28 replies to this topic

[questionmark]

Where exactly is it supposed that the Big Bang happened in the universe? And what is the evidence?

[OverSword]

Good question, I once saw a 3-d representation of the alleged shape of our universe and surprisingly it wasn't a sphere which if it was an explsion traveling outwards you would think it should be.

[Anomy91]

*grabs popcorn and sunglasses and runs towards the nearest chair*

[StarMountainKid]

For one thing, the universe is the Big Bang. We are inside the BB, so the BB happened everywhere.

By the way,  I don't want to imply I am one of the knowledgeable ones.

Edited by StarMountainKid, 05 July 2012 - 06:55 PM.

[questionmark]

StarMountainKid, on 05 July 2012 - 06:51 PM, said:

For one thing, the universe is the Big Bang. We are inside the BB, so the BB happened everywhere.

Then let me reformulate that: What is the point where all matter was concentrated when the big bang happened.

[StarMountainKid]

questionmark said:

Then let me reformulate that: What is the point where all matter was concentrated when the big bang happened.

Today, that point would be everywhere in the universe, because when the BB happened, the whole universe was at that point.

By the way,  I don't want to imply I am one of the knowledgeable ones.

[questionmark]

StarMountainKid, on 05 July 2012 - 07:37 PM, said:

Today, that point would be everywhere in the universe, because when the BB happened, the whole universe was at that point.

By the way,  I don't want to imply I am one of the knowledgeable ones.

I understand what you are trying to say, which from a philosophical point of view is totally correct. But just as you can determine where a fire started in a room by finding the most scorched place there must be a way to determine where the expansion started, was it in the center, somewhere in the periphery?

[StarMountainKid]

questionmark said:

I understand what you are trying to say, which from a philosophical point of view is totally correct. But just as you can determine where a fire started in a room by finding the most scorched place there must be a way to determine where the expansion started, was it in the center, somewhere in the periphery?

I would say my previous answer is not a philosophical point at all. The Big Bang didn't start in the universe. The Big Bang is the universe.

The expansion didn't start at some point within the universe. For that to have happened, the universe would have had to already existed when the BB occurred. The BB is not like an explosion where the center of the explosion can be determined.

No matter in which direction you look, everything is expanding away from you, and from every other position in space you observe the same phenomenon. And, the farther away you look, the faster the expansion is in all directions.

If there were a center of expansion, looking in that direction the expansion would be observed as occurring at a slower rate than looking away from the center.  This phenomena is not observed.

I don't want to imply I am one of the knowledgeable ones.

Edited by StarMountainKid, 05 July 2012 - 08:17 PM.

[questionmark]

StarMountainKid, on 05 July 2012 - 08:08 PM, said:

I would say my previous answer is not a philosophical point at all. The Big Bang didn't start in the universe. The Big Bang is the universe.

The expansion didn't start at some point within the universe. For that to have happened, the universe would have had to already existed when the BB occurred. The BB is not like an explosion where the center of the explosion can be determined.

No matter in which direction you look, everything is expanding away from you, and from every other position in space you observe the same phenomenon. And, the farther away you look, the faster the expansion is in all directions.

If there were a center of expansion, looking in that direction the expansion would be observed as occurring at a slower rate than looking away from the center.  This phenomena is not observed.

I don't want to imply I am one of the knowledgeable ones.

Again, imagine your are blowing up a balloon, that balloon gets bigger. Now this balloon is the universe. There is a definable circumference where the balloon was when you started to blow air in it, right?

And don't try it with your standard answer, we have seen it 3 times.

[sepulchrave]

questionmark, on 05 July 2012 - 08:37 PM, said:

Again, imagine your are blowing up a balloon, that balloon gets bigger. Now this balloon is the universe. There is a definable circumference where the balloon was when you started to blow air in it, right?

It is commonly accepted that the initial circumference was zero; i.e. the Universe truly had no spatial extent at the instant of the Big Bang.

It could also be argued from a philosophical point that if the entire mass/energy content of the Universe was a homogeneous plasma then the very concept of spatial extent is rather meaningless. (If everywhere you go looks exactly the same, are you really moving?)

