Hacker News Reader

I think it's more illustrative to think of atoms/molecules per cubic meter. If I remember correctly, 1 or 0.1 µbar is proportional to around 1 atom per cubic meter.

View on HN

That’s a lot of pressure made by one tiny little atom. I can’t believe that.

3x10^22 atoms per cubic meter of air. That micro is going to make it 3x10^16 atoms.

So 1 atom per cubic micrometer is about right for 0.1 microbar.

One cubic micrometer is 1mm³ right?

One cubic micrometer is 1µm³.

One cubic millimeter is 1mm³.

Oh yeah, duh. Thanks.

Right, a cubic micrometer is 1E-18 cubic meter. So there are ~2.5 molecules per cubic micrometer at ~0.1 microbar.

I think there's a few digits missing here even. 1 mol = 6.022E23 particles = 22.4 L at STP for an ideal gas, and 1 m^3 = 1000 L

Of course real air isn't quite an ideal gas, but some reasonable approximations [1] come out to 2.53E25 molecules (N2 and O2) per cubic meter at 15 C and 1 atm.

[1] https://www.quora.com/How-many-air-molecules-are-present-in-...

Right. So 0.1 µbar (1E-7 bar) means ~2.5E18 molecules per cubic meter.

You have ~1 molecule per cubic meter at ~1E-25 bar.

Reply on news.ycombinator.com