A region of space devoid of any fluid molecules resulting in a zero pressure in ideal cases. In practice, even space has a small but finite number of molecules.

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4
votes
3answers
703 views

Vacuum and repulsive gravity

How can one show from General Relativity that gravity is attractive force, and under which conditions it becomes repulsive, also why positive energy vacuum drives repulsive gravity?
1
vote
0answers
273 views

Gravitation and the QFT vacuum

I'm asking this to get yet another lessson in the inability of QFT and GR to cohabit. Many people believe GR must yield to quantization. The question here is as to why the activity of the vacuum ...
2
votes
4answers
3k views

Can heat be transfered via magnetic field in a vacuum?

Say you want to store hot coffee in a container surrounded by a vacuum. To remove all sources of conductive energy loss the container is suspended in the vacuum by a magnetic field and does not have a ...
3
votes
1answer
235 views

The vacuum as trigger

Do the apperance in the atomic nucleus of virtual matter-antimatter particle pairs play a role in the random nature of radioactive decay?
1
vote
1answer
176 views

In a low pressure (near vacuum), -20°C vessel, would sublimated moisture rise to the top or fall to the bottom?

If I have a strong vessel that I've cooled to say -20°C, and lowered the pressure below 0.006 atmospheres, the water in food placed inside will sublimate and freeze dry the food. But what happens to ...
3
votes
2answers
414 views

Effect of spacetime curvature on the sea of virtual particles

Does the nature of the assortment of virtual particles depend upon the warping of spacetime in a direct manner ?
4
votes
2answers
980 views

If I put a ping pong ball in a vacuum, would it pop?

If I put a ping pong ball in a vacuum, would it pop? If so, at what point would it happen? Any standard table ping pong ball is acceptable.
3
votes
1answer
833 views

Effects on a tree exposed to the vacuum of Space

My wife's kindergarten class asked, "What would happen to a tree planted on the moon?" Aside from the obvious that it would die from lack of water/air, what physical effects would happen to a tree ...
2
votes
2answers
303 views

Will physic object in a perfect environment last/exist forever?

We know,i.e. wood/steel tables in earth will completely broken or disappear in a very future day. If we put the table in a perfect/ideal environment (maybe in vacuum), will the disappear/broken still ...
1
vote
0answers
289 views

Creating the proper suction

I'm a bit rusty on my fluid dynamics. I'm experimenting with creating my own leaf vacuum. How would I determine how much suction a fan creates? Bernoulli's equation would apply correct? I would ...
-1
votes
1answer
547 views

The difference between free energy and perpetual motion [closed]

What is the difference between free energy (over unity) and perpetual motion? Please provide some examples, both real world and theoretical.
6
votes
2answers
872 views

Wheeler-Feynman theory, QED without fields, vacuum polarization

Initially Wheeler and Feynman postulated that, the electromagnetic field is just a set of bookkeeping variables required in a Hamiltonian description. This is very neat because makes the point of ...
0
votes
1answer
293 views

Volume of Matter in the Universe [closed]

What would the size of the universe be if it were physically possible to remove all of the empty space, leaving only matter?
6
votes
2answers
581 views