Beyond the Big Bang

[Mezolitik]

Hi guys,

I have a science question for you:

In the March 2011 issue of Astronomy Now, there's an image (page 16) depicting the major space-based telescopes and their optical range, i.e. how close they can get to the light of the galaxies that formed immediately after the Big Bang.

It works out that a new telescope is built every 2-9 years, from the Hubble to the James Webb Space Telescope, and that each subsequent model can see even deeper into the early universe than its predecessor.

Still with me? Ignoring all practical limitations, the telescope after the JWST could well discover the light from the oldest galaxies in the universe; that is, the first light from the Big Bang.

But what does that mean? Once we see the light that emerged seconds, minutes, or years after the Big Bang, is there anything beyond that point? Is that, in fact, the edge of the universe? Or is that where the edge of the universe was 14 billion years ago?

Hope that makes sense! And apologies if the answer is obvious; I may have over-thought things a bit

Thanks!

[JulianO]

We can already see back almost to the big bang, or at least very close. Redshift 10 or more has been detected allegedly - there are papers on it, but some dispute exactly how far away they are. The trouble being very distant objects, through various technical issues, tend to look very similar to not so distant faint things.

In a sense, the CMB background is as far back as we can go, and we have very good images of that. That is ~300,000 years after the big bang. The first galaxies started to form some 500 million years after the big bang. The bigger telescopes and the JWST will help us get better images of what we can already see.

There will be plenty for the new telescopes to do - and some of the earth bound telescopes such as the E-ELT will give the JWST a run for it's money.

[Pig]

I was watching something the other day and a 13 year old boy suggested there may have been more than one big bang and the one that we are part of could be just one of many !!!

[Mezolitik]

We can already see back almost to the big bang, or at least very close. Redshift 10 or more has been detected allegedly - there are papers on it, but some dispute exactly how far away they are. The trouble being very distant objects, through various technical issues, tend to look very similar to not so distant faint things.

In a sense, the CMB background is as far back as we can go, and we have very good images of that. That is ~300,000 years after the big bang. The first galaxies started to form some 500 million years after the big bang. The bigger telescopes and the JWST will help us get better images of what we can already see.

There will be plenty for the new telescopes to do - and some of the earth bound telescopes such as the E-ELT will give the JWST a run for it's money.

The galaxy I was reading about is the wonderfully named UDFj-39546284, at 10.3 redshift. It's quite interesting that Wikipedia notes it no longer exists.

I think where I had trouble was in assuming that galaxies appeared immediately after the Big Bang, so we could go right back to the second of the event and see galaxies; that, of course, was silly.

It's very complex, this universe thing.

[CptManering]

I was lead to believe that the furthest will will ever be able to see with the best telescopes ever created is the age of the universe in seconds multiplied by the speed of light. So at the moment 13.8 billion years (give or take a weekor two) times 299 792 458 m / s. The reason being is nothing can travell faster than light so if there is something 14 billion light years away it will not of had time to reach us yet. It take take another 200 million years for that light to reach us.

[JulianO]

I was lead to believe that the furthest will will ever be able to see with the best telescopes ever created is the age of the universe in seconds multiplied by the speed of light. So at the moment 13.8 billion years (give or take a weekor two) times 299 792 458 m / s. The reason being is nothing can travell faster than light so if there is something 14 billion light years away it will not of had time to reach us yet. It take take another 200 million years for that light to reach us.

Well - sort of true, but you have to take into account the expansion of the universe, so that, yes it was 13.8 billion LY away then, but it's now further than that.

High red shift stuff is incredibly messy to pick out. I have a colleague who does this stuff (red shift 3-7, ~600MY to ~2 billion years after BB), and the hoops you have to jump through to pin it down to make sure it really is that far away are taxing! The images you end up with are little more than a few smudged pixels too!

[CptManering]

So would that make the distance we could see shorter because the expanding universe has made more distance that light has to travel. Or has the expanding universe increased while expanding light, so the distance of where light started from is now greater and we will be able to see further. Omg head hurts just a little I mean how can any one even start to figure this stuff out.

[Planetesimal]

Yes, the latter.

[JulianO]

Yes - and the light gets redder, as the space is stretched in the meantime, so pulling out the wavelengths like a stretched slinky.

