# The Big Bang: Where Did It Happen?

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Aladdin, Dec 15, 2011.

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I'm imagining our Universe being more or less like a sphere, with its outer edge expanding at light-speed (or close to it). But any sphere has a center, and I would guess the Universe is no exception (if indeed it resembles that form). If we were to go backwards in time, all the matter in the Universe would converge towards this center point. And that's where I thought the Big Bang happened.

Then I googled a bit and found this page: "The best, non-mathematical description that any cosmologist can create for describing the Big Bang is that it occurred in every cubic centimeter of space in the universe with no unique starting point."

No unique starting point... how could that be? Any thoughts?

3. ### ULTRARealistically SurrealRegistered Senior Member

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Yeah. To me it seems simple enough. A random point of space suddenly realizes itself and creates a paradox. There is no time as there is nothing to measure it with. Suddenly, existence realizes it cannot not exist and bang. I think that's it as far as my corn gets popped.

5. ### wlminexBannedBanned

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Aladdin: Welcome to Sciforums . . . . . . .Well . . perhaps (acc/to SM ) . . . the BB originated from an infinitely "small point" (far less than 1 cc; <~ 1 Planck length?)) in "nothing". That infinitely small point represented the beginning of 'spacetime' which 'expanded' through the remaining 'nothing' to become our (now) observable universe . . . at least that's how it appears in SM . . . however, there are alternative models.

7. ### araucaBannedBanned

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I am going to Wallgreen to get me a model of the universe, is it less then 1 cm , and all the millions of galaxy are going inclosed in it , and the gravity will approach infinity Wow . There must be a priest in the 60 who dreamed up such thing.

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Everywhere

9. ### cosmictravelerBe kind to yourself always.Valued Senior Member

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Take a look at the ocean that we have here on earth. Can you tell where it starts from or where it ends? Same thing with the universe, it is like a cosmic sea, begining everywhere and never ending. Galaxies and planets inside of it everywhere forming islands of mass that we live on at times.

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If that is so wouldn't we then have a random movement of matter within the Universe?

Nope. But somebody can probably find out where the barycenter of the ocean is. Does the Universe has such a point?

(And yes, the barycenter is not necessarily the center of a spheroid object, as I assumed the Universe to be, unless the matter is distributed uniformly within it. But anyway, you got the idea, I believe...)

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13. ### hardaleeRegistered Senior Member

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The whole universe started at a point in the big bang.
That point expanded to become the universe. Everywhere was once a point.

14. ### CptBorkRobbing the Shalebridge CradleValued Senior Member

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The standard Big Bang picture basically treats the universe as a giant, infinite 3-dimensional grid (lattice) of points. Now imagine distributing an infinite amount of matter and energy amongst various points on this grid. If you take the math literally all the way to the "beginning of time", at time $t=0$ the physical distance between any two points on the grid is zero, as if all these points occupied a single dot in space. At any time after $t=0$, the physical distance between any two points is no longer zero, but is instead proportional to the amount of separation between these points and increases with time, i.e. space is stretching even though the universe is already infinite in size.

So in layman terms, the whole universe starts off contained within a single dot, then an infinitesimal moment after the "beginning of time", it pops up to infinite size, and the distance between any two points in the universe increases thereafter as space gradually stretches. Experimentally we don't know if the existing math actually tells the whole story all the way back to $t=0$, but we know it provides an accurate description of what happened very shortly thereafter and what's been happening ever since. You won't hear astronomers talking about the centre of the universe, because every point in the universe can be treated as the centre with equal validity.

15. ### wlminexBannedBanned

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. . . see all of the above . . . . that's what the SM conjures. . . based on limited, in-the-box thinking . . . (also . . . I have some beachfront property to sell you in Albuquerque!) . . . there are alternative models!!

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Infinite size? How could that be?

If everything started from a single point, and the matter spread out at the speed of light some 14 odd billion years ago, then any two points within the Universe couldn't be more than 28 billion light-years away. Am I wrong?

The analogy with the 3D lattice did help a bit -- thanks for bringing it up.

17. ### Boris2Valued Senior Member

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i guess to have a "unique starting point" then you must compare that to something. there wasn't anything else. this point wasn't in existing space everything we observe was, and still is, inside this point. there was and is no outside.

