About Vaccum

This thread is started because of:

People in the thread "[ The Big Bang Theory Wrong ]" keep posting about Vaccum. They can not agree what Vaccum is.

Cross posted in above mention thread, page 9.

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The definition of vaccum is problematic.

If we construct a true "Vaccum", then follows that. How far away must the particles be? 10^(-2000) m? 10^(4000) m? Gosh! That's a big chamber!

Since no one else is doing this. I hereby start a thread for people wanting to discuss diffrent aspects of "Vaccum". I call it "About Vaccum"Perhaps thats a lousy name - then start another thread, PLEASE.

VACCUM IS PROBLEMATIC. NOW YOU GUYS HAVE YOUR OWN THREAD ABOUT IT

Originally posted by bikingviking
[b]This thread is started because of:

People in the thread "[ The Big Bang Theory Wrong ]" keep posting about Vaccum. They can not agree what Vaccum is.

Cross posted in above mention thread, page 9.

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The definition of vaccum is problematic.

If we construct a true "Vaccum", then follows that ...[text shortened]... ther thread, PLEASE.

VACCUM IS PROBLEMATIC. NOW YOU GUYS HAVE YOUR OWN THREAD ABOUT IT[/b]

Personally I don't think the definition of vacuum is problematic -at least if you are talking about a total vacuum. The way I would personally define a total vacuum is simply it being a volume of space that doesn’t contain any particles of 'ordinary matter' where 'ordinary matter' includes atoms and stable ions but excludes virtual particles, neutrinos, dark matter etc.

If we construct a true "Vacuum", then follows that. How far away must the particles be? (misspelling corrected )

Not sure what you mean. If what you mean by “true vacuum" is one that has no particles of 'ordinary' matter and if you are referring to the distance between those non-existent particles of 'ordinary' matter then I don't see how the question makes any sense.

Originally posted by bikingviking
[b]This thread is started because of:

People in the thread "[ The Big Bang Theory Wrong ]" keep posting about Vaccum. They can not agree what Vaccum is.

Cross posted in above mention thread, page 9.

#############################################

The definition of vaccum is problematic.

If we construct a true "Vaccum", then follows that ...[text shortened]... ther thread, PLEASE.

VACCUM IS PROBLEMATIC. NOW YOU GUYS HAVE YOUR OWN THREAD ABOUT IT[/b]

Do you think there are virtual particles popping into and out of existence in the vacuum? If so what effects do they have on our world?

Originally posted by joe beyser
1. Do you think there are virtual particles popping into and out of existence in the vacuum?
2. If so what effects do they have on our world?

1. yes
2. http://en.wikipedia.org/wiki/Casimir_effect

There is also the quantum effect of particles not having an exact location, so any particle in the universe has a small but non-zero chance of being found in your vacuum.
Please correct me if I am wrong.

Originally posted by twhitehead
There is also the quantum effect of particles not having an exact location, so any particle in the universe has a small but non-zero chance of being found in your vacuum.
Please correct me if I am wrong.

You are correct.
In fact, there must be a miniscule but non-zero chance that, without warning, a load of whole chimpanzees, lions and stampeding elephants will suddenly and inexplicably appear in your living room as soon as you next sit down there for a rest
-ssurrPrrise!!!

Originally posted by humy
You are correct.
In fact, there must be a miniscule but non-zero chance that, without warning, a load of whole chimpanzees, lions and stampeding elephants will suddenly and inexplicably appear in your living room as soon as you next sit down there for a rest
-ssurrPrrise!!!

They would either need to shrink a bit, or my living room grow larger.

So tell me, if a particle interacts with another particle, is there still a non zero probability that it could be detected somewhere else that it could not get to except by travelling faster than the speed of light? ie is there a speed of light limit on a particles possible position?
If a herd of alien stampeding 'elephants' appeared in my living room, could I be sure that they were last seen at or before 100 million years ago on their home world which is 100 million light years away?

Originally posted by humy
You are correct.
In fact, there must be a miniscule but non-zero chance that, without warning, a load of whole chimpanzees, lions and stampeding elephants will suddenly and inexplicably appear in your living room as soon as you next sit down there for a rest
-ssurrPrrise!!!

Please excuse mr humy here. If he in his daily life see people (monkeys, zebras) start levitating that's perfectly fine with me. Perhaps they are green with feathers and having 8 legs and 5 horns in their forhead.

twistedhead: I did not think about that, but of course you are correct. Partly correct. I am no expert in this either. I guess that when you come even a tiny, guessing 10^(-16) m away from. Where the probability of finding said particle is the highest. Then quickly the extremly small probability start decreasing very rapidly. That means that it becomes zero. Not "close to zero" but zero. Like a probabuility of 10^(-1000) then less than that. Which is zero. Or else green monsters would be popping up every second. Which is not happening.