[Condescending]

questionmark, on 05 July 2012 - 08:37 PM, said:

Again, imagine your are blowing up a balloon, that balloon gets bigger. Now this balloon is the universe. There is a definable circumference where the balloon was when you started to blow air in it, right?

And don't try it with your standard answer, we have seen it 3 times.

When using the balloon anology one needs to remember that the 2-dimensional surface of the balloon is analogous to the 3 dimensions of space. The center of the baloon is not supposed to be seen as anything physical (only the surfae of the balloon is).

Try and regard points off the surface as not being part of the universe at all.

A normal explosion, as we know it, behaves a certain way in space.. The big bang was an explosion of space. We know of no central point of the Universe.

[Imaginarynumber1]

Quote

  It was an explosion of space, not an explosion in space.  According to the standard models there was no space and time before the Big Bang.  There was not even a "before" to speak of.  So, the Big Bang was very different from any explosion we are accustomed to and it does not need to have a central point.

Here's a short page that gives some good info: http://math.ucr.edu/.../GR/centre.html


As for evidence, here is a short blurb from wiki:

Quote

The earliest and most direct kinds of observational evidence are the Hubble-type expansion seen in the redshifts of galaxies, the detailed measurements of the cosmic microwave background, the relative abundances of light elements produced by Big Bang nucleosynthesis, and today also the large scale distribution and apparentevolution of galaxies^[54] predicted to occur due to gravitational growth of structure in the standard theory. These are sometimes called "the four pillars of the Big Bang theory".^[55]

Edited by Imaginarynumber1, 06 July 2012 - 01:08 AM.

[lightly]

May an unknowledgeable participate Q ?  I have no answers but i think i might have a good question too.
I keep hearing that the universe is expanding equally  .  I also keep hearing that it is expanding faster,  "farther away"  .
  WHICH IS IT ?       If there is no center..  then the question becomes... farther away from what?   Is our position in a center less universe somehow significant?¿? .. other than to us?
IF we could travel to one of these points "FARTHER"  away  that appear to be expanding "faster"  and look back  HERE...  Which has now become FARTHER away,  . . .  then HERE  should be expanding faster from our new perspective farther away?  .. unless it's some sort of cumulative effect ... and expansion APPEARS to increase at a distance.. from any point.  

Hm,   this bit from the first of imaginarynumber1's links seems to agree with what i just said!

  In 1929 Edwin Hubble announced that he had measured the speed of galaxies at different distances from us, and had discovered that the farther they were, the faster they were receding.  This might suggest that we are at the centre of the expanding universe, but in fact if the universe is expanding uniformly according to Hubble's law, then it will appear to do so from any vantage point.

** as long as i'm in this deep...   it isn't weird that the universe has no center, because the "center"  is EVERYWHERE.  The weird thing is that the universe has no edges!

  *resists temptation to say circle*

Edited by lightly, 06 July 2012 - 01:41 PM.

[questionmark]

sepulchrave, on 06 July 2012 - 12:20 AM, said:

It is commonly accepted that the initial circumference was zero; i.e. the Universe truly had no spatial extent at the instant of the Big Bang.

It could also be argued from a philosophical point that if the entire mass/energy content of the Universe was a homogeneous plasma then the very concept of spatial extent is rather meaningless. (If everywhere you go looks exactly the same, are you really moving?)

yes, you are unless standing still. And that is precisely the point.

But I passed on this question to several profs of several universities, and the answer I got is that they don't know as it all depends on the expansion model being used, the best I got is from Wolfgang Besgen (Emeritus Marburg, Germany) who said that if we use the inflationary model, for example, the expansion occurred very much like a cell binary fission and the expansion course would be undefinable in retrospective.

Thanks to all for your input.

[gentai]

i aint knowledgeble either but didnt they have a picture of the universe with a little "old school original video game sprite" red man looking area in the center? and i also thought they said our universe was on the outside of a "bubble"? i saw it on the computer somewhere.