[mattft]

You've also got the CMB which goes back to recombination. That happened about 300,000 years after the big bang by current models. So in some ways we can already see back to z=1000 or more.

[ollypenrice]

You're in london. A car driving towards Glasgow flashes a morse message at you as it goes past Birmingham, saying 'We are 150 miles away from you.' If we pretend for the sake of argument that the speed of light is only 50mph, then by the time you get the message, the car will no longer be 150 miles away but a good bit further, perhaps already in Glasgow. So light that we know has been in flight for 13.7 billion years does not tell us that the source is still 13.7 billion LY away because the galaxy that sent it has now receeded as far as... Glasgow!

Olly

[Stu]

The thing that always gets me is that we all say the universe is expanding, and that this expansion is accelerating.

But given that the distant light we see is also 13.8 billion year old, how do we know what it is doing now?

To use your example Olly, how do we know that the car didn't stop short of Glasgow because it forgot something and is now on its way back?

[ollypenrice]

The thing that always gets me is that we all say the universe is expanding, and that this expansion is accelerating.

But given that the distant light we see is also 13.8 billion year old, how do we know what it is doing now?

To use your example Olly, how do we know that the car didn't stop short of Glasgow because it forgot something and is now on its way back? ������������

Stu

To know about this we need to find a distance measure which is independent of the redshift, so the 'redshift distance' and the 'distance distance' can be compared. I think that the key tool here is the type 1A supernova which, it is hoped, makes a standard candle because it goes pop when a mass accreting white dwarf exceeds 1.6 solar masses and lights up with a standard brightness. SInce the redhift measures recession and the brightness can give us a distance by comparing aparent magnitude with absolute magnitude we can tell whether the car en route for Glasgow has slowed down or speeded up on its journey.

What Saul Perlmutter et al discovered was that it seems that the early universe was expanding more slowly than the present one. In short the car is going to overshoot Glasgow big time and hurtle into Tromso* where it will (appropriately enough) meet with a fate known as heat death... Brrr.

Olly

*or Spitzbergen or Franz Joseph Land. Ranulf Fiennes. The last man in the universe, bless 'im.

[Stu]

Although I seem to have run out of intellectual capacity at this point, I'm still clinging on by my finger tips!!

Is one implication of what you are saying that redshift is not directly proportional to distance, as was my previous understanding? Presumably one of the next generation scopes, JWT or OWL (or whatever the acronyms are) will be able to measure SN at those distances?

Because we cannot see what the distant universe is doing now, I struggle to see how we can make any judgements on whether is is still expanding or not....

Stu

[JulianO]

Red shift is proportional to distance out to a certain level, but after that it begins to have more and more error. If the universe were just expanding at a constant rate it would be, but the rate of expansion is increasing. This doesn't make much odds "locally" (where locally is a few 10s of mega parsecs), but becomes significant further away.

[Stu]

So at greater distances the acceleration reduces vs distance, implying that moving forward in time the expansion is increasing. Is that even vaguely correct?

Stu

[JulianO]

Well... it depends what you are doing and looking at.

If you stand on the Earth and look outwards, which is also back in time, then the universe is expanding, and expanding faster the further you look away.

Nearby it looks as though everything is moving away at constant speed, but very distant objects are moving away faster than that.

This is based mostly on super nova data, from type 1a's which go off with a very similar luminosity. They are not all quite the same, but there is a correction you can apply to bring them very close to a standard luminosity. Of course there is all sorts of other stuff to do before you get data you can believe, dust corrections, k-corrections etc etc.

The furthest away of these type 1a's no longer fit on the straight line, although the data is quite messy and its not so easy to see, but statistically it is sound.

However! The accelerating force is a property of space itself, so in the early universe it was pretty insignificant, as there wasn't that much space. So way back when, it wasn't so much of a force, and the universe wasn't accelerating much. Initially the universe was dominated by radiation, but that soon gave way to matter/gravity being the dominant force at about 70,000 years old. At about 5 billion years old, the dark energy acceleration force became the most dominant force, and remains so until this day, and we're pretty sure it will remain so for the future.

[Stu]

Thanks Julian. Bear with me, you are dealing with a mere mortal here.

The bits I can't reconcile are the fact that the further away you look, and thus the further back in time you go, the bigger the redshift/expansion. Yet you are also saying that the early universe wasn't expanding so much which makes sense if the expansion is accelerating. How do you reconcile these two things.

