:00:11. > :00:20.Last night we spoke to the last man on the moon. Tonight we are heading
:00:20. > :00:30.to the centre of our galaxy. I am Brian Cox, he is Dara O'Briain, and
:00:30. > :00:55.
:00:56. > :00:59.Welcome back to Jodrell Bank for the second night of Stargazing Live.
:00:59. > :01:03.Yesterday, we concentrated on the moon, which is a bit unfair because
:01:03. > :01:07.it did not rise for a couple of hours after we went off air. We
:01:07. > :01:12.were relying on people staying up late or getting up early, and
:01:12. > :01:21.people sent us a number of photographs. This is a beautiful
:01:21. > :01:30.picture of the Moon which was taken by James West. We have another one,
:01:30. > :01:36.it taken by James Dyson. I am fond of this picture. It is a beautiful
:01:36. > :01:40.picture of a cluster of young stars which were formed together. Most
:01:40. > :01:45.people can see about six or seven of them with the naked eye but you
:01:45. > :01:49.can see tens of them through a telescope. That transient. It will
:01:49. > :01:54.drift apart and will not be a cluster anymore. We have had the
:01:54. > :01:58.most incredible response so far. A lot of you have contacted us about
:01:58. > :02:01.Captain Cerna. Some of you wanted to know why the Stars and Stripes
:02:01. > :02:05.flag looked like it was flapping in the wind when there is no
:02:05. > :02:09.atmosphere in the -- on the moon. It sounds like a conspiracy
:02:09. > :02:13.question. The answer is there is a piece of metal in it because they
:02:13. > :02:18.would knew it would flatten if there was no atmosphere. If you
:02:18. > :02:25.think we did not land on the moon, turn over to ITV, I did not -- I do
:02:25. > :02:30.not want to! You can keep questions coming into us, or you can tweet us.
:02:30. > :02:35.You can join the online chatroom, Talk Stargazing, at
:02:35. > :02:39.bbc.co.uk/stargazing. To see what is in the skies over Macclesfield
:02:39. > :02:44.tonight, are there to mark and friends, and a very special guest
:02:44. > :02:48.astronomer. Good evening, I am joined not only
:02:48. > :02:51.by a veritable army of astronomers from the Liverpool and Macclesfield
:02:51. > :02:56.astronomy society, how are you doing? They sound like they're
:02:56. > :03:00.having some fun. They have joined us for our special star party at
:03:01. > :03:06.Jodrell Bank. You can find out details of the events around the
:03:06. > :03:12.country near where you are, at our website, bbc.co.uk/stargazing.
:03:12. > :03:21.Standing relatively close to this new telescope is Impressionist and
:03:21. > :03:25.space, Jon Culshaw. Well come. What is it about astronomy? I remember
:03:25. > :03:31.receiving a book by Patrick Moore when I was nine and I read it to
:03:31. > :03:36.cover to cover, and I was hooked. Any time there was a -- the Moon
:03:36. > :03:43.was out, I could not resist having a look. Do you use these binoculars
:03:43. > :03:49.often? Yes. I have not got a stand for them yet. You do need at quite
:03:49. > :03:56.an impressive stand. The sky is looking incredibly Claire so come
:03:56. > :03:59.back to us later on. -- incredibly clear.
:03:59. > :04:04.Ironically, the thing we are going to talk about is not actually
:04:04. > :04:10.visible. We are going to talk about black holes. The truth is that from
:04:10. > :04:15.a physicist's perspective, we do not really understand them. Here is
:04:15. > :04:18.an introduction to the enigmatic inhabitants of the cosmos.
:04:18. > :04:24.Black holes are some of the strangest, most mysterious and
:04:24. > :04:29.destructive things that exist in the universe. There is one here.
:04:29. > :04:34.And there is probably another one here. But you can't see them. And
:04:34. > :04:38.they can't be photographed. So we have to use computer graphics to
:04:38. > :04:43.try to explain what they are and how they are formed. Black holes
:04:43. > :04:51.are cosmic bodies with such immense gravity, nothing can escape them.
:04:51. > :04:56.For their lives to start, a star has to die. Stars are effectively
:04:56. > :05:03.huge nuclear reactors, fuelled by hydrogen. At the end of their lives,
:05:03. > :05:09.when the fuel runs out, they dive. When this happens, stars the size
:05:10. > :05:18.of our sun with the, to become much smaller bodies, known as white
:05:18. > :05:23.dwarfs. When bigger stars die, they destroy themselves in explosions
:05:23. > :05:28.known as supernovas. If the explosion is 30 times the mass of
:05:28. > :05:32.the Sun, black holes can be formed. As the outer layers of the star
:05:32. > :05:36.blow off into space, the core of the Star, which can be as big as a
:05:36. > :05:41.planet, is crushed down to almost nothing. The whole process can
:05:41. > :05:45.taste -- tastes -- take less than a second. What is left is an object
:05:45. > :05:50.that has the same mass as the core of the star, but is packed into a
:05:50. > :05:55.much less -- much smaller space. Despite being significantly smaller,
:05:55. > :05:59.it still exerts the same gravitational pull. This incredibly
:05:59. > :06:04.powerful entity, which is small but massive at the same time, is what
:06:04. > :06:10.we have come to know as a black hole. From the moment of their
:06:10. > :06:14.creation, some black holes begin firing out great jets of radiation.
:06:14. > :06:19.The immense gravitational pull from the holes means that anything that
:06:19. > :06:23.strays too close to them is powerless to escape. Even a nearby
:06:23. > :06:29.star would be torn apart, the matter from its surface being
:06:29. > :06:34.pulled into orbit around the hole. That poll from the black hole is so
:06:34. > :06:40.strong that eventually, it is eventually -- it is impossible to
:06:40. > :06:45.escape -- that poll. This terrifying point of no return is
:06:45. > :06:48.known as the event horizon. Everything in its path is sucked in,
:06:48. > :06:52.and the more -- the more it swallows, the bigger the black hole
:06:52. > :06:55.becomes. Beyond the event horizon, not even light can travel fast
:06:56. > :07:02.enough to escape. That is why you can't see them, and how they get
:07:02. > :07:07.their name. They are quite literally black holes in space. If,
:07:07. > :07:11.by some miracle, you were to survive the tidal forces at the
:07:11. > :07:17.Event Horizon and fell into a black hole, you would be ripped apart.
:07:17. > :07:21.But nobody knows how long that would take.
:07:21. > :07:25.We are going to go to the age of physics and also the heart of our
:07:25. > :07:29.Garroch -- galaxy. It is a journey we should start right here. Let's
:07:29. > :07:32.take a look at where we are in our galaxy. This is the Milky Way,
:07:32. > :07:37.taken from outside it, so it is a taken from outside it, so it is a
:07:37. > :07:41.graphic. That is the location of earth. We had this as a question
:07:41. > :07:46.from Gary in Belfast, how do we know where the earth is and how can
:07:46. > :07:52.we know what it looks like? There is something like between 200 and
:07:52. > :08:02.400 billion stars in the Milky Way. It from there, you can't see it all,
:08:02. > :08:03.
