0:00:13 > 0:00:20and we might even get a proper Welcome to Back to Earth. Luckily,
0:00:20 > 0:00:29we have an extra half-hour to contemplate 13.7 billion years of
0:00:29 > 0:00:35the universe! 13.75. Not 15. We want you to join in, too. If you
0:00:35 > 0:00:43have a cosmic query, send it in at stargazing@bbc.co.uk. We have
0:00:43 > 0:00:53Professor Brian Cox, Dr Joanna Dunkley, Dr Tim O'Brien, Professor
0:00:53 > 0:01:03
0:01:03 > 0:01:11Ed Copeland and Phill Jupitus. Where did you learn your cosmology?
0:01:11 > 0:01:15Episode of Futurama. It was a very good one. Really? There was a Big
0:01:15 > 0:01:21Bang and every particle fades to dark matter and then it starts all
0:01:21 > 0:01:26over again. Have Futurama done what we wanted to do in 24 minutes?
0:01:26 > 0:01:36little less detail. OK. That is shattering(!) Can I give you all a
0:01:36 > 0:01:38
0:01:38 > 0:01:45drink? We always do. You have yours. This is excitingly a space beer.
0:01:45 > 0:01:52Space stout! When you are in space, your tastebuds don't work as well.
0:01:52 > 0:02:02It should taste quite strong. what I did there? Space stout!
0:02:02 > 0:02:03
0:02:03 > 0:02:07have tested it. They have gone on to one of the planes? People
0:02:07 > 0:02:15drinking weightlessly! LAUGHTER They are very happy. How does it
0:02:15 > 0:02:21taste? It doesn't taste of anything at all! They have said, "You are in
0:02:21 > 0:02:31space, you can't taste anything!" It is very nice. We also have
0:02:31 > 0:02:41coming down the line from NASA's Jet Propulsion Laboratory Eric Idle.
0:02:41 > 0:02:42
0:02:42 > 0:02:48How are you? I'm very well, thank you. Can you hear me? We can. You...
0:02:48 > 0:02:57I want... No, this will go on for a while now! LAUGHTER What? Yeah.
0:02:57 > 0:03:02What? Yeah. OK. My name is on the Curiosity Rover. My name is on
0:03:02 > 0:03:04there. It certainly is. Very good. We will come back to you. We have
0:03:04 > 0:03:12issues of cosmology and space science that we want to discuss
0:03:12 > 0:03:20with you later on. Is that all right? I'm the natural expert to
0:03:20 > 0:03:29ask(!) LAUGHTER By the way, you have a beer as well, don't you?
0:03:29 > 0:03:36do! Thank you very much. Thank you. They call it "the vomit comet" I
0:03:36 > 0:03:44think. We will be back with Eric later. Can I come to you? Why was
0:03:44 > 0:03:50that number that you got 15 rather than 13.7? Anyone who tweeted 13.75
0:03:50 > 0:04:00billion cheated and looked it up on Wikipedia. Oh! Some of them might
0:04:00 > 0:04:08
0:04:08 > 0:04:18have made a genuine mistake. If you take the Hubble constant as 70
0:04:18 > 0:04:20
0:04:21 > 0:04:29kilometres km/s/Mpc. If you did the sums, you would get 15 billion. It
0:04:29 > 0:04:39wasn't a trick question. It was can you follow instructions? It's lucky
0:04:39 > 0:04:41
0:04:41 > 0:04:44it was a good approximation. Are we blaming dark energy for this?
0:04:44 > 0:04:48There is another aspect to this which is important in cosmology.
