Tag Info

0

It seems that most places I've read (on the web) people refer to the depressurization of water (in a vacuum or space) as "boiling" but I have very rarely seen this referred to as an out-gassing of the water's internal dissolved gases (nitrogen, oxygen, CO2, or any other gases that may be used in a space vehicle). However, unlike traditional boiling which ...

-3

You people make this overly complicated. If the vacuum exists, time absolutely exists as well. For example, if the vacuum were to exist near a source of radiation, particles. They could enter the given vacuum as time passes by so time absolutely exists. also, time as a count of existence progressing, also must be identically throughout the universe to our ...

0

To see if this is possible we can use a formal material selection approach of the kind presented in "Material Selection in Mechanical Design", Elsevier, M.F.Ashby. Our objective is to maximize buoyancy while keeping within the no-buckling constraint. To make things easier I suggest some simplifications. First, Poisson's Ratio does not vary much for most ...

3

That's rather an unusual question though interesting, but it amuses me to make an even more unusual answer. Disclaimer: this is in no way a rigorous answer, as many assumptions, simplifications have been made (even entire phenomenons such as gravity attraction if the velocity is not perpendicular, solar pressure from photons...) - only a reflection on drag ...

0

Yes. This is the idea behind some versions of Eternal Inflation. In that model, most of an infinite universe is assumed to be in a higher-energy vacuum state, in which pockets chaotically inflate. Some of those pockets also decay, and the combination produces Big Bangs which make universes like ours embedded in a large surrounding non-decayed, non-inflated ...

2

This is an instructive video on the double slit experiment with photons which is experimenting with single photons. At about 2.5 minutes it explains how the experiment is done with single photons. In a nutshell, by lowering the intensity of a light source to the point of zero emitted by the source and then slowly increasing it. The detection hinges on the ...

1

As other answers mention, it was originally (in QED) about getting a neutral vacuum. It is useful to go back to Schwinger's old version of QED, before Dyson's approach became accepted. See Pauli: Selected topics in field quantization. Pauli presents both ways of looking at it: 1) define the electric current as sum of two terms (p.20 [6.4]), such that the ...

2

The choice of normal ordering prescription $:~:$ is typically adjusted to the choice of vacuum state $|\Omega\rangle$ so that the bra-ket-sandwich of normal-ordered operators $$\langle \Omega|:\hat{\cal O}_1\ldots \hat{\cal O}_n : |\Omega\rangle~=~0$$ vanishes. The relation of normal ordering prescription to Wick theorem and other operator ordering ...

2

In classical physics, quantities are ordinary, commuting $c$-numbers. The order in which we write terms in expressions is of no consequence. In quantum field theory (QFT), on the other hand, quantities are described by operators that, in general, don't commute. Classical physics is a low-energy approximation of quantum physics - the road from quantum to ...

Top 50 recent answers are included