:08:03. > :08:09.we use telescopes like the Lovell, radio astronomy. Looking at the
:08:09. > :08:14.radio emission, you can see how bright the universe is. Also, by
:08:14. > :08:17.looking at how that shifts, you can see how fast it is moving. So you
:08:17. > :08:22.can work out precisely the structure and speed of rotation of
:08:22. > :08:25.our galaxy. When we look into the sky, every star we see is part of
:08:25. > :08:31.the Milky Way. Everything you can see with the naked eye apart from
:08:31. > :08:37.one thing. We have a life picture of that one thing. This is from
:08:37. > :08:41.Macclesfield now. Where are we? This is a picture of the Andromeda
:08:41. > :08:44.galaxy. This is the nearest neighbouring galaxy, about 2
:08:44. > :08:51.million light years away. There is something like a trillion stars in
:08:51. > :08:55.that galaxy. That is a live picture now of Andromeda. The Galaxy is
:08:55. > :09:00.basically a collection of stars? They are. That is the nearest
:09:00. > :09:03.neighbour, so there are two of them. This is one of the most famous
:09:03. > :09:08.pictures in astronomy. It is a picture of the piece of sky you
:09:08. > :09:13.would cover, if you took a five pence piece and held it about 25
:09:13. > :09:18.metres away, cover a little piece of sky. It was a piece of sky that
:09:18. > :09:21.is anti from the surface of the Earth as far as we could tell, but
:09:21. > :09:27.the Hubble take -- telescope took this picture and it is far from
:09:27. > :09:33.empty. There are over 10,000 galaxies in this image, the most
:09:33. > :09:40.distant his 13 billion light years away. If you extend that over the
:09:40. > :09:44.entire sky, there are around 350 billion galaxies. Although we can
:09:44. > :09:47.see the Andromeda galaxy in the night sky, that is pretty much the
:09:47. > :09:57.only visible to the naked eye in this hemisphere, but there is
:09:57. > :10:01.plenty more visible in the southern Welcome to the southern African
:10:01. > :10:04.large telescope in the middle of the Karoo desert. The weather has
:10:04. > :10:13.been rubbish again, but it looks like it might be clearing up, which
:10:13. > :10:18.is why the SALT telescope is moving into position. There are two
:10:18. > :10:22.galaxies visible to the naked eye, closer than Andromeda. A couple of
:10:22. > :10:25.nights ago I went galaxy gazing with budding astronomers from the
:10:26. > :10:30.nearby town. In the middle of the Karoo desert,
:10:30. > :10:34.about 200 miles north-east of Cape Town, lies the tiny town of
:10:34. > :10:37.Sutherland. Before the South African astronomical observatory
:10:37. > :10:45.relocated here in the mid-70s, this was just a small farming community
:10:45. > :10:50.with a few hundred people. But now, Sutherland is home to one of the
:10:50. > :10:54.largest telescopes in the world, and that has made it something of a
:10:54. > :10:59.tourist destination. Astronomers are also keen that the whole
:10:59. > :11:07.community understands just what a special star-gazing spot this is.
:11:07. > :11:12.Anthony runs the Observer drew's outreach programme. -- the
:11:12. > :11:16.observatory's outreach programme. Why are they flying kites? You have
:11:16. > :11:21.to look up, it is a way of exposing them to the night sky. As the stars
:11:21. > :11:25.come out, they will change their attention... To what is happening.
:11:25. > :11:30.Sometimes before a lucky, we get a shooting star, and somebody will
:11:30. > :11:37.ask, what just happened? One of the astronomers down here, at David
:11:37. > :11:42.Gilbank, will be talking to the kids about galaxies later on.
:11:42. > :11:46.good way to describe a galaxy is as a city of stars. Our Milky Way is
:11:46. > :11:50.all the stars that belong to the Star City. If we can see our galaxy
:11:50. > :11:55.from the outside, we would see something that looks like the East
:11:55. > :11:59.shape of a dinner plate. We live about two-thirds of the way out
:11:59. > :12:02.from the centre. When we look at the night sky, we are actually
:12:02. > :12:07.looking into the thickest part of the stars, as if we are looking
:12:07. > :12:13.through the edge of the plate. many stars are in the Milky Way?
:12:13. > :12:17.good question. They are about 100 billion within our own galaxy.
:12:17. > :12:23.is the closest galaxy to our own Milky Way? The nearest galaxy is
:12:23. > :12:27.called the Andromeda galaxy, but there are lots of much that smaller
:12:27. > :12:33.galaxies in between. -- the mirrors that is the same size. This misty
:12:33. > :12:39.patch looks like a small version of the Milky Way.
:12:39. > :12:44.This is called the Large Magellanic Cloud. This is the satellite galaxy
:12:44. > :12:48.of the Milky Way. The Large Magellanic Cloud is the satellite
:12:48. > :12:53.galaxy of the Milky Way that orbits around us. What you are looking at
:12:53. > :12:59.through the telescope, it looks like a bright patch, this is called
:12:59. > :13:05.the tarantula nebula. It looks like little legs of the Spider. It is a
:13:05. > :13:10.cloud of gas in which stars are being born. You can see there are
:13:10. > :13:15.new starts by looking around, we can see bright blue luminous stars.
:13:15. > :13:21.Why are the new stars blue? If you think about the taps on the sink,
:13:21. > :13:25.blue is cold, bread is hot, it is the opposite in astronomy. -- red
:13:25. > :13:29.is hot. Imagine taking a piece of iron into a fire, it will start of
:13:29. > :13:33.glowing red hot, that is the coolest you can get. If you heat it
:13:33. > :13:39.further, it will glow white hot. If you could eat it furthered without
:13:39. > :13:49.the metal Motty, it would be blew hot. Blue is the hottest iPod star
:13:49. > :13:53.
:13:53. > :13:57.-- without the metal nothing. Back These very bright stars do not live
:13:57. > :14:02.very long. If you see these hot blue stars in the galaxy, you know
:14:02. > :14:07.they have been put there recently. If there is no new star formation
:14:07. > :14:12.going on, you will only see these older stars, which will appear red.
