freyar
Extradimensional Explorer
As the wave passes through matter, it will give a bit of that energy to the matter, but it won't lose more than a small fraction of its energy. So it will just continue spreading out from the initial event, with the energy getting less and less dense as it spreads out. (It's worth mentioning that there are some subtleties involved in defining what you mean by the "energy" of a ripple in spacetime, but it's fairly clear when the ripple is very small like what LIGO measured. Right when it left the black hole merger was potentially more difficult.)Was just wondering: What is the eventual fate of the energy emitted as gravitational radiation by an event like this? Does it mostly radiate into the background, never to interact with matter, always to remain as a ripple in spacetime?
Wow, the ultimate fate of everything in the universe? Big question! But people have thought about this to some extent. It's possible that the universe's expansion could eventually stop and reverse, leading to a "Big Crunch." Given that we know the expansion is accelerating, it's more likely that it expands forever. In that case, yes, any mass that isn't converted into radiation will eventually end up in rather large black holes (this is extremely long after the stars all burn out). And eventually, there'd just be one large black hole in any region that could be seen. Now if we wonder how much of the mass might be converted to gravitational waves during this agglomeration process, it probably is a few percent of the mass that gets converted to gravitational radiation at most. I haven't done the math, but I'd think that a smaller percentage of mass gets converted to gravitational waves if a smaller object falls into a really big black hole.If most matter eventually goes through this sort of process, what percentage of energy will eventually be converted to gravity waves? This one event had about a 5% conversion rate. If we look at one of the big (billion solar mass+) black holes at the centers of galaxies, depending on the sequence of mergers which happened, a big percentage of the mass energy of the black hole might have been radiated away.
Though, the milky way galaxy is estimated at about 10^12 solar masses (1 trillion), so that's a small percentage of the milky way mass lost.