How do solar sails defy the laws of physics?

Click For Summary

Discussion Overview

The discussion revolves around the mechanics of solar sails and how they operate under the influence of light, particularly focusing on the concept of momentum transfer from photons to the sail. Participants explore the implications of photon momentum and its effects on both the sail and the light-emitting source.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant notes that light pushes the sail as it is reflected, questioning how this is possible given that photons have no mass.
  • Another participant explains that photons carry momentum, which allows for the operation of solar sails through conservation of momentum.
  • A participant draws an analogy to magnets pushing each other, suggesting a conceptual understanding of the forces involved.
  • There is a question raised about whether the emission of light results in a force acting in the opposite direction on the emitting object.
  • A later reply supports the idea that the emission of light does create a resultant force, mentioning a plan to use a laser to aid in pushing the solar sail.

Areas of Agreement / Disagreement

Participants generally agree on the concept that photons carry momentum and can exert force on the sail. However, there are unresolved questions regarding the implications of light emission on the emitting source and how this relates to the overall mechanics of solar sails.

Contextual Notes

Some assumptions regarding the definitions of momentum and force in the context of light and its interaction with matter remain unaddressed. The discussion does not resolve the implications of light emission on the emitting object.

BlakeG.
Messages
4
Reaction score
0
I briefly researched this and all i found out was that the light pushes the sail as it is reflected off of its surface.

So i am left wondering how this is possible because photons apparently have no mass therefor they can't push anything. I'm sorry if this is ignorant i am no physicist. Thanks!

and if this belongs in a different area just let me know.
 
Last edited:
Physics news on Phys.org
Even though photons have no mass, they do carry momentum. Even in classical electromagnetism (in which photons do not appear), electromagnetic waves carry momentum and energy. All you need to explain the operation of a solar sail is conservation of momentum.
 
Thank you! sort of how magnets push each other i'd assume.
 
When a light source emits light, if the light has momentum, does this mean that there is a resultant force in the opposite direction for the light emitting object?
 
Denton said:
When a light source emits light, if the light has momentum, does this mean that there is a resultant force in the opposite direction for the light emitting object?

yes i think so because one plan to aid pushing the solar sail was to mount a laser on it to push the sail along
 

Similar threads

  • · Replies 5 ·
Replies
5
Views
4K
  • · Replies 11 ·
Replies
11
Views
4K
Replies
1
Views
6K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 17 ·
Replies
17
Views
4K
  • · Replies 2 ·
Replies
2
Views
5K
Replies
35
Views
6K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 21 ·
Replies
21
Views
6K
Replies
2
Views
2K