:14:12. > :14:16.They are red because they are older? That is right. What stops
:14:16. > :14:21.star formation in galaxy? To form stars we need these nebula, these
:14:21. > :14:23.clouds of gas. We know something must be removing the gas and
:14:23. > :14:31.preventing it from forming stars, but we don't know what that is,
:14:31. > :14:35.this is one of the things I am trying to answer in the work I am
:14:35. > :14:41.doing with SALT. There is also a Small Magellanic
:14:41. > :14:46.Cloud in the southern hemisphere. In fact, SALT altered its viewing
:14:46. > :14:49.window in order to observe it in its entirety. It has about a 10th
:14:49. > :14:53.of the stars of the large cloud, and it is more elongated and the
:14:53. > :14:57.large one, but we look at it head on from Earth. The magellanic
:14:57. > :15:01.clouds are part of this local group of galaxies, what is the local
:15:01. > :15:05.group? It is the name we give to the collection of nearby galaxies
:15:05. > :15:08.bound together by gravity. It consists of three big galaxies
:15:08. > :15:13.including the Milky Way and Andromeda, and debris several dozen
:15:13. > :15:16.smaller galaxies. -- may be several dozen. You have been attempting to
:15:16. > :15:26.find out how many galaxies there are in the universe, you have
:15:26. > :15:27.
:15:27. > :15:34.looked at 3% of the sky, what have We are mainly looking for galaxy
:15:34. > :15:38.clusters and we have found 38,000, which amounts to 3 million galaxies
:15:38. > :15:41.in one tiny speck of the sky. Galaxies are everywhere you look.
:15:41. > :15:44.They are distributed across the universe in a cosmic web of
:15:44. > :15:50.filaments and astronomers are only just beginning to understand what
:15:50. > :15:54.that might look like. Join me later when I find out how galaxies growth.
:15:54. > :16:02.Apparently the Milky Way is in for a bumpy ride.
:16:02. > :16:07.Here is a positive message for those people needing more exercise.
:16:07. > :16:14.You cannot be at rest. We travel around the sun but also around the
:16:14. > :16:18.Milky Way. Of course we travel round the Sun every year. But the
:16:18. > :16:22.sun is one of 200 billion stars in the Milky Way galaxy. Our whole
:16:22. > :16:27.solar system is travelling around the galactic centre. We think it
:16:27. > :16:30.takes about 225 million years to make one orbit. If you think about
:16:30. > :16:35.that, that means that since this formation of the solar system we
:16:35. > :16:39.have made 20 orbits, which is 20 galactic years, if you like. The
:16:39. > :16:44.most remarkable thing about that is if you think that humans have been
:16:44. > :16:52.around for a long time, we have been around for 11 thousandth of a
:16:52. > :16:56.single galactic year, which is like a afternoon. We will get an
:16:56. > :17:06.explanation of how that formation happens but first let's go into the
:17:06. > :17:09.
:17:09. > :17:15.field. This guy's a miraculously clear for us. -- the sky is run
:17:15. > :17:25.Cristie Kerr for us and we have found the Andromeda galaxy. For you
:17:25. > :17:27.
:17:27. > :17:31.are not mood to astronomy. -- you are not new to astronomy. That is
:17:31. > :17:37.right. A bit of cloud has gone across and it can be quite helpful
:17:37. > :17:42.if it takes away some of the glare. But not too much. Oh exactly.
:17:42. > :17:46.was the first time that you have seen galaxies? The first time I saw
:17:46. > :17:52.Andromeda was in the 80s. I think my favourite view of our galaxy,
:17:52. > :17:58.the Milky Way, was in Kenya a few years ago. Far away from any kind
:17:58. > :18:03.of light pollution. We have a wonderful, polished sky tonight so
:18:03. > :18:07.we can make out the stars. It is beautiful. It seems that two thirds
:18:07. > :18:11.of Western Europe cannot see our galaxy because of light pollution.
:18:11. > :18:21.That is basically excess and intrusive light that Brighton's the
:18:21. > :18:22.
:18:22. > :18:26.night sky. On your screens is Europe, and it looks spectacular
:18:26. > :18:30.but that is basically the glare from streetlights, offices and
:18:30. > :18:34.houses. The effects of excess lighting are plentiful. It affects
:18:34. > :18:38.the environment, wasting vast amounts of money, and it can
:18:39. > :18:48.disturb wildlife. It can even affect your own body clock. More
:18:49. > :18:49.
:18:49. > :18:52.crucially it is disastrous for I have come to the Royal
:18:52. > :18:59.Observatory in Greenwich, one of my favourite places and a real
:18:59. > :19:05.landmark of British astronomy. I am here to meet a group of stargazers
:19:05. > :19:09.who all live nearby in London. I want to know about their experience
:19:09. > :19:14.of astronomy in the city and find out how they are affected by light
:19:14. > :19:18.pollution. So what is it that you find frustrating about light
:19:19. > :19:23.pollution? It is just the glowing in the sky that prevents me from
:19:23. > :19:28.seeing what I want to see. Especially when I am with my
:19:28. > :19:32.children. I see the images in books and on television and they always
:19:32. > :19:37.ask why they cannot see things like that. Clearly the answer is light
:19:38. > :19:41.pollution. It is constant, really. Your eyes never adapt fully to the
:19:41. > :19:50.night sky. Security lights at debating where animals in gardens,
:19:50. > :19:54.constantly flashing. -- activating by animals. Some of the brighter
:19:54. > :20:00.stars we cannot even say because of the constant orange glowing that is
:20:00. > :20:05.there all the time. When Greenwich Observatory was first founded in
:20:05. > :20:10.the 1600's, it was a long way outside the centre of London. Now
:20:11. > :20:16.it looks straight out over the city. And all of these lights from the
:20:16. > :20:24.Millennium Dome to the individual street lights have blocked the sky
:20:24. > :20:28.it from view. As London astronomers, these people rarely get to
:20:28. > :20:32.experience proper darkness. I am taking them somewhere to experience
:20:32. > :20:36.stars without the glowing. I am taking you to a proper dark sky.
:20:36. > :20:41.What would you like to see? naked eye view of the Andromeda
:20:41. > :20:45.galaxy which people say is possible. That would make my day. I am
:20:45. > :20:49.longing to see the Milky Way. I just love seeing it in photographs
:20:49. > :20:55.because it is beautiful. Just to see that with my own eyes would be
:20:55. > :21:00.a dream, really. How about yourself? I am dying to see a
:21:00. > :21:08.galaxy, any galaxy will do! Just to see it with my own eyes, in real
:21:08. > :21:14.time, something that is so far away, that would be amazing. So to fulfil
:21:14. > :21:20.the wishes of the city astronomers, we are leaving the bright lights
:21:20. > :21:24.behind and heading somewhere really, really dark. Now we have come all
:21:24. > :21:34.the way from London. We have diligently kept our heads down.
:21:34. > :21:35.
:21:35. > :21:44.Three, two, one. Take a look. How is that? Beautiful. Amazing. There
:21:44. > :21:53.is just so much to see. Just so many stars. It is overwhelming and
:21:53. > :21:58.disorientating. Beautiful. This is the stone circle in the Cotswolds.
