Infinite Rocks Collide: Is the Impact Elastic?

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Discussion Overview

The discussion revolves around the nature of a hypothetical collision between an infinitely large rock and an infinitesimally small rock, specifically questioning whether the impact would be elastic. The scope includes theoretical considerations of collision mechanics and relativistic effects.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions if the collision between an infinitely large rock moving infinitesimally slow and an infinitesimally small rock moving infinitely fast can be considered elastic.
  • Another participant argues that elastic collisions are practically impossible and suggests that the terms "infinitely fast" are not acceptable in the context of matter, proposing that the small rock would shatter instead.
  • A third participant draws an analogy to shooting a bullet into a mountain, implying that the outcome of such a collision would be negligible.
  • A later reply reiterates the analogy and discusses the implications of mass and velocity, referencing Einstein's equation e=mc² to suggest that a bullet traveling at relativistic speeds would have a significant effect on a mountain, while also noting that even lower speeds would still have noticeable effects.

Areas of Agreement / Disagreement

Participants express differing views on the nature of the collision, with some challenging the feasibility of the scenario and others exploring the implications of mass and velocity. No consensus is reached regarding the classification of the collision as elastic or inelastic.

Contextual Notes

The discussion includes assumptions about the definitions of "infinitely large," "infinitesimally small," and "infinitely fast," which may affect interpretations of the scenario. The implications of relativistic physics are also noted but not fully resolved.

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If an infinitely large rock is traveling infinitesimally slow along a straight line and an infinitesimally small rock is traveling infinitely fast towards the infinitely large rock along the same axis, is the collision elastic?
 
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In practice elastic collisions are almost impossible. As far as I know only molecules in the kinetic theory are treated with elastic collisions.

And terms as "infinitely fast" for matter is not acceptable.
If you change your words to 'really big', 'really small', 'really slow', and 'really fast', I would say the small rock would just shatter and pulverize.
 
The problem you're setting is just like shooting a bullet in a mountain. What do you think would happen?
 
Dr Lots-o'watts said:
The problem you're setting is just like shooting a bullet in a mountain. What do you think would happen?

I think that is why he is specifying the high/low mass and high/low velocity. According to e=mc2 a bullet would have no effect on a mountain. But a bullet traveling at .9999c would have a very noticeable effect on a mountain.

EDIT: Not that a bullet wouldn't have still a very noticeable effect on a mountain at speeds of lower than .9999c.
 

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