Orbital Mechanics: GR vs Newton's Laws

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Discussion Overview

The discussion centers on the comparison between General Relativity (GR) and Newton's laws in the context of orbital mechanics, specifically regarding their ability to predict the trajectories of solar objects. It explores theoretical implications, practical applications, and the accuracy of predictions in various gravitational scenarios.

Discussion Character

  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants assert that GR can predict the trajectories of solar objects, suggesting it is a more precise theory than Newton's laws.
  • One participant claims that Newton's laws serve as a weak field, low-speed approximation to GR, indicating that GR can predict all scenarios that Newton's laws can, but with greater accuracy in certain cases.
  • Another participant notes that while the differences in predictions between GR and Newton's laws are often too small to measure with current technology, there are specific cases where these differences are detectable and confirm GR's superiority.
  • Questions are raised about the specific GR formulas needed to calculate planetary distances, orbital periods, and average velocities around the sun, indicating a need for more detailed information.
  • A later reply emphasizes that the topic is too broad for the thread and suggests starting a separate discussion for specific inquiries related to GR formulas.

Areas of Agreement / Disagreement

Participants express differing views on the applicability and accuracy of GR compared to Newton's laws. While some agree on GR's superiority in certain contexts, the discussion remains unresolved regarding the specifics of GR formulas and their practical applications.

Contextual Notes

The discussion highlights limitations in addressing broad topics within a single thread and the need for specific references or questions to facilitate more focused discussions.

Peter Riedt
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9/1/2016 Orbital mechanics Wikipedia, the free encyclopedia
This reference states:
"General relativity is a more exact theory than Newton's laws for calculating orbits, and is sometimes necessary for greater accuracy or in highgravity situations (such as orbits close to the Sun)".

Can GR predict/calculate the trajectories of solar objects?"
 
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Yes, it can.
 
Peter Riedt said:
Can GR predict/calculate the trajectories of solar objects?

Newton's laws are a weak field, low speed approximation to GR. So every scenario that you can predict with Newton's laws, you can predict with GR. In many applications in the solar system, the difference in the predictions between the two is too small for us to measure with our current technology. But there are enough cases where the difference is detectable for us to have confirmed with high confidence that GR is more accurate than Newton's laws wherever the two's predictions differ.
 
What are the GR formulas to calculate a planetary distance to the sun or orbital period around the sun or average velocity around the sun?
 
Peter Riedt said:
What are the GR formulas to calculate a planetary distance to the sun or orbital period around the sun or average velocity around the sun?

This is covered in most GR textbooks, including how Newtonian gravity is derived as a weak field, slow motion approximation to GR. It is much too general a topic to address in a PF thread. If you have specific questions about statements in a specific acceptable reference (textbook or peer reviewed paper), please start a separate thread. This thread is closed.
 

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