:21:58. > :22:01.It is so dark here that we have to use a special light intensifying
:22:01. > :22:09.camera that is thousands of times more sensitive than any normal
:22:09. > :22:13.camera. Can I tell you away for just a moment? I know it looks
:22:13. > :22:19.impressive. I know you want to make the most of it but we have got a
:22:19. > :22:25.challenge for you. You have to work for this. If I use my laser pointer,
:22:25. > :22:30.can you see the consolation of Pegasus? The winged horse. It is
:22:30. > :22:34.the square that we are interested in. I am guessing that you can pick
:22:35. > :22:41.out those stars back in London, just about. You challenge is to
:22:41. > :22:45.count how many you can see within the Square of Pegasus. Really?
:22:45. > :22:55.I can't normally count any inside it. So from London you can't see
:22:55. > :22:56.
:22:56. > :23:02.any? 1, two, three... 10. Nine. There leaven. I have got 12.
:23:02. > :23:09.have 12. I have one that might be a discrepancy because it is on the
:23:09. > :23:13.line. Borderline! Let's say that it is. You can see 12 stars within the
:23:13. > :23:19.Square of Pegasus. That is a fantastic measure of how dark the
:23:19. > :23:24.sky is. To see 12 is incredible. And zero in London. It makes you
:23:24. > :23:33.realise the beauty of what you get. I have a treat for you. If we take
:23:33. > :23:37.the top corner stark of the Square of Pegasus, -- corner star, and we
:23:37. > :23:43.hop further to the North, there is one there and a faint one there.
:23:43. > :23:50.You can make out that fuzzy blob just there. That is the Andromeda
:23:50. > :23:53.galaxy. Mind-blowing, isn't it? Truly amazing. We have seen some
:23:53. > :23:56.pretty incredible things are so far but the crowning glory, the thing I
:23:56. > :24:01.am pretty sure you could not normally see from your houses in
:24:01. > :24:10.London, is that overhead, running all the way from the horizon over
:24:10. > :24:15.there. The Milky Way. Fantastic. That is actually the combined light
:24:15. > :24:19.from all the stars in our galaxy. As you can see, there are thousands
:24:19. > :24:24.and thousands of them. Even our specialist cameras are not
:24:24. > :24:33.sensitive enough to pick up the Milky Way. But here it is in all
:24:33. > :24:38.its glory. It was taken on a long exposure from exactly where we are
:24:38. > :24:43.standing. It is incredible. takes a moment to take it all in.
:24:43. > :24:49.So overwhelming. I have seen it in pictures. All this time, there it
:24:49. > :24:57.is. I am awestruck because I have never seen so many stars in such
:24:57. > :25:03.clarity. It is just awesome. It really is. My have just never seen
:25:03. > :25:10.it before. -- I have just never seen it before. It goes to show
:25:10. > :25:14.that the beauty of the night sky is taken from us by pollution.
:25:14. > :25:18.It is incredible how much more you can see in the correct conditions.
:25:18. > :25:22.Dark Sky Discovery is a network of groups that puts together of dark
:25:22. > :25:28.areas in the country near you. don't have to be in the middle of
:25:28. > :25:37.nowhere. We have some images of some of the areas. This one, for
:25:38. > :25:41.example, is a science centre in Winchester in Hampshire. That
:25:41. > :25:45.stunning picture was taken from there. Then we have this
:25:45. > :25:53.observatory in Northumberland. Again a beautiful scene of the
:25:53. > :26:00.North Star with the start trials rotating around it. -- star trails.
:26:00. > :26:07.Actually we are the ones rotating. And this one near London. And now
:26:07. > :26:13.this car-park on the Isle of Skye. The sun is very active at the
:26:13. > :26:21.moment. If you are in the North of the UK, you can see quite a lot.
:26:21. > :26:30.All of the information is on our website, as always. You will find
:26:30. > :26:33.details of how to find an area of darkness. It just needs to be far
:26:33. > :26:37.away from light pollution and with a clear horizon. Light pollution is
:26:37. > :26:42.not just from office blocks. We are all guilty of it because even the
:26:42. > :26:46.smallest communities create a lot of light. Tomorrow we are going to
:26:46. > :26:51.ask a small town to switch off all of their lives simultaneously on
:26:51. > :26:54.air. Here is the low-down on what we are trying to pull off. This
:26:54. > :27:00.rural town may not be the kind of place you would associate with
:27:00. > :27:04.light pollution. Only 1600 people live here and it is near to an area
:27:04. > :27:09.of Exmoor which has the darkest skies in Britain. That is precisely
:27:09. > :27:14.why we have chosen this town for the challenge. Even a town this
:27:14. > :27:19.small generates a lot of excess light. As the sun sets, the lights
:27:19. > :27:23.go up and a familiar orange glow descends on Dulverton. We should be
:27:23. > :27:28.able to see the Milky Way from here, but like 90% of the UK, we can't.
:27:28. > :27:32.We decided to give every single person the challenge of turning off
:27:32. > :27:42.every single light. Last week we cent mark down there to help to
:27:42. > :27:43.
:27:43. > :27:48.make it happen. With 40 shops and cafes, three pubs, a sports ground
:27:48. > :27:52.and all those houses, there was plenty to do. There are literally
:27:52. > :27:56.thousands of lives here and it will take some serious powers of
:27:56. > :28:00.persuasion to get everybody on board. There are also some
:28:00. > :28:03.technical hurdles. As it turns out, most of the street lights are
:28:03. > :28:07.controlled individually by automatic light sensors, so there
:28:07. > :28:11.is no big button that we can use to turn them all off. This challenge
:28:11. > :28:17.will not be easy but if it works, it will really bring this community
:28:17. > :28:21.together. We might even get to see the night sky as nature intended.
:28:21. > :28:26.The last couple of weeks, Mark has been trying to spread the word
:28:26. > :28:29.among the inhabitants of Dulverton. How is that going? It has been a
:28:29. > :28:35.challenge, I will say that, but the people in Dulverton seem to be
:28:35. > :28:43.getting on board with it. I have had posters, fly is a letter boxes,
:28:43. > :28:50.and even shops putting up special displays, including a space cake. -
:28:50. > :28:55.- flyers in letterboxes. They probably think you are weird. What
:28:55. > :28:58.is the chance of success? We have to rely on everybody. Not just the
:28:58. > :29:04.council, the shops, but on everyone doing their thing. Until tomorrow
:29:04. > :29:09.night, we just don't know. Mark will be going down to Somerset to
:29:09. > :29:13.persuade the town before coming live from doll that in itself for
:29:13. > :29:18.the big switch off tomorrow night. If you are from there, he is
:29:18. > :29:24.legitimate! It is not just a massive burglary heist. Don't take
:29:24. > :29:29.him out of town! Aside from the amazing array of planets, stars and
:29:29. > :29:34.galaxies, occasionally things crop up that do not make sense. Look at
:29:34. > :29:43.his picture. If you think it is a UFO, you should have already turned
:29:43. > :29:48.over to Celebrity Big Brother! Having said that, why she is -- my
:29:48. > :29:58.machine is not working. It is not too bad. Apart from the faeces that
:29:58. > :30:03.the seagull is dropping behind him. That is the giveaway. UFOs
:30:03. > :30:13.generally do not drop faeces. How come so many people are seeing
:30:13. > :30:15.
