General Question

oratio's avatar

Is the mass and energy of the universe constant?

Asked by oratio (8905points) June 7th, 2009

I hesitate to ask this, since there is so much information out there, but it is a bit confusing, and a lot to go through. It is maybe not the easiest questions to answer.

As I have understood it, particles are continually brought into existence, and there seems to be the aspect of particle degradation where particles leaves existence. There is the Hawking Radiation that is supposed to radiate from black holes with positive particles and their negative counterpart particles goes into the gravity well and decrease the mass of these “holes”.

The universe seems to be accelerating too, which leads me to wonder if the universe increases in energy. Or is this explained by Dark Energy?

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9 Answers

mattbrowne's avatar

As far as I know based on established cosmological models the answer is yes which include the properties of black holes. The mass in them is still part of our universe. The quantum tunneling effect does not make particles leave the universe.

I think the puzzling part comes indeed from dark energy which seem to have had little effect during the first half of our universe’s existence. Now the acceleration of all the mass steadily increases kinetic energy while the total mass as such remains basically the same (some of course being converted to energy during nuclear fusion in stars). Let’s see what some of our real experts like Ivan have to say about this. Excellent question!

AnnieOakley's avatar

Thank you for asking this question. My mind appreciates it!! I am now inspired to go back and finish the book I started reading on Quantum String Theory – although I have no insightful response to your question.

westy81585's avatar

The entropy of the universe is always increasing….. So no, they are not constant.

oratio's avatar

@westy81585 Yes, I know that the entropy of the universe increases towards a maximum, but does that mean that the universe’s energy is not constant?

@AnnieOakley Glad to help a western hero. You seem to have your own complex string theory going on there by the looks of it. =) Maybe you can come back and enlighten us.

Ivan's avatar

Hawking radiation does not result in a net loss of mass/energy in the universe. “Ordinary” mass and energy do remain constant in the universe. The acceleration of the universe’s expansion is currently explained by “dark energy,” but that’s more of a place holder than anything.

AstroChuck's avatar

Theoretically our universe could gain or lose mass and energy as well as gravity via “leakage” from/to somewhere in the multiverse.

mattbrowne's avatar

@Ivan – How does the additional kinetic energy from the acceleration influence the overall mass/energy balance sheet?

Ivan's avatar


Well that’s the big question. There has to be some sort of driving force. We just don’t understand what is imparting all of this energy.

FireMadeFlesh's avatar

Yes, it is constant. The laws of conservation say that for any closed system, the sum mass-energy is constant. As far as we know, the universe is a closed system. Before I go on, to our knowledge this has nothing to do with dark matter or dark energy. We don’t know what they are, or for certain that they exist, so we cannot postulate much at all about their properties. Personally I don’t think they exist, just like the ether.

Hawking radiation decreases the mass of black holes, but increases the mass of everything outside the black hole. The antiparticle (not positive and negative, particle and antiparticle) annihilates matter in the black hole to give gamma photons. However the particle that is outside the event horizon escapes, and so mass is maintained.

The only possible avenue of energy loss I know of is Thermodynamics. In any heat engine, the output energy is always less than the input even if the engine has essentially 100% efficiency, according to the Second Law of Thermodynamics. However I am quite certain that if the universe began to contract rather than expand this law would reverse, and the output would yield more energy than we should expect.

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