How much energy is there in the Universe?

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Discussion Overview

The discussion revolves around the concept of energy in the universe, specifically whether the total energy is zero and the implications of such a scenario. Participants explore theoretical frameworks, particularly General Relativity, and the relationship between mass, energy, and gravitational effects. The conversation includes speculative ideas about negative energy and its behavior in relation to positive energy.

Discussion Character

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

Main Points Raised

  • Some participants suggest that if the total energy of the universe is zero, then there must be an equal and opposite amount of negative mass/energy, raising questions about how this negative energy would interact with positive energy.
  • One participant notes that General Relativity complicates the definition of energy, making it difficult to arrive at a definitive answer regarding the total energy of the universe.
  • Measurements from WMAP are cited as suggesting that the universe is flat, which implies an average energy density of zero.
  • Another viewpoint is that a zero energy universe could spontaneously exist without violating conservation of energy, as the existence of the universe itself is presented as evidence for this idea.
  • Some participants express skepticism about the conservation of energy in the universe, pointing to the Cosmic Microwave Background (CMB) as evidence of energy loss without a clear source for that energy.
  • There is a discussion about the concept of negative energy in gravitational fields, with examples provided to illustrate how energy can be perceived as lost in certain scenarios.
  • One participant raises the issue of energy loss due to cosmic expansion, suggesting that this could lead to a net loss of energy over time, complicating the discussion further.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the nature of energy in the universe. Multiple competing views are presented, particularly regarding the implications of a zero energy universe and the behavior of negative energy.

Contextual Notes

The discussion highlights limitations in the definitions and frameworks used to understand energy in General Relativity, as well as the unresolved nature of energy conservation in the context of cosmic expansion and gravitational effects.

Alutoe
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How much energy is there in the universe?

I've heard a lot of people saying the total amount of energy in the universe is 0, if this is the case the total amount of mass in the universe is 0. In this scenario there is an equal and opposite amount of mass/energy in the universe. How would the "negative" mass/energy act? It would need to be something when brought in contact with "positive" mass/energy would exactly annihilate each other and bring the system back to a state of 0 (with no "positive" or "negative" fluctuations). Do we see anything of this nature? Upon first look it seems like a weird concept both required and disallowed by the laws of physics, but I have the sense that I'm just not look at it from the right perspective yet.

Thanks for your help!
 
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Alutoe said:
How much energy is there in the universe?

I've heard a lot of people saying the total amount of energy in the universe is 0, if this is the case the total amount of mass in the universe is 0. In this scenario there is an equal and opposite amount of mass/energy in the universe. How would the "negative" mass/energy act? It would need to be something when brought in contact with "positive" mass/energy would exactly annihilate each other and bring the system back to a state of 0 (with no "positive" or "negative" fluctuations). Do we see anything of this nature? Upon first look it seems like a weird concept both required and disallowed by the laws of physics, but I have the sense that I'm just not look at it from the right perspective yet.

Thanks for your help!

I don't understand it, but the basic idea is that gravity is negative.
 
To take into account ALL of the universe we need to use General Relativity and it's math to describe it. Unfortunately there is no specific definition of energy that is fully accepted in General Relativity, so it makes it difficult to answer you. On top of that, different ways of "setting up the problem" changes things also. I know there is one "solution" if you will that says that the total energy of the universe is 0, however this is only one possible solution.

I can't explain it very well, but I know we have a thread or two here on PF about it. Try using the search function to find it.
 
Another bit of evidence is that the universe exists at all. Only a zero energy universe can spontaneously pop into existence without violating conservation of energy.
 
mrspeedybob said:
Another bit of evidence is that the universe exists at all. Only a zero energy universe can spontaneously pop into existence without violating conservation of energy.

Doesn't the universe ignore the conservation of energy as a whole? Take a look at the CMB. It's losing energy as time passes without that energy showing up somewhere else.
 
Drakkith said:
Doesn't the universe ignore the conservation of energy as a whole? Take a look at the CMB. It's losing energy as time passes without that energy showing up somewhere else.

I think it's losing positive and negative energy at the same rate. Otherwise the universe would not remain flat.
 
DrZoidberg said:
I think it's losing positive and negative energy at the same rate. Otherwise the universe would not remain flat.

How is it losing negative energy?
 
A gravitational field is a form of negative energy. Imagine you had a single planet somewhere alone in space. Far away from any galaxies. Now on this planet you have a matter to energy converter that consumes matter and releases photons. These photons are then send into space in form if a laser beam. Far away from that planet there is a photon to matter converter that receives the laser beam and turns it back to matter. As the photons move away from the planet their wavelength increases due to gravity which means they lose energy. As a result the amount of matter created by the photon to matter converter is smaller than the matter lost by the planet. Positive energy is being lost. Seemingly vanished into nowhere. But at the same time the gravitational field around the planet has decreased, so an equal amount of negative energy was lost as well.
 
  • #10
I understand your example, but consider that expansion causes even further energy loss of radiation as time passes. If your photon-matter converter was far enough away so that expansion caused it to recede from your planet then it would produce less and less matter over time as the photon energy falls. This energy is simply gone.
 

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