0:04:48 > 0:04:52You are dealing with such huge numbers. How have you got any idea
0:04:52 > 0:04:57whether you are right or wrong? That ability to make a quick
0:04:57 > 0:05:02estimate of things is a useful tool to have at hand. It is a remarkable
0:05:03 > 0:05:09thing. By doing some simple maths, based on simple observations, you
0:05:09 > 0:05:14can get an estimate for the age of the universe. If we said, "Work out
0:05:14 > 0:05:22how old everything is." It is a difficult problem. It is quite easy
0:05:22 > 0:05:28to solve in a sense. If I went back to my Mum and said, "The universe
0:05:28 > 0:05:32is 15 billion "she would go, "Excellent." It was formed on what
0:05:32 > 0:05:36day? LAUGHTER That is what she would want to know. Was it
0:05:36 > 0:05:44Wednesday? Was it Wednesday? long is it till we have that level
0:05:44 > 0:05:50of precision? I don't think we will have that level of precision!
0:05:50 > 0:05:56Planck will help us more. You would turn up on the wrong week! Loads of
0:05:56 > 0:06:00questions coming in. Many are asking this. What is the universe
0:06:00 > 0:06:05expanding into? This is a great question. It is not expanding into
0:06:05 > 0:06:07anything. When you think of that, you maybe think of the Big Bang as
0:06:07 > 0:06:11happening in one place and everything expanding from that
0:06:11 > 0:06:16point. Then it has an edge and you say, "What happens beyond that
0:06:16 > 0:06:21edge?" That is not how space is. We think it is expanding everywhere.
0:06:21 > 0:06:27It has no edges. One of the big problems - I shouldn't blame TV for
0:06:27 > 0:06:31things - we see these pictures... Not on TV! We see these pictures of
0:06:31 > 0:06:35the Big Bang as an explosion. that one. Like the left-hand edge
0:06:35 > 0:06:40of that where there is a flash of light. In a sense, that is telling
0:06:40 > 0:06:45us we are looking at this explosion from the outside. In fact, we are
0:06:45 > 0:06:52inside the explosion. So it is not possible to have that God's eye
0:06:52 > 0:06:56view of the Big Bang. It's unsatisfactory. I get asked that
0:06:56 > 0:07:01question a lot. Space, time began at that point, you are not allowed
0:07:01 > 0:07:06to ask questions like what happened before? Are we to really believe or
0:07:06 > 0:07:13do we really believe that is the situation? There is no cause for
0:07:13 > 0:07:18this thing. Could it be there is a cause for the Big Bang? You are not
0:07:18 > 0:07:25being very fair. Every question you are giving me, I don't know the
0:07:25 > 0:07:32answer! Phill?! LAUGHTER One thing you can say - this issue over the
0:07:32 > 0:07:37singularty at the beginning is a real e-- singularity at the
0:07:37 > 0:07:43beginning is a real effect. The hot Big Bang Model had to end up with a
0:07:43 > 0:07:53singular point at what you would think of as the star. Hawking did
0:07:53 > 0:07:55
0:07:55 > 0:08:00this when he was 21. Don't hate the player! LAUGHTER Of course, we also
0:08:00 > 0:08:08know that our mathematics breaks down. We can't trust what is going
0:08:08 > 0:08:15on there. So it could be that something else, some quantum effect,
0:08:15 > 0:08:19some quantum gravity-type effect has come into play at that point
0:08:19 > 0:08:23and maybe the universe has indeed popped out in a very natural way
0:08:23 > 0:08:33from some process. We don't yet know what it is. There are models
0:08:33 > 0:08:41out there that people have put forward. Hawking got one. There are
0:08:41 > 0:08:48other models which are cyclical. Lots of people love that. It breaks
0:08:48 > 0:08:54lots of energy conditions which are usually assumed with general
0:08:54 > 0:09:02relativity. I don't know your wife. Is it important that that is her
0:09:02 > 0:09:08favourite? How many of you like that idea? One! LAUGHTER I like the
0:09:08 > 0:09:13idea. There are big problems with this initial moment. One of them is
0:09:13 > 0:09:17the old nature of the thing. In many of my most miserable
0:09:17 > 0:09:23programmes we talked about this idea where the universe falls to
0:09:23 > 0:09:28bits so it gets more and more disordered. More disordered set-ups.
