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saln1
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As the title states, if I go to space and detect several atoms per square meter of space, does this suggest that the space between these atoms is essentially void of all forms of matter? Thus is this a perfect vacuum?
Vanadium 50 said:Yes.
Of course the same thing is true on Earth - the space between atoms in the atmosphere is also vacuum.
saln1 said:So when I was told a perfect vacuum is impossible, I was told a lie?
DaveC426913 said:The upshot is that you can never get those last few atoms out. The atoms per cubic metre will drop towards zero but never reach it in any reasonable time frame.
Read up on sublimation.JDługosz said:So chill the walls. Next "bounce", the atom becomes frost.
Or, start with a solid with no gap, and introduce a gap by moving parts away from each other. This can be done easily with mercury, for example.
There are other ways of producing vacuum that don't have the same specific limitations.
JDługosz said:So chill the walls. Next "bounce", the atom becomes frost.
DaveC426913 said:...how does a slower moving atom result in vacuum?
What does this have to do with the question being asked?cragar said:we would also have the energy from the G field . And also i can't think of a place in space that you couldn't see a star . all tho their might be one .
adaptation said:I mean is there such a thing as a space so small it precludes the existence of virtual particles?
JDługosz said:No. See Casimir's force.
JDługosz said:So chill the walls. Next "bounce", the atom becomes frost.
Or, start with a solid with no gap, and introduce a gap by moving parts away from each other. This can be done easily with mercury, for example.
There are other ways of producing vacuum that don't have the same specific limitations.
Unless you live inside a nuclear reactor, you shouldn' bre encountering too many flying neutrons...macrylinda said:Don't forget the constant flow of neutrons everywhere!
Beta radiation? Geez, I hope not.macrylinda said:And randomly flying free electrons!
If I'm not mistaken, QFT postulates that particles are points and take up no space. So I don't think there is a volume of space so small that a particle couldn't be there. Quantum physics dissuades us from speaking of things we can't measure. Since you can't measure the number of virtual particles in a small volume of space, you aren't supposed to express knowledge of it. That is, you can't say whether there is a vacuum or not. Did I get that right, or am I missing something?adaptation said:I mean is there such a thing as a space so small it precludes the existence of virtual particles?
Jimmy Snyder said:If I'm not mistaken, QFT postulates that particles are points and take up no space. So I don't think there is a volume of space so small that a particle couldn't be there. Quantum physics dissuades us from speaking of things we can't measure. Since you can't measure the number of virtual particles in a small volume of space, you aren't supposed to express knowledge of it. That is, you can't say whether there is a vacuum or not. Did I get that right, or am I missing something?
johng23 said:There is no perfect vacuum because you can't obtain zero pressure. Pressure is a macroscopic quantity of course, it doesn't make sense to say that there is zero pressure between atoms. If you measure the pressure in space, it will not be zero because there are atoms present. If you specify a certain region and try to isolate it in some way while all the atoms are elsewhere, you can't do that...
Pythagorean said:Well... If you apply a big enough electric field to a vacuum, won't positron-electron pairs split out of space? What's getting "ionized"?
Photons can get ionized? I'd think atoms got ionized (lose/gain electrons).Pythagorean said:A photon, of course, is what's getting ionized.
If that were true then you could never have a vacuum unless it were in complete darkness and at absolute zero.Pythagorean said:Don't photons count as non-vacuum?
DaveC426913 said:Photons can get ionized? I'd think atoms got ionized (lose/gain electrons).
If that were true then you could never have a vacuum unless it were in complete darkness and at absolute zero.
I'm pretty sure any normal definiton of vacuum includes matter only.
mugaliens said:Fermions ("matter"), however, include the six quarks, the six leptons (which include neutrinos, electrons, and muons), as well as the four bosons (which include photons, etc.)
Thus, the question becomes - is there anywhere in space actually devoid of matter (fermions)?