1. ### Replacing bremsstrahlung tubes with solid-state alternatives?

What are the reasons X-ray vacuum tubes could not be replaced by solid state alternatives?
2. ### B Torricelli Vacuum Experiment

If Evangelista Torricelli truly created a vacuum, then there would be nothing in it, yet you can see through it which means light is obviously still in there (and who knows what else), right? If there was truly nothing in it, and glass is a highly viscous fluid, and fluids conform to fill empty...
3. ### I Blow a soap bubble in space?

This is an experiment I would have liked to do from the ISS, but an approximation could be done in a vacuum chamber on Earth. How big a soap bubble, polymer bubble, or glass bubble could you blow in the vacuum of space? How to calculate the evaporation rate in vacuum? A liquid exposed to vacuum...

5. ### I Radiometer rotation speed as function of pressure

I am experimenting with using a radiometer as an approximate indicator of pressure in my homemade high vacuum system, running a small turbo pump. I am interested in the relationship between pressure and vane rotation speed, with light intensity being constant. I have only been able to find...
6. ### I Vacuum quality

Does the real vacuum pressure/underpressure depends only on the amount of impurities? In the case of theoretical Torricelli vacuum test, when no purities left in the vacuum: Is the vacuum 0Pa at 1m height (with 760mm of Hg) and also the same at 10m height (also with 760mm of Hg) of the test...
7. ### Calculate the thickness of a plate to withstand a specified uniform pressure

In exploring the feasibility of constructing a vacuum chamber, I am trying to calculate the thickness of rectangular polycarbonate sheet needed to withstand 100kPa of pressure, given dimensions of 30.5cm by 61cm (12 by 24 inches) and clamped edges. I have found some calculators that will tell...
8. ### Misc. Generating as much suction with as little weight as possible

Hello all, as my final project to attain my bachelors, I have tasked myself with designing some sort of device to collect insects from the canopy of soybean plants that can be suspended under a UAS (quad copter/drone). What I am trying to do is essentially build some sort suction device. The...
9. ### I Pressure differences in a leaking vacuum vessel

Hello all, I'm new to this forum and I'm mucking about with some self-made physics conundrums, and I need some help! So, What I am aiming for is a roughly cylindrical vessel (it can, and I think probably has to, be tapered to achieve the effect) with the air being pumped out of one end, and a...
10. ### How do wet/dry vacuum cleaners work? What is the physics behind them?

I have a problem designing and understanding Wet and Dry vacuum cleaners. I understand some of the basics behind pressure however things I need to know is: what pressure/ velocity is needed to suck up water? how to calculate the pressure and velocity generated by the fan? (some examples of...
11. ### I Ion sensor for 1e20 ions/m3 density

What kind of ion sensor can I use in the range 1e19to 1e22 ions/m3? (corresponds to 0.1 to 5 pascals if non ionized) Does it exist any sensor based in the charge capacity?
12. ### B Why does time pass in an isolated vacuum?

I read a little bit on the arrow of time and how some physicists think that it points in the direction of increasing entropy. This made sense until I thought about a vacuum. From what I read, entropy does not increase nor decrease in a vacuum so if we used this definition on the "arrow of time"...
13. ### A Vacuum in interacting QFT and physical particles

After some reading, I'm quite confused about the vacuum state in interacting QFT. I've read the @A. Neumaier post on "The Vacuum Fluctuation Myth," where he notes that "bare quantum field theory with a cutoff, the vacuum is a complicated multiparticle state depending on the cutoff – though in a...
14. ### B No sound in vacuum? So can I clap more?

I was just wondering (Wondering!? Stop wasting our precious time!) about clapping my hands. *Claps* It's sound energy. A little energy is released as heat. Good. This means that I have used some energy from my body. In making those two energies. Right. <<Mentor note: rant removed>> So, I am in a...
15. ### I Does the Uncertainty Principle imply a linear cosmology?

If the uncertainty in the age of the Universe is ##\Delta t## then the Uncertainty Principle implies that it has an uncertainty in its energy ##\Delta E## given by $$\Delta E \ \Delta t \sim h.\tag{1}$$ If this energy fluctuation excites the zero-point electromagnetic field of the vacuum then a...
16. ### What would happen to a blob of mercury in space?

