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25

When a bell vibrates in air, it pushes air molecules out of the way which will make the vibrations "decay". If you strike a bell in vacuum, this loss mechanism will not be there so the bell will "ring" for longer (but nobody can hear it). This doesn't mean the initial amplitude is significantly greater - just that it persists longer. Obviously if you rang ...


14

If you simply held a cup upside down in zero gravity, the liquid ought not to pour out. However, things in zero gravity still obey Newton's laws. If you pull away the cup, the water ought to stay behind. In reality, a sudden move of the cup would create a lower pressure behind the water than in front so the air pressure would try to keep it in the cup, but ...


12

Freeze it in liquid helium. Any gas inside will condense out. Spin it quickly then stop it. The internal turbulence of the spinning gas will be visible with a sensitive detector. Apply a short sharp impact to one side. If there is gas inside, the sound energy peak from the sound transiting the gas will be temporally distinct from the spectrum of the sound ...


11

The biggest, immediate problem with "openning the door" of a spacecraft is not that you would die immediately from exposure to the vacuum of space: you don't - you have of the order of minutes to do something about it. The problem is the violent outrush of air. User rob offers this answer to the Physics SE question Do airlocks in space decompress violently ...


10

Pour? No such thing without gravity. In NASA TV (see video), I saw the prototype coffee cups. They are shaped with a sharp crease, to allow liquid to ride up the groove. More advanced product would also mix waxy and wettable surfaces to keep it stuck to the inside of the cup but not crawl over the brim, except at the sip line. The pictures are hard to ...


6

For 1. In principle, the refractive index of a true vacuum is identically 1. For air at atmospheric pressure, the index is 1.000293 for visible light. Therefore, you should be able to determine the deviations between in refractive angles for a jar filled with air and one under vacuum. Since we're talking deviations on the order of one in ten thousandth, it's ...


5

people in spaceships opening doors and closing them again with no suits on. Is it possible in "real life" No, it is not. Any sane engineer will build doors that open inward, or have latches that over-center when closed so it is simply impossible to open an airlock in a pressurized vessel. An aircraft, for example, has about 6-8 tons of pressure holding ...


4

You can use electric discharge of appropriate frequency, as its threshold in gas depends on pressure (and frequency).


4

The bell will not vibrate harder, but will take much longer to decay. The chief dissipation mechanisms are air, bell suspension mount, and internal friction in the metal. A well made bell's mount will be such that the fundamental vibrational mode of the bell does not produce much vibration or energy loss in the suspension point. The internal friction of a ...


3

The fact that the energy-momentum tensor is called the source of curvature doesn't mean that there can't be any curvature where there is no energy-momentum. In fact, even if $T_{\mu\nu}=0$ across all spacetime, there are still nontrivial solutions of Einstein's equations, in the form of gravitational waves. You should remember that $T_{\mu\nu}$ is a ...


3

Remember the laws of Newton. In this case the water will only accelerate with the forces you apply when tilting the cup. Assuming not fierce tilting of the cup: By the hydrogen interactions the water will therefore most like just float around shaped as one or more slightly deform bubbles in mid-air, or inside the cup depending on the "tilting forces".


2

The adhesive force between the water molecules and the interior of the cup should... Even in absence of adhesive force, the water will never move in 0-gravity, because there is no up nor down, no force is acting on it. You can clearly see in this video at 1:15 that in order to get the water out of a plastic cup you have to tap it on the bottom


2

It will help if you study this diagram of what a vacuum tube is If a cathode is heated, it is found that electrons from the cathode become increasingly active and as the temperature increases they can actually leave the cathode and enter the surrounding space. When an electron leaves the cathode it leaves behind a positive charge, equal but ...


2

Hmmn, an interesting question. The most logical answer is that nothing would happen, since there is nothing to react with. But in science, it all boils down to empirical evidence. Which can only be acquired with experiments.


2

Bad Things Happen The air, as it has no pressure or enough gravity to keep it in the ship, will attempt to expand. Air, in fact, attempts to expand to fill the container it is placed in. If there is no walls to the container, like on a planet, it will only be stopped by gravity. When the airlock is unsafely open or a hole is made in a spaceship, the air ...


1

We first note that the vanishing of the Ricci tensor does not imply the vanishing of the Riemann tensor. Thus the vacuum equations, $R_{\mu\nu}=0$, do not imply that spacetime is flat. The vacuum equations tell us that certain linear combination of components of the Riemann tensor vanishes. When solving differential equations, one usually has to worry ...


1

(Moving this from my comment to an answer) Yes, the electric field simply penetrates the glass wall and charges (the electrons) placed in that field will feel a force and move. The glass does not really interact with the charges on either side, so you might as well remove it completely (theoretically).


1

It all depends on what kind of sensitivity you want in pressure measurement. If you just want to distinguished a vaccum state from atmospheric pressure, then there are many non-destructuve ways: index of refraction of air at atmospheric pressure (and a few orders of magnitude down) is different from 1 - optical interferometry. if you apply a temperature ...


1

You would have quite a problem to keep your water liquid. Normally, the water will evaporate when pumping. So you should go to low temperatures, but it freezes there. I thin you should thing about some other material to make bubbles in vacuum.


1

The best vacuum we can make is about 10^-12 Pa. Atmospheric pressure is about 10^5 Pa, so it's 17 orders of magnitude lower pressure. The best vacuum recorded is the intergalactic void, at about 10^-17 Pa. Even if you managed to remove all matter, there would still be energy from any light or electric fields.



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