Newton's third law of motion - why?

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SUMMARY

The discussion centers on the fundamental principles of Newton's Third Law of Motion, which states that for every action, there is an equal and opposite reaction. Participants explore the reasoning behind this law, questioning why forces are equal and opposite, particularly in gravitational interactions between massive bodies like the Earth and the Sun. The conversation highlights the importance of conservation laws, specifically momentum conservation, and introduces Noether's Theorem as a pivotal concept linking symmetries in physics to conservation principles. The discussion concludes that while Newton's laws are accepted as fundamental truths, the quest for deeper understanding continues through modern physics.

PREREQUISITES
  • Understanding of Newton's Laws of Motion
  • Familiarity with conservation laws, particularly conservation of momentum
  • Basic knowledge of gravitational forces and interactions
  • Awareness of Noether's Theorem and its implications in physics
NEXT STEPS
  • Study the implications of Noether's Theorem on conservation laws
  • Explore advanced concepts in gravitational physics, focusing on the Earth-Sun interaction
  • Research the historical development of Newton's laws and their acceptance in the scientific community
  • Investigate modern interpretations of Newton's Third Law in the context of quantum mechanics
USEFUL FOR

Students of physics, educators, and anyone interested in the foundational principles of motion and forces, particularly those seeking to deepen their understanding of classical mechanics and its modern implications.

  • #31
xts said:
Well... Have you tried to read Principia? I don't expect you reading Newton's Latin, but even modern translation?
Yes, I have, and yes, it is painfully difficult. Newton did not have the modern mathematics that makes the modern interpretation of Newton's laws easily comprehensible. Vectors? Vectors are a modern development, about a hundred years old. Reading any physics paper that dates from before the very end of the 19th century is extremely tedious. Vectors clean things up so very nicely. Algebra? Newton tended toward geometric reasoning rather than algebraic reasoning. Modern algebra was in its infancy in Newton's time. Calculus? While Newton and Leibniz are viewed as having independently developed the calculus, it is Leibniz form that we typically use nowadays, later modified extensively by Weierstrass. Newton's calculus was a bit (more than a bit) idiosyncratic.
 
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