How big was the big bang?

  • Thread starter Javaxcore
  • Start date
  • #26
OCR
862
712
The question of size when applied to the Big Bang doesn't even make much sense, since the event (BB is an event in time, not an explosion in space) marks the early stages of the whole universe. Since it happened everywhere in the universe, its size was 'as big as the universe', including the possible case of 'infinitely large'.
My strike-through...
Since it happened everywhere in the universe, its size was 'as big as the universe', including the possible case of 'infinitely large'.
Sorry for being nitpicky, but... you do see the issue, right ?
 
Last edited:
  • #27
Bandersnatch
Science Advisor
2,913
1,823
you do see the issue, right ?
No. Unless you're one of them brown-shirt grammarians who can't stand redundancy in a sentence, even if evidently used for intensive purposes and without introducing any ambiguity.
 
  • #29
80
16
i dont think the entire universe as we see it was compacted in the size of an electron .... does anyone..... it all mathematically works out until we try to explain why things are still accelerating? :) We have all these complex formulas and calculations that all go to pot, and we just interject the biggest variable possible.. a variable greater than the subject matter, that of " Dark Matter", and say that it is causing things to accelerate and not decelerate as we would first guess.
so many holes, but humans with all the ego, dont want to accept something that can t be explained. there might have been a big bang event, but i dont think everything exploded from something the size of an electron, do you?? im thinking something the size of a galaxy, maybe! :)
My thoughts exactly!

This is very timely for me....I've seen & heard so many un-supported statements that prior to the BB, all the mass of the (observable) universe was contained in
a volume infinitely smaller than e.g. a proton. (re: The Universe S1 E14, "Beyond the Big Bang").

I don't have a math background higher than basic calculus, so maybe that's what prevents me from grasping, if not embracing, the proposition of there being a singularity prior to the BB.

Even though you can extrapolate backwards, why is it not possible that all the mass was contained in a volume, e.g. the earth? Or
the MilkyWay? How could a singularity possibly be stable pre-BB???

My pardon.....I just realized I'd missed page 2, and Marcus' post about the LQC Bounce, which
seems much more reasonable to me, mathematically challenged as I am. ;)
 
Last edited:
  • #30
3,379
943
You must always keep in mind that these singularities which appear in some BB and black hole models are not representative of some physical object.
They are generally taken to imply that the mathematical model breaks down at at this point.
The model is incomplete, something must be happening physically which is outside of our present knowledge.
However GR describes 'normal' spacetime very accurately and that is useful.
Since I have no expectation of suddenly being transported to the centre of a black hole, or to the initial moment of the big bang,
I won't be losing sleep over this, (although some might), but it is intriguing to think (speculate?) about it.
 
Last edited:
  • #31
80
16
You must always keep in mind that these singularities which appear in some BB and black hole models are not representative of some physical object.
They are generally taken to imply that the mathematical model breaks down at at this point.
Maybe even waaaaay before that point. Math may predict it, but it seems like an impossibility,
and there's no way to prove it directly. But your answer gives me some peace of mind. =)

it is intriguing to think (speculate?) about it.
Yes, it is......so many mind boggling speculations!
E.g., to trace the origins/paths of the atoms/particles that make up our bodies during our lifetimes. =O

One thing.....I greatly appreciate the help of you all who have great understanding of higher mathematics and
physics....that you try to communicate with those of us who don't, but are interested and intrigued by the
mysteries of life & the Universe (observable or not). I don't take it for granted. ;)

Thank you.
 
  • #32
1,796
53
In my humble opinion, it is precisely mathematics that gives us a reasonable answer to this and many other puzzling phenomena about the Universe but unfortunately it is an emergent one; one that only comes from a long, tedious, time-consuming study of non-linear differential equations. We so often wish to pursue understanding of Nature by continuous means, applying what is known, to what is not known and although that is successful in many cases, such an approach often fails because Nature is massively non-linear and non-linear systems very often have critical-points which cause the system to change qualitatively. It is the intuitive understanding of that property that comes from studying non-linear DEs and is key I think to finding solace in coming to terms with many questions about Nature.