:30:15. > :30:23.There are some things that just seemed to belong in Hollywood movie.
:30:23. > :30:26.And not on roads in Wiltshire. But this is a surprising statistic. One
:30:26. > :30:36.in five people in Britain are convinced that aliens have visited
:30:36. > :30:43.
:30:43. > :30:48.In fact, the government took sightings of UFOs sufficiently
:30:48. > :30:53.seriously that until 2009, the MoD had a department investigating them.
:30:53. > :30:59.Over 11,000 cases were examined by MoD staff. David Clark has been
:30:59. > :31:05.studying them, and he wins a prize for best job title of the show.
:31:05. > :31:09.have got reports from police officers, coastguards, military air
:31:09. > :31:15.crew. And some quite silly reports from people who have seen things
:31:15. > :31:21.whilst leaving the pub and that kind of thing. A couple of sighting
:31:21. > :31:26.stand out. In 1996, a strange light was spotted in the sky above
:31:26. > :31:29.Skegness in Lincolnshire. It was made all the more credible by the
:31:30. > :31:34.fact that the key witnesses in this case were police officers. In the
:31:34. > :31:38.end, one of the police officers went on to the top of the police
:31:38. > :31:42.headquarters in Boston and started making a film. The police alerted
:31:42. > :31:48.the RAF, who saw an odd blip on their radar which stayed there for
:31:48. > :31:52.hours. The UFO caused such a step, the newspapers had a field day.
:31:52. > :31:57.Another strange case was that of Alex Bird, who took this photograph
:31:57. > :32:01.in Sheffield. It was examined by intelligence officers, there was a
:32:01. > :32:07.full report produced. Quite something for a 14-year-old lad in
:32:07. > :32:10.the 1960s. By an eerie coincidence, Alex was privy to another UFO
:32:10. > :32:15.sighting when he took this photograph, more than 40 years
:32:15. > :32:19.later, of Retford Town Hall in Nottinghamshire. When he got home,
:32:19. > :32:23.he was looking at the negatives and he could not believe it, on one of
:32:23. > :32:28.the images, there is a classic flying saucer, by the side of the
:32:28. > :32:32.town hall. It is clear that many perfectly normal members of the
:32:32. > :32:35.public are spotting UFOs all over the place, but not everybody is
:32:35. > :32:39.convinced they have everything -- anything to do with aliens visiting
:32:39. > :32:43.Earth. There are many things we don't fully understand about the
:32:43. > :32:49.atmosphere. Just because you don't know what something is, doesn't
:32:49. > :32:54.mean it is a flying saucer, or an alien spacecraft. It may simply be
:32:54. > :33:01.something we don't understand. to expect aliens to even reach
:33:01. > :33:05.Earth is asking quite a lot. Most people have very little idea of the
:33:05. > :33:10.enormous distances between the stars. We are talking like Cheers.
:33:10. > :33:16.At our current rocket speed, it would take tens of thousands of
:33:16. > :33:19.years for our own spacecraft to go outside of our solar system and
:33:19. > :33:27.reach another star system. We have no reason to believe there would be
:33:28. > :33:37.any other civilisation with many, many light years of Earth. If we
:33:37. > :33:41.are not seeing aliens, what are we seeing? In the case of the Boston,
:33:41. > :33:45.it is rather embarrassing. They consulted the Greenwich Observatory
:33:45. > :33:49.and their opinion was from the directions and times, what the
:33:49. > :33:53.police had not -- observed was the bright planet, Venus, which was
:33:53. > :33:59.really prominent in the sky at the time. This is quite a common
:33:59. > :34:06.mistake. Venus is known as the Queen of the LSO's -- de UFOs,
:34:06. > :34:11.because it is often mistaken for something mysterious. It was
:34:11. > :34:17.concluded that Alex Birch's UFOs were most likely ice crystals, and
:34:17. > :34:21.the one in Red that was most likely caused by a more Strood drop it on
:34:21. > :34:28.his camera lens -- Moorish Je drop it. Some are also as a result of
:34:28. > :34:33.the latest military hide where. Their forces are often
:34:33. > :34:39.experimenting with new technologies and they can be 10 or 20 years
:34:39. > :34:43.ahead of what you see on the news. I favour it was this one by NASA,
:34:43. > :34:50.launched in 1961 -- my favourite. It was a vast spherical metal
:34:50. > :34:55.balloon which was launched into the upper atmosphere, used to bounce
:34:55. > :34:58.communications from one part of the world to another. For decades, the
:34:58. > :35:05.military have been flying exotic objects around the site, and they
:35:05. > :35:09.are still doing it. By the 1980s, much of the US Air Force's
:35:09. > :35:14.technological research was going into stealth aircraft, and the
:35:14. > :35:18.enormous Stealth bomber. By the time the Stealth aircraft had been
:35:18. > :35:22.publicly revealed, it is probably no coincidence that the general
:35:22. > :35:29.trend in UFO sightings was moving away from the circular disc,
:35:29. > :35:32.towards something that was more triangular in shape. And a lot of
:35:32. > :35:37.UFO reports are down to people simply not knowing what is in the
:35:37. > :35:41.night sky. Satellites for example. There is a group of satellites,
:35:41. > :35:45.they are communication satellites in very high orbits. Most of the
:35:45. > :35:49.time you don't see them but often - - every so often they catch the
:35:49. > :35:52.light of the Sun for 10 or 15 seconds. Anyone looking at that,
:35:52. > :35:57.seeing it get brighter, might think it is something coming straight
:35:57. > :36:00.towards them, and then as it faded they might think it had turned
:36:00. > :36:06.around and whizzed away, but it is the satellite going across the sky
:36:06. > :36:10.and catching the light of the Sun for 10 or 15 seconds. Satellites,
:36:10. > :36:16.water drops, planets, secret military planes, that is that
:36:16. > :36:20.settled, then, hey? No matter how many cases you explain, people will
:36:20. > :36:28.always be seen something new and asking for an explanation. I don't
:36:28. > :36:32.think UFOs will ever really die. We may mention more about UFOs and
:36:32. > :36:36.aliens tomorrow. An apology on behalf of my colleague, Celebrity
:36:36. > :36:40.Big Brother does not start until nine. He is not the professor of
:36:40. > :36:43.everything! Liz Bonnin got an amazing view of the closest port
:36:44. > :36:47.galaxy to earth and now she has moved to a larger telescope to get
:36:47. > :36:52.a more detailed look -- closest dwarf galaxy.
