Explaining Gravity: Newton's Universal Law and its Proof

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Discussion Overview

The discussion revolves around Newton's universal law of gravitation, specifically questioning how Newton proved the law and whether he explained the underlying reasons for gravitational attraction. The scope includes historical context, mathematical formulation, and philosophical implications of the law.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Historical

Main Points Raised

  • Some participants note that Newton's law states that all bodies attract each other but question whether he provided an explanation for this attraction.
  • Others argue that even contemporary physics does not fully explain the reason for gravitational attraction, mentioning Einstein's contributions that relate mass, energy, and pressure.
  • Several participants inquire about how Newton proved the equation F = (Gm1m2)/r², with some emphasizing that this equation does not explain the reason for attraction but rather calculates the gravitational force between two objects.
  • One participant highlights that the law is a mathematical relationship derived from empirical observations, suggesting a distinction between the law and its explanatory power.
  • A later reply discusses Newton's derivation of Kepler's laws from his law of gravitation, providing historical context about his publication process and initial inconsistencies in applying his theory to the moon's position.

Areas of Agreement / Disagreement

Participants generally agree that Newton's law is a mathematical formulation based on empirical observation, but there is no consensus on whether Newton provided an explanation for gravitational attraction or how he proved the law.

Contextual Notes

Some limitations include the lack of clarity on the assumptions made by Newton and the unresolved nature of the philosophical implications of gravitational attraction. The discussion also reflects varying interpretations of historical accounts regarding Newton's work.

johncena
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Newton's universal law of gravitation states that every bodies in this universe attracts each other.Was Newton able to explain the reason for this attraction?
 
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No. We can't even explain it today. But Einstein expanded the discussion to include not ony mass but energy and pressure...via the Einstein tensor...somehow all are related at some fundamental level...
 
How did Newton prove that ,

F = (Gm1m2)/r2
 
johncena said:
How did Newton prove that ,

F = (Gm1m2)/r2

This doesn't prove how or why they are attracted this is only used to find the force due to gravity between the two objects.
 
The Law of Universal Gravitation is just that: a law. It is a mathematical relationship derived from empirical observation.
 
johncena said:
Newton's universal law of gravitation states that every bodies in this universe attracts each other.Was Newton able to explain the reason for this attraction?

Is this a homework question? This direcly pertains to an oft quoted passage in Principia: "hypotheses non fingo..."; I make no hypothesis...
 
johncena said:
How did Newton prove that ,

F = (Gm1m2)/r2

To my knowledge he did show that from his law of gravitation (and some assumptions) you can derive Kepler's laws of planetary motion, which up to that point were more or less unexplained. I'm no historian, but according to Bate [1], Newton didn't originally publish his results due to a small inconsistency when he applied his theory to calculate the position of the moon and only by chance 20 years later through conversations with Halley did he get around to start working on Principia.


[1] Fundamentals of Astrodynamics, Bate, Mueller, White. Dover, 1971.
 

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