Do Atoms Exist in a Perfect Vacuum?

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Atoms do not exist in a perfect vacuum, as a perfect vacuum is defined as having no matter at all. However, in practical terms, a vacuum in space contains atoms and electromagnetic (EM) radiation. The discussion revolves around whether EM radiation exists between atoms in a vacuum, with some arguing that it does, while others suggest that the question is too hypothetical. It is noted that in reality, a vacuum cannot be completely devoid of EM radiation. The conversation highlights the complexities of defining a vacuum and the implications of various scientific principles.
  • #51


One more thing...the change in the speed of light is due to a change in the "phase velocity", i.e. the speed of the propagating wavefront, and not the velocity of the photons.
 
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  • #52


thopsy said:
One more thing...the change in the speed of light is due to a change in the "phase velocity", i.e. the speed of the propagating wavefront, and not the velocity of the photons.

I'm assuming that they aren't one in the same?
 
  • #53


Jeez, I hope not. My knowledge ends here. :(
 
  • #54


The answers on the definition of a vacuum and a perfect vacuum tell you about atoms existing in a vacuum. Electromagnetic radiation can pass though a vacuum, otherwise as soon as a wave encountered a volume of perfect vacuum, what would happen to it?
Given the low density of atoms in space, and decreasing in interstellar space this would kind of mess with the electromagnetic waves we need to observe the universe with.

You can also consider the occurrence of
1) blackbody photons

2) vacuum fluctuations which are virtual particles that appear and disappear in a vacuum, observed via the Casimir effect of quantum field theory.
 
  • #55


So, in saying, a "perfect vacuum" is defined as having no matter, is the space around atoms void of matter? And, if so, would that mean atoms exist in a vacuum?
 
  • #56


santhony said:
So, in saying, a "perfect vacuum" is defined as having no matter, is the space around atoms void of matter? And, if so, would that mean atoms exist in a vacuum?

You're referring to the spaces within the atom itself? Between the nucleus and electron etc?
 
  • #57


jarednjames said:
You're referring to the spaces within the atom itself? Between the nucleus and electron etc?

No. Honestly, I'm referring to the space surrounding an atom.
 
  • #58


santhony said:
No. Honestly, I'm referring to the space surrounding an atom.

What space would that be then if it isn't the space of the atom itself?
 
  • #59


Is there no space surrounding atoms? I was told by someone, who says he has a Bachelor's Degree in Physics, "the spaces between atoms -- even in a solid -- contain nothing but empty space. So there's lots of vacuum all over the place." Is this true?
 
  • #60


santhony said:
Is there no space surrounding atoms? I was told by someone, who says he has a Bachelor's Degree in Physics, "the spaces between atoms -- even in a solid -- contain nothing but empty space. So there's lots of vacuum all over the place." Is this true?

Yes, the atoms are 'surrounded by empty space' - this is the part relating to the electrons.
 
  • #61


But, in a solid, aren't the atoms bonded together?
 
  • #62


The atom nuclei don't touch. The electrons can be shared though.
 
  • #63


So, between the subatomic particles exists empty space?
 
  • #64


santhony said:
So, between the subatomic particles exists empty space?

I'm not the person to discuss this with as I know very little about it. This subject should perhaps be the subject of a separate thread as you'll get a far better scope for responses.
 
  • #65


santhony said:
So, between the subatomic particles exists empty space?

The nucleus is about 1 billionth the size of the whole atom I believe. Between the nucleus and the electrons is effectively empty space.
 
  • #66


Well, seeing an atom or anything, for that matter, could not be logically held together by a vacuum, it would seem the definition for "vacuum" is merely a product of arbitration.
 
  • #67


santhony said:
Well, seeing an atom or anything, for that matter, could not be logically held together by a vacuum, it would seem the definition for "vacuum" is merely a product of arbitration.

Atoms aren't held together by a vacuum. In fact, I don't think anything is 'held together' because of a vacuum.

Again, a vacuum is an area that has as little matter in as possible.

A perfect vacuum has no matter in it what-so-ever.

I don't see what's arbitrary about that. And the make up of an atom certainly has no bearing on it.
 
  • #68


jarednjames said:
Atoms aren't held together by a vacuum. In fact, I don't think anything is 'held together' because of a vacuum.

Again, a vacuum is an area that has as little matter in as possible.

A perfect vacuum has no matter in it what-so-ever.

I don't see what's arbitrary about that. And the make up of an atom certainly has no bearing on it.

It is my understanding, and maybe I'm wrong, that, between the nucleus of an atom and its electrons exists a "vacuum", as it's defined.
 
  • #69


santhony said:
It is my understanding, and maybe I'm wrong, that, between the nucleus of an atom and its electrons exists a "vacuum", as it's defined.

When a specified volume contains no matter, it is considered a perfect vacuum. So any volume, regardless of size - whether between two electrons or two planets - devoid of matter is considered a vacuum.

This has absolutely nothing to do with what binds the atom together.

The definition of a vacuum is simply an area with no matter in it.
 
  • #70


In current theories, elementary particles are point(!) particles (contrasting with string theory in which they are 1-D strings). Meaning they take up no space at all, and, so if you want to go to those scales, I guess you could say everything is a vacuum. But the sense of a vacuum sort of loses its meaning at those scales.

These "singularities" introduces problems (e.g. infinite energy is required to compress a charge e into a point), which is beyond my realm of knowledge (something to do with renormalization).

Usually we say "vacuum" in a macroscopic way.
 
  • #71


jarednjames said:
When a specified volume contains no matter, it is considered a perfect vacuum. So any volume, regardless of size - whether between two electrons or two planets - devoid of matter is considered a vacuum.

This has absolutely nothing to do with what binds the atom together.

The definition of a vacuum is simply an area with no matter in it.

