Does space have a "radiation pressure" caused by subatomic particles? If space is not actually a void, then there's something shooting around in it, I'm guessing a lot like molecules in a gas.  Could we apply a $(PV/T = k)$ -like gas law to it.  Obviously we're not measuring a regular everyday gas but some theoretical "fluid" that we don't know enough about yet.  Also regular radiation might also be part of the total pressure, and there's a wikipedia article on that.
What are your thoughts on this?
If there is such a fluid, and it obeys the gas law, then there's either an infinite amount of this fluid in our currently observable universe or the universe is finite in volume.
 A: Inside the solar system the solar wind consists of sub-atomic particles that form a plasma, one of the four states (phases) of matter along with solid liquid and gas.  Plasma is basically a gas of charged particles--normal gas laws don't apply as moving charges create magnetic fields and magnetic fields influence moving charges, thermodynamic gas laws assume equilibrium which won't generally be present.
From Wikipedia:

In the universe, plasma is the most common state of matter for ordinary matter, most of which is in the rarefied intergalactic plasma (particularly intracluster medium) and in stars.

Perhaps concepts like pressure can still be broadly applied at the scales "space" implies.
For example the Heliopause could be seen as the the sphere where the outward pressure of the solar wind equals the inward pressure of winds from extra-solar sources. Also see solar sail. The Wikipedia article evokes "radiation pressure" but connecting that to a gas law would be drawing a very long bow.
A: In a sense this could be an interpretation of gravitational waves. In this case, anything with energy or mass or momentum (relating by the stress-energy tensor in GR) could bend space-time producing gravitational waves.
hopefully I'm understanding you correctly.
