Question of the Week

Would a helium balloon float on the moon?

Sun, 23rd Nov 2008

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Jake, South Dakota asked:

Would a helium balloon float on the moon?


An arch of colourful party balloonsWe put this to Phil Rosenberg of the MET Office, Facility for Airborne Atmospheric Measurement

As far as the balloonís concerned you need two things to make a balloon float. First you need an atmosphere for it to float in. The second thing you need is gravity. Thatís because the reason why a balloon floats is that the balloon itself is less dense than the air around it so gravity pulls on the air around it more than the balloon. The air around it actually tries to push underneath the balloon. That forces the balloon up and makes it float. Unfortunately the moon hasnít got an atmosphere at all. Therefore youíre missing one of the two things that you need to make a balloon float. In that case a balloon on the moon wouldnít float at all. It would just land on the floor. However, that doesnít mean you canít have balloons or other bodies in space at all. Actually the Russians launched a space mission in the 80s called Vega. That involves putting a balloon in the atmosphere of Venus which is the second-closest planet to the sun. Balloons in space are possible and have been done in the past. Looking to the future thereís a possibility we might be looking at putting balloons on titan which is one of Saturnís moons. Titan has got an atmosphere and itís really cold there. Thereís obviously gravity there. Therefore youíve got all the things you might need to have a balloon on Titan. The reason to do that would be to have atmospheric instruments that you would hang from the bottom of the balloon and they would measure Titanís atmosphere. Thatís exactly what weíve done on Venus with the Vega mission.  So unfortunately no balloons on the moon but they do have uses elsewhere in the solar system. Not just on the Earth.


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The density of helium in a party balloon would be much greater than the moon's atmosphere, so the balloon would not float.

Helium balloons float in air because helium is less dense than Earth's atmosphere. RD, Mon, 17th Nov 2008

And because the difference in density times the volume gives enough upthrust to support the payload + the envelope weight.
A gram of Helium, released on the Moon would still spread out and float largely at the top of the atmosphere. (I'm assuming that the Moon's atmosphere doesn't consist of Hydrogen) lyner, Mon, 17th Nov 2008

so the balloons would stay on the surface and the party guests would 'float'...

I'm liking the way you think... JnA, Mon, 17th Nov 2008

I'm thinking that the balloon will just explode because the pressure inside the balloon is greater than the outside so it explodes to adjust/try and even out the pressure, Chemistry4me, Wed, 19th Nov 2008

Chemistry4me is correct ofc. This is why an astronaut requires a pressurised suit to stop our bodies exploding in space.

Interesting that the astronauts on the Lunar Landings didn't have pressurised gloves judging by the footage of the landings, but there you go.
Andrew K Fletcher, Thu, 20th Nov 2008

A typical balloon filled with Helium here on earth has just over 1 atmosphere pressure of gas in it. The excess pressure is the pressure required to strech the rubber.You could inflate a balloon on the moon perfectly well, you would need just enough pressure to strech the rubber. Equally, you could inflate a baloon at the bottom of the ocean, but that would need a lot more helium.

"Interesting that the astronauts on the Lunar Landings didn't have pressurised gloves judging by the footage of the landings, but there you go."
Is there some way you could tell or is that just a bit of "we didn't go to the moon" trolling?
Bored chemist, Thu, 20th Nov 2008

Points taken. Was referring to a standard balloon filled here on earth and let loose on the moon. But you are correct we could inflate a balloon on the moon just as we can here on earth, but with far less pressure required.

The gloves shown on the footage of the lunar landings are not pressurised as one would expect. This is very odd considering that the lack of pressure on the surface of the moon would not be sufficient to collapse the gloves. Ofc there may be a logical explanation in that the gloves were of such design that even when pressurised hidden ribbing in the material would not allow them to expand. Just a valid observation pointed out in the lunar conspiracy video's that I have yet to hear an explanation for and relevant to the inflation of a balloon. But again I will concede that this could divert the focus from the original post and humbly ask forgiveness.

Andrew K Fletcher, Fri, 21st Nov 2008

How could you tell the gloves weren't pressurised? What good would they be if they were to inflate like sausages? lyner, Wed, 26th Nov 2008

Exactly.  They need to be stopped from doing that.  What would you expect a properly functioning space glove to look like?  An inflated rubber glove? Flyberius, Wed, 26th Nov 2008

Although space gloves are designed from very strong fabric, so they don't stretch and inflate, there is still a big problem with the joints. Because they are essentially tubes filled with air, if you want to bend the tube, the volume of the tube decreases so you are pressurising gas inside the suit which is very hard work. This tends to make astronaughts tiered very quickly. There has been work on making very tight fitting rubber gloves which maintain pressure elastically not with air inside, which would be a lot easier to work in a vacuum with. daveshorts, Tue, 9th Dec 2008

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