Linked Questions

1
vote
0answers
55 views

Where does the dark energy of space expansion come from? [duplicate]

Space has a constant density of dark energy, that means dark energy does not dilute with space expansion. By consequence, any space generated by space expansion does generate new dark energy. ...
62
votes
4answers
34k views

Why can't energy be created or destroyed?

My physics instructor told the class, when lecturing about energy, that it can't be created or destroyed. Why is that? Is there a theory or scientific evidence that proves his statement true or ...
20
votes
5answers
6k views

Hubble's law and conservation of energy

If all distances are constantly increasing, as Hubble's law say, then lots of potential energies of form ~$\frac{1}{r}$ changes, so how is the total energy of the Universe conserved with Hubble's ...
22
votes
3answers
16k views

Is the law of conservation of energy still valid?

Is the law of conservation of energy still valid or have there been experiments showing that energy could be created or lost?
20
votes
5answers
8k views

Conservation law of energy and Big Bang?

Did the law of conservation of energy apply to the earliest moments of the Big Bang? If so, what theoretical physics supports this? I hear that Einstein's theory of relativity disputes the law of ...
21
votes
3answers
13k views

Photons in expanding space: how is energy conserved? [duplicate]

If a photon (wave package) redshifts (stretches) travelling in our expanding universe, is its energy reduced? If so, where does that energy go?
10
votes
6answers
1k views

Is the mass of a black hole somewhere at all?

The Schwarzschild vacuum solution describes the gravitational field and thus the spacetime curvature of a black hole. The mass of a black hole is sometimes associated with its singularity as pointed ...
9
votes
2answers
1k views

Is the conservation of energy simply assumed or can it be accurately tested?

Has anyone conducted experiments demonstrating the conversation of energy or is it simply assumed to be true? Testing the conversation of energy would entail accurately measuring the joules of the ...
7
votes
3answers
720 views

Is energy conserved in general relativity? Does $\nabla_aT^{ab}_{\rm matter}=0$ represent the conservation of energy and momentum?

For example, the radiation dominated cosmology, the energy density of radiation is proportional to $a^{-4}$ and the volume is proportional to $a^3$, where $a$ is the scale factor. So the total energy ...
2
votes
4answers
2k views

What is fundamentally physically impossible?

Mathematical logic defines quite clearly what is true or false in math, and also that some theorems are impossible to prove. This resulted in some clear definitions of axioms set like Peano, ZF or ZFC,...
15
votes
4answers
600 views

What is the experimental evidence for the gravitational field having positive energy density?

Recent direct observation of gravitational perturbations attributed to merging black holes and merging neutron stars has reliably confirmed the existence of gravitational waves. The observed fact that ...
5
votes
3answers
1k views

Vacuum energy and perpetual motion

The part of the Einstein equations of general relativity referred to vacuum energy, introduce a repulsive term in gravity. This means that as the space become bigger and bigger, vacuum part become ...
2
votes
3answers
637 views

Is the accelerated expansion of the universe consistent with conservation of energy? [duplicate]

If energy can neither be created nor destroyed, how come the universe is expanding at an accelerating rate? Where does this energy come from?
5
votes
3answers
401 views

How does dark energy allow the universes expansion to accelerate?

I was wondering how dark energy is effecting the rate at which the universes expansion occurs.
2
votes
2answers
1k views

Energy conservation and General Relativity

Generally, we know that energy is conserved and there is Hamiltonian mechanics which describes particle motion by energy conservation and conversion. Quantum mechanics is completely based on the ...

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