0:09:28 > 0:09:33This is quite a disordered thing we have now. More disordered set-ups
0:09:33 > 0:09:36are more likely. People have said to me, "That means, if you wanted
0:09:36 > 0:09:41to have some random thing, it is more likely the universe began now
0:09:41 > 0:09:47than it is at any time in the past?" It was more ordered in the
0:09:47 > 0:09:52past. So you are not allowed to give these random ideas. That means
0:09:52 > 0:09:57it was more likely it popped into existence now and now and now!
0:09:57 > 0:10:02Every moment it gets more likely it popped into existence. All my
0:10:02 > 0:10:07memories are at random. We popped into existence now. There is no
0:10:07 > 0:10:17past. It is pretty unlikely. Those are big problems. How did it get
0:10:17 > 0:10:22
0:10:22 > 0:10:31into that ordered state? We are not going to answer that question! Dara
0:10:31 > 0:10:36has some fluff. Fluff?! We are going to go to some photographs.
0:10:36 > 0:10:42Mark, we have been inundated, haven't we? We are looking at stars
0:10:42 > 0:10:48so it is lovely to see this picture of the Sun taken by Robert Arnold
0:10:48 > 0:10:54yesterday. It was taken with a particular filter and it shows a
0:10:54 > 0:11:01fine level of detail. We have the Sun just there. The second picture
0:11:01 > 0:11:10was taken by Alan in October last year. It shows the star trails and
0:11:10 > 0:11:20a beautiful Aurora display. That was taken towards the end of last
0:11:20 > 0:11:21
0:11:21 > 0:11:30year. A beautiful picture of the Greater Orion Nebula. It is easily
0:11:30 > 0:11:36visible tonight. Keep them coming in. All the details on the website.
0:11:36 > 0:11:41A question from Logan. Do you think we will ever be able to warp space
0:11:41 > 0:11:51and travel faster than light? It will probably take too much
0:11:51 > 0:11:51
0:11:51 > 0:11:56energy to warp the space? Being lazy! No, a lot of energy. It is
0:11:56 > 0:12:00this whole idea that you have got to get from here to here and it is
0:12:00 > 0:12:06too far to go. The speed of light would take you forever. So you
0:12:06 > 0:12:12curve space and make those two points next to each other and jump
0:12:12 > 0:12:15through that gap. The amount of energy is extreme to do that.
0:12:15 > 0:12:20theoretically possible? What kind of energy are you talking about?
0:12:20 > 0:12:27Any mass in space bends it a bit. By being here, we are bending space
0:12:27 > 0:12:33a bit. And time. We don't weigh that much to make it really super-
0:12:33 > 0:12:39warped. There are solutions where you can connect these two regions
0:12:39 > 0:12:43with worm holes. As far as I can tell, as soon as you decide to go
0:12:43 > 0:12:53through it, the worm holes go unstable. They just disappear on
0:12:53 > 0:12:56
0:12:56 > 0:13:06you. How can a seven-year-old ask that question?! His parents would
0:13:06 > 0:13:07
0:13:07 > 0:13:14have been thrilled - "Don't ask me, ask Uncle Brian!" Ask Dara, you
0:13:14 > 0:13:24will get fluff! If you can do that, you will be
0:13:24 > 0:13:25
0:13:25 > 0:13:29able to build a Time Machine. It would be illogical. Stephen Hawking
0:13:29 > 0:13:36has a protection conjecture. cannot go backwards. You may
0:13:36 > 0:13:42possibly be able to go forwards in time. We travel in time. Every day.
