0:00:29 > 0:00:33Good evening. The Sky At Night is now 55 years old.
0:00:33 > 0:00:36And in celebration, we're going to take you on a journey
0:00:36 > 0:00:39to the edge of the known universe,
0:00:39 > 0:00:40and perhaps even beyond,
0:00:40 > 0:00:43assuming, of course, that there is a beyond.
0:00:43 > 0:00:47With me are the two Chrises - Chris Lintott and Chris North.
0:00:47 > 0:00:51Chris, something about the speed of light itself.
0:00:51 > 0:00:53Absolutely, because if we're going to explore this vast
0:00:53 > 0:00:57universe of ours, we'd better go as fast as we possibly can.
0:00:57 > 0:00:58We know, thanks to Einstein,
0:00:58 > 0:01:02that the fastest thing in the universe is light itself.
0:01:02 > 0:01:04- And Einstein has always been right. - That's right.
0:01:04 > 0:01:07So, as far as we know, this is the fundamental cosmic speed limit.
0:01:07 > 0:01:09Nothing can travel faster than light.
0:01:09 > 0:01:15And light travels at about 186,000 miles every second, which is a lot.
0:01:15 > 0:01:18It's so fast that it was actually rather difficult for most
0:01:18 > 0:01:21- of the last few hundred years to try and measure that speed.- Indeed.
0:01:21 > 0:01:27And so this ridiculous speed, 186,000 miles per second, which incidentally,
0:01:27 > 0:01:30I like to think of, it's about a foot every billionth of a second.
0:01:30 > 0:01:32- Ha!- So, a foot per nanosecond,
0:01:32 > 0:01:35which makes it slightly more comprehensible, I think.
0:01:35 > 0:01:37But it's this speed that we have to attain
0:01:37 > 0:01:39if we're to get anywhere in the universe.
0:01:39 > 0:01:42Light reaches us from the sun in about 8.6 minutes.
0:01:42 > 0:01:45And from the moon in just over a second.
0:01:45 > 0:01:49That means that once we look beyond the Earth and the moon,
0:01:49 > 0:01:52our view of the universe is bound to be very out of date.
0:01:52 > 0:01:55Absolutely, and that can cause some problems.
0:01:55 > 0:01:58Yes, logistically, when operating space probes
0:01:58 > 0:02:01and Mars Rovers elsewhere in the Solar System,
0:02:01 > 0:02:04they have a problem that the signal from Earth that we might want
0:02:04 > 0:02:08to send to Mars, to a Rover, takes somewhere between five and 20
0:02:08 > 0:02:10minutes to get to Mars, depending on where it is in its orbit.
0:02:12 > 0:02:14The response from the Rover, which might say, "Yes,
0:02:14 > 0:02:17"I've moved that meteor you wanted me to move,"
0:02:17 > 0:02:20also takes between five and 20 minutes to get back to Earth.
0:02:20 > 0:02:22So if someone sends an instruction for the Opportunity Rover,
0:02:22 > 0:02:25for example, to drive just to the edge of that cliff,
0:02:25 > 0:02:28they can send that instruction,
0:02:28 > 0:02:31but it might be more than half an hour before they find out whether it
0:02:31 > 0:02:34did it, or whether it ran off the edge of the cliff, or anything.
0:02:34 > 0:02:35Logistically, that can cause problems.
0:02:35 > 0:02:39You can't drive the Mars Rovers with a joystick in real time,
0:02:39 > 0:02:40as fun as that would be.
0:02:40 > 0:02:45The nearest star beyond the sun is over four light years away.
0:02:45 > 0:02:46Absolutely, Patrick,
0:02:46 > 0:02:49but we should explore the rest of the Solar System first,
0:02:49 > 0:02:51- don't you think? - Yes, we should indeed.
0:02:51 > 0:02:55I've got this torch here, I've turned it on, with a beam of light.
0:02:55 > 0:02:59That beam of light is going to go through the Solar System and beyond.
0:02:59 > 0:03:01And Pete and Paul have been in my garden
0:03:01 > 0:03:04and they're going to go along with this beam of light.
0:03:07 > 0:03:10So, Patrick has sent out a beam of light from Farthings.
0:03:10 > 0:03:12Now that is heading out through space at the amazing speed
0:03:12 > 0:03:15of 186,000 miles every second.
0:03:15 > 0:03:17It is, and we are going to chart
0:03:17 > 0:03:19its journey through the known universe.
0:03:19 > 0:03:22- So let's first start off here on the planet Earth.- OK.
0:03:22 > 0:03:25We'll be Intergalactic Lollipop Men! There's the Earth.
0:03:25 > 0:03:27As it's the 55th anniversary,
0:03:27 > 0:03:30let's go out to a position which is 55 light hours out.
0:03:30 > 0:03:32So what we're going to do is use Patrick's garden
0:03:32 > 0:03:34to introduce a sense of scale.
0:03:34 > 0:03:36This garden gets used for an awful lot.
0:03:36 > 0:03:38I don't think it's ever been used to represent the universe before!
0:03:38 > 0:03:42No, it hasn't. Let's mark the position of 55 light hours here.
0:03:42 > 0:03:45That indicates the position in the Solar System where light,
0:03:45 > 0:03:47travelling at 186,000 miles per second,
0:03:47 > 0:03:49would have reached after 55 hours.
0:03:49 > 0:03:52Let's put in the rest of the Solar System. I have here Pluto.
0:03:52 > 0:03:55- Why don't you be Pluto? Can you catch?- OK, yeah.- Catch!
