Does gravity break down in the big bang?

In summary: The break down of our mathematical models in such circumstances is precisely why physicists are currently looking for better ones.
  • #1
daanaerts
2
0
Dear all,

I just read something in a book by Lawrence Krauss which I don't understand. I hope you can answer my question:

Kraus makes the argument that if you take quantum mechanics and gravity, something is more energetically favorable than nothing. Hence if you take nothing, at some point something will arise.

My question is:

Doesn't gravity (or maybe quantum mechanics, too) break down, like the nuclear forces, in the big bang?

If so, then does Kraus's argument still hold? Or do I interpret it wrongly?

I'm a biologist and only read bits a pieces about physics, so forgive me if I've said something ignorant, which I know is easy to do.

Kind regards,
Daan from Amsterdam
 
Physics news on Phys.org
  • #2
I haven't read Krauss' book and so can't comment on the larger argument and whether or not it holds.

As for your particular question, though, it's important to distinguish between "X breaks down" and "our understanding of X breaks down". Our mathematical models for gravity (and other forces) break down at the Big Bang (which is the reason physicists borrowed the word "singularity" from the mathematicians for such situations). That doesn't necessarily mean the forces themselves break down at the Big Bang, just our current understanding of them. The break down of our mathematical models in such circumstances is precisely why physicists are currently looking for better ones.
 
  • #3
daanaerts, one of the things you should keep in mind is that pop science discussions sometimes fail to distinguish between the two meanings of the term "big bang". There really is a big bang EVENT and a big bang MODEL. The event is what is also called the singularity and since our math models break down there, we don't know WHAT that was all about. The model is also called the "Big Bang Theory" and has nothing to do with the singularity but only discusses what happened about one Plank time AFTER the singularity and from there forward.

I think Krauss's discussion is an attempt to discuss the singularity as an evolution out of "nothing", whatever that is, via quantum foam --- A Universe from Nothing is the title of one of his books.
 
  • #4
Alright, thanks for your responses.

But then my problem is that, in my mind, nothing (which I can't and never will be able to imagine) doesn't have dimensions, forces, anything whatsoever.

So in any case, he postulates to get something from nothing, you need gravity. But isn't an empty space with gravity not nothing? Because that already has three spatial dimensions and gravity.
 
  • #5
daanaerts said:
So in any case, he postulates to get something from nothing, you need gravity.

Uh ... why?
 
  • #6
edit: ' he postulates to get something from nothing, you need gravity.' he probably means a dynamic geometry...a changing spacetime...see below...
nothing (which I can't and never will be able to imagine) doesn't have dimensions, forces, anything whatsoever.

'You'll have to define what you mean by 'nothing'...Is it different from 'empty', or the 'vacuum'...for example ...those descriptions were once thought to apply to space but quantum mechanics suggests a different understanding is required. And another view of that is via gravitational and electromagnetic fields, for example, which seem to permeate everything everywhere. But there is more:

“...Vacuum energy is the zero-point energy of all the fields in space...the energy of the vacuum, which in quantum field theory is defined not as empty space but as the ground state of the fields...

As if this were not crazy enough, such vacuum energy contains, some say is caused by, virtual particles...particles we can't detect as such but which manifest as forces...And this leads to some aspects of the big bang: vacuum energy can spawn REAL [locally detectable] particles. Cosmological inflation, which shortly followed the big bang, was apparently part of a phase transition from a high vacuum energy unstable state to the separate forces, time, matter and energies we observe today as separate entities. In other words, dynamic spacetime, or dynamic geometry if you wish, together with the vacuum energy of the early universe produced most of what we observe around us today.
Doesn't gravity (or maybe quantum mechanics, too) break down, like the nuclear forces, in the big bang?

Well, what 'broke down' was a single high energy symmetric entity for which we don't have a complete theory. It's a 'grand unification' entity of some sort. This state was unstable and resulted in 'spontaneous symmetry breaking'... that's the phase transition I just mentioned. So time, energy, some of the fundamental elements, electromagnetic [light] energy, time, gravity, all emerged from that symmetry breaking. And something from that still powers the expansion of the universe right now...some call it the cosmological constant, some dark energy. It's part of the 'nothingness' of space...really, of spacetime.

I know that on some level it makes little sense, but just wait another 100 years and see what happens!
 
  • #7
daanaerts said:
Dear all,

I just read something in a book by Lawrence Krauss which I don't understand. I hope you can answer my question:

Kraus makes the argument that if you take quantum mechanics and gravity, something is more energetically favorable than nothing. Hence if you take nothing, at some point something will arise.

My question is:

Doesn't gravity (or maybe quantum mechanics, too) break down, like the nuclear forces, in the big bang?

If so, then does Kraus's argument still hold? Or do I interpret it wrongly?

I'm a biologist and only read bits a pieces about physics, so forgive me if I've said something ignorant, which I know is easy to do.

Kind regards,
Daan from Amsterdam

anything breaks beyond big bang, quantum mechanics, relativity mechanics, read in this forum FIREWALLS.
 

1. What is the relationship between gravity and the big bang?

The big bang theory is the most widely accepted explanation for the origin and evolution of our universe. Gravity is one of the fundamental forces that govern the behavior of matter in the universe, and it plays a crucial role in the big bang theory. In fact, the theory itself is based on Einstein's theory of general relativity, which describes gravity as the curvature of space and time caused by massive objects.

2. Does gravity behave differently during the big bang?

During the big bang, the universe was extremely hot and dense, and the laws of physics as we know them today did not yet exist. At this point, the force of gravity was much stronger than it is now, and it behaved differently than it does in our current universe. However, as the universe expanded and cooled, gravity began to behave according to the laws of general relativity.

3. Can gravity break down in the big bang?

No, gravity does not break down in the big bang. The laws of general relativity still apply, even in the extreme conditions of the early universe. However, some scientists believe that there may have been a brief period of time (known as the Planck era) where gravity and the other fundamental forces were unified, but this is still a subject of ongoing research and debate.

4. How does gravity affect the expansion of the universe during the big bang?

Gravity is the force responsible for the formation of structures in the universe, such as galaxies and clusters of galaxies. In the early stages of the big bang, gravity played a key role in the formation of these structures as the universe expanded and cooled. However, as the universe continued to expand, the force of gravity became weaker in comparison to the expansion, causing the universe to expand at an accelerated rate.

5. How does the theory of inflation relate to gravity in the big bang?

Inflation is a period of rapid expansion that is believed to have occurred immediately after the big bang. This theory helps to explain some of the observed properties of our universe, such as its overall homogeneity and flatness. Gravity is thought to have played a role in driving this period of expansion, and it is still being studied how exactly gravity and inflation are related.

Similar threads

Replies
28
Views
3K
Replies
1
Views
752
Replies
27
Views
3K
Replies
6
Views
635
Replies
5
Views
1K
  • Special and General Relativity
Replies
2
Views
738
Replies
26
Views
4K
  • Cosmology
Replies
10
Views
2K
Replies
6
Views
1K
Replies
11
Views
1K
Back
Top