I Gravity Propagation: How Does Time Affect Orbital Modeling?

TheGalaxyOfGold
Messages
7
Reaction score
1
I was thinking about the idea of looking up at a particular minuscule spot in the sky to see a particular planet at a very precise time, say, with a telescope. I was considering how light takes a matter of minutes to reach us. But then, remembering that gravitational forces must travel through space in order to be realized by the orbiting object some minutes later. This sort of ran me for a loop where I couldn't reason whether the gravitational force acting on an object, which traveled at the speed of light to get there and be realized is really calculated properly in models considering a planet has moved by the time the force arrives. Of course, I'm sure there are models that understand this well, and probably it's not as convoluted a question as it seems to me, but how does the propagation of gravity taking time to get to its destination affect a model that is intended to accurately play out the orbits of planets according to their present (not observed) position, with respect to, say TBD.

Perhaps I'm calling out a silly time scale to use. Please correct me if so.
 
Physics news on Phys.org
In Newtonian mechanics, gravity is instantaneous. It has to be in order for orbits to be stable.
In GR, it travels at the speed of light. However, in GR, there is also a velocity-dependent component to gravity, and those interactions cancel out the aberration from the finite speed.
So both theories give the same results, and one can e.g. send ships to other planets using only Newtonian mechanics.
This paper: https://arxiv.org/abs/gr-qc/9909087 shows this mathematically.
 
  • Like
Likes Dale
Thank you!
 
Thread 'Can this experiment break Lorentz symmetry?'
1. The Big Idea: According to Einstein’s relativity, all motion is relative. You can’t tell if you’re moving at a constant velocity without looking outside. But what if there is a universal “rest frame” (like the old idea of the “ether”)? This experiment tries to find out by looking for tiny, directional differences in how objects move inside a sealed box. 2. How It Works: The Two-Stage Process Imagine a perfectly isolated spacecraft (our lab) moving through space at some unknown speed V...
Does the speed of light change in a gravitational field depending on whether the direction of travel is parallel to the field, or perpendicular to the field? And is it the same in both directions at each orientation? This question could be answered experimentally to some degree of accuracy. Experiment design: Place two identical clocks A and B on the circumference of a wheel at opposite ends of the diameter of length L. The wheel is positioned upright, i.e., perpendicular to the ground...
According to the General Theory of Relativity, time does not pass on a black hole, which means that processes they don't work either. As the object becomes heavier, the speed of matter falling on it for an observer on Earth will first increase, and then slow down, due to the effect of time dilation. And then it will stop altogether. As a result, we will not get a black hole, since the critical mass will not be reached. Although the object will continue to attract matter, it will not be a...
Back
Top