0:03:55 > 0:03:56I'll be the planet Saturn.
0:03:56 > 0:03:59The planet Saturn is a mere eight inches away from the Earth.
0:03:59 > 0:04:01In actual terms, it is about 1.5 light hours.
0:04:01 > 0:04:04Of course, we have the lovely Cassini spacecraft out there doing
0:04:04 > 0:04:07wonderful things. So, if I send out a transmission to Cassini,
0:04:07 > 0:04:09it takes 1.5 hours to get to it.
0:04:09 > 0:04:12Right. And anything that Cassini sends back to the Earth
0:04:12 > 0:04:13also takes an hour and half.
0:04:13 > 0:04:16That's right. It's a very slow conversation!
0:04:16 > 0:04:18- Now, you've got the planet Pluto there.- I have.
0:04:18 > 0:04:19And Pluto would sit
0:04:19 > 0:04:22about a metre away from the Earth.
0:04:22 > 0:04:24So that's the sort of scale out to Pluto.
0:04:24 > 0:04:26Of course, that isn't the end of it, is it?
0:04:26 > 0:04:27- There's more beyond that.- There is.
0:04:27 > 0:04:29There's a little man-made object.
0:04:29 > 0:04:30Do you remember Voyager 1?
0:04:30 > 0:04:32I've got a little prop here for it.
0:04:32 > 0:04:33- Have you drawn those?- I have,
0:04:33 > 0:04:35for the lack of anything else.
0:04:35 > 0:04:38Voyager 1, launched in the late '70s,
0:04:38 > 0:04:41went out into space and surveyed the planets.
0:04:41 > 0:04:44That, even travelling at the speed
0:04:44 > 0:04:45it is, is little more
0:04:45 > 0:04:47than a third of the distance away.
0:04:47 > 0:04:48OK, so a third of the distance
0:04:48 > 0:04:51- from the Earth to our 55 light hour marker.- That's right.
0:04:51 > 0:04:52The furthest man-made object.
0:04:52 > 0:04:53And just look at that, Pete.
0:04:53 > 0:04:55That's incredible.
0:04:55 > 0:04:56The small bit of Solar System,
0:04:56 > 0:04:57the furthest man-made object,
0:04:57 > 0:04:58but look how much distance
0:04:58 > 0:04:59there is still to go.
0:04:59 > 0:05:01So that is actually the edge of
0:05:01 > 0:05:02the Solar System there,
0:05:02 > 0:05:03where Voyager is?
0:05:03 > 0:05:06What have we got in this space beyond the Solar System?
0:05:06 > 0:05:09There's not really a tremendous amount, apart from the odd comet,
0:05:09 > 0:05:11- which you might find. I have a comet in my pocket.- Do you?
0:05:11 > 0:05:13- We can put that there. - Must be uncomfortable!
0:05:13 > 0:05:16This is a picture of a comet with a tail, of course.
0:05:16 > 0:05:19Now, out this far, the influence of the sun would be pretty weak.
0:05:19 > 0:05:22So any comet out here probably wouldn't have a tail
0:05:22 > 0:05:24or anything around it like that.
0:05:24 > 0:05:27It's only when it gets into the inner part of the Solar System
0:05:27 > 0:05:28that all those effects take over.
0:05:28 > 0:05:31- That takes us back to the very first Sky At Night.- It does.
0:05:31 > 0:05:32The very first one was accompanied by
0:05:32 > 0:05:34Comet Arend-Roland,
0:05:34 > 0:05:37which has now been flung out of the Solar System and will never return.
0:05:37 > 0:05:38But to go out further,
0:05:38 > 0:05:41so we're going out into the stars,
0:05:41 > 0:05:44we have to look at scales which are much, much larger than this.
0:05:44 > 0:05:48We do. We have to up from light hours to light years.
0:05:50 > 0:05:53Our light beam is now travelling beyond 55 light hours
0:05:53 > 0:05:56and we're going to 55 light years.
0:05:56 > 0:05:58Let's find out what's out there.
0:05:58 > 0:06:02We've gone out now to 55 light years.
0:06:02 > 0:06:06So, let's pause to see what we've found on the way.
0:06:06 > 0:06:09Well, we've already passed about 200 of the naked-eye stars,
0:06:09 > 0:06:12the ones we can see from Earth without telescope or binoculars.
0:06:12 > 0:06:14And those are the stars that are cheating, really,
0:06:14 > 0:06:17that appear bright in our sky, because they're not intrinsically
0:06:17 > 0:06:21brilliant, they're not particularly luminous, but they're close
0:06:21 > 0:06:23and so they appear bright. We've left them behind us.
0:06:23 > 0:06:27Interestingly, we've passed a couple of thousand stars now,
0:06:27 > 0:06:30and 80 of those we now know have planets.
0:06:30 > 0:06:33So we may well have passed other worlds like the Earth
0:06:33 > 0:06:36and other solar systems like our own.
0:06:36 > 0:06:38Given that this is out here at 55 light years,
0:06:38 > 0:06:42we are just receiving the first transmission of The Sky At Night.
0:06:42 > 0:06:46If there is life on any of those thousands of stars that we've passed,
0:06:46 > 0:06:48they'll be enjoying your programmes.
0:06:48 > 0:06:51- They'll now know all about us. - Absolutely.
0:06:51 > 0:06:53I'm sure they're entering your competitions and writing in
0:06:53 > 0:06:56and sending in their observations as we speak.
