The constancy of the energy of the universe?

You seem to see it as a foregone conclusion that those theories are true. You're a tad bit premature.

 

Please correct me if I read your post wrong but first you state that the Universe is a closed system, then you state that gravity "leaks" out of it. That would imply that the universe isn't a closed system wouldn't it?

 

Does the universe "leak" Hawking radiation at its event horizon? Do two separate observers perceive differing cosmological boundaries, perhaps differing energies, for the universe? Are fundamental constants, like the Planck energy, truly invariant over all spacetime? Is local vacuum energy indicative of its global manifestation of energy conservation?

 

An important thing to remember Cygni, that you mentioned in your first post, is that

Total Energy = KE - PE not KE + PE

If you have plenty of similar questions on Cosmology and Universe Physics, I recommend "The Cosmic Onion" as an excellent book dealing with elementary particle physics, and unified theories in general (Don't worry, there's nothing you won't struggle to understand). Hope this was helpful,

V

 

That is certainly NOT true. The total energy, or, more precisely, the "Hamiltonian" of the system is KE+ PE. What you give, KE- PE is the "Lagrangian" which not in any sense the "total energy".

 

Sorry to mislead you Cygni, I've always been used to dealing with Lagrangians and negative PE. Regardless, I recommend the book. Your school/local library may well have it.

V

 

Iv often pondered the same thing Cygni and have come to believe the total energy in the universe is not necessarily constant, but is infinite. Also I have come to believe that given a certain astronomical unit of volume, T^3*, the average energy (and mass) per this volume throughout the universe is constant.

Also, M-theory isn't technically a theory, its a postulate. As was first suggested don't believe everything you read.

*I call this constant "T", Topher's constant. :) Sort of similar to Planc's constant but on a cosmological scale at which the universe can be considered a homogeneous mixture of mass and energy.

My $0.02 whether you asked for it or not.

 

This is not correct. You need to refer back to a thermo text and figure out why what you have stated is wrong.

While we certainly do not mind and welcome questions such as this in PF, at some point, we need to base it on the correct understanding of basic physics. It would be impossible to answer such question AND have to keep on going back to basic physics, because we will be backtracking every few posts.

Start with the foundation first. THEN to extrapolate out of those foundations. If not, this would be come highly speculative and would be beyond what is allowed in the PF Guidelines.

Zz.

 

Zapper, according to my thermo text he is correct. Are you sure you are not confusing a closed system with an isolated system?

 

Although I would have agreed with ZZ, a quick browse of wikipedia finds:

Closed systems are able to exchange energy (heat and work) but not matter with their environment. A greenhouse is an example of a closed system exchanging heat but not work with its environment. Whether a system exchanges heat, work or both is usually thought of as a property of its boundary.

 

Hum... maybe that's what I meant.

Zz.

 

Seems to me that if energy could be shown to somehow "leak" out of the universe, we'd simply re-define "universe" to contain the leak :)

 

As a general rule, I would not use concepts from theories that you do not have an complete understanding of mathematically (Not to insult you personally Cygni). This helps prevent confusion, and innacuricies in discussion.

Energy cannot be created or destroyed, only transferred, thus energy throughout a multiverse system (if that is what our universe "leaks" into) would be constant, surely. Really, the whole question smacks of similarities with "What would happen if one fell into a black hole?". Whilst it may be interesting, there is no exact answer, and not really an exact question either, as "What" has a huge scope of meanings.

V

 

The constancy of the energy of the universe breaks down in plain old General Relativity, there is no need to consider QM or ST or beyond. For example, think of all the red shifted photons, as their wavelength increases their energy decreases, with no effect to compensate. I am not an expert in this area, but I had these questions at one time, and all the experts I asked said that the energy conservation of the universe fails in GR cosmology.

 

In cosmology, the red shifted photons are coming from galaxies and other bodies accelerating away from us, so shouldn't the "Missing" energy be found in these Galaxies? Not wanting to deviate too much, as this is not a cosmology forum, but it is a universal energy question.

 

is anyone conisder the dark matter & dark energy?
what i mean: is the dark matter & dark energy have constant energy(potential+kinetic)??? or not?

 

Sure GR fails, but wouldn't SR hold true for photon red shift since our frame is not stationary relative to the body emitting the photons? That is, given ds^2 = dx^2 + dy^2 + dz^2 - c^2 dt^2 predict the Doppler effect although that c term might create trouble. Maybe I'm just over thinking this but since the Lagrangian in classical mechanics of one of these photons can easily predict the Doppler effect a successful theory like SR should be able to as well.

When it comes to dark matter/energy, I haven't seen enough evidence to convince me that the theory is even remotely correct. In my opinion its not much more useful then M-theory.

 

No, the cosmological redshift is not due to the Doppler effect, this is a frequent misconception. It is a convenient way to explain things to students and the public, but for working cosmologist the redshift comes from the expansion of space predicted by the http://en.wikipedia.org/wiki/Friedmann_equations" [Broken]. Intuitively, the wavelength of light increases because the space that it is in expands.

Not to sidetrack the thread, but dark matter/energy has a lot more experimental support then M-Theory, which is not yet ready to make any predictions. Dark matter is supported by measurements of galactic rotation curves, gravitational lensing, and the large scale structure formation of the universe.