Think about the concept of "swimming". At the critical point of freezing, swimming looses meaning. It no longer makes sense to ask, "How does one swim in (pure) water at the point of freezing or at a colder temperature?" The dynamics of water and temperature reaches a critical point as the system qualitatively changes state. (Some) of the old laws above the freezing point, must be replaced by new laws below it.

This phenomenon, critical point phase-transitions, are a very common property of our Universe; we see them everywhere and one not unreasonably wonders if this is a local property of our Universe or something more general. It may have been a critical-point transition that led to the creation of the Universe so that the physical laws we observe now in Nature might not be applicable to describing the dynamics at the time of creation or before it: the laws may have been qualitatively different. So to ask "how big the BB was?" could be an ill-posed question because concepts such as size, matter, energy, distance, speed and other physical qualities we observe on this side of the critical-point (BB), may not be applicable in describing both the critical point and the pre-existence. We may need to create a qualitatively different physics to describe the critical-point and beyond simply by virtue of the intrinsic non-linear dynamics and the evidence we see all around us of other non-linear systems transitioning across critical points.
 
  • #33
80
16
Just found this amazing site/sight. I don't know if it is based on the Big Bang or the Big Bounce, but is
wondrous to behold.
 
  • #34
Bandersnatch
Science Advisor
2,913
1,823
Just found this amazing site/sight. I don't know if it is based on the Big Bang or the Big Bounce, but is
wondrous to behold.
Illustris visualises the evolution of cosmological structure in the recent times, past the recombination period - i.e., the contentious issues of very early history is completely irrelevant.
I do agree (and who wouldn't?) that it's a marvel to behold.
 
  • #35
3
0
In the light of this all, I have a question regarding the travel of light since the beginning of the universe. I thought about opening a new topic for it, but maybe I can post the question here.
People talk about the light traveling 13 or so billion years to reach us when we look as far as we can through telescopes to see the outer limits of the universe.
My problem is, when light travels 13 billion years to reach us, and 13 billion years ago the universe started to expand, at the beginning the light was already ´here´, at the same place ´we´ also were. So how did it travel? One thing I can think of is that the expansion in the beginning was much faster than the speed of light.
 
  • #36
Bandersnatch
Science Advisor
2,913
1,823
the beginning the light was already ´here´,
It wasn't.
The oldest light we see (the cosmic microwave background radiation, or CMBR) was emitted about 380 000 years after the big bang singularity (understood here as the limiting point of the theory rather than a physical entity). Before that time, the universe was so dense and so hot that all the matter was in the plasma state, which is opaque to light. The gas that emitted CMBR was 40 million ly away from the gas that ended up as our galaxy.
The oldest galaxies we see needed time to form, and during the few hundred million years the expansion kept on doing its thing, and much more rapidly than it does today. The farthest, oldest galaxy we can observe was at about 3 billion ly distance when it emitted the light we get to see now.

One thing I can think of is that the expansion in the beginning was much faster than the speed of light.
While you're right that the rate of expansion in the early universe was much higher than today's, it makes no sense to talk about the whole expansion being of any speed. It always depends on which galaxy (or more generally, which object) you look at. At any given time in the history of the universe you'll have objects that are receding from the observer at speeds in excess of c.
For example, galaxies currently observed as receding at c lie at the so-called 'Hubble radius' distance, which in terms of proper distance (meaning how far away something is NOW) is equal to ~14.4 billion light years. Those same galaxies, if observed at the time they were forming, would recede at over 3c, and the gas that ended up as those galaxies would be seen receding at over 20 c at the time of recombination (when the universe stopped being opaque).
 

Related Threads on How big was the big bang?

  • Last Post
Replies
13
Views
3K
  • Last Post
Replies
5
Views
2K
  • Last Post
Replies
20
Views
4K
  • Last Post
Replies
8
Views
4K
  • Last Post
3
Replies
58
Views
12K
Replies
4
Views
751
Replies
5
Views
833
  • Last Post
Replies
5
Views
3K
  • Last Post
Replies
2
Views
1K
  • Last Post
2
Replies
41
Views
12K
Top