0:13:42 > 0:13:47No, further than that. I want to travel in time. "You are right
0:13:47 > 0:13:55now!" LAUGHTER You can travel as far as you want into the future
0:13:55 > 0:14:00relative to other people. You could get into the 10,000 years, 50,000
0:14:00 > 0:14:06years into the future of Earth by getting on a spaceship and flying
0:14:06 > 0:14:16around very quickly. Yeah. If you could manage it! It is time for the
0:14:16 > 0:14:23
0:14:23 > 0:14:27Back to Earth brain-teaser brought Hello, I am K9. I am not the first
0:14:27 > 0:14:30non-human intelligence to have journeyed into space. Which of the
0:14:30 > 0:14:39following creatures were among the very first travellers to voyage
0:14:39 > 0:14:49around your moon? Monkeys, dogs, catalogues, Rack's or tortoises or
0:14:49 > 0:14:50
0:14:50 > 0:15:00So which one of those was the first to pass over the dark Side Of the
0:15:00 > 0:15:04
0:15:04 > 0:15:11Moon? Dog, cat, monkey, taught us? I would go cat. Monkey. Dog. I have
0:15:11 > 0:15:18no idea! That is the way guesses work, Brian! Scientists don't
0:15:18 > 0:15:25guess! Let's find out the answer from K9.
0:15:25 > 0:15:29Here is the answer. Two of the first Earth creatures to travel
0:15:29 > 0:15:36beyond the dockside of your moon were a pair of Russian steppe
0:15:36 > 0:15:41tortoises. They made the journey on 18th September 1968. As you might
0:15:41 > 0:15:46say, that is one a small step for mankind, one giant leap for a
0:15:46 > 0:15:52tortoise! Until tomorrow, master. Farewell.
0:15:52 > 0:15:57Thank you, K9. Always a treat to see him back. Would you want to go
0:15:57 > 0:16:05into space? I shouldn't mind a go at it, it has to be said, but you
0:16:05 > 0:16:12either go up and its -- and pay millions and millions or you become
0:16:12 > 0:16:20a cosmonaut. You do the one that goes up, the parabolic flights.
0:16:20 > 0:16:26They are quite manageable. Yeah, they just give you a sheet saying,
0:16:26 > 0:16:35this is a Russian for "excuse me". Because that is all... You have to
0:16:35 > 0:16:38leave now! Most of the space tourism flight some very short hops
0:16:38 > 0:16:48essentially into... Just at the very top of the atmosphere. 45
0:16:48 > 0:16:49
0:16:49 > 0:16:59minutes. You would need a playlist, I would presume. You mustn't forget
0:16:59 > 0:16:59
0:16:59 > 0:17:05to swipe your oyster card. That is so 4! Space oddity is the space pop
0:17:05 > 0:17:12tune. It has got to be. Would everyone pick that? It is either
0:17:12 > 0:17:16that or we are all made of stars. If you've got to go with David
0:17:16 > 0:17:21Bowie because it was his birthday yesterday. Yes, we already
0:17:21 > 0:17:27mentioned that. The one I haven't been able to get out of my head is
0:17:27 > 0:17:35Eric Idle's one. Hello, Eric, how are you? You have probably
0:17:35 > 0:17:45contributed the primary space song at the end of the -- at the end of
0:17:45 > 0:17:49The Meaning Of Life. Yes, that is right. But since we have ensured
0:17:49 > 0:17:56more detailed and accurate measurements but our knowledge
0:17:56 > 0:18:04keeps expanding. Let's have a reminder of one of the most
0:18:04 > 0:18:07insanely catchy songs. # Our galaxy itself contains 100
0:18:07 > 0:18:09billion stars. # It's 100,000 light years side to
0:18:09 > 0:18:12side. # It bulges in the middle, 16,000
0:18:12 > 0:18:15light years thick. # But out by us, it's just 3,000
0:18:15 > 0:18:18light years wide. # We're 30,000 light years from
0:18:18 > 0:18:21galactic central point. # We go round every 200 million
0:18:21 > 0:18:23years. # And our galaxy is only one of
0:18:23 > 0:18:33millions of billions. # In this amazing and expanding
0:18:33 > 0:18:44
0:18:44 > 0:18:47Brian how -- Brian, how much of that would you like to correct?
