Is my reasoning correct? Energy "before" the big bang?

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Discussion Overview

The discussion centers around the concept of energy conservation in relation to the Big Bang and the notion of "nothingness" before it. Participants explore theoretical implications of energy conservation laws, the nature of time, and the validity of different models in physics, including general relativity and special relativity.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Exploratory
  • Technical explanation

Main Points Raised

  • Some participants argue that the conservation of energy implies there could not have been a state of nothingness before the Big Bang, as this would violate the principle that total energy is constant.
  • Others contend that without a universe, conservation laws cannot apply, suggesting that "before the Big Bang" is a meaningless concept if the universe originated with it.
  • It is noted that general relativity does not support global energy conservation, and some participants question the implications of this on the understanding of dark energy and the cosmological constant.
  • Some participants express uncertainty about whether total universal energy is conserved in isolated systems and how this relates to special relativity.
  • A later reply raises the possibility that the total energy of the universe could be zero, referencing Lawrence Krauss' ideas, which challenges the assumption that energy must always be positive.
  • Participants discuss the implications of time and whether the Big Bang represents the origin of time or merely an event within it, questioning the foundational assumptions of current models.
  • Some participants clarify that energy conservation holds locally in general relativity, despite the lack of global conservation.

Areas of Agreement / Disagreement

There is no consensus among participants; multiple competing views remain regarding the nature of energy conservation, the implications of the Big Bang, and the concept of nothingness before it.

Contextual Notes

Participants express varying degrees of understanding regarding the application of energy conservation laws in different contexts, including general relativity and special relativity. There are unresolved questions about the definitions and implications of energy in cosmological models.

toothpaste666
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It seems as though that according to conservation of energy, there could never have been a point in the timeline of the universe where nothingness existed. It seems to me that the claim that there was nothingness before the big bang would violate these laws. For example if E is the total energy of the universe then the law states that E = constant. If E1 is the total energy of the universe at an arbitrary time t1 and E2 is the total energy of the universe at arbitrary time t2 , then E1 = E2. let's say t1 is before the big bang and t2 is right now. If there was nothingness before the big bang, then E1 = 0. Since right now it is obvious that E2 > 0 , or , E2 != 0, then E1 != E2 which would violate conservation of energy. Is this line of reasoning correct? if not, why?
 
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Without a universe, there is no conservation law a big bang could violate. "Before the big bang" is meaningless if the universe started with it, and you cannot assign an energy to something that does not exist.

By the way: general relativity does not have global energy conservation.
 
Conservation of energy arises due to the time translation symmetry of the laws of physics (see Noether's theorem).

Our current theories say that there is effectively no time before the Big Bang (in the geometric sense that one cannot go further north than the North Pole). If that's true, then one simply cannot translate from the Big Bang further into the past and say the laws of physics remain invariant.

If there is no time translation symmetry at the point of the Big Bang, there is likely no conservation of energy (as we know it) either.

At least currently, we can only speculate about what the laws of physics were like before the big bang (if there even was a "before").
 
mfb said:
By the way: general relativity does not have global energy conservation.
Is that not what "dark energy" and the "cosmological constant" is for?

Time translation symmetry is certainly a tricky thing in general relativity, but is there really no workaround?
 
jfizzix said:
Is that not what "dark energy" and the "cosmological constant" is for?
No. There is no unique meaningful way to define "the energy of the universe at a specific point in time", and as far as I know no matter how you define it there is a process that could change it.
 
toothpaste666 said:
It seems as though that according to conservation of energy, there could never have been a point in the timeline of the universe where nothingness existed. It seems to me that the claim that there was nothingness before the big bang would violate these laws. For example if E is the total energy of the universe then the law states that E = constant. If E1 is the total energy of the universe at an arbitrary time t1 and E2 is the total energy of the universe at arbitrary time t2 , then E1 = E2. let's say t1 is before the big bang and t2 is right now. If there was nothingness before the big bang, then E1 = 0. Since right now it is obvious that E2 > 0 , or , E2 != 0, then E1 != E2 which would violate conservation of energy. Is this line of reasoning correct? if not, why?
Why do you think it's obvious? It is not.
There is a possibility that E2=0. See Lawrence Krauss' book "A Universe from nothing", for example.
 
How do we know that the big bang is the origin of time and not just an event that happened in time? Is there a mathematical/scientific reason or is it an axiom we have adopted?

If total universal energy is not conserved in GR , is it still conserved in isolated systems? Is it also true that universal E conservation does not apply to SR?

As for the current total E being 0... How is this possible? Wouldn't that mean nothing can happen?
 
toothpaste666 said:
How do we know that the big bang is the origin of time and not just an event that happened in time? Is there a mathematical/scientific reason or is it an axiom we have adopted?
We don't know, we just have a model that represents reality incredibly well and as has already been stated, it is unable to handle what happened at or before the big bang singularity (aka t=0) or if there even IS a "before".

If total universal energy is not conserved in GR , is it still conserved in isolated systems? Is it also true that universal E conservation does not apply to SR?
Just today I made a post claiming that energy is conserved in closed systems and was told that that is wrong. See here:

https://www.physicsforums.com/threads/universe-already-existed.795055/#post-4993340
 
  • #10
Ok thanks i have some stuff to read now. Btw sorry i didnt realize such a similar question had been posted. In fact i just realized how often you guys probably get this exact question. Sorry :( in school i am still studying classical physics so i have so far only been taught that total E is always conserved and have even done several experiments myself that demonstrated this, so the idea that the energy laws do not always hold is new to me
 
  • #11
Energy is conserved in special relativity, and there is still local energy conservation in general relativity (which means your lab experiment won't find a deviation).
 

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