we cannot see
24:38an excellent analogy is that of a big strong man and a very small light woman
24:45as they swing each other around the man hardly moves and the woman just by the balance of their weights moves much more
24:56calculations show that V 404 orbits her heavy mysterious partner once every six and a half days to achieve speeds like these the partner must be very heavy indeed
25:15the mass that we measure by this process is 12 solar masses 12 times the mass of the Sun
25:26that means it is substantially heavier than what we think is the the largest mass of a neutron star
25:33we are virtually certain it's a black hole
25:41the 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
25:51as this material spirals towards the hole it heats up and sends a last desperate x-ray signal to the outside world
25:58nearly a dozen similar objects have now had their presence betrayed to astronomers in the same way by x-ray signals
26:05one of the first was cygnus x1
26:23i had a bet with stephen hawking as to whether cygnus x1 a particular object from which one saw x-rays coming off
26:29uh it was a black hole
26:32uh it was a black hole
26:35Stephen Hawking bet that it wasn't
26:38that was not because i didn't believe in black holes
26:43rather it was because i wanted an insurance policy
26:48i had done a lot of work on black holes
26:51and it would all have been wasted if it had turned out that black holes didn't exist
26:56exist but at least I would have had the consolation of winning the bet when
27:03Hawking and Thorne made the bet in 1974 the evidence was thin but as the years
27:09rolled on and the evidence mounted Hawking felt it was safe to concede the
27:14wager in 1990 Stephen Hawking happened to be visiting Los Angeles he broke into
27:22my office and thumbprinted off on this bet I had given Kip Thorne a year's
27:29subscription to Penthouse much to his wife's disgust this handwritten bet has
27:37come to symbolize the first real acknowledgement by the scientific
27:41establishment that black holes are really out there but for every black hole
27:48clutching a star in deadly embrace there must be many more solitary ones yet
27:53unseen I'd love to get close to a black hole I'd love to see the distorted
28:01images of stars and galaxies as light from them bends around the black hole the
28:07rings of light around the black hole contemplate what was going on down
28:11inside the black hole it would just be wonderful wonderful but could it ever be
28:19possible
28:29one of the areas of advanced space transportation that NASA is interested
28:35in is in the area of breakthrough propulsion physics these areas that have
28:40some tenuous theoretical basis but they're beyond present-day technology
28:46if we're always going to be limited by the basic speed limit of the universe
28:52being the speed of light 186,000 miles per second then I would say it's going to
28:58be very difficult for us in any one person's lifetime to travel or to even get
29:05data from a black hole because of the distances that we think all of these are
29:10artifacts are from from the earth
29:17but if breakthrough propulsion physics finds a method for us to travel at or
29:22beyond the speed of light then I'd say by definition yes we're going to go to a
29:26black hole
29:331
29:401
29:412
29:431
29:472
29:502
29:512
29:54I don't know.
30:24Our mothership travels fast enough to insert into a safe orbit around the hole.
30:31A different fate awaits the probe.
30:38As I approach the black hole, I will start to feel a gravitational tug on myself.
30:46It's a different kind of a gravitational tug or pull than you're accustomed to.
30:51Normally you think you're just pulled down.
30:53As I sit here in this chair, my head is farther away from the center of the earth than my chest.
31:03And so my head is pulled less strongly than my chest is.
31:08So in fact, there's a difference in the pull.
31:10My head is being pulled less strongly than my chest, so I'm actually being slightly stretched apart by gravity.
31:15As you approach a black hole, that difference in pull becomes larger and larger.
31:25As you get closer to the center, gravity will get more extreme, you will be squeezed and distorted.
31:32Spaghettification is the name some people use for this experience.
31:37Spaghettification is an experience nothing can survive.
31:42The fragments streak down and into the blackness of the hole.
31:54You or I falling into the black hole will get stretched and our bodies will get mutilated before we even reach the horizon.
32:01It's no good. We can't break free.
32:05Get him out, Alan. He's accelerating. We can't hold him.
32:09Something else strange happens well before the event horizon is crossed.
32:17Not only space is being stretched, so is time.
32:31The closer the probe gets to the event horizon, the harder light from it struggles to escape.
32:37The mothership sees the probe slow down until it seems to stop.
32:44Time doesn't change for the probe because gravity is stretching its whole existence.
32:51But from the mothership's perspective, the probe has become frozen in time.
