Dark Energy?

I've heard of dark matter but not dark energy.

My understanding of dark matter is that it is the invisible material or force that holds everything (galaxies) together while gravity or whatever force (maybe kenetic energy) tries to rip everything (galaxies) apart.

It's the universe's answer to superglue.

I'm guessing dark energy is the product/force of dark matter?

The whole concept of dark matter is still a mystery to science.

Has dark matter/energy anything to do with "Z" particles?


Dark energy is the name we give the mystery force that's acting against gravity to speed up the expansion of the universe when it should otherwise be slowing down. We have no idea what it is really.

Cant we just call it anti-gravity?

Hi

I was listening into a podcast recently about a new theory of Dark Energy that suggested that dark energy was in fact an optical illusion.

The idea being that the light from distant objects is travelling to us though regions of space that are of various densities of matter. When it is travelling through the galactic clusters, the extra matter there makes time travel slower then when it is travelling through the void between the galaxies when time will be travelling faster.

This gives the effect of light seeming to travel further then it actually has travelled and consequently making things seem further away then they actually are.

I wonder if anyone else has heard of this idea?

DB

Dave i think the show on Discovery Science that i saw on dark matter/energy did offer up this theory as one possibility.

It's so weird. You would expect galaxies etc to slow down as they get further from the point of origin (can we call it the event horizon?)........but they actually seem to be speeding up.

This flies in the face of the natural laws of physics (as we know them).

There must be some other factor involved.

I cant help but think of the difference between observing the moon and Saturn.

The moon is closer to us then Saturn and appears to travel out of our FOV in a scope slower then Saturn which is further away.

Bad comparison i know........................

Gravity - a simple explanation. It is not a force. It is merely the result of matter curving spacetime. Why? - we don't know yet. A body will continue in a staight line unless acted upon by a force. No force causes a planet to orbit the Sun, it is merely the planet carrying on in a straight line through curved spacetime. Hence an elliptical or circular orbit, depending on the curvature of spacetime. Nearer the massive body (e.g. Sun) spacetime is more curved (inverse squared law). Gravity is the old newtonian way of thinking, Einsteins General Realtivity thought us a new way to think about "gravity", and it is definitely not a force in its own right. Unfortunately in order to explain things to lay people scientists still roll out Newtonian classical forces as being the truth, when they are merely an easier model for us to understand. I am not saying that Einsteins theories are the whole truth and nothing but, merely that they are the most accurate model we currently have of reality (whatever that is.).

Dark Energy is just the current model we have until something better comes along to explain why the Universe is expanding at the rate it is (without Dark Energy the maths just doesn't work). However its not as far fetched as it sounds. Seemingly empty space is teeming with energy and particles popping into existence and anhilating almost simultaneously. Fact in this case is stranger than fiction, as anyone who has studied quantum mechanics can attest.

Gravity - a simple explanation. It is not a force. It is merely the result of matter curving spacetime. Why? - we don't know yet.

Thats interesting, its abit like a doctor treating the symptoms of an illness while not knowing the cause, anyone got any theories?

However its not as far fetched as it sounds. Seemingly empty space is teeming with energy and particles popping into existence and anhilating almost simultaneously. Fact in this case is stranger than fiction, as anyone who has studied quantum mechanics can attest.

Well maybe these particles get a chance to exert a force on each other before they go pop, so the more space, the more particles, the more force, so the whole thing accelerates on and on.
I suppose if I think about it enough, I might be able to explain global warning using this quantum mechanics. :lol:

Thats interesting, its abit like a doctor treating the symptoms of an illness while not knowing the cause, anyone got any theories?

Well nobody yet knows why matter has the effect it does on spacetime. Until the LHC comes online and maybe discovers the Higgs Boson (reckoned to give matter its mass) and its properties - then the answer may be forthcoming.

Well maybe these particles get a chance to exert a force on each other before they go pop, so the more space, the more particles, the more force, so the whole thing accelerates on and on.
I suppose if I think about it enough, I might be able to explain global warning using this quantum mechanics.

A simple experiment will prove what I say above, known as the Casimir effect. In fact space itself may be (probably is) quantum in nature. And given that space is expanding (the Universe has to have something to expand into) and space in itself is energetic, therefore energy is also expanding. The polarity (if you will) of this energy however is oppsite to what we are accustomed to i.e. mass etc. therefore it has an opposite effect to normal mass/energy i,e, negative curvature of spacetime resulting in expansion of the Universe. If you follow this through to its conclusion the Universe will continue to expand at a faster and faster rate.
Thats the easiest way I know to explain it - sorry if its not clear - my fault.