Can Light and Gravity Cause a Scale to Register Weight?

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Discussion Overview

The discussion explores whether light and gravity can cause a scale to register weight, considering scenarios involving gravitational fields and the interaction of light with surfaces. The scope includes conceptual reasoning and theoretical implications of light's momentum and pressure.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant proposes a scenario where a scale with a mirror could register weight if light is bent into the scale by a strong gravitational field.
  • Another participant asserts that light has momentum, suggesting it can exert a force.
  • A question is raised about whether the momentum of light implies it has mass, referencing the relationship between weight and mass.
  • It is noted that light exerts pressure on surfaces, which can be related to the concept of radiation pressure and its effect on the scale.
  • A later reply indicates understanding of the concepts discussed, suggesting clarity on the topic.

Areas of Agreement / Disagreement

Participants express varying views on the implications of light's momentum and its relationship to mass and weight. The discussion remains unresolved regarding the specific conditions under which a scale would register weight due to light and gravity.

Contextual Notes

Participants reference different physical principles, such as radiation pressure and the relationship between force, pressure, and area, without resolving the implications of these principles in the context of the original question.

Who May Find This Useful

Individuals interested in the interactions between light, gravity, and force, as well as those exploring concepts in physics related to momentum and pressure.

cragar
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if we had a scale with a mirror on top then we zeroed the scale and the scale was on Earth well in our case we need a stronger gravitational
field and a light beam comes by the scale and then enters the strong gravitational field
thus the light is bent into the scale and hits the mirror and bounces off would the scale register a weight? all-be it a small one. or if we had a space-craft in outter space with mirrors on it and we shined a huge laser at it would the space-craft move , for every action there is an equal but opposite reaction.
 
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Yes. Light has momentum.
 
does this imply that light has mass, cause if the scale registers weight
w=mg i know p=E/c for a photon
 
Light (a whole bunch of photons) exerts a pressure on the scale's surface. See link: http://en.wikipedia.org/wiki/Radiation_pressure.

Weight is a force, w = mg. Pressure (radiation pressure in this case) times area is a force too, F = pA.
 
i see that makes sense now .
 

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