What are “solar winds” (or other such phenomena) and how do they affect spacecraft if space is essentially emptiness and vacuum?

Question

I’ve heard how space probes use their “sails” to make use of “solar winds” to travel distances. But isn’t space just vast emptiness with no resistance/ friction?

In: 4

Answer 1

Because essentially empty is not the same as totally empty. The two most relevant things to solar sails which pass through space are solar wind and light. Solar wind is a constant stream of charged particles released by the Sun’s atmosphere (wind from the sun, solar wind). These particles carry momentum and can therefore push objects. These particles are also responsible for things like Aurora.

The light emitted by the sun also carries momentum, when you have a sheet of something being hit by light it will feel a radiation pressure which pushes it in the direction the light is going.

Basically the Sun is big and powerful, so even though space is mostly empty you can take advantage of the momentum transfer from the Sun to you, and the fact there is very little resistance or friction means that those small forces can add up to large changes in position and velocity over a long time.