0:06:56 > 0:06:58One of the fascinating things about going so far out
0:06:58 > 0:07:00is that we've gone 55 light years,
0:07:00 > 0:07:03we've only passed a couple of thousand stars.
0:07:03 > 0:07:06It sounds like a lot, but if you look at the distance
0:07:06 > 0:07:09between the stars, it's actually immense compared to the size
0:07:09 > 0:07:10of the stars themselves.
0:07:10 > 0:07:13So if we scaled the sun down to a millimetre across,
0:07:13 > 0:07:16that's about the size of a pinhead, and we put it in the middle of London,
0:07:16 > 0:07:19outside the Houses of Parliament, on top of Big Ben or something,
0:07:19 > 0:07:23the next nearest star on that scale would be where the M25 is,
0:07:23 > 0:07:2725 miles away, that kind of distance.
0:07:27 > 0:07:30They are incredibly far apart, given their size.
0:07:30 > 0:07:34So what this tells us is that in terms of stars,
0:07:34 > 0:07:36space is pretty empty.
0:07:36 > 0:07:38There's a bit of gas and dust there as well.
0:07:39 > 0:07:43We've explored 55 light years, it's time to move on.
0:07:43 > 0:07:46Pete and Paul can show us where we're going next.
0:07:46 > 0:07:51So, Paul, as we represent our light beam journey across space
0:07:51 > 0:07:54with our garden scale model, I've got the Earth here,
0:07:54 > 0:07:58I've got a marker indicating a position 55 light hours out from Earth,
0:07:58 > 0:08:02and you're indicating the position 55 light years from Earth.
0:08:02 > 0:08:06That's right. But we want to step up to the next level, which is 5,500.
0:08:06 > 0:08:08And I've got a marker to indicate that one here.
0:08:08 > 0:08:11Once more, we've become galactic lollipop men.
0:08:11 > 0:08:13Let's compress space and set the model up.
0:08:13 > 0:08:17- So, I'm going to bring the 55 light years back down here.- OK.
0:08:18 > 0:08:21And I'll mark the position here,
0:08:21 > 0:08:24which represents where the light beam would have got
0:08:24 > 0:08:28if it had been travelling at light speed for 5,500 hundred years.
0:08:28 > 0:08:31So, I'm going to remove the 55 light hours
0:08:31 > 0:08:35and here becomes the distance to 55 light years.
0:08:35 > 0:08:38I'll tell you what, Paul, the view from here is mighty fine.
0:08:38 > 0:08:41- Yes, that's most of the stars we can see in the sky.- That's right.
0:08:41 > 0:08:44Every individual star we can see in the night sky
0:08:44 > 0:08:47sits in a sphere around the Earth,
0:08:47 > 0:08:50which has approximately got a radius of 5,500 light years.
0:08:50 > 0:08:53Well, as we've set up the scale model, Pete,
0:08:53 > 0:08:55- let's put in some of our favourite night sky objects.- OK.
0:08:55 > 0:08:58Here we have the Earth, 55 light years.
0:08:58 > 0:09:00All the little bystars go in this little bit.
0:09:00 > 0:09:02So, we have Syrius.
0:09:02 > 0:09:05- That's the brightest star in the night sky.- Right.
0:09:05 > 0:09:068.5 light years.
0:09:06 > 0:09:07- So, let's plonk that there.- OK.
0:09:07 > 0:09:11- Vega.- OK.- Lovely star, blue star in the Summer Triangle.
0:09:11 > 0:09:13We'll plonk that there.
0:09:13 > 0:09:16And in the constellation of Orion, of course, Betelgeuse.
0:09:16 > 0:09:19- "The armpit of the central one," its name means.- Oh, lovely.
0:09:19 > 0:09:20You've just ruined it now.
0:09:20 > 0:09:23We're going to put that around about the 700 light-year mark.
0:09:23 > 0:09:24- OK.- About there.
0:09:24 > 0:09:28I have a representation for the Pleiades open cluster,
0:09:28 > 0:09:31that beautiful cluster known as the Seven Sisters.
0:09:31 > 0:09:33That's about 420 light years out.
0:09:33 > 0:09:35So that would be about...
0:09:35 > 0:09:36- there?- Yeah.- OK.
0:09:36 > 0:09:40So you realise that 5,500 light years is an incredibly long way away
0:09:40 > 0:09:44from the Earth, but you can still see individual stars out that far.
0:09:44 > 0:09:46If we go right to the very boundary,
0:09:46 > 0:09:48we find a star which is known as
0:09:48 > 0:09:50Mu Cepehei, or Herschel's Garnet Star.
0:09:50 > 0:09:53- A lovely deep red star. - It's a very deep red star.
0:09:53 > 0:09:55That sits roughly in this position here.
0:09:55 > 0:09:57Isn't that remarkable?
0:09:57 > 0:09:58From the Earth out to 5,500 light years,
0:09:58 > 0:10:02the naked eye can see one little star.
0:10:02 > 0:10:04- That's amazing, isn't it? - That is remarkable.
0:10:07 > 0:10:10We are now leaving 5,500 light years behind
0:10:10 > 0:10:12and we are on our way to 5.5 million.
0:10:12 > 0:10:16But first, we've reached a crossroads.
0:10:16 > 0:10:19We have a decision to make now. What do you think, Chris?
0:10:19 > 0:10:20The decision is a tricky one,
0:10:20 > 0:10:23because we could keep going through the Milky Way.
