If an object runs an infinite distance in universe....?

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Discussion Overview

The discussion revolves around the concept of potential energy for an object falling from an infinite distance towards Earth, specifically examining the implications of using the formula E=mgh in this context. Participants explore theoretical aspects of potential energy, the nature of infinity, and the limitations of various equations in gravitational physics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that if an object falls from an infinite distance, it would possess infinite potential energy according to E=mgh, assuming h is infinite.
  • Others argue that it would take an infinite amount of time for such an event to occur, suggesting that the scenario is not physically realizable.
  • Some participants assert that any object at infinity has no influence on the observable universe, emphasizing that infinity is a concept rather than a physical reality.
  • A later reply introduces the full equation for gravitational potential energy, E = -GMm/R, and explains that even an object falling from infinity would only gain a finite amount of energy, specifically $$\frac{GMm}{R0}$$, where R0 is the radius of the Earth.
  • Another participant reiterates that E=mgh is an approximation valid only for small heights near the Earth's surface, reinforcing the idea that the full gravitational potential energy equation must be considered for larger distances.

Areas of Agreement / Disagreement

Participants express disagreement regarding the implications of potential energy at infinite distances, with some asserting infinite potential energy and others refuting this claim based on physical principles. The discussion remains unresolved, with multiple competing views presented.

Contextual Notes

Limitations include the dependence on the definitions of potential energy and the assumptions regarding the applicability of E=mgh versus the full gravitational potential energy equation. The discussion does not resolve these limitations.

Noduagga
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...(after infinite distance) falls into earth, would exist infinite potential energy if E=mgh and h is infinite?
 
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Since it would take an infinite amount of time, it would never happen.

If you are asking whether any object at an infinite distance from the Earth has infinite potential energy, the answer is no, absolutely not and it is easy to see why if you study "escape velocity".
 
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Irrelevant, anything at infinity has no influence on the observable universe
 
Chronos said:
Irrelevant, anything at infinity has no influence on the observable universe
Everybody remember infinity is a "concept" (a very useful one) but not a physical "thing!"
 
Noduagga said:
...(after infinite distance) falls into earth, would exist infinite potential energy if E=mgh and h is infinite?

I think the real answer to your question is that E = mgh is just an approximation for small values of h near the Earth's surface. The full equation for the potential energy of an object of mass m at a distance R from the Earth's center is that E = -GMm/R, where M is the mass of the Earth, and G is Newton's constant of gravitation. Near the Earth's surface, R is approximately constant, so we can write
R = R0 + h where h <<R. Then the potential energy can be approximated by $$ E=-\frac{GMm}{R0+h} \approx -\frac{GMm}{R0}(1-h/R0) = -\frac{GMm}{R0} +\frac{GM}{R0^2} mh$$ Then, for changes in the potential energy, we ignore the first term, since it doesn't change, and we call the quantity $$\frac{GM}{R0^2}$$ g, and then you have your formula E=mgh. So if you use the full formula, even an object falling from infinity only gains an amount of energy equal to $$\frac{GMm}{R0}$$, which is a finite quantity.
 
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Noduagga said:
...(after infinite distance) falls into earth, would exist infinite potential energy if E=mgh and h is infinite?
E=mgh is only an approximation, valid for objects near the Earth's surface.
 

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