5 ms·
We can already see how the laws of physics might accommodate energy not being conserved - and from there a small hop to perpetual motion machines. Energy conse
by cjg 5y ago
We can already see how the laws of physics might accommodate energy not being conserved - and from there a small hop to perpetual motion machines.
Energy conservation relies on time translation symmetry. In other words, that the laws of physics do not change over time. Well, perhaps they do change slowly.
A prime example of this is the expansion of spacetime, which can reduce the energy of a photon travelling through empty space - it's redshifted. This has been experimentally observed.
See https://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/ https://www.preposterousuniverse.com/blog/2010/02/22/energy-... for more details.
- Koshkin 5y agoIsn't redshift a results of the change in the observable wavelength, i.e. the photon's momentum?
- LegitShady 5y agoThe energy of a photon is defined as E = (hc)/λ where h is the planck constant, c is the speed of light, and λ is the wavelength. As a redshift is the increase in wavelength it is an actual decrease in the energy of the photon. This makes more sense when you consider that a photon is mass-less, and so its total, energy is bound up in its momentum rather than momentum and mass.