:36:52. > :36:58.We are in the control room of SALT with ape Peter who we met last
:36:58. > :37:02.night. -- with Petri Vaisanen. Tell us what that SALT image is there.
:37:02. > :37:06.We were looking at this contracting colliding galaxy about 400 million
:37:06. > :37:10.light years away. It is a major galaxy, smaller than the Milky Way
:37:10. > :37:17.but bigger than the magellanic clouds. How do galaxies get that
:37:17. > :37:20.big? They grow by accumulating smaller galaxies around them,
:37:20. > :37:24.eating up other galaxies. The bigger the galaxy, the faster it
:37:24. > :37:31.will grow. Little galaxies are coming up to bigger ones but bigger
:37:31. > :37:36.ones interact and merge. This is of colliding galaxies? That is right.
:37:36. > :37:41.They are two major galaxies, and a small reward in interaction and
:37:42. > :37:45.basically a collision. -- smaller one. The individual stars did
:37:45. > :37:49.actually collide, they are too far apart from each other, they are
:37:49. > :37:53.very small -- don't actually collide. The gas and dusts collides
:37:53. > :37:59.and when that compresses, new stars are born. The more violent the
:37:59. > :38:05.interaction is, the more spectacular starburst you get.
:38:05. > :38:10.is a beautiful image but you are interested in more? Yes, we take
:38:10. > :38:13.spectra and from that a lot of the science comes. We can measure
:38:13. > :38:17.masses and their star formation history is, and try to piece
:38:17. > :38:23.together where they came from, where they went, how they changed.
:38:23. > :38:27.Fascinating, thank you very much. Another SALT astronomer is Steve
:38:27. > :38:31.Crawford. I believe the Milky Way is on a collision course with
:38:31. > :38:35.Andromeda, is that right? That is true. They are expected to merge
:38:35. > :38:42.together in about four and a half billion years. Not too soon, what
:38:42. > :38:45.is going to happen? If we look at the simulation, we can see the two
:38:45. > :38:50.spiral galaxies merging together for top they are literally going to
:38:50. > :38:57.pass through each other? What is going to happen to our solar system
:38:57. > :39:00.and Planet Earth? It depends on where in the Milky Way It -- where
:39:00. > :39:07.in the solar system the Milky Way is, it could be floating out into
:39:07. > :39:11.deep space. What will the resulting galaxy look like? They will form
:39:11. > :39:19.together to make a new elliptical galaxy. What are we going to call
:39:19. > :39:24.it? Milkdromeda? What do you reckon? I might go with Andromeda's
:39:24. > :39:28.milkshake! It is a really good name! I don't think we have to
:39:28. > :39:33.worry about it quite yet. Coming up tomorrow, or we are going to go
:39:33. > :39:37.right across the plateau to check out this, it is called Superwasp,
:39:37. > :39:41.super wide angle search for planets. It has found 75 exo planets and is
:39:41. > :39:46.looking for more as we speak. I will be finding out how that works
:39:46. > :39:52.tomorrow. See you then. Thank you. We will also find out
:39:52. > :39:57.how our search for a planet has gone. Let's go back to see how Mark
:39:57. > :40:03.and the observers are getting on. John has had a great time but he
:40:03. > :40:06.has had to head back into the studio. The skies are still clear
:40:06. > :40:10.for the second night running, which is remarkable. The guys have been
:40:10. > :40:16.taking some beautiful images and joining me is Steve from the Mac
:40:16. > :40:24.has filled astronomers society, he has taken a beautiful image -- the
:40:24. > :40:29.Macclesfield. It is an assembly of 109 of the 110 Messier 83 objects
:40:29. > :40:32.because one of them is never visible from my back garden. As the
:40:32. > :40:36.seasons have rolled by, I have made a conscious effort to try to
:40:36. > :40:41.capture the more obscure ones in a digital camera, attached to a
:40:41. > :40:44.telescope. Whilst my sky conditions are orange and challenging, overall
:40:44. > :40:49.I am plight -- quite pleased with the result. From the back garden,
:40:49. > :40:54.it is incredible. Stay tuned for Back To Earth, where I have a guide
:40:54. > :41:04.to find what -- to show what you can find in the night sky. But with
:41:04. > :41:09.Thank you, the cleverness of the skies has been a real treat but
:41:09. > :41:16.things are different tonight -- clear theirs. Thicker cloud has
:41:16. > :41:22.spread in. ICloud dulling the sky in one or two spots, you will have
:41:22. > :41:27.to get out quickly -- high cloud, dulling the sky. We are going to
:41:27. > :41:30.see those cloud layers spread southwards and eastwards, bringing
:41:30. > :41:35.mist and rain for the most part. By the end of the night, before the
:41:35. > :41:39.sun gets up, you might get clear skies into the north-west of
:41:40. > :41:43.Scotland. It is a case of getting out early if you can for tonight.
:41:43. > :41:47.Tomorrow we split the country into two. Southern parts of England and
:41:47. > :41:57.Wales, a lot of cloud with outbreaks of rain. North Wales,
:41:57. > :42:05.
:42:05. > :42:09.Midlands, East Anglia, you might One of the biggest questions is how
:42:09. > :42:13.the Milky Way was formed. We asked Oxford University to do something
:42:13. > :42:16.they have never done on this scale before, to run a computer
:42:16. > :42:21.simulation to show how it started from the beginning of time from the
:42:21. > :42:25.Big Bang, how our galaxy formed. Fiat to show us the result is Dr
:42:25. > :42:31.Andrew Pontzen, this is not a simple task -- here to showers were
:42:31. > :42:38.that it is not. We started with programming a computer with simple
:42:38. > :42:42.physics. We then set up the computer with what we think the
:42:42. > :42:49.universe look like near the big bang. So you say the basic laws and
:42:49. > :42:57.you press go? That is basically it. So the earlier slide we can see in
:42:57. > :43:02.years after the Big Bang. Yes, it had tiny ripples in it which we
:43:02. > :43:12.think came from quantum processes at the start. This is the beginning
:43:12. > :43:13.
:43:13. > :43:16.Talk us through what we are seeing now. You are seeing the matter that
:43:17. > :43:20.started out being quite uniformly spread out, it is starting to clump.
:43:20. > :43:26.As well as the whole universe expanding, it is forming comes out
:43:26. > :43:29.of what was originally quite smooth. What is the green? I have coloured
:43:29. > :43:35.it green because it is dark matter so normally would not be able to
:43:35. > :43:40.see it at all. But we can pick out anything in the virtual universe.
:43:40. > :43:45.We have picked it out in green. have frozen 1.7 billion years after
:43:45. > :43:50.the Big Bang. Dark matter, we should talk about that a bid. The
:43:50. > :43:54.universe is dominated by staff that is not this. Yes, something like
:43:54. > :44:00.four fifths of the stuff, we think, is not like the stuff that you and
:44:00. > :44:04.I are made out of. We can infer its presence, we are fairly certain how
:44:04. > :44:10.much there is. We can measure it through the cosmic microwave
:44:11. > :44:15.background. What we are seeing is the visible matter. That is right.