Now I start mixing apples and lemons. It is like the thing with gravity and the universe. You could expect everything (meaning particles with mass) to be very very evenly divided in the universe. Like in a glass of milk kind of. Homogenus. Now we find that not to be the case. Instead we have planets, stars, astroids. That is because of probabuility. We have infinately (not mathematic infinity of course) more configurations of space, where the particles is collected in things like planets. Than the very very few configurations in which the universe is a homogenus milk-like soup. Because of gravity and probabuility. I guess the mathematical reasons of why you do not find particles in vacuum (now correctly spelled!) is very similar.

A very very very wild guess is that temperature perhaps affect the probabuility as well. Since in vacuum that temperature would be something like 0 kelvin. (Perhaps you know of a warmer vacuum, I don't). 🙂

Originally posted by twhitehead
They would either need to shrink a bit, or my living room grow larger.

So tell me, if a particle interacts with another particle, is there still a non zero probability that it could be detected somewhere else that it could not get to except by travelling faster than the speed of light? ie is there a speed of light limit on a particles possible position ...[text shortened]... en at or before 100 million years ago on their home world which is 100 million light years away?

They would either need to shrink a bit, or my living room grow larger.

LOL. I think they would also have a job to fit into my living room. Couldn't they be midget animals? -this is just getting weirder. If I saw that I would go to a doctor.

is there still a non zero probability that it could be detected somewhere else that it could not get to except by travelling faster than the speed of light?

Yes!

If a herd of alien stampeding 'elephants' appeared in my living room, could I be sure that they were last seen at or before 100 million years ago on their home world which is 100 million light years away?

No! However, if you do see this, go to a doctor.

I have to confess, quantum physics is not quite my area of expertise although I know vastly more about it than the average layperson but, if I understand quantum physics correctly, quantum physics allows things to go over c although, in purely practical everyday terms, only by allowing certain relatively trivial exceptions to relativity.

Originally posted by humy

They would either need to shrink a bit, or my living room grow larger.

LOL. I think they would also have a job to fit into my living room. Couldn't they be midget animals? -this is just getting weirder. If I saw that I would go to a doctor.
[quote] is there still a non zero probability that it could be detected somewhere else that it c ...[text shortened]... /i] everyday terms, only by allowing certain relatively trivial exceptions to relativity.

You are talking about phase velocity vs group velocity and the like?


http://en.wikipedia.org/wiki/Faster-than-light

Originally posted by sonhouse
You are talking about phase velocity vs group velocity and the like?


http://en.wikipedia.org/wiki/Faster-than-light

No, we are talking about the Schrodinger equation (I think):
http://en.wikipedia.org/wiki/Schr%C3%B6dinger_equation

My understanding is that although the equation for the probability of finding a given particle in space tails off (gets very close to zero), it is never quite zero. I don't know this for sure which is why I asked for confirmation from those more knowledgeable than I.

Originally posted by bikingviking
Like a probabuility of 10^(-1000) then less than that. Which is zero.

No, less than that is not zero.

Originally posted by twhitehead
No, we are talking about the Schrodinger equation (I think):
http://en.wikipedia.org/wiki/Schr%C3%B6dinger_equation

My understanding is that although the equation for the probability of finding a given particle in space tails off (gets very close to zero), it is never quite zero. I don't know this for sure which is why I asked for confirmation from those more knowledgeable than I.

I wonder if quantum laws can be tweaked in such a way as to allow c+ velocities? Like the LIGO, they are making gains in the sensitivity of the system by using what they call 'squeezed light' which is saying they bend one of the rules of quantum mechanics at the expense of another so the net result is a more sensitive system.

I am wondering if they can do that with space propulsion (of course when we get to the capability of getting very close to c, which won't be happening in the 21st century for sure, but maybe in century 22).

http://www.nature.com/nature/journal/v500/n7461/full/nature12307.html

Originally posted by twhitehead
There is also the quantum effect of particles not having an exact location, so any particle in the universe has a small but non-zero chance of being found in your vacuum.
Please correct me if I am wrong.

In principle you are correct (given relativistic constraints of course). Through the exchange interaction, everything is connected to everything, so for a "complete" description one would have to describe the universe with a single wavefunction describing all particles. Fortunately, one can often neglect the exchange interaction between subsystems of the universe.

Aside from these considerations, there are technical reasons which make it practically impossible for humans to create a pure vacuum. But theoretically, there are no issues with the concept of vacuum and in most respects one can consider the purest vacuums that we can make as good enough to reproduce the properties we expect for a pure vacuum.

Originally posted by KazetNagorra
In principle you are correct (given relativistic constraints of course). Through the exchange interaction, everything is connected to everything, so for a "complete" description one would have to describe the universe with a single wavefunction describing all particles. Fortunately, one can often neglect the exchange interaction between subsystems of th ...[text shortened]... vacuums that we can make as good enough to reproduce the properties we expect for a pure vacuum.

Do you include virtual particles in your definition of a pure vacuum? If so, there can't even be a theoretical pure vacuum since it is impossible to eliminate those ephemeral particles that come and go so fast I don't think they can be directly counted at least not yet, which is what leads to the Casimir force.