0:18:47 > 0:18:54Well, we did actually correct it together and we have written the
0:18:54 > 0:19:02song, which will be in my new series! Genuine a 27th of BBC Two
0:19:02 > 0:19:07at 8pm. -- 27th January. There is a wonderful list of things that you
0:19:07 > 0:19:13got wrong or has actually changed. One thing you admitted is that the
0:19:13 > 0:19:17sun is the source of all-out power. And he admitted to that? Well, that
0:19:17 > 0:19:22is because you gave me a lot of criticism for it because we wrote
0:19:22 > 0:19:27the song entirely with Brian and the entirely new lyrics are about
0:19:27 > 0:19:30the origins of life, not about biology, and also about the width
0:19:30 > 0:19:34and size and dimension of the universe as opposed to the galaxy
0:19:34 > 0:19:38because we now have some insight. And Brian would sit in a corner
0:19:38 > 0:19:45with a pencil saying, that is problematic, but is not enough
0:19:45 > 0:19:49stars! He would say, I think it is more like a million, billion stars.
0:19:49 > 0:19:53And then you have said it is only 30 billion light years from side to
0:19:53 > 0:20:02side yet some people say because of the time it has taken Hayes like to
0:20:02 > 0:20:07get here, the universe is now 190 billion light years! -- it has
0:20:07 > 0:20:12taken my ears. So he is not the easiest to write his song with!
0:20:12 > 0:20:19you tell us why you wrote the song? Were you out of France gazing at
0:20:19 > 0:20:24the sky and it inspired you to musical heights? -- out in France?
0:20:24 > 0:20:28Yes, I became obsessed with reality after working on Monty Python soil
0:20:28 > 0:20:33used to look at the Galaxy and the stars at night in France and a few
0:20:33 > 0:20:41glasses of pink wine and it makes you very cosmic! He Eric, was there
0:20:41 > 0:20:47any time in the process when you write in with Brian that you wanted
0:20:47 > 0:20:53to shake him and say, it is only a joke!? Are but he is always smiling
0:20:53 > 0:21:03so it is a joke anyway! Thank you for joining us. I know you are
0:21:03 > 0:21:03
0:21:03 > 0:21:08going to enjoy having a look around NASA there. Thank you so much. One
0:21:08 > 0:21:15of the most popular questions, and we are running out of time, from
0:21:15 > 0:21:21London, how cantinas expend -- how can the universe expand faster than
0:21:21 > 0:21:26the speed of light? You can't have any signals travelling faster than
0:21:26 > 0:21:32the speed of light so you can't travel and you can't communicate.
0:21:32 > 0:21:38You cannot tell one part to the other party has compost.
0:21:38 > 0:21:43mentioned inflation briefly and we think that has expanded way faster
0:21:44 > 0:21:47than the speed of light. These things you see in the Hubble Deep
0:21:47 > 0:21:52Field are moving faster than the speed of light but it is the space
0:21:52 > 0:21:59in between rather than be galaxies themselves physically or any other
0:21:59 > 0:22:06significant information. Chris and David say, how can the universe be
0:22:06 > 0:22:09both expanding and infinite? How can it start infinite? So the bit
0:22:09 > 0:22:15that is expanding his our observable universe. That is what
0:22:15 > 0:22:20is still expanding. And it is a very difficult concept, this idea
0:22:20 > 0:22:28of a spatially flat universe which is formally infinite, but we have
0:22:29 > 0:22:32our own horizon, are observable bit, which can expand beyond that.
