Is energy conserved at the origin of the universe?
Response to a Quora Question
Disclaimer—the answer below first appeared on Quora. Their policy, which I presume is an agreement, is that they retain non-exclusive rights to answers by members. Changes made here but not made in the Quora answer are marked in differently colored font.
Today’s physics does not have an answer to this question. But why or how does physics so far not have an answer (see the universe revealed by science.html for more on the limits of today’s physics)?
The only realistic model we have is the big bang model which, using general relativity, “extrapolates” back in time from current observations. If one projects back, based on one observation (the earliest was the cosmic microwave background) to an initial dense hot state one might say “maybe”. However, there are so many observations that are simultaneously and coherently explained by the same model that we have confidence in it.
But the model projects back to an infinitely dense state—a state so dense that the laws of physics used to “predict” it break down.
There are various suggestions regarding this problem but they are speculative.
That is why today’s physics does not have an answer. We don’t know whether energy was conserved or even whether conservation of energy held before the point at which the laws “began” to hold (the quotes indicate that current physics does not enable us to talk of time with confidence “before” that point). Let’s call the point at which our physics breaks down t0.
But even if we do find laws of physics that project to before t0, it will not necessarily solve our problem for they too might have a limit (it’s a guess but I’d say that such a limit is likely).
The limit in question is not just one of getting enhanced laws. The laws explain how the physical world behaves; they don’t explain how the laws themselves came about.
That would seem to take a different kind of explanation.
Obviously, then—at least as it seems to me, we know very little about “absolute origins” or reasons for the existence of the universe-as-we-know-it.
But since the final explanation, if there is one, will not make assumptions—if it did it would not be final—it makes sense to claim that it will be an explanation ex nihilo, i.e. out of nothing.
And scientists and philosophers seem to agree that such an explanation is at best remote.
There’s that Latin phrase—ex nihilo nihil fit or nothing comes from nothing.