18. ### araucaBannedBanned

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Would you believe that .? a point " less the 1 cm. " were was the point ? in a cup, were was the cup ? was it in space . It must have been in a space , sense there was much energy released , some were the energy must have dissipated in order to end up with the present space temperature of 2.7 K. Wait , we have dark matter to absorb 70 % if the energy.
Is that how it goes ? Please correct me so I can be enlightened .

19. ### araucaBannedBanned

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Why should you be wrong , The bang should go in all direction I agree 28 billion from side to side .
QUOTE=
The analogy with the 3D lattice did help a bit -- thanks for bringing it up

20. ### araucaBannedBanned

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[You won't hear astronomers talking about the centre of the universe, because every point in the universe can be treated as the centre with equal validity.[/QUOTE]

In my astronomy the sun is my center my universe and at some point Saturn will be behind the sun and the earth will be in front if the earth

21. ### Robittybob1BannedBanned

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Those two statements seem at odds. For if we were standing on an essentially flat surface, but in fact on a large globe, and could only see in 2 dimensions then we would be in the centre with equal validity. Trouble is we can see in all directions we aren't on a flat surface, but in a 3D lattice, but then try and make each point of that lattice the centre and I can't imagine what shape that is.

Unless the lattice is so enormous it is just something that can't be determined, so each point has "equal validity", since there is no logic that can validate any point.

22. ### SarkusHippomonstrosesquippedalo phobeValued Senior Member

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Yes, you are wrong.

First, the universe does not spread out from a single point. Imagine the surface of a balloon... if you put a lattice of dots on the surface of an uninflated baloon they are quite close... but blow the balloon up and the dots move apart, but with no dot being the centre of expansion. If the dots are far enough apart, then their relative distance apart increases faster than light can travel to bridge that distance.

Using this idea, every object moves apart by a given % from every other object. Say the distance increases by 10% each year.
So if X and Y are 1 LY apart at t=0, then at t=1 they will be 1.1 LY apart. at t=2 they will be 1.21 LY apart and so on... so from the point of view of X, Y will be seen to be moving away faster and faster.

At some point that apparent expansion will exceed the speed of light.
And when it does, light emitted from Y will no longer be visible to X... ever.

Then there is the distinction between the distance that light has travelled to get to us, and the distance to that object now.
For example, if I am travelling at 10 m/s away from you, and I am 100m away and throw something to you at 20 m/s relative to you... you will catch that thing in 5 seconds and work out that when I threw the object I was 100m away. But when you catch it I would have travelled a further 50m away.

And the effect of the expansion of the universe is significant...

The 14 billion LY figure that you're using gives us the age of the observable universe, and is a measure of how long it has taken for the light emitted at the time the universe became transparent (about 400,000 years after the big-bang) to reach us. At that time the observable universe was c.1100 times smaller than it is today, and the light that took 14 billion years to reach us was emitted from objects no more than 40-50 million light years away. But it has taken 14 billion years for that light to reach us due to the expansion of the universe.

Basically, what this boils down to, is that current estimates of the observable universe put it at around 45 billion LY radius... which means that light reaching us now (whether we can practically detect it or not) could be from objects that are currently up to about 45 billion LY away, although they would have been much closer when they emitted that light. So the observable universe is currently thought to have a diameter of 90+ billion LY.

The furthest galaxy we have seen, for example, is from about 600 million years after the Big Bang (see http://cosmiclog.msnbc.msn.com/_news/2010/10/20/5322427-scientists-pinpoint-the-farthest-galaxy).
I have read somewhere else that at the time the light was emitted the galaxy only was c.3 billion LY away, the light took 13 billion years to reach us, and is now c.30 billion LY away... although I can't find the source.

I also recall reading that the universe, in its early days, was expanding some 50x the speed of light, and the edges of the observable universe are still expanding at c.3x speed of light.
It also results in the rather odd concept that while the observable universe expands, the number of objects in that observable universe actually gets less, as more and more start getting further away from us at a rate > C (and thus become unobservable).

Of course the "observable" universe is observer-centric, so every point in the universe has its own "observable" universe.
And the actual total universe (i.e. including what is beyond the observable) could be infinite.

I hope this hasn't confused you too much.