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Author Topic: Would gravitational waves affect the trajectory of a moving astronomical body?  (Read 518 times)

Offline D

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Would gravitational wave have any effect on the speed or kinetic or potential energy? i mean if there is a massive comet moving at high speed in one direction and a gravity wave moving in the opposite direction would the speed of that comet be affected in any way? The gravitational wave going to stretch and squeeze the spacetime, one would think it should have some kind of an effect? maybe?
« Last Edit: 11/04/2016 18:06:50 by chris »


 

Offline evan_au

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The recent gravitational wave detected on Earth was so weak that a 4km-wide comet would have been squeezed by a tiny fraction of the width of a proton, and back again a couple of milliseconds later.

Given that we have trouble measuring the width of a big comet to better than 100m, the impact of weak gravitational waves is undetectable with our current technology.

However, if we have two orbiting black holes, they would clear matter out of a volume of space which has a radius about twice their separation distance. So a large comet venturing near orbiting black holes would be likely to be flung back out - or swallowed by one or another of the black holes. But this only needs Newton's simpler version of gravity, and does not need gravitational waves.

The recent gravitational wave event is estimated to have converted about 3 solar masses into gravitational waves, over a period of 10ms or so. This is an enormous blast of energy, but it interacts only weakly with matter.

I imagine that nearby objects (just outside the exclusion zone mentioned above) would have been subject to some crushing forces (which would have reversed just a few milliseconds later).  So a nearby large comet may have been pulverized by the gravitational waves, but it's overall course (speed, direction and energy) would not have changed much, because any change in direction would have been reversed by an opposite and (almost) equal tug a few milliseconds later.

Its potential energy would have changed a bit, because initially it was orbiting a pair of black holes with a combined mass of around 63 solar masses; at the end it was orbiting a single black hole with a mass of around 60 solar masses. This would mean that its future course would be a more eccentric ellipse.
« Last Edit: 11/04/2016 22:18:03 by evan_au »
 

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