0:22:32 > 0:22:39we have a suspicion because we know it goes way beyond that horizon and
0:22:39 > 0:22:43I think the most accurate measurement needed is one that
0:22:43 > 0:22:49implies it is spatially infinite. We can only measure that from the
0:22:49 > 0:22:53bit of the universe we can observe. It is hard to imagine an infinite
0:22:53 > 0:22:57universe but it is also hard to imagine a finite universe because
0:22:57 > 0:23:07then you have to imagine it is curved back on itself and there is
0:23:07 > 0:23:07
0:23:08 > 0:23:14an outside somewhere. Well, those doughnuts are there to demonstrate
0:23:14 > 0:23:24a very important cosmological point! So just eat them! I am
0:23:24 > 0:23:27
0:23:27 > 0:23:32talking! Here's Mark and his Starcast to show you how they found
0:23:32 > 0:23:36the Andromeda. It can be difficult to locate at
0:23:36 > 0:23:39first but it becomes easier with practice. Niqab the area about a
0:23:39 > 0:23:49third of the way up from the horizon to the point directly
0:23:49 > 0:23:51
0:23:51 > 0:23:55overhead. Start looking for the great Square of Pegasus. Despite
0:23:55 > 0:24:01being in the Great Square, this star is the brightest in the
0:24:01 > 0:24:11constellation of Andromeda. Then imagine an elongated and quite
0:24:11 > 0:24:16
0:24:16 > 0:24:26faint the letter pattern of stars. It is about halfway up the woman's
0:24:26 > 0:24:30
0:24:31 > 0:24:40body. It does take some practice to see but it is like a faint smudge.
0:24:41 > 0:24:48
0:24:48 > 0:24:50You can also moved up from If you can imagine the lower half
0:24:50 > 0:24:55is an arrowhead it points to the rough location of the Andromeda
0:24:55 > 0:25:01Galaxy. When you find it, you will be looking at a spiral galaxy like
0:25:01 > 0:25:10our own Milky Way. It is estimated to be around 260,000 light years
0:25:10 > 0:25:13across, more than double the size It contains approximately one
0:25:13 > 0:25:17trillion stars and it is heading our way on a collision course at
0:25:17 > 0:25:24about 70 miles per second but no need to panic because it won't hit
0:25:24 > 0:25:30us for another 4 billion years! If you want to get hold of one of
0:25:30 > 0:25:37Lucy's excellent Star Guide, go to the website.
0:25:37 > 0:25:44Back to Dara. He will probably talk over me
0:25:44 > 0:25:52anyway! We will be unveiling the model of the William Herschel
0:25:52 > 0:25:56telescope tomorrow. It is a real model. Yes. We will have more
0:25:56 > 0:25:59information on Mars. By the way, talking about Andromeda, and if you
0:25:59 > 0:26:09worried about whether it is going to collide with us, you can keep an
0:26:09 > 0:26:10
0:26:10 > 0:26:15eye on it. It is right there. So, we are OK! Gets and a live shot of
0:26:15 > 0:26:24Orion. We couldn't do this last night because we were draped in
0:26:24 > 0:26:30cloud. And that is the telescope we used last night to see the water.
0:26:30 > 0:26:36What's the other shot you had of the top? With the supernova?
0:26:36 > 0:26:42Betelgeuse. Top left. The top left corner. If we go out again for a
0:26:42 > 0:26:52wide shot. There it is. That is the one we hope will explode sometime
0:26:52 > 0:26:59
0:26:59 > 0:27:09on the show! It is looking brighter It is not... Vibrating or changing
0:27:09 > 0:27:09
0:27:09 > 0:27:12its colourful stop who he -- its colour. Her we know the type.
0:27:12 > 0:27:17will explode in the next few hundred, 1,000 years, but you
0:27:17 > 0:27:25cannot predict it or pin it down to the day. But when it goes it is
0:27:25 > 0:27:34minutes. Yes, the central core of the star collapses in seconds and
0:27:34 > 0:27:39the rest of the stars are flung out into space. Why can Andromeda be on
0:27:39 > 0:27:43course for us if the universe is expanding? Well, it is bound
0:27:43 > 0:27:50towards the Milky Way. There is a local group of galaxies bound
0:27:50 > 0:27:54together so it is only on the very large scales, but on smaller scales
0:27:54 > 0:27:58you can have objects that were bound together by gravity. Would
0:27:58 > 0:28:03you prefer we collided with Andromeda, that space itself is