Quote:
Originally Posted by sjastro
You are displaying an ignorance of General Relativity.
The conservation of energy is a Newtonian concept based on static space-time at non cosmological scales where objects move in space-time rather than carried along by space-time such as the recession velocity of galaxies.
In fact the recession velocity vs distance of galaxies even before the discovery of dark energy might have provided you with a valuable clue the conservation laws don't apply.
When space time is not static such as an expanding Universe or the passage of a gravitational wave, General Relativity is used.
Where as energy is conserved in Newtonian physics, energy-momentum is not necessarily conserved in General Relativity.
This has been known since the 1920s but requires a knowledge of tensor calculus in order to be understood.
In laymans terms if space time is not static the conservation of energy is not applicable.
Another obvious example is the cosmological redshift of photons.
This is an energy loss. Where do you think the energy goes?
Similarly GWs undergo energy loss at cosmological scales due to redshift.
At local scales GW energy loss is due to the work done on expanding/compressing matter.
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thanks very much for the insight - I hadn't taken this on board, even though I was well aware that redshift reduces photon energy (it never occurred to me to ask where it went)
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I found this blog by a CalTech physicist that is clear enough for me to understand.
http://www.preposterousuniverse.com/...not-conserved/