The Big Bang - where?

[legion48]

Albatross,

If you are looking for a read on the subject, try 'The Universe A Biography' by John Gribbin published by Penguin (ISBN 978-0141021478 ) only £5.99 on Amazon at the moment.

http://www.amazon.co.uk/Universe-Biography-John-Gribbin/dp/0141021470/ref=sr_1_1?ie=UTF8&s=books&qid=1218091271&sr=1-1

Thanks for that. I just ordered a copy.

[beamer3.6m]

I still don't undertsand how there can be no centre.

If the 'big bang' was a massive outward surge of energy then surely it would have surged in all directions at the same time and speed, leaving the original big bang in the middle.

Plus, if everything is moving away from us and to others we are moving away from them, how come we are all not moving towards anything.

[narrowbandpaul]

Hubble (edwin, not the telescope, although it has aswell) showed in the 1920's that the distance between galaxies was increasing. And the rate of increase was proportional to the distance that the galaxy was away.

What is strange however is, if you moved your body to a distant galaxy, say a quasar, that is very distant, and therefore moving away from us very fast, what would you see?

The answer to the question, is that you would see all other galaxies expanding away from you, in exact accordance with Hubbles Law. This is explained by the expanding balloon mentioned earlier. all points expand from all other points in a way governed by hubble's Law.

From this quite remarkable property we can deduce that wherever you are you carry your very own universe, 13.6 Billion light years in extent, centered exactly on you.

This means that if you were to go to the edge of the visible universe, you would still have this 13.6 Billion light year universe surrounding you. For this reason, the universe has no edge, even though the universe came from a point, 13.6 Billion years ago. It has a radius of 13.6 Billion light years but no edge!

Using the same argument, you can show that the universe has no centre, even though it came from a point

hope this answers your question, but its bound to raise a billion more

Paul

[Andrew1972]

.Where was the 'ball of pure energy' located prior to the big bang? That's surely the centre of the universe but to find that out you'd surely need to know what existed before the big bang(?)

With regards expansion, I know a balloon is quite often used as a (simple) analogy. Draw loads of dots on an uninflated balloon and then as you blow it up the dots begin to move away from each other. In theory you could be any of the dots and see yourself as the centre of the 'expanding universe'.

[narrowbandpaul]

correct electricblue. The big bang created time and space, so the progenitor of the big bang did not have a location (x,y,z), as they had yet to exist

Paul

[beamer3.6m]

Can we not just run the whole history of the universe in reverse and see where they all merge.

[Paxo]

B3.6m,

They have done, albeit through computer simulations. They have gone back to a hundred-billionth of a yoctosecond (10^-35 seconds) which is the start of the inflation era. Before this, a period known as The Planck Era, no current laws of physics can describe what happened in the universe at this time, though several 'theories' have been proposed.

The big bang was not an explosion in space, but an expansion of space which happened everyhere.

Steve..

[beamer3.6m]

So what was the result of running it backwards, where did all the galaxies etc come from or I suppor to be more precise where were they all moving away from.

[narrowbandpaul]

dont forget that it is the spacetime that is expanding, running the expansion in reverse, means that the spacetime contracts, more and more, until the universe exists in a single point. Within the point are the physical dimensions, so there can still be no way of locating some coordinates for the beginning of the universe. The Big Bang theory is a theory of what happened after the bang.

We shall never know this. The furthest look back possible is 380,000years after the big bang, when photons were free to travel unimpeded. Before this the universe is opaque.

using theoretical physics we can get back to less than 1ns after the bang, but after that things get more and more speculative. Then we hit the planck timescale, where gravity is expected to merge with other forces. It is the shortest measurable unit of time...in theory. We cant speculate even at this time, as we require a theory of quantum gravity...

[narrowbandpaul]

B3.6M,

just as a thought experiment, how would you try to measure where the central point of the universe is?