0:10:23 > 0:10:26We'd hit the centre of the galaxy in about 25,000 light years' time.
0:10:26 > 0:10:30It's an interesting place, very dense stars, black hole in the centre.
0:10:30 > 0:10:32You now, I want to get a view that we've never had before.
0:10:32 > 0:10:35I want to head up out of the disk of our galaxy
0:10:35 > 0:10:37and look back on the Milky Way,
0:10:37 > 0:10:39the island universe that has been our home.
0:10:39 > 0:10:41- See it as it really is.- Exactly.
0:10:41 > 0:10:44And the interesting thing is, it doesn't take that long for us
0:10:44 > 0:10:46to leave the disk of the galaxy.
0:10:46 > 0:10:48The disk is only a few thousand light years thick.
0:10:48 > 0:10:53As we rise up above it, we'll see first the little spur of a spiral arm
0:10:53 > 0:10:56that the sun lives in. You'd like to think we're in an important place,
0:10:56 > 0:10:57but we're not in the middle,
0:10:57 > 0:10:59not even in one of the impressive spiral arms.
0:10:59 > 0:11:02We are in a little side arm, the suburbs of the galaxy.
0:11:02 > 0:11:05As we head out, the first thing we encounter
0:11:05 > 0:11:08as we get hundreds of thousands of light years away from the Milky Way
0:11:08 > 0:11:09are some smaller galaxies.
0:11:09 > 0:11:13- Oh, yes, dwarves.- Yeah, so the Milky Way is by no means alone.
0:11:13 > 0:11:17Surrounding it are a whole host of much, much smaller galaxies.
0:11:17 > 0:11:19The largest of these smaller galaxies,
0:11:19 > 0:11:21we call the Large Magellanic Cloud.
0:11:21 > 0:11:24The second largest is called the Small Magellanic Cloud.
0:11:24 > 0:11:26They are imaginatively named.
0:11:26 > 0:11:29As we moved outwards and we carry on going,
0:11:29 > 0:11:31we'll see more of these dwarves.
0:11:31 > 0:11:33Eventually, we'll get far enough out
0:11:33 > 0:11:35to start seeing some bigger galaxies.
0:11:35 > 0:11:39If we get to 2.5 million light years away, we encounter
0:11:39 > 0:11:42the brightest galaxy in our naked-eye sky,
0:11:42 > 0:11:44the Andromeda Galaxy.
0:11:44 > 0:11:48There is a third one, and that's the Triangulum Galaxy.
0:11:48 > 0:11:53These three, along with a couple of dozen smaller galaxies,
0:11:53 > 0:11:56make up a local group.
0:11:56 > 0:11:58We said earlier on that stars are very, very far apart
0:11:58 > 0:12:00compared with their sizes,
0:12:00 > 0:12:02and so stars almost never collide.
0:12:02 > 0:12:05Galaxies are much, much closer together
0:12:05 > 0:12:06compared to their own sizes,
0:12:06 > 0:12:09so we do sometimes see them collide.
0:12:09 > 0:12:10But they are much, much closer
0:12:10 > 0:12:13together than the stars are compared to their own sizes.
0:12:13 > 0:12:15They are indeed.
0:12:15 > 0:12:17So let's go back now to Pete and Paul in my garden
0:12:17 > 0:12:21to show us the scale of the local group.
0:12:21 > 0:12:25Let's get the cosmic wanderers to map out our journey
0:12:25 > 0:12:28from 5,500 light years to 5.5 million.
0:12:30 > 0:12:34- We have a model here of our own galaxy.- Look, The Sky At Night plate.
0:12:34 > 0:12:36This is a wonderful model. Made by Chris North, actually.
0:12:36 > 0:12:38He did a very good job here.
0:12:38 > 0:12:40We've got the core of the galaxy represented here
0:12:40 > 0:12:43and then the spiral arms coming off, like so.
0:12:43 > 0:12:46And we have little companions around the galactic core.
0:12:46 > 0:12:48We have globular clusters.
0:12:48 > 0:12:51That's right, these are little, sort of, condensations of stars
0:12:51 > 0:12:53in a halo around our galaxy.
0:12:53 > 0:12:57All gravitationally bound. M13 in Hercules is a good example.
0:12:57 > 0:13:00They sort of hover around the galactic core, like this.
0:13:00 > 0:13:02They do, but the globular clusters...
0:13:02 > 0:13:04M13 is a good one you've mentioned.
0:13:04 > 0:13:05That's an amazing object.
0:13:05 > 0:13:09You can see that from the UK through a telescope.
0:13:09 > 0:13:10It is beautiful thing to look at.
0:13:10 > 0:13:14It contains anywhere up to an estimated million stars
0:13:14 > 0:13:16in a sphere which is 145 light years across.
0:13:16 > 0:13:18- Quite impressive.- Very impressive.
0:13:18 > 0:13:20They look like glowing spiders' nests to me.
0:13:20 > 0:13:23I've never seen that, but OK.
0:13:23 > 0:13:25- We have companions to our own galaxy too.- We do.
0:13:25 > 0:13:29- Our own galaxy is, what, about 100,000 light years across?- Yeah.
0:13:29 > 0:13:30So, next to our own galaxy,
0:13:30 > 0:13:32we have two companion galaxies. In fact, there are a lot of
0:13:32 > 0:13:33companion galaxies,
0:13:33 > 0:13:35but these are two of the most prominent.
0:13:35 > 0:13:37The large and small Magellanic clouds.
0:13:37 > 0:13:39Right, visible from the Southern Hemisphere.