How long would it take for a blob of mercury (the size of a marble or so) to freeze in space? I'd emagine it would have to boil in some way first, and that would send pieces of it flying around, but the surface tension of mercury is much greater than that of water, or urine (as we'd seen...
17. ### Parallel vacuum sources

I have two vacuum sources each pulling 1 inHG. If I connect the vacuum sources to a Y-connector, with identical sized hoses, so that each pulls on one tip of the Y, will I get 2 inHG vacuum on the remaining hose, or will I get 1 inHG with more cfm? Thank you, B
18. ### I How can I go about making a "Space Proof" coating?

So im planning on launching a Satellite to promote the Dogecoin cryptocurrency. One of the main points is printing/painting (Or whatever) the logo on the side of a metal panel. How can I make it so it doesn't melt off or turn white from radiation so quickly?
19. ### A Vacuum in QFT: Fock space or effective potential?

There seem to be two ways of defning what a vacuum is in QFT: 1. It is state $|0\rangle$ such that $$a_k|0\rangle = 0$$ for all anihilation operators $$a_k$$, with creation operators $$a_k^{\dagger}$$. Thus, it is defined in Fock space. 2. It is state $$|0\rangle$$ such that derivative...
20. ### B Why do microcontrollers fail in a Vacuum?

I was trying to log data inside a vacuum chamber, tried an arduino and a rasperry pi. When reaching -30inHg the devices just stopped working, they powered off, no data in or out and would not work ever again. Why? And no, they did not overheat.
21. ### I Does space have its own density?

Does space have its own density? i.e. a mass density distinct from the mass density of 'particles' in it? or may it have a uniform density of some kind of vast particle(s)? If so, would the effect on observable masses largely cancel out? One answer from...
22. ### How can I get my Pi 3 to work in a vacuum?

Im trying to do some data logging, using a raspberry pi 3 would be super easy as it has a built in WiFi and Bluetooth receiver as well as an SD card. However when the vacuum gets to about -30inHg the Pi shuts off and the red light starts flashing as if there is no OS. Temperatures arent crazy...
23. ### I Should the energy density of the vacuum be zero?

According to [Dark Energy and the Accelerating Universe](https://ned.ipac.caltech.edu/level5/March08/Frieman/Frieman5.html) quantum field theory says that the energy density of the vacuum, ##\rho_{vac}##, should be given by \rho_{vac}=\frac{1}{2}\sum_{\rm...
24. ### I Is it possible to use the vacuum to launch a rocket?

Hey I'm new to Physics. I have a question. Is it possible to use the force generated when air entera a vacuum tube to launch something into space? Can anybody throw some light on this in simple words please. Thank You.
25. ### Question about vacuum powered projectiles

I'm writing a novel and wanted to research a possible weapon I came up with to make sure the physics are at least possible. However, I could not find anything on vacuum-based projectiles other than ping-pong balls, while this is interesting, but it doesn't answer my question on what would happen...
26. ### A Could vacuum decay fundamentally change our universe?

If the universe suffered a false vacuum decay, would this change physical laws? Could it change the universe so much that it would allow our universe to be a multiverse of level 1, 2, 3 and 4? https://en.wikipedia.org/wiki/Multiverse
27. ### A String vacua and particles?

I've been doing a little bit of reading on string theory, and the very large number of string vacua that are possible (i.e., perhaps 10^500 or more). One thing that is not clear to me is exactly what constitutes a 'vacuum' in string theory. In QFT theory, the vacuum is defined as the state with...
28. ### I No sublimation for human body in vacuum? [Thermodynamics]

In my Thermodynamics course, we recently learned about the saturation pressure and saturation temperature of different substances -mainly water. As you know, the saturation temperature at which a substance begins to boil is specific to a fixed saturation pressure. Water only boils at 100...
29. J

### I Evaporation under vacuum; surface area

I run a vacuum distillation unit that is used to distill ethylene glycol. The old glycol is subjected to 25Hg of vacuum at a temp of 275 degrees F. There are burner tubes submerged in the glycol to heat it up. The vessel has a diameter of 36 inches and is 124 inches long. We fill the vessel...
30. C

### I Does moisture escaping from powders decrease chamber vacuum?

I'm drying some wet powders using vacuum oven and start seeing some condensation on the window after few minutes. The vacuum level stays pretty constant which puzzles me as i thought that the moisture escapes from the powder into the air will increase the chamber pressure or decrease the vacuum...