Light's Mass: 0 N = Infinite Acceleration?

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Discussion Overview

The discussion revolves around the concept of light's mass and the implications of applying Newton's second law (F=ma) to light, particularly in the context of relativistic physics. Participants explore whether light, having zero mass, can be associated with infinite acceleration and the appropriateness of classical mechanics in this scenario.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants assert that light has zero mass, questioning the application of F=ma to light and suggesting that it leads to misunderstandings about acceleration.
  • Others argue that F=ma is rooted in Newtonian physics and does not apply to relativistic contexts, indicating that different equations are necessary for light.
  • A participant mentions that the notation "0 N" refers to Newtons, a unit of force, and not mass, which complicates the interpretation of the original question.
  • Some contributions highlight that dividing by zero is a common misconception, with one participant suggesting that this question might be more appropriate for a homework section rather than a physics discussion.
  • Another participant introduces the idea that photons cannot be accelerated from rest to the speed of light, emphasizing the limitations of applying classical mechanics to light.

Areas of Agreement / Disagreement

Participants express differing views on the applicability of classical mechanics to light, with no consensus reached on whether light's zero mass implies infinite acceleration. The discussion remains unresolved, with competing interpretations of the relationship between force, mass, and acceleration in the context of light.

Contextual Notes

Limitations include the potential misunderstanding of the terms used (e.g., mass vs. force) and the applicability of classical versus relativistic physics. The discussion does not resolve the mathematical implications of dividing by zero or the nature of light's mass.

unscientific
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F=ma a = F/m Light's mass: 0 N = infinite acceleration? :rolleyes:
 
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unscientific said:
F=ma a = F/m Light's mass: 0 N = infinite acceleration? :rolleyes:
Why is this on the relativity board? And if 0 N means "0 Newtons", ie F=0, this will mean a=0 for a finite mass, not a=infinity.
 
unscientific said:
F=ma a = F/m Light's mass: 0 N = infinite acceleration? :rolleyes:
F=ma is Newtonian classical physics. Cannot apply to relativistic concepts.
 
light has 0 mass, and I am talking about light being 0 mass here, jessem
 
unscientific said:
light has 0 mass, and I am talking about light being 0 mass here, jessem
light has zero rest mass!
 
unscientific said:
light has 0 mass, and I am talking about light being 0 mass here, jessem
But F=ma doesn't apply in relativity, although on this thread masudr mentioned that there is a similar equation relating the force 4-vector to the momentum 4-vector, [tex]f_{\mu} = \frac{d}{d\tau}p_{\mu}[/tex]. Also, you said "0 N", I assumed the N was short for "Newtons", which is a unit of force, not mass.
 
Last edited:
This isn't even a physics question! Every sixth grader tries to divide by zero thinking the answer is infinity. This belongs in the homework section.
 
actionintegral said:
This isn't even a physics question! Every sixth grader tries to divide by zero thinking the answer is infinity. This belongs in the homework section.
It is true in a sense in calculus, though--the limit of 1/N as N approaches zero is infinity.
 
what i have heard is that photon, since it is already flying at the speed of light, cannot be slowed down. so it cannot be going slower than the speed of light and then accelerated to the speed of light. neither can it be accelerated from the speed of light beyond the speed of light. so F = ma has no application to light.
 

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