0:13:39 > 0:13:42We can represent them in this rough position down here.
0:13:42 > 0:13:46- So let's put the galaxy plate down here.- And the Magellanic clouds.
0:13:46 > 0:13:49- The two clouds, yes.- Let's go see what's in the neighbourhood.
0:13:49 > 0:13:51Let's go and meet the neighbours.
0:13:51 > 0:13:55- And look at this!- Another plate! - This is the Andromeda Galaxy.
0:13:55 > 0:13:58So, we are 2.5 million light years from Earth.
0:13:58 > 0:14:01- This galaxy is much larger than ours, isn't it?- It is.
0:14:01 > 0:14:04This is quite an easy thing to see in the night sky
0:14:04 > 0:14:08if you've got clear skies. Actually, if we look at that...
0:14:08 > 0:14:11If you have that galaxy face-on like that, the Andromeda Galaxy
0:14:11 > 0:14:15is tilted over a bit, so you see it as an elongated smudge.
0:14:15 > 0:14:17We have these little satellite galaxies - NGC205
0:14:17 > 0:14:19and M32 that accompany it.
0:14:19 > 0:14:21If you look at them through a telescope,
0:14:21 > 0:14:25a small telescope, it'll show those satellite galaxies quite closely.
0:14:25 > 0:14:27- You need a wide field to see it.- You do.
0:14:27 > 0:14:29- What do we have here? - This is a bit further.
0:14:29 > 0:14:31This is just over three million
0:14:31 > 0:14:33light years away. This is
0:14:33 > 0:14:36the Triangulum Spiral, Messier 33.
0:14:36 > 0:14:37This is a lovely galaxy,
0:14:37 > 0:14:40although it is very difficult to see with the naked eye.
0:14:40 > 0:14:44Where we had that one slightly tilted over, this one is face-on to us.
0:14:44 > 0:14:45We see it like that.
0:14:45 > 0:14:49And because of that, its light is spread out over a big area of sky.
0:14:49 > 0:14:52It is. It is three degrees, which is six lunar diameters.
0:14:52 > 0:14:55In the sky, it's not too far from the Andromeda Galaxy.
0:14:55 > 0:14:58It's in the neighbouring constellation of Triangulum.
0:14:58 > 0:15:01This is about three million light years away from Earth.
0:15:01 > 0:15:03It is, so all these galaxies here,
0:15:03 > 0:15:06and including some others, are what are known as the local group.
0:15:06 > 0:15:08They're a group of galaxies
0:15:08 > 0:15:10which are all gravitationally bound together.
0:15:10 > 0:15:13- A family of galaxies, if you like. - A family of galaxies.
0:15:13 > 0:15:15This is all our local family and neighbourhood.
0:15:15 > 0:15:17Right, the local galactic neighbourhood.
0:15:17 > 0:15:19But the galaxies are all moving through space together.
0:15:19 > 0:15:22To find out where they're going, we're going to have to go
0:15:22 > 0:15:26a little bit further than our 5.5 million light-year marker.
0:15:28 > 0:15:31Our journey continues to the edges of the known universe.
0:15:33 > 0:15:36Well, I'm travelling with my beam,
0:15:36 > 0:15:39starting from my garden in Sussex.
0:15:39 > 0:15:45We've travelled 5.5 million light years, and that's quite a distance.
0:15:45 > 0:15:46Well, Chris, where next?
0:15:46 > 0:15:50Everything we've talked about, after all, isn't static, it's in motion.
0:15:50 > 0:15:52The Earth is going round the sun,
0:15:52 > 0:15:55the sun is going round the centre of the Milky Way Galaxy.
0:15:55 > 0:15:58The Milky Way itself is moving to create those cosmic collisions,
0:15:58 > 0:16:00those interactions with Andromeda
0:16:00 > 0:16:03and M33, the Triangulum Galaxy that we talked about.
0:16:03 > 0:16:06But from out here, all this way out, we can see that the local group
0:16:06 > 0:16:08itself is moving, and it's being pulled
0:16:08 > 0:16:13by the gravitational attraction of our nearby city of galaxies,
0:16:13 > 0:16:17what we call the Virgo Cluster - a vast collection of many,
0:16:17 > 0:16:19many galaxies, most of them more massive than our own.
0:16:19 > 0:16:22One of the interesting things that can happen,
0:16:22 > 0:16:24you get these enormous clusters of galaxies that they themselves
0:16:24 > 0:16:27start colliding. You get clusters reaching clusters.
0:16:27 > 0:16:30If you go even further out, instead of talking about hundreds
0:16:30 > 0:16:33of millions of light years, we talk about billions of light years,
0:16:33 > 0:16:35thousands of millions of light years.
0:16:35 > 0:16:37Then you really start to see the honeycomb structure.
0:16:37 > 0:16:42And you see the galaxies are arranged not just in walls,
0:16:42 > 0:16:45but in a huge sort of arrangement of...
0:16:45 > 0:16:48- Filaments.- Yeah. - Leaving huge voids.- Yes.
0:16:48 > 0:16:52There are areas where there are very, very few galaxies.
0:16:52 > 0:16:54What would it be like to be in a galaxy there?
0:16:54 > 0:16:55Very lonely, I think.
0:16:55 > 0:16:58You'd have fewer astronomers to study the universe
0:16:58 > 0:17:00cos you'd think you were in a special place.
0:17:00 > 0:17:03If you were one of those few galaxies floating in the voids.
