Question: why are there no particles in space

Stuart Archer answered on 19 Jun 2013:

Believe it or not, there are actually loads of particles in space! This is especially true within solar systems, where you have things such as the ‘solar wind’, which is a constant stream of high energy particles (such as really fast hydrogen atoms or radiation). The solar wind is what is responsible for the Northern Lights (the Aurora Borealis)

There are also lots of larger particles – things like ‘micrometeorites’, tiny chunks of rock travelling at incredible speeds. The reason that they say space is ’empty’ is that these particles tend to be very far apart – hundreds of thousands of miles in some cases for things like micrometorites!

The most common thing to find in space is hydrogen atoms – there are between 1-1000 of these per cubic centimeter of space on average (it varies depending on where you are). To put this is perspective, if you were to fill a 1 cubic centimeter box on Earth with Hydrogen it would contain around a billion billion atoms! Space is really empty – but not completely!