Since vacuums are a lower pressure than the atmosphere of the earth(and probably many or all other planets) then why doesn't the vacuum of space rip the earth apart or suck all the gasses on it away and distribute them around the universe?

My theory is that it's because earths gravity is strong enough to hold all of the gasses and other particles in.

  • 1
    $\begingroup$ Vacuum isn't a force. Despite what you think, it doesn't "suck". Rather, in the presence of a vacuum, pressure from other sources pushes matter (air, whatever) in the direction of the vacuum (because there's nothing pushing back). In the case of the earth (and the sun), gravity pushes air (and the gasses of the sun) inward. $\endgroup$
    – Hot Licks
    Apr 7, 2018 at 0:56
  • $\begingroup$ I was taught that in an area where there are 2 different pressures, they will balance out. For example, if you have a bottle and fill it with compressed air, the air will "shoot" out (for lack of better terms) if you open the bottle because the regular atmospheric pressure is lower than inside the bottle. $\endgroup$ Apr 7, 2018 at 2:43
  • $\begingroup$ I actually was not taught this in school yet, I taught myself by watching tv. Tell me if I'm incorrect with anything I said. $\endgroup$ Apr 7, 2018 at 3:29
  • $\begingroup$ Still vacuum sucks. It is what we are doing when we suck. Point is that the vacuum should be enough. $\endgroup$
    – Alchimista
    Apr 7, 2018 at 7:40
  • $\begingroup$ Yes, absent other forces, the pressure between the open bottle and the outside will "equalize". But gravity is a substantial force, when considered on a global scale. $\endgroup$
    – Hot Licks
    Apr 7, 2018 at 12:09

2 Answers 2


Yes, it's gravity that holds planets and other celestial bodies together. In particular, a solid object on a planet would have to be moving faster than the planet's escape velocity in order to overcome the planet's gravity and go off into space. The Earth's escape velocity, in particular, is about 40,000 km/hour (that's about 25,000 MPH if you're from the U.S.), so essentially no solid objects on Earth move that fast naturally.

However, gasses on a planet do drift off into outer space, which is called atmospheric escape. The most common mechanism for that happening is called Jeans escape. In a gas like the atmosphere, the gas molecules move at a range of different speeds, called the Maxwell-Boltzmann distribution. At any given temperature, most of the gas molecules are moving fairly slowly, but a few of the molecules wind up moving so fast that they're faster than the escape velocity, and the gas molecule goes off into space.

The Sun and other stars have an atmosphere that's much hotter than a planet's atmosphere, which makes it even more likely that a particle will wind up going faster than the star's escape velocity. The particles that escape from the sun like that are called the solar wind.

  • $\begingroup$ If gasses escape earth's atmosphere regularly, then how is there still an atmosphere on earth. $\endgroup$ Apr 7, 2018 at 2:38
  • 2
    $\begingroup$ @daniel Because the amount of gas we lose per year is a minute fraction of the total quantity in the atmosphere. Also, the main gas we lose is hydrogen, because its light molecules are relatively fast at a given temperature, and we pick up some fresh hydrogen from the solar wind, and some hydrogen is also produced in the upper atmosphere by ultraviolet light splitting water molecules. Sadly, we lose much of our atmospheric helium to space. $\endgroup$
    – PM 2Ring
    Apr 7, 2018 at 3:09
  • 3
    $\begingroup$ Also note that Earth receives about 15000 tons of rocks and dust from space per year, some of that stuff contains water, or minerals that contain elements that will eventually contribute to our atmosphere. And volcanic action can dump gases into the atmosphere too. $\endgroup$
    – PM 2Ring
    Apr 7, 2018 at 3:17

Because it's not a perfect absolute zero vacuum.

  • 2
    $\begingroup$ The question doesn't assume they are a perfect absolute zero vacuum, just lower pressure. $\endgroup$
    – JMac
    Jul 13, 2019 at 0:21

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.