Thanks

Stu

[ollypenrice]

Exciting stuff. Redshift is not a property of distance but of recession velocity, though for many purposes z can be used as a shorthand for distance. However, there's another interesting offshoot from the difference between the redhift distance and the otherwise-estimated distance. As I understand it, when galaxy distances are measured using redhift-free methods like the Tully-Fisher Relation they give a systematically different result from the redshift distance, suggesting that in certain parts of the sky the galaxies are being gravitationally dragged against the Hubble Flow by a gravitational source such as the spookily-named Great Attractor.

I hope Julian will have a second to comment properly on this.

Olly

[JulianO]

Lets see if the car analogy can be bent into an expanding universe!

So we're sitting in London looking at cars on the motorways. Most of the nearby ones seem to be moving away from us, and the further away we look the faster they are going. So at about 100 miles away, they are going 10 mph away from us. 150 miles away 15 mph. You might think cars at 200 miles away should be going at 20 mph, but when you measure it they are actually going at 20.2 mph, at 250 miles 25.4 or something like that.

However if you look towards the edge of the universe, say 1000 miles away, then things look a bit odd, because not only is it no long linear, X miles = X/10 mph, but now we're looking into the matter dominated era so gravity is winning currently, cars are actually going slower than we would predict based on local data - say at 900 miles, they may be going at 85mph.

Not sure if that helps - the universe isn't a terribly simple place!

In this analogy - the cars should really not be moving, they should be fixed to the roads, and the roads actually growing. The inflating balloon analogy helps here, but doesn't help much with the early universe stuff.

It's because we're subject to at least 3 forces governing the universe.

• Radiation pressure, this falls off very quickly as the universe gets bigger - so its very important very early on, but quickly becomes insignificant.
  
• Matter dominated, gravity between objects is always there, tending to pull things together.
  
• Dark matter dominated, this get bigger as the universe gets bigger.
  

[Stu]

Thank you both. I think it is beginning to make sense. I had this fixed idea of distance equals speed of expansion but what you have explained really helps to me to begin to understand the complexities.

I confess to being a bit of a Luddite in terms of Dark Matter/Dark Energy. I will believe it when it is proved but it is such a weird concept and so far outside anything I can 'visualise' it is tricky to accept.

Thank you for your explanations :-)

Stu

[JulianO]

Exciting stuff. Redshift is not a property of distance but of recession velocity, though for many purposes z can be used as a shorthand for distance.

Yes - its a key concept in extra galactic astronomy. Redshift is tossed around both as a distance, a time and a state of the universe. We idly throw around gigayears, Megaparsecs and so on as though they're trivial things

However, there's another interesting offshoot from the difference between the redhift distance and the otherwise-estimated distance. As I understand it, when galaxy distances are measured using redhift-free methods like the Tully-Fisher Relation they give a systematically different result from the redshift distance, suggesting that in certain parts of the sky the galaxies are being gravitationally dragged against the Hubble Flow by a gravitational source such as the spookily-named Great Attractor.

I don't know much about these, except they are oddities in the universe. I think they are just cases of unexpectedly high peculiar velocities (so that's an odd peculiarity - my head hurts!). Measuring such things can be a challenge, and there is dispute about the exact size of these things. it may well be aliens messing around

[stevegaze]

Hi

i know we can see almost back to the big bang.....does that mean we can actually see our own part of the universe being created and actually our own local group of galaxies being formed...for some reason this baffles me at times....they can see now take photos of clusters of galaxies 13 billion light years away when it was more condensed..do we know if some of these galaxies are now...we may be seeing galaxies from 13 billion years ago but due to expansion like a balloon we could be part of these cluster of galaxies......just every now and again i think like this lol .......plus if there was a big bang why cant there also be other big bangs somewhere out in the far reaches of space and due to expansion can galaxies from these other big bangs interact with ours ..............right will have my tablets now and get back to normal

[freeflyjay]

I was watching something the other day and a 13 year old boy suggested there may have been more than one big bang and the one that we are part of could be just one of many !!!

i`ve thought that since i was about that age and i`m 41 now, so the idea has probably been around a lot longer than when i thought it!

[stevegaze]

i was talking to a professor at college years ago and he said space just goes on forever and there could be loads of big bangs ....he would not say universe cos it only means one lol ...