32:57It is both destroyed in an instant and hovering for eternity, depending on your point of view.
33:08Nevertheless, if you are inside that spaceship looking back at me, you can wave, you can see me.
33:15You may think I can see you, but I can't.
33:17And you go inside the event horizon, you can still see out, you still see me on the outside.
33:22Right up to the point that you die, you can still see me on the outside.
33:26Oh my god, I'm gonna be sucked into a black hole, I'm gonna be sucked into a black hole, I'm gonna be sucked into a black hole, I'm gonna be nothing, and what's gonna be coming out the other side, I don't know.
33:33I'll save you, dad.
33:37I can't get any closer.
33:39You'll have to jump.
33:43Piece of cake, son.
33:44Piece of cake.
33:47Crap, crap, crap, crap, crap, crap, crap, crap, crap, crap, crap!
33:56ieli-
34:06happen deep inside a black hole if you were to fall directly in it could be
34:12that something even stranger happens to space under these conditions something
34:16like what happens at the beginning of the universe and indeed some people have
34:21speculated that in general it may be possible to avoid the complete
34:26singularity and emerge somewhere else some say that if you pass through a
34:30rotating black hole you end up in a new universe a new dimension
34:38we've entered I recall a movie in which at the end of the film the spaceship goes
34:45inside the black hole and comes out the other side into another universe that
34:50don't happen it just doesn't happen at all the fundamental laws of physics say
34:56that at the center of the black hole there is a singularity a region where
35:00space and time are infinitely warped a region where when matter flows into it
35:06matter gets destroyed but does this have to be so this is a work place yet speculation
35:22that tamed black holes may provide a way of cheating the laws of physics have
35:26become a hallmark of science fiction physicist Igor Novikov likes to
35:32speculate on what would happen if you joined two black holes together to make a
35:36wormhole
35:38wormholes are real bizarre objects we can imagine a wormhole as two holes and some
35:49kind of a tunnel between them but this tunnel is not in our space and it is in
35:57some kind of hyperspace outside of our dimensions
36:01this is really neat gene this is a neat place for us to play to make such a wormhole we would
36:07have to engineer space-time first bend it until it begins to form a black hole but not so
36:15much that a singularity is born then join the bottom of this gravity tunnel to the bottom of
36:23a second time to make two holes connected by a continuous tube through hyperspace
36:28step two would be to move one hole to wherever it was you wanted to travel one of them can be near
36:45our earth another in another galaxy but this tunnel can be extremely short say a few meters
36:58the tunnel would also be very fragile prone to collapse as soon as a traveler attempted to pass
37:04through it but if we could develop the technology to tame the ferocious forces at work we would
37:11have opened an interstellar shortcut he can travel from one galaxy to another galaxy only during well
37:22let's say a few seconds where a black hole is a one-way street with a dead end of the singularity
37:29a wormhole will be a freeway to the stars
37:33I have to say these things are driven by by uh sort of romantic science fiction ideas which is fine I
37:49mean a lot of science is driven that way and you and you do good things I have nothing against that
37:54directly it's just that it seems to me the scientific evidence is just that this is not going to happen
38:00it's just not possible Oxford University's Roger Penrose pushes the mathematics of black holes in a
38:08different direction he's formulated a way to extract enormous quantities of energy from the way black
38:17holes spin at the same time as sending enormous quantities of garbage to oblivion in the real
38:26universe most black holes should spin because the stars that form them would have been spinning as
38:32they collapsed their massive gravity swirling the fabric of space around them like water around a world
38:45Penrose's energy extraction process would require building a power station at a safe distance around the
38:51spinning hole you could imagine firing a lot of particles or bodies into the neighborhood of
38:58the spinning hole in the right direction the forces of spaghettification will rip these particles apart
39:08one particle carries negative energy into the hole and that means that the the partner has more energy
39:16than the the one that fell into it so you can actually extract energy from a black hole through this
39:23process the particles could be any old rubbish you never wanted to see again half would disappear into the
39:32hole half would be flung outwards with a slingshot of gravitational energy that could be used to drive a
39:38turbine the source of that energy is in effect the slowing down of the black holes rotation because as
39:45these particles keep falling into the hole they gradually slow it down but since there's usually an
39:51enormous amount of rotational energy in a rotating black hole this would be an extraordinarily efficient way
39:56of extracting energy
