The vacuum in interstellar space compares to the best vacuum achieved here on Earth as air under normal pressure compares to a wall of stone.
| condition | pressure in mbar | applications/matter density |
| normal pressure | 1000 | respiration / at 20 C, 5 X 1019 molecules/cm3 |
| rough vacuum | 1000-100 | vacuum cleaner, milking devices, vacuum packaging |
| intermediate vacuum | 1-10-3 | simple chemical procedures, metal coating, metallurgy |
| high vacuum | 10-3 | as above; light bulbs, picture tubes |
| ultrahigh vacuum | below 10-6 | chip manufacture, elementary particle acceleration below 1010 molecules / cm3 |
| Earth's atmosphere at 250 km | 10-7 | 109 molecules / cm3 at about 20° C |
|
Earth's atmosphere at 400 km Vacuum tube of LEP rings |
10-9 | 107 molecules / cm3 |
| Best vacuum reached today | 10-13 | 103 molecules /cm3 |
| matter density in interstellar space | 1 hydrogen atom / cm3 | |
| "critical matter density" | 10-7 hydrogen atoms / cm3 | |
| average matter density of visible matter in the universe | 10-9 hydrogen atoms / cm3 |