Gravity Propagation: How Does Time Affect Orbital Modeling?

In summary, the conversation discusses the concept of looking at a specific planet in the sky at a precise time using a telescope. The speaker brings up the idea of gravitational forces taking time to travel through space and how this affects models of planetary orbits. They mention that in Newtonian mechanics, gravity is instantaneous, while in general relativity it travels at the speed of light. However, the speaker also notes that both theories give similar results and that this has been shown mathematically in a paper.
  • #1
TheGalaxyOfGold
7
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.
 
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  • #2
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.
 
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Likes Dale
  • #3
Thank you!
 

What is gravity propagation?

Gravity propagation is the phenomenon of gravitational force traveling through space and affecting the motion of objects. It is a key factor in understanding orbital mechanics and how objects move in space.

How does time affect orbital modeling?

Time plays a crucial role in orbital modeling as it is a fundamental component of the equations used to calculate the motion of objects in space. The passage of time affects the position and velocity of an object in orbit, which in turn affects its trajectory.

What is the relationship between gravity and time in orbital modeling?

In orbital modeling, gravity and time are closely related. The strength of the gravitational force between two objects is determined by their masses and the distance between them, but it also depends on the time at which the force is measured. As time passes, the gravitational force between two objects can change, resulting in changes in their orbits.

How does gravity propagation impact spacecraft trajectories?

Gravity propagation has a significant impact on spacecraft trajectories. The gravitational pull from other objects in space, such as planets and moons, can cause deviations in the spacecraft's intended path. These deviations must be accounted for in orbital modeling to ensure accurate predictions of the spacecraft's movement.

What research is being done to further understand gravity propagation and its effects on orbital modeling?

Scientists are continually conducting research to better understand gravity propagation and its impact on orbital modeling. This includes studying the behavior of gravity in extreme conditions, such as near black holes, and developing more precise mathematical models to accurately predict the motion of objects in space.

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