Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: jackyjoy123 on 06/02/2021 09:59:35

Title: vacuum measurements ?.
Post by: jackyjoy123 on 06/02/2021 09:59:35

Hello,

Somebody told me that the vacuum inside a certain container was 0.5 mbars. I did not have the opportunity to ask him to expand on how the mbar scale works. So I wonder if someone out there can help?

thanks
jackyjoy

Title: Re: vacuum measurements ?.
Post by: vhfpmr on 06/02/2021 10:10:56

1 bar = 100kPa,
so 0.5mbar = 50Pa

Atmospheric pressure is 1.013 bar at sea level, so give or take 1.3%, one bar is usually regarded as atmospheric pressure.

Title: Re: vacuum measurements ?.
Post by: evan_au on 06/02/2021 10:56:15

Quote from: OP

the vacuum inside a certain container was 0.5 mbars

They had definitely pumped most of Earth's atmosphere out of the container.
- It had a much lower pressure than the surface of Mars (about 10 mbar).
- But it had a much higher pressure  than the vacuum that the International Space Station flies through (at 400km altitude).

According to this table, you could expect to find 0.5mbar of pressure at an altitude of 40km above sea level (apologies for the US standard definition of SI pressure...)
https://www.engineeringtoolbox.com/standard-atmosphere-d_604.html