Hi Liz,

That's a good question! I believe that term "solar wind" was first used by a scientist named Eugene Parker around 1958. However, scientists had postulated the existence of the solar wind for quite some time before this. I think that astronomer Arthur Eddington suggested the existence of a stream of electrons or ions something like the solar wind around 1910, and the famous polar explorer and physicist Kristian Birkeland suggested that this stream consisted of both electrons and ions around 1916. However, as far as I know, neither Arthur Eddington nor Kristian Birkeland used the term solar wind.

Even though we cannot breathe in outer space, and for most practical purposes outer space is a better vacuum than we can achieve in a vacuum chamber using fancy cryopumps here on Earth, outer space is not completely empty. The spaces between the planets in our solar system and even between the stars in our galaxy are filled with an ionized gas of electrons and ions (mostly hydrogen) that scientists call a "plasma." I don't know the exact reasons why Eugene Parker decided to use the term "solar wind" to describe the steady stream of ionized gas (or plasma) that flows outward from the Sun into interplanetary space. I think his usage of this term may have been related to observations of comet tails that streamed back like they were being blown in the wind.

The plasma in the solar wind is not very dense - you typically might find only 1-3 electrons and/or ions in about 1 cm^-3 (a volume of space equivalent to a sugar cube). In contrast, a sugar cube contains millions of electrons and ions.

You can read more about Eugene Parker in this article from National Geographic

http://news.nationalgeogr...yotoprizeparker.html

Kris