[Paxo]

Beamer, to summarise (deep breath)

After inflation, fundamental particles such as quarks and antiquark pairs formed and then anhialated back to energy continually. This period has often been likened to a particle soup with bosons (gluons), and perhaps gravitons (which are theoretical gravity carrying particles) and higgs bosons forming and being subsequently anihalated. At about a nanosecond after the start of time, the temperature has dropped sufficiently enough to allow some of these particles to freeze out, some of the quarks become bound into heavier particles by gluons. At about a microsecond, composite particles (known as hadrons) begin forming, these include protons, neutrons (this process has been called quark confinement).

Continuing on, at a millisecond, considerable further cooling has occured, and leptons formed (electrons and neutrino's). A period of nucleosynthesis occured where neutrons gradually converted into protons as the universe cooled, but when there was about 1 neutron for every seven protons, most remaining neutrons combined with protons to make helium nuclei, each with 2 protons and 2 neutrons.

What followed for the next 300,000 years was an opaque time (which is what Paul mentioned above)with particles in a constant state of interaction with photons making the universe "foggy". At the end of this period many more free protons existed than helium nuclei. The scene was set for the first atoms, about 9 hydrogen atoms were produced for every helium atom. A few lithium and deuterium also formed.

What followed is known as the matter era where photons are free to travel through the universe, and most electrons are bound to atoms until the first stars formed, reheating the matter.

Gravity caused matter (mainly hydrogen and helium) to form into dense areas which formed the first stars 200 million years after the 'big bang'. These stars would have been extremely large and only lasted a few million years. Stars then captured into galaxies at about 500 million years, and the rest they say is history. Expansion is moving the universe apart on a large scale, but gravity effects have allowed the formation of clusters of galaxies and super clusters.

I hope that helped.

Steve

[spacemonkey]

Here, there and everywhere. Everything came from the big bang and therefore it started everywhere at the same time.

Kaptain Klevtsov

It actually started in the middle of here -

http://en.wikipedia.org/wiki/Nowhere_%28Norfolk%29

There's a footpath nearby, I've been there. It's nothing special, but it probably looked different 14.6 billion years ago.....

Dave the cosmic explorer

[MartinB]

The thing I now understand about astro physics is that it isn't intuitive. The concepts are understood on a mathematical rather than an intuitive basis.

One thing that always puzzled me was being told that the most distant objects in the universe were so far away that their appearance gave us information about the universe when it was very young. I couldn't understand why the light hadn't passed us close to the time of the big bang. Now I sort of understand that big bang wasn't a big explosion with matter being flung out from a central point but was a "happening" in which from an infintesimal point the whole universe came into being. If the universe is expanding it isn't as a result of our concept of an explosion.

Who was the Russian physicist who woke up one morning and realised that the universe was the same whichever way we looked at it? He spent years proving it mathematically and eventually won the Nobel prize. Can't remember his name, clever bloke!!

[kpax]

Perhaps we are taking the Mountain to Mohammad when we measure the hubble constant. Has anyone ever considered for example that there could be some force acting upon the equipment that measures the constant such as the effect of gravity or spacetime. The light which travels into our telescopes may not be subject to gravity and spacetime in the way the telescope is and therefore appears redshifted as the telescope moves through spacetime along with the Earth. Sounds simple but you never know.

kpax

[narrowbandpaul]

i dont suppose the russians name was minkowski...as in the guy who worked on the geometry of spacetime?

[Paxo]

Here's a link to the physics prize winners if it helps:

http://nobelprize.org/nobel_prizes/physics/laureates/index.html

A sobering quote from Minkowski:

"Henceforth space by itself, and time by itself are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality."

That's cheered me up no-end! I don't think Minkowski every won the prize but Antoon Lorentz did in 1902 for Lorentz transformations which are linked to the Minkowski metric known as Minkowski Space.

Steve..

[narrowbandpaul]

i think that quote appears in brian green's, the elegant universe

[gurney]

Hi albatros,

I think we all feel your pain, and I can see that everyone is trying their best to help you get a grasp of this concept.

May I add to the attempts by offering the following (building on the comment about basketball surfaces above):

You're thinking very 3 dimensionally. Our universe is at it's simplest form at least 4 dimensional when you include time as another dimension.

