But it's a pretty good approximation, since they typically have a getter to remove stray molecules.A vacuum tube of course does not have a vacuum in it ....
But it's a pretty good approximation, since they typically have a getter to remove stray molecules.A vacuum tube of course does not have a vacuum in it ....
Hi,My limited interpretation tells me that an absolute vacuum is NOT the absence of EVERYTHING in the volume of the absolute vacuum.
There’s always SOMETHING there.
Consider a thought experiment. Place a large magnet in a glass (or any non-magnetic material) containment vessel. Before evacuating the vessel, measure the strength of the magnetic field at the periphery of the vessel. Do you get a reading? Write it down. Then start evacuating the vessel. At a pre-determined vacuum delta values, document the degree of the vacuum and the measured magnetic field.
Vote. How many say the magnetic strength will change? How many believe it will be constant.
My point is that while particles maybe absent, a field will still exist in a vacuum.
I'm curious to see how people will vote on this possible change in magnetic field strength. Please give some reason for your choice so we don't have to guess.Hi,
The field will change if there was something in the vessel to begin with, but depending on what was in there it may change a lot or jsut a little.
But isn't that the same thing though as the bucket example?
Just because you can put stuff in the bucket does not mean it can never be empty.
Move the magnet into deep space, then measure the fields just outside of the vessel.
Hi,I'm curious to see how people will vote on this possible change in magnetic field strength. Please give some reason for your choice so we don't have to guess.
Then definition of an ocean is: "a water completely void of any waves, whirlpools, streams [energy]".Yes the definition of a vacuum is "a space completely void of any matter".
That is the 19th century definition. In modern physics, space is comprised of various fields -- the fields are space -- and so notions such as "empty space" don't even make sense. Instead, physicists use the word vacuum to refer to the ground state (i.e., lowest energy state) of some particular field.Yes the definition of a vacuum is "a space completely void of any matter".
Hi,Then definition of an ocean is: "a water completely void of any waves, whirlpools, streams [energy]".
Hi,That is the 19th century definition. In modern physics, space is comprised of various fields -- the fields are space -- and so notions such as "empty space" don't even make sense. Instead, physicists use the word vacuum to refer to the ground state (i.e., lowest energy state) of some particular field.
Note that this isn't just a pedantic distinction in terminology; we cannot cogently reason about electrons using classical concepts (such as empty space). The past century of physics history makes this abundantly clear.
Hi,The problem is that every practical vacuum is a matter of degree. It's like a bald man, if you pluck one hair at a time, when does he become bald?
That quote can cover so much ground. Like, one man's old computer in his garbage is another man's source for recycled gold or a kid's source for electrical parts for a new homemade computer and is another man's source for someone's personal info left on the hard drive. Like you say, it all depends on your application. With 2 rooms full of hobby stuff to get rid of, collected over 53+ years, I can really relate to that these days.Hi,
Yes, and the real crux of the issue is what application are we working with. One mans vacuum is another man's junk yard
Hi,That quote can cover so much ground. Like, one man's old computer in his garbage is another man's source for recycled gold or a kid's source for electrical parts for a new homemade computer and is another man's source for someone's personal info left on the hard drive. Like you say, it all depends on your application. With 2 rooms full of hobby stuff to get rid of, collected over 53+ years, I can really relate to that these days.
There are times when you just need to let it go.Hi,
Oh wow yeah i can relate to that too, i have containers and containers of electrical parts that i dont use anymore. Decades worth. Might donate to Rutgers University which is not too far from here (5 miles).
It's crazy what i have collected over the years.
You're missing the point. There's nothing wrong with talking about vacuum -- in the sense of empty -- in appropriate contexts. But in the particular context of electron physics, that word has a very different meaning than the common usage. The OP had a question about electrical conductivity (electron physics) in "absolute vacuum" (common usage), which is a bit like asking if leeching can fix chromosomal damage. The two concepts are not in the same scope.That's the definition in the English language.
But you could not know what you know unless you know what a perfect vacuum is. You'd never have the word.
I know that things have changed, no question there, but we know they changed because we know the concept of a perfect vacuum.
How would we know we have an imperfect vacuum without that.
In QFTs, there is only one notion of vacuum. There is, however, a scary possibility that we're living in a false vacuum, i.e., that the apparent equilibrium of the universe's energy state is only a local minimum. A universe in true vacuum is stable, but a universe in false vacuum is meta-stable and will eventually decay to its ground state. If this happens, the universe as we know it would be destroyed. Experimental data strongly suggests that the electroweak field is indeed in a false vacuum. Since vacuum decay propagates at the speed of light, it's possible the process has already started somewhere in the universe. Sweet dreams!Also, i already stated that it comes down to the application what is a vacuum and what is not for the practical cases.
The eventual fate of the universe because of unstable AdS vacuum regions? Loud snoring, wake me up in several billion years to check that.You're missing the point. There's nothing wrong with talking about vacuum -- in the sense of empty -- in appropriate contexts. But in the particular context of electron physics, that word has a very different meaning than the common usage. The OP had a question about electrical conductivity (electron physics) in "absolute vacuum" (common usage), which is a bit like asking if leeching can fix chromosomal damage. The two concepts are not in the same scope.
In QFTs, there is only one notion of vacuum. There is, however, a scary possibility that we're living in a false vacuum, i.e., that the apparent equilibrium of the universe's energy state is only a local minimum. A universe in true vacuum is stable, but a universe in false vacuum is meta-stable and will eventually decay to its ground state. If this happens, the universe as we know it would be destroyed. Experimental data strongly suggests that the electroweak field is indeed in a false vacuum. Since vacuum decay propagates at the speed of light, it's possible the process has already started somewhere in the universe. Sweet dreams!