Eli5 how solar sails work?
In: 5
So, all of these “light has momentum but no mass” answers are correct, but I’ve never found them very satisfying. It’s much nicer to just think of light in terms of electromagnetic waves. Then you don’t have to wrestle with the concept of massless particles that have momentum.
When light travels, it’s the electric and magnetic fields wiggling back and forth.
When light hits something that has electric charge, say the protons in an atom, the wiggling electric field makes those charged particles bob up and down.
That electric field is accompanied by a magnetic field too. One of the basics of electromagnetism is that charged particles moving in a magnetic field will get pushed perpendicular to their movement.
So, you have charged particles bobbing up and down in a magnetic field. That up and down bobbing in a magnetic field pushes them forwards. It just so happens that the direction they get pushed is exactly the same direction the light was moving.
These charged particles bobbing up and down cause their own electromagnetic waves (any wiggling charge will make an electromagnetic wave).
The electromagnetic waves caused by the particles bobbing up and down cancel out the original light, and travel back in the opposite direction, essentially “reflecting” the original light.
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All together this means:
– Light hits solar sail
– Solar sail particles start wiggling up and down
– Up and down wiggling + magnetic field from light makes sail travel forwards
– Up and down wiggling reflects the light back in the direction it came from.
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