A useful metaphor for getting your head around what's going on is to think of the universe like a balloon, but instead of everything which exists filling the volume of the balloon, you've got to think of everything simply existing on the balloon's surface. As the balloon expands so objects on the surface get further and further apart. BUT, and here's the big BUT in relation to your problem, the physical nature of the universe, the 3 dimensions of your understanding of space that you want us to point a finger in and show you where the centre is, ALL exist on the surface of the balloon, and we CAN'T point to the centre of the balloon and say "Look, there is the middle". We're stuck on the surface and can only point in the directions along the surface.

The reason for this is, also as stated in other posts above, that space-time itself was created in the Big Bang and didn't exist before hand. Within that big bang blast the very fabric that we exist within was put into being and it's all expanding out with us from that moment. We're literally bringing the centre with us, but spread out so thin and in every bit of space that it's everywhere and nowhere.

The only thing we can do is look back in time, and that's where we see the background radiation. But the background radiation is all around us at the very edge of the observable universe. So instead of looking to the centre, we must look to the edges. It is as thought the universe has blasted itself inside out. If you want to see the inside you must look to the edge.

Yes it is all very baffling.

One thing if I may - and I know we're not allowed to talk religion here, but necessarily we do need to ask the question about the foundations of the big bang itself...

The quote of John Gribbin, given by Paxo above says this at the beginning:

"The story begins 14 billion years ago. Somewhere in a vacuum (one school of thought would have it), a quantum ripple upset the apple cart and – BAM! One-ten-thousand-billionth of a second later a ball of pure energy, 1029 degrees Kelvin, begins its inevitable task, as described by the Standard Model of particle physics, of creating the universe.

What is interesting to me is that this presupposes the existence of the laws of physics outside the existence of the universe, or at least outside the existence of any space-time. The 'quantum ripple' he speaks of is a shorthand way of saying that quantum physics existed in that non-space-time vacuum. Indeed, the word vaccum conjurs an image in my mind at least of a physical nothingness (eg, a vacuum jar - a very real something which contains no gas, or 'the vacuum of space' meaning the emptiness which is contained between the stars), but in fact the vacuum was TOTAL, no matter, no energy in any direction anywhere, and absoutely no fabric of space or time either! A quite mind numbing nothingness the likes of which we struggle to comprehend...and yet for the big bang to work in this theory, there must have been something... the laws of physics, and they must have worked despite their being nothing to work with. And in that nothingness the quantum ripple, wandering lonely as a cloud randomly creates the ball of energy so helpfully.

We all have faith in something, even atheists. It is for me a HUGE illogical inconsistency to presuppose that the laws of physics existed on their own in nothingness, and it is them alone which created all that we now see.

[GazOC]

I think Gribbin using the phrase "one school of thought would have it" is showing that he's not taking things on faith, he's not saying "this is what happened" or even "this is what we/I think happened", he's just acknowledging there's a gap or dissent in our understanding of this area and moving on quickly to get to the to the subject matter of his book.

[Paxo]

Gurney,

I think what Gribbin is saying is that they do not know what 'rules' existed at the point of the big bang and by assumption before hand, the laws of physics he talks about are those well known laws which governed the development of the universe following the big bang. All before that is pretty much supersition which can only be backed with theory derived from computer simulation. Paul mentioned that point (in the opaque era) at which WMAP has measured the microwave background at 380,000 years after the big bang, this is as far as it is possible to look back, so all before this point is theorised.

Who knows who will turn out to be right (if we ever know that is), we will all continue on with our 'faiths' whatever they may be

Steve..

[NeutrinoWave]

Here, there and everywhere. Everything came from the big bang and therefore it started everywhere at the same time.

Kaptain Klevtsov

Agreed on this and by intuition an Isotropic and Homogeneous Universe is all around us.

However there some advocates of Anisotropic Inhomogeneous Cosmologies but then it all gets complicated ...

[Marmite]

The currant bun explanation of recession has always seemed more suitable than the balloon model, imho.