I agree, that is the physical definition of a "vacuum". But, being void of matter doesn't mean being void of everything. The point, that, I was trying to make was, if you were to ask the average person on the street to define a "vacuum", for the most part, it would be defined as empty space or space containing nothing.
 
  • #72


santhony said:
I agree, that is the physical definition of a "vacuum". But, being void of matter doesn't mean being void of everything.

Never said it was. That isn't the purpose of the word vacuum.

Vacuum only deals with matter - I'm sick of saying this now.
The point, that, I was trying to make was, if you were to ask the average person on the street to define a "vacuum", for the most part, it would be defined as empty space or space containing nothing.

All well and good, but this has no bearing on the scientifically accepted definition. The 'people on the street' are wrong on a lot of things, it doesn't make what they believe to be true correct in any way.

You've jumped from atoms to people on the street. Do you have a question you need answering or are we just going to traverse the entire field of physics discussing random matters of the vacuum?
 
  • #73


Matterwave said:
In current theories, elementary particles are point(!) particles (contrasting with string theory in which they are 1-D strings). Meaning they take up no space at all, and, so if you want to go to those scales, I guess you could say everything is a vacuum. But the sense of a vacuum sort of loses its meaning at those scales.

These "singularities" introduces problems (e.g. infinite energy is required to compress a charge e into a point), which is beyond my realm of knowledge (something to do with renormalization).

Usually we say "vacuum" in a macroscopic way.

I'm not even going to begin to say, I know much about physics. Just, that, I have an interest in learning. So, please, excuse my ignorance. If elementary particles take up no space, seeing all matter is made of elementary particles, wouldn't it go to reason, we would take up no space, either? In other words, no matter how many times you add up zero, it still equals zero.
 
  • #74


santhony said:
I'm not even going to begin to say, I know much about physics. Just, that, I have an interest in learning. So, please, excuse my ignorance. If elementary particles take up no space, seeing all matter is made of elementary particles, wouldn't it go to reason, we would take up no space, either? In other words, no matter how many times you add up zero, it still equals zero.

Please, let's not go down this route.

Suffice to say, no it does not mean that.
 
  • #75


Code: 
You've jumped from atoms to people on the street. Do you have a question you need answering or are we just going to traverse the entire field of physics discussing random matters of the vacuum?

For one thing I don't believe my question is straying away from my original topic of a vacuum. I believe it's going to the very heart of it. Sorry, but I find it hard to except something just because an authority says it's so, especially if it doesn't seem to be consistent, and hopefully you have a healthy dose of skepticism, yourself. Science was never meant to be a religion, and I would appreciate it if you would not treat as such. You are under no obligation to answer my question. And, apparently the fact that it is not an irrational question is betrayed by the fact that you have said, "I'm sick of saying this now."
 
  • #76


santhony said:
For one thing I don't believe my question is straying away from my original topic of a vacuum. I believe it's going to the very heart of it. Sorry, but I find it hard to except something just because an authority says it's so, especially if it doesn't seem to be consistent, and hopefully you have a healthy dose of skepticism, yourself. Science was never meant to be a religion, and I would appreciate it if you would not treat as such. You are under no obligation to answer my question. And, apparently the fact that it is not an irrational question is betrayed by the fact that you have said, "I'm sick of saying this now."

Science is not a religion. No one is treating it as such.

The "authority" on this matter is science, worldwide science and the associated scientists - not the people on the street. There is absolutely no debate on what a vacuum consists of and the definition is consistent wherever you see it.

Vacuum has a scientifically accepted definition. That's the end of it.

Every dictionary has the same definition of a vacuum - what the people think is irrelevant. If the people don't understand a word then that is their problem. It doesn't make their use correct.

I'm sick of giving the definition. It isn't going to change and there's no debate on that matter. Vacuum describes an area with no matter in it.
 
  • #77


santhony said:
I'm not even going to begin to say, I know much about physics. Just, that, I have an interest in learning. So, please, excuse my ignorance. If elementary particles take up no space, seeing all matter is made of elementary particles, wouldn't it go to reason, we would take up no space, either? In other words, no matter how many times you add up zero, it still equals zero.

I only brought up my point to try to get you to steer away from trying to consider length scales that are much smaller than the nucleus of an atom when considering the word "vacuum". Vacuum is operationally defined as a region of space that is devoid of matter. If we start looking too close at distance scales on par with the sizes of the particles which make up "matter", the word "vacuum" begins to lose it's meaning. In those scales, perhaps the word "space" is better.

P.S. No it doesn't mean macroscopic objects, which are made of many particles, take up no space. Even though the elementary particles have no finite spatial extent, we still have distances between these elementary particles, which has a meaning.
 
  • #78


If there was a perfect vacuum, what effects would have? and would these change something in science?
 
  • #79


el.fisico said:
If there was a perfect vacuum, what effects would have? and would these change something in science?

Given how close space is to a perfect vacuum (~1 hydrogen per metre cubed) it really wouldn't make much difference.

There would be no changes to science and no "effects".
 
  • #80


Thanks to everyone who contributed to answering my question, "Do atoms exist in a vacuum?" I can see, now, using the standard definition of "vacuum", that, they do exist. In fact, they are in more places than I previously imagined.

However, my last question, for future reference, is, does a word exist that explains a space free of everything, including energy?
 
  • #81


santhony said:
Thanks to everyone who contributed to answering my question, "Do atoms exist in a vacuum?" I can see, now, using the standard definition of "vacuum", that, they do exist. In fact, they are in more places than I previously imagined.

Note, atoms do exist in all vacuums because we can't get a perfect vacuum.

A perfect vacuum however contains no atoms.
However, my last question, for future reference, is, does a word exist that explains a space free of everything, including energy?

Not as far as I'm aware.
 

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