I think the ultimate souvenir would be not a moon rock or a martian, but space "nothing", but I wonder if this is physically possible... Can an astronaut go out to space with an open container, close and seal it and bring it back to Earth? Is there a container that could withstand the pressure of Earth's atmosphere upon reentry? If this is possible, what does my container of space "nothing" truly consist of?

  • $\begingroup$ It depends how deep into 'space' you go. The official start of space is 100Km up, but the upper reaches of the atmosphere still slow the ISS at 400Km. Then for the solar system there is the Heliosphere, then we go to lower densities again in interstellar space, lower again in voids and inter galactic space. But AFAIU, even in the last two, there are still hydrogen and other atoms, and the occasional compound, just very sparsely. $\endgroup$ May 21 '14 at 3:18
  • $\begingroup$ "Is there a container that could withstand the pressure of Earth's atmosphere upon reentry?" Huh? Do you mean the heat of re-entry or the pressure on the leading side of the craft during re-entry, or 1 atmosphere of pressure on landing at sea level? Well the returned space probes, manned space craft and sample containers would suggest - yes, they are capable of withstanding re-entry (heat & pressure) and subsequent conditions when undamaged. $\endgroup$ May 21 '14 at 3:22
  • $\begingroup$ I didn't know there were varying densities of space particles depending where you were in space. I should have specified; I didn't mean actual reentry, but just the pressure and gravity of Earth's atmosphere in general. $\endgroup$ May 21 '14 at 15:13

Space is not quite as empty as you might think, and your average jam jar is easily strong enough to hold atmospheric pressure against an internal vacuum. More to the point, there wouldn't be any need to go into space to create a jar full of nothing. Current technology can easily create a vacuum that would compare with that of "outer space".

As for what your container will contain, it depends on your point of view. In everyday terms, there is nothing, except perhaps a few stray particles bouncing around. If you agree with the relevant underlying theory, your container is full of quantum foam. But then, the quantum foam is everywhere, and the container just happens to be empty of anything else.

  • $\begingroup$ Thanks for your answer! I know it's possible to create a vacuum seal on Earth, but it's not quite as cool as my theoretical jar of space nothing :) Can I add a follow-up question? Would any stray particles in this jar fall to the bottom from Earth's gravity? And if the jar is clear, would light pass through it differently? $\endgroup$ May 21 '14 at 15:18
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    $\begingroup$ @TheSmallestOne: the "particles" would be Hydrogen molecules, and the effect of gravity on them would be irrelevant compared to thermal energy. And light would pass through the jar a little different than if it were filled with air due to the different angle of refraction. Probably only a very small difference, though. $\endgroup$ May 22 '14 at 14:07
  • $\begingroup$ And any difference in light-refraction due to the vacuum would be lost via the diffraction of the glass. $\endgroup$
    – john3103
    May 22 '14 at 15:06

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