:44:15. > :44:20.We have switched and the faint blue stuff is gas, the white stuff is
:44:20. > :44:24.stars. If he did not run this would be dark matter in the simulation,
:44:24. > :44:29.would it work -- you did not? you would not see this. There would
:44:29. > :44:36.not be a big enough gravitational pull. We need the dark matter to
:44:36. > :44:40.create the galaxies. Yes. We can roll the clock on again. I think we
:44:40. > :44:47.keep it frozen for a moment. We are zooming in. The blobs might have
:44:47. > :44:53.looked like single stars, they are many galaxies, they have up to 100
:44:53. > :44:58.million stars in their -- meanie galaxies. We can see that all of
:44:58. > :45:06.these are surrounded, we call them halos of dark matter. We have these
:45:06. > :45:16.irregular shaped things that have already formed, the real matter is
:45:16. > :45:17.
:45:17. > :45:21.Yes, when we see what happens next, the dark matter controls it. The
:45:21. > :45:26.little galaxies all merged together. What is notable about this process
:45:26. > :45:31.is that it carries ongoing. It is not just that a few little galaxies
:45:31. > :45:35.come together and that is a galaxy, it carries on happening. This is
:45:35. > :45:38.the history of our galaxy through time. We started as a small clump,
:45:38. > :45:48.then we mashed with other ones, spinning around to create larger
:45:48. > :45:51.galleries. -- galaxies. Yes. And if we skip to the present day, we can
:45:51. > :45:59.see enormous spiral galaxy and fly in to see what it looks like from
:45:59. > :46:02.inside. This is a simulation of the creation of the universe. You have
:46:03. > :46:07.put in some basic physics, basic data about the distribution of dark
:46:07. > :46:11.matter and you have pressed go. You sit there and this galaxy emerges,
:46:11. > :46:15.looking like the Milky Way. This is a picture of the real Milky Way,
:46:15. > :46:18.and if we cross fade them, you can see how similar it is. It is a
:46:18. > :46:24.testament to the power of what we know from basic physics that we can
:46:24. > :46:29.do this. That is the simulated Milky Way and that is the real one.
:46:29. > :46:32.Are we leaving anything out of this model? Yes, there are certainly
:46:32. > :46:37.things that we do not fully understand at the moment. We have
:46:37. > :46:41.black holes in there. We don't really understand fully what we are
:46:41. > :46:46.doing with those black holes. are one of the big unknowns in the
:46:46. > :46:51.galaxy formation. That is because nobody has ever seen one. How do we
:46:51. > :46:54.know for sure that they definitely exist?
:46:54. > :47:04.Ask any physicist about black holes and they will tell you that they
:47:04. > :47:04.
:47:04. > :47:09.exist. But I could say there is the Unicorn in these would lens, and
:47:09. > :47:14.you would rightly say that there is not because you cannot see it. --
:47:14. > :47:17.this woodland. I could say that it is there but it is invisible and
:47:17. > :47:22.you would probably think I was daft at best. But what is the difference
:47:22. > :47:28.between my imaginary Unicorn and a black hole? But goals by definition
:47:28. > :47:32.are invisible. You cannot see them so how do we know they exist? --
:47:32. > :47:36.black holes are by definition invisible. The first clue that
:47:36. > :47:42.black holes are real came from here, in the Cambridgeshire countryside.
:47:42. > :47:46.It was in the 1950s. While the rest of the country was this thing into
:47:46. > :47:56.wireless radio at home, out here they were listing into a different
:47:56. > :47:57.
:47:57. > :48:01.radio signal. Radio signals from outer space. This is the mallard
:48:01. > :48:05.Radio Observatory. Back in the 1950s some of the first radio
:48:05. > :48:15.telescopes in the world were built here. When they turned them to the
:48:15. > :48:29.
:48:29. > :48:33.Nobody could work out what it was and what it was coming from.
:48:33. > :48:37.Imagine that this thought is a beam of radio waves. Telescopes in the
:48:37. > :48:41.1950s could detect radio sources in the sky. They could tell roughly
:48:41. > :48:46.where the beams were coming from. Somewhere over there. But they
:48:46. > :48:53.could not tell precisely. Then an of astronomer at the very clever
:48:53. > :48:58.idea indeed. -- had a very clever idea indeed. He knew that on 25th
:48:58. > :49:04.August, 1962, the Moon would be in the same patch of sky as the radio
:49:04. > :49:09.source. So he watched and he waited and he saw that as the moon
:49:09. > :49:15.travelled across the sky, it went in between the Earth and the radio
:49:15. > :49:22.source, and carted off. Then as it continued its journey across the
:49:22. > :49:28.sky, the radio source reappeared. By measuring precisely when the
:49:28. > :49:34.been disappeared and appeared, the astronomer was able to pinpoint
:49:34. > :49:38.precisely the source of the beam. It was tracked to what looked like
:49:38. > :49:44.a faint star in the constellation Virgo. One tiny dots of light among
:49:44. > :49:51.the millions of others in the sky. This is an image of that piece of
:49:51. > :49:55.sky. That point of light just there is the source of the radio signal.
:49:55. > :50:01.Pretty much every point of light that you can see in this image is a
:50:01. > :50:07.star inside our galaxy, inside the Milky Way. But this point of light,
:50:07. > :50:15.the origin of that radio signal, is 3 billion light years away. And yet
:50:15. > :50:21.it can still be seen. No star could shine that brightly. So what could
:50:21. > :50:31.that possibly be? The astronomers called it acquired the stellar
:50:31. > :50:33.
:50:33. > :50:36.object, quasar for short. -- Scientists could only think of one
:50:36. > :50:40.way that stars could appear that bright, and that is if they were
:50:40. > :50:43.falling into a black hole. Stars falling into a black hole would be
:50:43. > :50:51.completely ripped apart. Gas and dust would be torn from their
:50:51. > :50:54.services as they spiral inwards at tremendous speeds. They would in it
:50:54. > :50:59.so much radiation that it could be seen right across the universe and
:50:59. > :51:02.that would mean we could detect it on earth. -- they would emit
:51:02. > :51:08.radiation. The astronomers in Cambridge realised that the quasar
:51:08. > :51:15.that they were seeing was actually a black hole, a giant black hole,
:51:15. > :51:17.and the light and radio waves were coming from entire stars having
:51:17. > :51:25.light and dust ripped off them and spiralling to destruction inside
:51:25. > :51:30.the black hole. Over 100,000 quasars have now been discovered.
