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However it has been suggested that the expansion of space may not be totally uniform over the entire universe and may occur more in areas where there is very little ordinary matter or greater concentrations of dark matter but this would be very difficult to detect.
I do not believe that you are thinking correctly here. You appear to be thinking that the dominant effect renders minor effects non existant. If I have three lights in a room one is one watt one ten watts and one one hundred watts. It will not make much difference if I switch either the one watt or ten watt lights on or of but when they are all on there are still three lights in the room it is the same with the dark energy expansion it may not make any difference but it is still there.
As for dark matter concentrations increasing the overall expansion of the universe. Just consider for a moment if some of the dark matter was in some way "particles of space" with a small mass and lots of energy but only interacting gravitationally. let these particles very rarely interact with one another to create another particle of space by converting some of its energy into another bit of space. This could create a situation where the universe as a whole expanded but it would expand faster where these particles were most concentrated.
GR says "Matter warps spacetime and spacetime tells matter how to move". It does not, though, state how matter warps spacetime.
QuoteGR says "Matter warps spacetime and spacetime tells matter how to move". It does not, though, state how matter warps spacetime.Yup - as gravity acts over great (potentially infinite) distances, this is key to it all. There is a clear implication that something (let's say a particle of some sort) originating from the mass ends up distant to the mass.
Karen You're in space outside your space-lab being still, holding your trusty lighted light-bulb at your side, brightly shining.Then you see that evil space-monster coming crablike towards you, you throw your glowing ligh-bulb at him as fast as you humanely can, while you grab hold of that trusty space-labs door, ready to hide.What will that monster see in form of the lights wavelength, when the light-bulb travels toward him.As the bulb flies towards him the light-waves 'shooting out' from it will be seen as 'compressed' from the monsters side.But from your side, as the light-bulb now is speeding away from you, (you did try to throw it at the monster after all) Those light-waves traveling back at you will seem 'spread out' as they have a constantly larger distance to travel as the light-bulb moves away from you.The reason for this is that light, no matter from where you measure it will have the same speed in space 'c'.But somehow it will have to take care of the added energy it gets when it meets you though, as well as the lost energy we see it loosing when it's moving away from you.If you think of a police-car passing you, the same effect will be noticed as the sound gets compressed when the car is speeding towards you, and then change pitch again as it travels away from you.(Thinking of cars crashing at different speeds, I believe we all agree that different speed creates different energy-impacts:)The way it takes care of that energy is by stretching out the waves when moving away(You<---->light-bulb), that's called redshifting as the colorspectrum gets redshifted when you see that light. When moving towards you the waves from that object (light-bulb ---><--- monster) will become more energized as it gets compressed, and that's blueshift. Energetic light is a bluish white (the Sun)We all know what cold is, don't we:)It's when all movement stops inside a moleculeThe stiller that molecule becomes the colder it will be.But did you know that the same is true for a photon (no waves at all will be very coold...)And that's how they stopped light, by cooling the waves/photons using lasers to quench those light waves.If I got that right:) So now you either have gotten a better grip on photons redlight/bluelight or you're even more confused:
Quote from: LeeE on 06/11/2008 11:22:40QuoteGR says "Matter warps spacetime and spacetime tells matter how to move". It does not, though, state how matter warps spacetime.Yup - as gravity acts over great (potentially infinite) distances, this is key to it all. There is a clear implication that something (let's say a particle of some sort) originating from the mass ends up distant to the mass.LeeE - that doesn't necessarily follow. If you pull 1 end of a piece of elastic, it will have an effect on the other end, but no particle has been sent there. If, on the quantum level, space is cohesive, then all that dark energy building up in 1 place could have a knock-on effect.
Spacetime is itself could be the medium of propogation through its interaction with cark energy & gravitons.
Just consider for a moment if some of the dark matter was in some way "particles of space"[...]
I understand that there has been electromagnetic Radiation that has been covering all matter sense the big bang.... How does this in effect create the cooling of the universe?
Well, yes I suppose so. It depends when you want to 'stop' the universe. Obviously if you stop it at the singularity then minimum entropy reigns and nothing happens.