3 ms·
Gravitational waves change the definition of length and time. If you have some baseline pressure in a room, a pressure wave causes a small region to be briefly
by jjk166 5y ago
Gravitational waves change the definition of length and time. If you have some baseline pressure in a room, a pressure wave causes a small region to be briefly higher or lower pressure. If you have a meterstick and a stopwatch, a gravitational wave causes the meter to grow bigger or smaller and the stopwatch to run fast or slow. It's as if you are briefly closer to some immense object like a black hole which causes time dilation - indeed that's exactly what it is. No matter how ridiculously far away they are, as two celestial objects orbit each other they are continually moving closer and then further away from you, and while gravity drops off with distance it never goes to zero. You are feeling the gravitational pull of that celestial object on the other side of the universe getting infinitesimally stronger and weaker as the distance between you and it shrinks and grows, or more accurately as the distance between you and where it was all those millions of years ago when the waves were first emitted shrinks and grows.
- galaxyLogic 5y agoSo you're saying that measuring gravitational waves means we measure how much a given distant mass pulls us towards it and the value of that pull-force goes up and down like a wave? Can we measure the "pull" of a specific distant mass? Or do we measure something else like the change in distance between two points?
- jjk166 5y agoWell the pull of gravity is really just the warping of spacetime. A gravitational wave communicates the change in the gravitational field caused by an accelerating mass. We measure this by shooting lasers along two paths and comparing how long it takes light to traverse the paths, the warping of spacetime causes this value to change. You could use this value to directly calculate how much the pull of the distant object upon us varied. But we can only see the variation, not the absolute pull, of these distant objects; and even then only for extreme cases like black hole and neutron star pairs moments before they collide.
- galaxyLogic 5y agoGood explanation thanks. // we can only see the variation Can we also see the direction from which the wave is coming from ?