0:17:03 > 0:17:07But you can see those void galaxies tend to be younger, so they're only
0:17:07 > 0:17:10just forming now, cos they haven't had this long history of interaction.
0:17:10 > 0:17:13And most of the action takes place in the filaments
0:17:13 > 0:17:16and in these giant clusters where the filaments cross.
0:17:16 > 0:17:20There is this very dynamic picture of galaxy formation.
0:17:20 > 0:17:24Because by coming out to something like 5.5 billion light years,
0:17:24 > 0:17:28I guess is the next natural stop, coming all this way out,
0:17:28 > 0:17:30although we're seeing a huge scale, of course,
0:17:30 > 0:17:31we're seeing processes that have happened
0:17:31 > 0:17:35right across the 13.7 billion years of cosmic history.
0:17:35 > 0:17:38So we can talk about these filaments colliding, galaxy clusters forming.
0:17:38 > 0:17:41Don't you think the Milky Way looks insignificant
0:17:41 > 0:17:43when you see a map of the universe like this?
0:17:43 > 0:17:46Oh, it's very... It means nothing at all.
0:17:46 > 0:17:47One more parochial note,
0:17:47 > 0:17:49cos we should finish this tale of where we're moving.
0:17:49 > 0:17:53We got as far as the local group heading towards the Virgo Cluster,
0:17:53 > 0:17:56so you might want to know - what's pulling Virgo and the Virgo cluster?
0:17:56 > 0:18:00And we've given a name to the thing. We call it the Great Attractor.
0:18:00 > 0:18:02The Great Attractor.
0:18:02 > 0:18:05Which sound like a terrible sci-fi movie, but the reason
0:18:05 > 0:18:08we don't know much about the Great Attractor is that it's in a place
0:18:08 > 0:18:10that's awkward for us to see from Earth.
0:18:10 > 0:18:13If you remember, if you go back, we made that decision to come
0:18:13 > 0:18:16out of the plane of our galaxy, to go up above the Milky Way.
0:18:16 > 0:18:17Yes, we did.
0:18:17 > 0:18:19But within the plane, the Great Attractor is hidden in
0:18:19 > 0:18:23- what we call rather wonderfully the Zone Of Avoidance.- Yes.
0:18:23 > 0:18:26The part of the sky that we can't really look into the distance in
0:18:26 > 0:18:28because it's blocked by the nearby galaxies.
0:18:28 > 0:18:31So there's something down there, probably a very large cluster
0:18:31 > 0:18:34or a place where a couple of these filaments cross
0:18:34 > 0:18:37is this Great Attractor, this cluster to end all clusters
0:18:37 > 0:18:41that is attracting something even as large as Virgo.
0:18:41 > 0:18:43It would be very easy to get lost on this scale,
0:18:43 > 0:18:45so we should probably take a brief pause
0:18:45 > 0:18:47and look at something we'll be doing in a second
0:18:47 > 0:18:50of our special episodes to celebrate the 55th anniversary
0:18:50 > 0:18:52of The Sky At Night. It's called a Moore Marathon -
0:18:52 > 0:18:55things you would actually see in the night sky.
0:18:55 > 0:18:58And it's something you came up with in the 1960s, Patrick,
0:18:58 > 0:19:00and we've managed to find some old Sky At Night footage.
0:19:00 > 0:19:02Long, long ago.
0:19:16 > 0:19:18Good evening.
0:19:18 > 0:19:22So our first Sky At Night went out just over five years ago
0:19:22 > 0:19:24and we have been told we can have more programmes,
0:19:24 > 0:19:30which is just as well, because 1962 is going to be a busy year.
0:19:30 > 0:19:33We've had a Russian and now an American, John Glenn,
0:19:33 > 0:19:36in space, and the young President of America, John F Kennedy,
0:19:36 > 0:19:39says he wants to land a man on the surface of the moon.
0:19:39 > 0:19:42The Russians want to do the same and get there first.
0:19:42 > 0:19:44It's really rather like a race.
0:19:44 > 0:19:47There are, of course, a great many things to observe in the night sky
0:19:47 > 0:19:52and people are frequently asking me, "Patrick, what shall I look at?"
0:19:52 > 0:19:54It is for this reason I've come up with something new -
0:19:54 > 0:19:59a Moore Marathon, full of objects observable in the night sky
0:19:59 > 0:20:03throughout April, and I've chosen 55.
0:20:03 > 0:20:06Seems like a good, symmetrical number to me.
0:20:06 > 0:20:08Don't worry if you don't have a telescope,
0:20:08 > 0:20:11a great many of these objects are visible with the naked eye,
0:20:11 > 0:20:14although you may need to find a dark side.
0:20:14 > 0:20:20So number one should be my old favourite object, the moon.
0:20:21 > 0:20:23This is my moon globe here.
0:20:23 > 0:20:27Visible is the missing section, the side normally turned away from us.
0:20:27 > 0:20:31The Russians sent their Lunik 3 probe here to take a look.
0:20:31 > 0:20:33Finally putting paid to that story
0:20:33 > 0:20:36that the moon is made of green cheese.
0:20:37 > 0:20:39For my April Moore Marathon,
0:20:39 > 0:20:41I've included a great many constellations,
0:20:41 > 0:20:43such as Cassiopeia at number four
0:20:43 > 0:20:45and the Pleiades at number 14.
0:20:45 > 0:20:47Should be visible with the naked eye,
0:20:47 > 0:20:53but once again, by 2012, you might need to visit a dark side.