40:02according to Einstein even a small body like the earth should drag space with it as it spins not by much but
40:13it should be measurable all that day yeah okay here we go the gravity probe B satellite will put this
40:22theory to the test protected from disturbance deep in the interior of the satellites vacuum capsule will
40:33be four of the world's most perfect gyroscopic spheres mounted in a block of pure quartz as the
40:42satellite orbits the poles it should be dragged ever so slightly off course by the way the spinning earth
40:48drag space around with it the gyroscopes will accumulate this miniscule deflection after each
41:02week in orbit it will be like trying to measure the width of a human hair from a distance of 15
41:07kilometers the gyroscopes have to be machined so smoothly that if they were the size of the planet the
41:17tallest mountain would be only two meters high
41:33but there is a long way to go before observational science catches up with the wildest speculations of black hole theory
41:40another country another telescope the hunt takes Phil Charles to Australia Australia has access to the southern hemisphere of the sky and there we can see the Magellanic Clouds
41:59in 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
42:11we need to get maybe 20 or 30 so that you can really see the the the population of black holes that we're looking at do they all have similar mass are they a spread of mass do they all come from the same kinds of original stars we can start to work that out once we can get a
42:29another thing while Phil Charles turns his sights on the stars of our neighboring galaxy other astronomers are probing galaxies further afield
42:38here they are finding objects of staggering immensity formed not from the death of a single star but from the collapse of enough matter to make millions
42:50such objects astronomers now believe are supermassive black holes
42:57ever since radio telescopes began eavesdropping on the heavens the strongest and most puzzling signals have come from the hearts of distant galaxies
43:16astronomers now suspect these radio signals are generated by central supermassive black holes
43:23mighty jets of energised particles are blasted into space for a beautiful fire
43:41suspect these radio signals are generated by central supermassive black
43:46holes. Mighty jets of energized particles are blasted into space from an invisible
43:54engine that drives these so-called radio galaxies like great wheels through the
43:59heavens. Nameless stars are ripped apart by an immense gravity to feed central
44:09disks of white-hot matter, shining a hundred times more brightly than a whole
44:14galaxy of stars like our Milky Way.
44:24Powering everything is the hidden central object, as small as our solar system, but
44:31where enough matter to make millions or even billions of stars has undergone a
44:36titanic gravitational collapse.
44:46Tonight we're looking at the radio galaxy M87. M87 is a nearby giant galaxy which is
44:56very unusual in having a large powerful jet coming out of it.
45:07M87's jet is like an enormous death ray of charged particles moving close to the speed
45:13of light and 6,000 light-years in length.
45:17The jet is a signature of the way the black hole is swirling matter and space around it.
45:23Astronomers use the speed of this swirling matter to calculate the black hole's mass.
45:29Well, we're talking about a black hole which is a billion solar masses or more, which is
45:40therefore is much larger than anything we are used to seeing in our own galaxy, but it's fairly
45:46typical of what we think many radio galaxies have in their nucleus.
46:01Astronomers suspect radio galaxies are those galaxies with plenty of matter left for the black hole to eat.
46:08If a galaxy appears quiet, it's probably because the black hole has run out of food.
46:14If we look in the centre of almost any galaxy, there should be lurking a dark mass of millions of solar masses at least,
46:27which may be the remnant of some past activity in that galaxy.
46:31And in the last few years, there's been growing evidence that these dark masses actually do exist.
46:42But seeing them is still beyond us.
46:44Even the latest high-resolution Hubble images can show only the bright central disk,
46:50the jets of energized particles, but not the black speck in the middle.
46:56As you know, the problem with black holes is that they're black and they're holes,
47:00they're extremely difficult to show that they're there.
47:03If you see a hole in the road, you know the hole is there because of the surrounding road,
47:08not because of the hole itself.
47:10And similarly, we are doing the kind of work of looking at material around the black hole
47:14and clinching the case that there really is the black hole in the centre.
47:19We're looking at a galaxy in the constellation of Centaurus.
47:22At the centre of this galaxy, we think that there's a massive black hole,
47:26perhaps a hundred million times the mass of the Sun.
47:29And matter is falling into that black hole, making it very bright in X-rays.
47:34These X-rays are the last gasps from matter like iron, holding on until the bitter end.
47:41Their spectral signatures are stretched in just the way theory would expect
47:45from X-rays struggling to escape a deep pit of gravity.
