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> Not gravitational waves. Yes, gravitational waves. You are correct that in the case of the Earth, other causes will lead to its demise long before said wave

> Not gravitational waves. Yes, gravitational waves. You are correct that in the case of the Earth, other causes will lead to its demise long before said waves would amount to any significant effect. But even in an ideal case where a single planet like the Earth revolved around, say, a black hole with the same mass as the Sun, which would emit no particles, it would still not orbit indefinitely due to the energy lost to gravitational waves emitted as a result of its revolution around another body. The amount of energy lost in one revolution is tiny, but is not zero (according to this calculation [0], for the Sun-Earth system it amounts to about 200W). [0] https://en.wikipedia.org/wiki/Gravitational_wave#Power_radiated_by_orbiting_bodies https://en.wikipedia.org/wiki/Gravitational_wave#Power_radia...

Nomentatus 10y ago
Yes, two bodies create a gravitational wave that affects other bodies - but I don't see how those variations represent work - and they aren't observable on the two bodies themselves, so one wouldn't expect any effect upon those two bodies. Throw in the other planets and you might have a better argument, for example that Jupiter-Sun waves affect earth. Still, gravity "waves" aren't like water waves, as far as we yet know they don't represent (changes in) the impact of particles. However if you wish to argue that Higg's Bosons mediate gravity (some have, I believe) this objection of mine might be overcome. In other words, though I might be wrong, I just don't think we're at the point where we can deduce friction from gravitational waves, and we certainly aren't at the point where we can empirically measure such friction (as opposed to the "wave" - variation in gravitational field.) PS, sorry: there should have been a question mark in my previous post asking whether you were thinking about flares.
- fmihaila 10y ago
  > Yes, two bodies create a gravitational wave that affects other bodies - but I don't see how those variations represent work - and they aren't observable on the two bodies themselves, so one wouldn't expect any effect upon those two bodies The lost energy results in orbital decay, eventually leading to the two bodies colliding. The page I linked to explains it in more detail.
  - Nomentatus 10y ago
    Asserts it, yes - but my last sentence still applies. We don't have a fine-grained understanding of gravity; we'd need it for such a deduction. As it happens, I don't think we've ruled out that gravity itself - not just waves - slowly decays orbits. I rather expect this to be so, in fact, but on the basis of an eccentric theory of gravity.
- JumpCrisscross 10y ago
  > I just don't think we're at the point where we can deduce friction from gravitational waves Where do you think the energy we measure in a gravitational wave comes from? The whole concept arose to explain the last parsec problem of orbital collapse.
  - Nomentatus 10y ago
    There is a change in gravity, true - but a net slowing is another matter. That an explanation of X was needed doesn't justify any sufficient-if-true explanation Y.

Nomentatus 10y ago

Yes, two bodies create a gravitational wave that affects other bodies - but I don't see how those variations represent work - and they aren't observable on the two bodies themselves, so one wouldn't expect any effect upon those two bodies. Throw in the other planets and you might have a better argument, for example that Jupiter-Sun waves affect earth. Still, gravity "waves" aren't like water waves, as far as we yet know they don't represent (changes in) the impact of particles. However if you wish to argue that Higg's Bosons mediate gravity (some have, I believe) this objection of mine might be overcome. In other words, though I might be wrong, I just don't think we're at the point where we can deduce friction from gravitational waves, and we certainly aren't at the point where we can empirically measure such friction (as opposed to the "wave" - variation in gravitational field.) PS, sorry: there should have been a question mark in my previous post asking whether you were thinking about flares.

fmihaila 10y ago
> Yes, two bodies create a gravitational wave that affects other bodies - but I don't see how those variations represent work - and they aren't observable on the two bodies themselves, so one wouldn't expect any effect upon those two bodies The lost energy results in orbital decay, eventually leading to the two bodies colliding. The page I linked to explains it in more detail.
- Nomentatus 10y ago
  Asserts it, yes - but my last sentence still applies. We don't have a fine-grained understanding of gravity; we'd need it for such a deduction. As it happens, I don't think we've ruled out that gravity itself - not just waves - slowly decays orbits. I rather expect this to be so, in fact, but on the basis of an eccentric theory of gravity.
JumpCrisscross 10y ago
> I just don't think we're at the point where we can deduce friction from gravitational waves Where do you think the energy we measure in a gravitational wave comes from? The whole concept arose to explain the last parsec problem of orbital collapse.
- Nomentatus 10y ago
  There is a change in gravity, true - but a net slowing is another matter. That an explanation of X was needed doesn't justify any sufficient-if-true explanation Y.