I have been somewhat of a fan of astronomy and cosmology, but I am not trained physicist. So please correct me kindly in case I have stumbled with some terminology.

The causes of big bang are somewhat of a mystery. But I would like to dig a bit more into the details...
What caused or determined the total amount (it's a number) of matter or energy created/released during big bang? As I understand, this total has been constant over the evolution of Universe. So from "where all this amount came from"?
Why not less or even more?
Please note, I am not asking, "where the mass and energy came from" or whether it existed or was created. I am interested only - what caused the amount, or to which other important properties or laws the amount is related to?
The amount is a number. We often explain numbers in physics and cosmology.

Some theories state that big bangs occur by chance alone. Some state that the universe has always existed in some yo-yo state. Okay with both... But now, are such big amounts of mass and energy also so naturally tied with such "chances" or "permanences"? Would it not be more likely to have a smaller universe being created by "chance"? Or to have infinite amounts, in case it is permanent? Or is there likely something more needed for explaining such big amount we have in "our case"?

Could the amount be derived from some cosmological constants somehow?

Regarding anthropic principle:
Is the total amount at least somewhat related to some other important parameters and laws we have, that are in turn related to support for life?
For example Earth and Sun are rather normal among other similar sky objects that just "might" support life like ours. Which means their size is meaningfully related to other physical properties leading to support of life.
I do not see such anthropic-principle connection with the total amount of energy and matter in our Universe.

A slightly related question, though I would not constrain my question only to this theory. Also the amount still needs explanation: Is it possible that the Big Bang was caused by virtual particle creation?

  • $\begingroup$ Although the total amount of energy/matter has been estimated, no one knows where the energy/matter came from or why the energy/matter exploded into our universe. The current cosmological models only work back to a fraction of a second after the supposed singularity erupted. $\endgroup$
    – MaxW
    Dec 13, 2016 at 13:58
  • $\begingroup$ @MaxW Hi, thanks. I am not focusing on the cause of the event. I would like to understand the number. Usually physics is at least capable of explaining the numbers, even when it cannot explain the cause of the laws. $\endgroup$ Dec 13, 2016 at 14:03
  • $\begingroup$ Suppose (to make the situation a million times more theoretically well-understood) you ask me what caused the exact mass of the system to be what it was when the solar accretion disk was formed that ultimately resulted in our solar system: what sort of explanation would satisfy you? It sounds like you'd be upset with the obvious "well there just happened to be that much mass around in a big gas cloud," or with what physics can provide, which is "well given the amount of mass now and what we know about how mass has been entering and leaving the solar system here's how much it must have been." $\endgroup$
    – CR Drost
    Dec 13, 2016 at 15:29
  • $\begingroup$ @CRDrost As I understand, Solar System's mass can be reasonably well explained by anthropic principle and some additional physical laws and fundamental constants relevant to this approach. $\endgroup$ Dec 13, 2016 at 15:33
  • $\begingroup$ Hi Roland, I am not sure you are getting answers to all your questions, because you have a lot in your post that you would like explained. Could I suggest that you split them up. The very best of luck with them. $\endgroup$
    – user108787
    Dec 13, 2016 at 15:52

2 Answers 2


The simplest answer is that the total energy at the time of the Big Bang was exactly zero, and remains zero today. What determined that energy was the conservation of energy principle, which is assumed to have been valid at all times.

Gravitational energy is negative, and that negative energy offsets the positive energy of mass. In view of this, UC Berkeley's Alex Filippenko and Caltech's Sean Carroll have referred to the universe as the ultimate free lunch.


In Quora I found this answer. I do not know whether it is adequate.
What is interesting, is that it seems that according to this source, the initial amount was rather small.


Brent Follin, PhD student in Theoretical Cosmology Written Apr 16, 2014

Almost all energy in the observable universe is a result of the exponential expansion of space-time during inflation.

During inflation, the inflaton field exhibited slow-roll and behaved as an effective transient cosmological constant. As such, its density across space was constant through time, but the amount of space it pervaded expanded exponentially by a factor of at least $e^{60}\simeq10^{26}$, and quite possibly much more. So, the total energy of the universe increased by at least that same amount (actually more, since dark energy has added about one more factor of $e$ to that total). The universe now contains about $10^{80}\text{ GeV}$ of mass/energy, so we had to start with at most $10^{54}\text{ GeV}$, which is about the mass of Jupiter.

If the observable universe started at Planckian scales as many scientists believe (and we trust the BICEP2 results which give us a handle on the energy scale of inflation), we get the total necessary initial energy of the observable universe somewhere between half a muon and an RNA molecule.

Where that half a muon of energy came from, I can't say.


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