0:20:53 > 0:20:55Then, we reach our binocular objects.
0:20:55 > 0:20:58I recommend a good pair of binoculars.
0:20:58 > 0:21:02These once belonged to a German U-boat commander.
0:21:02 > 0:21:05I picked those up during my time in the RAF.
0:21:05 > 0:21:07And this takes us to our telescope objects.
0:21:07 > 0:21:11And so, let's go outside to my telescopes.
0:21:15 > 0:21:19My dear friend Arthur C Clarke has some futuristic ideas about
0:21:19 > 0:21:23a space station with people on board orbiting around the planet Earth.
0:21:23 > 0:21:26So, I've included that at number 15.
0:21:26 > 0:21:28I'm calling it the International
0:21:28 > 0:21:30Space Station because we will all
0:21:30 > 0:21:32have to work together internationally
0:21:32 > 0:21:33if we are to explore space.
0:21:37 > 0:21:40Now, this is my wonderful brass three-inch telescope
0:21:40 > 0:21:41I received as a boy.
0:21:41 > 0:21:44And the rings of Saturn look quite superb in it.
0:21:44 > 0:21:49So, at number 39 in the Moore Marathon, the rings of Saturn.
0:21:53 > 0:21:56I've been mapping the moon recently and I picked out some
0:21:56 > 0:22:00fascinating objects for you to observe, visible even with a small scope.
0:22:00 > 0:22:05Number 45 is the Alpine Valley, and at 46, the crater Clavius.
0:22:05 > 0:22:07Quite, quite spectacular.
0:22:07 > 0:22:10Mars, as you know, a great favourite of mine,
0:22:10 > 0:22:13and in at 49, Syrtis Major on Mars.
0:22:13 > 0:22:16There is still some debate as to whether or not this is vegetation
0:22:16 > 0:22:19and we won't know for sure until a spacecraft is sent there.
0:22:19 > 0:22:23And that won't be for quite some time yet.
0:22:23 > 0:22:25So, back to mapping the moon.
0:22:25 > 0:22:28Someone from the National Aeronautic and Space Administration
0:22:28 > 0:22:29has been on the telephone.
0:22:29 > 0:22:31As I was saying, they want to land a man on the moon
0:22:31 > 0:22:34and need some advice as to where to go.
0:22:34 > 0:22:37I shall recommend the Mare Tranquillitatis.
0:22:37 > 0:22:41It's hard to think that one day, there will be cities on the moon.
0:22:41 > 0:22:43I wonder!
0:22:47 > 0:22:52Patrick has set us the challenge of seeing 55 objects in the April sky.
0:22:52 > 0:22:54If you go to our website at...
0:22:56 > 0:22:58..you can find out how to take part.
0:22:58 > 0:23:01And next month, we'll report how everyone got on.
0:23:02 > 0:23:07Now, to return to our fantastical journey on a beam of light.
0:23:07 > 0:23:10We travelled from 5.5 million light years
0:23:10 > 0:23:12all the way to 5.5 billion.
0:23:12 > 0:23:14And Pete and Paul are going to try and set out
0:23:14 > 0:23:18this truly cosmic scale.
0:23:18 > 0:23:23So, our light beam travelling from Patrick sent it off from the Earth,
0:23:23 > 0:23:26it's now gone past the 5.5 million light years and, look,
0:23:26 > 0:23:30- 5.5 billion is the next target. - And that's a huge distance.
0:23:30 > 0:23:34In fact, it's absolutely vast. So, what are we going to find out here?
0:23:34 > 0:23:36First of all, we have the Virgo-Coma Cluster,
0:23:36 > 0:23:38about 50, 60 million light years out.
0:23:38 > 0:23:40- So that's actually... - Quite a pathetic distance.
0:23:40 > 0:23:42- Right down there.- OK.
0:23:42 > 0:23:46Let's go out now to an even greater astronomical distance,
0:23:46 > 0:23:48cos you've found a quasar that amateurs can image.
0:23:48 > 0:23:50Well, these distances are absolutely vast
0:23:50 > 0:23:54and when you're using amateur equipment, you can still see,
0:23:54 > 0:23:58amazingly, things out at these incredibly vast distances.
0:23:58 > 0:24:02Now, the other day, I took an image of what is called a quasar.
0:24:02 > 0:24:05That is called 3C273, which is in Virgo.
0:24:05 > 0:24:07Quasar comes from quasi-stellar object.
0:24:07 > 0:24:09It's a contraction of those two words.
0:24:09 > 0:24:13That basically means it looks a bit like a star, rather than a galaxy.
0:24:13 > 0:24:17Isn't it remarkable that amateurs can get this far out
0:24:17 > 0:24:19with just a telescope?
0:24:19 > 0:24:21- It's quite remarkable.- It is.
0:24:21 > 0:24:24The light left that 2.4 billion years ago, which is incredible.
0:24:24 > 0:24:26Let's leave our quasar behind
0:24:26 > 0:24:29and head on out to 5.5 billion light years.
0:24:29 > 0:24:31There really isn't much out here for the amateur, is there?
0:24:31 > 0:24:35No, it starts to fall off, because the light is so dim from these
0:24:35 > 0:24:38objects that amateur equipment has trouble picking it up,
0:24:38 > 0:24:41so you're in the realm of the really large, professional telescopes.
0:24:41 > 0:24:44Until you get out to this area here.
0:24:44 > 0:24:47Yeah, and here, we have the edge of the observable universe.