47:51It seems Fabian is very close to seeing the event horizon of the black hole itself.
48:00We will never be able to appreciate the full majesty of a supermassive black hole from Earth.
48:05Time for our spacecraft to make another journey.
48:17If one was to take a journey starting in the outer part of a galaxy and moving in,
48:22you would see very hot glowing gas filling the galaxy,
48:26which is being heated by some mysterious powerful central source.
48:29You would find gas orbiting in a disc, swirling at nearly the speed of lights and getting very hot.
48:38Getting so hot that it radiates not just visible lights,
48:42but very energetic radiation like X-rays.
48:59It is one of the great cosmological contradictions that the larger the black hole,
49:14the weaker the gravitational forces near the event horizon.
49:19This time, there is no spaghetti.
49:24As we approach the event horizon,
49:26the intense gravitational curvature wrenches the light from the universe
49:30to a bright point directly overhead.
49:35We have reached the point of no return.
49:40We are now inside the black hole.
49:43But where is the singularity?
49:47If you are falling into a black hole,
49:49and the singularity, you knew from your calculations
49:52that the singularity was out there and you're heading for it,
49:54you look at it, you don't see it.
49:58It's like the singularity that you're heading for in the future,
50:02and you don't actually see it.
50:07The singularity is where science ends and speculation begins.
50:14Space and time have ceased to exist,
50:17replaced by a seething chaotic mass we can call quantum foam.
50:21Into this bizarre conjecture has disappeared all the mass and energy
50:27that has ever fallen inside the event horizon.
50:30This is where Einstein's laws fail.
50:34This is where the laws of quantum mechanics fail.
50:37This is where the secrets of the universe are hidden.
50:42The singularity is an object at the core of a black hole
50:47that is governed not by the ordinary laws of physics
50:50that we're familiar with, but by the laws of quantum gravity,
50:53which we only are beginning to glimpse and understand.
50:57If the probe was strong enough,
51:00it would fall towards the singularity for perhaps an hour,
51:03until it blindly met its future at the end of space and time.
51:07You would then experience the final crunch in the center,
51:12learning in your final moments the new physics prevailing at those times perhaps,
51:17but you'd be able to send no signal to the external world of the interior region.
51:21What really happens to it at the end is as unknown as what happened before the Big Bang.
51:32It's the other end of that story.
51:33We do expect to find singularities in the Big Bang.
51:34Well, of course, that was the first one we saw in the beginning.
51:35We do expect to find singularities in the Big Bang.
51:36Well, of course, that was the first one we saw in the beginning.
51:37We do expect to find singularities in the Big Bang.
51:47Well, of course, that was the first one we had to worry about.
51:51Black holes, and in the Big Crunch, you think?
51:54It's about the very old temperature. The electrons may be rather cool.
52:11What we have, of course, is two tornadoes orbiting inside a larger tornado
52:16and coming together and colliding and coalescing.
52:18The world's leading cosmological minds can now gather to talk with facts and figures
52:25about what was not long ago dismissed as flights of fancy.
52:29What we're showing, of course, is that observationally it can't be a neutral star.
52:39It seems our understanding of the nature of the universe is accelerating almost day by day.
52:44These are the facts, it seems, that most nearby galaxies, and perhaps therefore most galaxies,
52:49harbor a central black hole.
52:52Our galaxy would seem rather underprivileged if it didn't have one as well.
52:56The evidence has come only in the last few months that makes this a compelling case.
53:03Astronomers are virtually certain that hidden behind the dust in the center of our own Milky Way galaxy,
53:08there is a black hole weighing three million times the mass of the Sun.
53:17Even as little as five years ago, people thought that we could get away with not having to have black holes in our own galaxy.
53:25We could explain almost everything we see by neutron stars.
53:29No theorist now believes that we're dealing with ordinary neutron stars anymore.
53:40There are things out there that they have to be compact and they have to be explained.
53:45And I think that's an extremely exciting prospect.
53:47Everybody has trouble coming to terms with black holes.
54:06Locked within these prisons of light are the secrets of the universe.
54:11Where did it come from and where is it going to?
54:13We may never answer these questions.
54:17But for once, we know where the answers are hidden.
54:21Join us next week as we answer some of the big questions about the Sun, next Thursday morning at 11.
54:31And tonight, the answers to many questions of genetics and eco-friendly office blocks are revealed on Catalyst, tonight at 8 on ABC.
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