Why will an object in space continue moving foever?

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Discussion Overview

The discussion centers around the question of why an object in space continues to move indefinitely if it is in dynamic equilibrium, exploring the implications of Newton's Laws and the principles underlying them. The scope includes theoretical considerations and conceptual clarifications regarding motion and the foundations of physical laws.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants inquire about the implications of Newton's Laws regarding the motion of objects in space, particularly in dynamic equilibrium.
  • Others express a desire to understand the validity of Newton's Laws, suggesting that they are based on experimental agreement.
  • A participant mentions that the law of conservation of momentum can be derived from the principle of uniformity of physical laws across different locations, referencing Noether's theorem.
  • There is a discussion about the equivalence of situations where one object is moving and another is at rest, questioning the expectation of motion without an external cause.
  • Some participants argue that proving the correctness of Newton's Laws is complex and that shifting the question does not resolve the underlying issues.
  • One participant reflects on the relationships between conservation laws and their corresponding physical quantities, noting the connection to the uncertainty principle.

Areas of Agreement / Disagreement

Participants express differing views on the nature of Newton's Laws and their foundations. While some agree on the experimental basis of these laws, others challenge the ability to prove their correctness and raise questions about the implications of Noether's theorem. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Limitations include the lack of consensus on the foundational aspects of Newton's Laws and the implications of Noether's theorem. The discussion also highlights the complexity of proving physical laws and the assumptions underlying various arguments.

THP
Why object in the space will continue moving foever if the object is in dynamic equilibrium?
 
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THP said:
Why object in the space will continue moving foever if the object is in dynamic equilibrium?
Are you asking which of Newton's Laws implies this, or why Newton's Laws are true?
 
I want to know why Newton's laws are true
 
THP said:
I want to know why Newton's laws are true
Scientific laws are ultimately based on experiment. Experiment agrees that Newton's first law holds good in all the situations where we have tested it.

One can drive a bit deeper. The law of conservation of momentum can be shown to follow from the principle that the laws of physics over here are the same as the laws of physics over there. Experiment agrees with that principle as well.

https://en.wikipedia.org/wiki/Noether's_theorem#Basic_illustrations_and_background
 
THP said:
Why object in the space will continue moving forever if the object is in dynamic equilibrium?
If you are moving and the object is at rest, it's an identical situation, and you certainly wouldn't expect space object to start moving out of the blue for no reason.
 
David Lewis said:
If you are moving and the object is at rest, it's an identical situation, and you certainly wouldn't expect space object to start moving out of the blue for no reason.
I don't think you can prove the correctness of Newton's law this way. You just shift the question.
As jbriggs wrote, the law was based on observation, while Noether's theorem shows how it follows if the laws of physics are the same everywhere, but there is no way to prove that either.

On Noether's theorems, I have always been intrigued by the pairing of concepts that arises in two contexts:
  • Momentum and position.
  • Angular momentum and angular position.
  • Energy and time.
In each case, conservation of the first follows from the laws of physics being invariant under displacements in the second.
In each case the (dot) product of the pair has dimension of action. Indeed, the product relates to the Planck/Heisenberg uncertainty.
 

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