0:24:47 > 0:24:50Anything beyond this, its light can never reach the Earth,
0:24:50 > 0:24:52it's completely cut off.
0:24:52 > 0:24:55So we don't get any information back about what is beyond here.
0:24:55 > 0:24:59I think the best way of describing this region here is to call it
0:24:59 > 0:25:00the Great Unknown.
0:25:00 > 0:25:04That's a very good name because we have no idea what is out here.
0:25:04 > 0:25:09We've come as far as we can riding Patrick's beam of light
0:25:09 > 0:25:11and we've reached the end of our journey.
0:25:11 > 0:25:13In our final stages, we've passed stars,
0:25:13 > 0:25:16nebulae and galaxies which looked rather familiar,
0:25:16 > 0:25:19although from Earth, they are a very different sight.
0:25:19 > 0:25:24It's taken us 5.5 billion years to get to this part of the universe.
0:25:24 > 0:25:26If we sent Patrick's beam of light back to Earth,
0:25:26 > 0:25:30its return journey would equally take billions of years.
0:25:30 > 0:25:33And so when astronomers left back at home
0:25:33 > 0:25:35look out to these distant realms,
0:25:35 > 0:25:37they see things as they were when the light left.
0:25:37 > 0:25:40They see a snapshot of the cosmic past.
0:25:41 > 0:25:44In the Hubble Ultra Deep Field, we see a part of the universe
0:25:44 > 0:25:49as it was when the light left, more than ten billion years ago.
0:25:49 > 0:25:51And so the galaxies appear mere babies.
0:25:51 > 0:25:55They're young, with lots of new stars being born.
0:25:55 > 0:25:57But there is a boundary to how far back in time we can go,
0:25:57 > 0:26:03how far we can see, and beyond it is quite simply the Great Unknown.
0:26:04 > 0:26:07There is a limit and we don't think there's nothing beyond there.
0:26:07 > 0:26:09In fact, we're pretty sure there is stuff beyond there.
0:26:09 > 0:26:11There simply hasn't been enough time
0:26:11 > 0:26:14for the light to travel from those most distant regions
0:26:14 > 0:26:16to the Earth for us to see it.
0:26:16 > 0:26:20And so you'd think that that limit was 13.7 billion light years away,
0:26:20 > 0:26:23because the universe is 13.7 billion years old,
0:26:23 > 0:26:25but in fact, in that time,
0:26:25 > 0:26:27the universe has been expanding.
0:26:27 > 0:26:28So the observable universe,
0:26:28 > 0:26:33the stuff we can see, is actually at 45 billion light years across.
0:26:33 > 0:26:34And in that volume,
0:26:34 > 0:26:39we've got probably 100 billion galaxies with 100 billion stars.
0:26:39 > 0:26:42But all of that is probably only a tiny fraction
0:26:42 > 0:26:44of the whole universe.
0:26:44 > 0:26:45And out in the Great Unknown,
0:26:45 > 0:26:49beyond the limits of the observable universe, our theories tell us
0:26:49 > 0:26:51that we think the universe could be infinite.
0:26:51 > 0:26:54And if that's true, there will be infinitely many galaxies,
0:26:54 > 0:26:56between them, infinitely many stars
0:26:56 > 0:26:59and around them, infinitely many planets
0:26:59 > 0:27:01with, on them, infinitely many Patrick Moores
0:27:01 > 0:27:04celebrating the 55th anniversary of The Sky At Night.
0:27:04 > 0:27:08I wonder. We're looking now into the Great Unknown.
0:27:09 > 0:27:11So what do you think is out beyond the Great Unknown?
0:27:11 > 0:27:14I have no idea, it's a fascinating thought.
0:27:14 > 0:27:16- Shall we go and explore it? - That's a good idea.
0:27:16 > 0:27:18Do you think there will be a pub?
0:27:18 > 0:27:20- There might be an infinite number of pubs.- Your round...
0:27:27 > 0:27:30So, the Great Unknown, that part of the universe
0:27:30 > 0:27:35that is so distant that what exists there is not actually visible to us.
0:27:35 > 0:27:38So I've always had a great fascination with what may be
0:27:38 > 0:27:39discovered there.
0:27:39 > 0:27:43And most reassuringly, by Jove, it's me.
0:27:43 > 0:27:44Hello again, Patrick.
0:27:44 > 0:27:48Hello, Patrick. What a surprise to find you here.
0:27:48 > 0:27:51Yes, it's most reassuring. I couldn't resist having a look,
0:27:51 > 0:27:54how have the 55th anniversary celebrations of The Sky At Night
0:27:54 > 0:27:55been going?
0:27:55 > 0:27:56Very well, Patrick.
0:27:56 > 0:28:00We are celebrating our 55th anniversary of The Sky At Night
0:28:00 > 0:28:04and next month, we're going to do a Moore Marathon.
0:28:04 > 0:28:08Yes, I remember thinking of a Moore Marathon in 1962,
0:28:08 > 0:28:13and I wish everyone great success with it in 2012.
0:28:13 > 0:28:15And as for the Great Unknown,
0:28:15 > 0:28:19what can exist there? A void? A vacuum?
0:28:19 > 0:28:22Perhaps an infinity of universes? Well, one thing is for sure...
0:28:22 > 0:28:26We just don't know.
0:28:26 > 0:28:28No, we certainly don't.
0:28:28 > 0:28:31So, from all of us here, until next time...
0:28:31 > 0:28:32Goodnight.
0:28:43 > 0:28:48Subtitles by Red Bee Media Ltd