:51:30. > :51:35.All are thought to be super massive black holes, actively feeding on
:51:35. > :51:40.stars. And all of them are found in exactly the same place, right in
:51:40. > :51:45.the centre of galaxies. So does that mean there is a black hole at
:51:45. > :51:49.the centre of every galaxy? Our galaxy, the Milky Way, could not
:51:49. > :51:54.have a quasar like the one discovered in Cambridge because we
:51:54. > :51:59.would see it. It would shine as brightly as the full moon, visible
:51:59. > :52:03.in the daytime. But imagine a black hole that had eaten all the nearby
:52:03. > :52:09.star systems, so there is no gas and dust to spiral own and no
:52:09. > :52:18.radiation to make it bright. So it could still be that there is a
:52:18. > :52:22.super massive black hole at the heart of the Milky Way. One group
:52:22. > :52:28.of scientists spent 16 years painstakingly searching for it.
:52:28. > :52:32.This is what they found. I think this is one of the most remarkable
:52:32. > :52:38.graphics in recent scientific history. It is a picture of the
:52:38. > :52:42.centre of our galaxy and the stars that orbit around it. In a two
:52:42. > :52:50.stars that you can see are orbiting very fast around some central
:52:50. > :52:54.object. They reach speeds of around 11 million mph. When you plot the
:52:54. > :52:59.orbits out precisely, you can calculate the mass of the object
:52:59. > :53:03.that they are orbiting around. It turns out that the mass of that
:53:03. > :53:08.object is 4 million times the mass of the sun. But it is more than
:53:08. > :53:16.that, because you can also work out the maximum size that it can be. In
:53:16. > :53:21.a star get close to that central object, as close as Neptune gets to
:53:21. > :53:27.the sun. We have an object 4 million times the mass of our son,
:53:27. > :53:32.compressed into a space smaller than our solar system. And it is
:53:32. > :53:38.invisible. The only thing that could be is a black hole. The
:53:38. > :53:42.centre of our galaxy. Black holes started out in the imagination of
:53:42. > :53:47.physicists. But we now have evidence to prove that they are
:53:47. > :53:55.real. Not only do black holes exist, but we now suspect that they formed
:53:55. > :53:59.the heart of nearly every galaxy in the universe. Including arrow. --
:53:59. > :54:02.including our own. Someone up there we know there is a super massive
:54:02. > :54:06.black hole at the centre of our galaxy and the solar system is
:54:06. > :54:12.orbiting around it. Why do we orbit around a black hole? We need to
:54:12. > :54:17.explain how gravity works. This is the theory of relativity and it
:54:17. > :54:21.showed us this. It was the interaction of a planet and how we
:54:21. > :54:25.twisted the space around it. This is traditionally shown by
:54:25. > :54:30.physicists by using spandex. wondered where my trousers had
:54:30. > :54:34.gone! It is a large mass and it twists the space around it.
:54:34. > :54:38.Something going past it is sent off course. Einstein said that things
:54:38. > :54:42.follow a straight line through space and time. Mass is curved
:54:42. > :54:45.space and time, so if you do not know that the space and time is
:54:45. > :54:49.curved and you are travelling through it, then it will look to
:54:49. > :54:52.you that you have curved around the mass. If you enter the density at
:54:52. > :54:57.the right speed, you will be spinning round and round, and that
:54:57. > :55:05.is what an orbit is. You can think of Einstein's gravity as a
:55:05. > :55:11.fictitious force, at the space and time be incurred by massive -- be
:55:11. > :55:16.incurred by massive objects. This is the curve that you get from a
:55:16. > :55:20.black hole. The black hole curves the space so far, that when
:55:20. > :55:24.something approaches bit... This could be a photon, a particle of
:55:24. > :55:28.light. What happens in a black hole is that the photon approaches and
:55:28. > :55:33.it cannot escape when it crosses the boundary, which is called the
:55:33. > :55:37.event horizon. Eyes and's theory predicts that if you get close to
:55:37. > :55:41.the centre of the black hole, which is caused the singularity,
:55:41. > :55:45.infinitely dense, infinitely small, space and time are infinitely
:55:45. > :55:48.curved, and the theory itself breaks down. This is probably the
:55:48. > :55:53.most fascinating thing about black holes on the physicist's
:55:53. > :55:59.perspective. The best theory we have, the theory of relativity,
:55:59. > :56:05.predicts its own demise somewhere down there. Spandex cannot read as
:56:05. > :56:14.much as space can, of course. -- cannot stretch. There is literally
:56:14. > :56:18.no way out for anything. Yes. Tim O'Brien, associate director here,
:56:19. > :56:28.has been telling us that that holes a one of the specialist subjects
:56:28. > :56:35.here. -- black holes of one of the specialist subjects. Yes. This is
:56:35. > :56:39.the Hubble telescope. And some other telescopes. This is a radio
:56:39. > :56:42.image of the sky. We can see through the dust cloud that block
:56:42. > :56:52.our view of the centre of the galaxy. In the middle, that is
:56:52. > :56:58.Sagittarius, the black hole. This is new research, essentially.
:56:58. > :57:02.just last week. The quasar is in the middle and this is the optical
:57:02. > :57:07.view, the black dot in the middle. We can zoom in and look at the
:57:07. > :57:11.radio image. Where the black hole is the bright spot in the middle.
:57:11. > :57:17.The thing that shoots off to the left is a jet of particles we think
:57:17. > :57:21.out from the black hole, almost at the speed of light. -- rushing out
:57:21. > :57:25.from the black hole. The shape of it is like a corkscrew. It is
:57:25. > :57:31.spinning like that. One way in which that might happen would be if
:57:31. > :57:35.this were the result of a merger between two galaxies. When the
:57:35. > :57:40.galaxies merge, the two black holes end up whipping around each other
:57:40. > :57:45.and that causes this. Do they fall into each other over time? Yes.
:57:45. > :57:49.They will. They spiral closer together. They create ripples in
:57:49. > :57:53.space and time, predicted by Einstein. Not yet directly detected
:57:53. > :57:58.but we are working on that with this telescope across Europe.
:57:58. > :58:02.of the most remarkable things about these images, these experiments, is
:58:02. > :58:06.that we are trying to look for a breakdown in relativity. The
:58:06. > :58:11.breakdown in Einstein's theory. For me this is what science is all
:58:11. > :58:16.about. We are trying to test our theory to destruction. We have
:58:16. > :58:21.discussed this for a long time. The show carries on for another half an
:58:21. > :58:26.hour in this very room and you can ask more questions. We need help to
:58:26. > :58:31.fight our own exo-planet. 60,000 of you have taken part so far and the
:58:31. > :58:40.more of you that take part, the more likely it is that we will find
:58:40. > :58:43.one. You can download your star guide from the website. We are
:58:43. > :58:50.going off and now here but we are coming back on in 10 seconds to go
:58:50. > :58:55.and sit over there. -- going off- air. We will be talking about black
:58:55. > :59:00.holes and you can send in your questions for us to answer. Jon