Do Atoms Exist in a Perfect Vacuum?

[santhony]

Do atoms exist in a vacuum?

 

[JaredJames]

That depends.

Strictly speaking, in a perfect vacuum, there is nothing.

But it's impossible to have a perfect vacuum and so in terms of the vacuum of space, yes there are atoms present.

 

[santhony]

I know that atoms exist in space. But, I guess my question really boils down to this: does eletromagnetic radiation exist between atoms and to what extent?

 

[JaredJames]

does eletromagnetic radiation exist between atoms and to what extent?

Well that has absolutely nothing to do with your initial question.

Unfortunately, I'm not able to answer that as I really don't know much about it.

 

[santhony]

Sorry, for not being clearer... I'm having a discussion with someone else. And, he's insisting that nothing exists between atoms. I believe that electromagnetic radiation does. But, since as he claims, he's the "expert" on the subject, my arguing with him is pointless.

 

[pallidin]

Santhony, I'm not sure your 2nd question can be adequately addressed without the involvement of quantum physics.
If you are OK with that, perhaps you could start a new thread on that particular question in the quauntum physics sub-forum, as that type of question has been addressed there many times.

 

[russ_watters]

I don't think the question has anything to do with QM: whether a space is a vacuum or not has nothing at all to do with whether there is EM radiation in it...and there's always EM radiation in it.

 

[JaredJames]

I don't think the question has anything to do with QM: whether a space is a vacuum or not has nothing at all to do with whether there is EM radiation in it...and there's always EM radiation in it.

Yes, but the question asked isn't the one from the OP.

It is:

"does eletromagnetic radiation exist between atoms and to what extent?"

So if we took two atoms, with nothing at all around them (a perfect vacuum), would there be EM forces acting between them (assuming we isolated any outside sources)?

 

[russ_watters]

(assuming we isolated any outside sources)?

That's the assumption that'll get you.

 

[JaredJames]

That's the assumption that'll get you.

There's a reason I can't answer this.

It's a hypothetical none-the-less and I don't see why someone in the know couldn't answer it.

Besides, why can't we assume two atoms free from external influence?

 

[russ_watters]

I guess it all depends on how hypothetical the OP wants to get. You can find volumes of a few cc of perfect vacuum in space, but these spaces have EM radiation traveling through them. That's the answer to the OP's questions in reality: You can't, in real life, have a space with no EM radiation traveling through it.

So if the OP wants to assume a space completely insulated from EM radiation, then s/he will have to be specific about which scientific laws should apply to this space and which shouldn't. The answer depends on the choice of assumptions.

 

[JaredJames]

I guess it all depends on how hypothetical the OP wants to get. You can find volumes of a few cc of perfect vacuum in space, but these spaces have EM radiation traveling through them. That's the answer to the OP's questions in reality: You can't, in real life, have a space with no EM radiation traveling through it.

So if the OP wants to assume a space completely insulated from EM radiation, then s/he will have to be specific about which scientific laws should apply to this space and which shouldn't. And the answer depends on the choice of assumptions.

You need to forget the vacuum question.

It's about whether two atoms have EM acting between them in the same way two masses have gravity acting between them.

 

[santhony]

I guess what I'm really trying to get at is, if a vacuum is filled with eletromagnetic radiation, can it be classified as a "perfect vacuum"?

 

[pallidin]

I guess what I'm really trying to get at is, if a vacuum is filled with eletromagnetic radiation, can it be classified as a "perfect vacuum"?

I don't know, but try this: if a vacuum area by virtue of EM shielding has less EM internally, is it more "perfect" than one which has no shielding?

 

[JaredJames]

Well, I'm way off then.

Apologies russ, seems like you were on the right track.

 

[mrspeedybob]

Sorry, for not being clearer... I'm having a discussion with someone else. And, he's insisting that nothing exists between atoms. I believe that electromagnetic radiation does. But, since as he claims, he's the "expert" on the subject, my arguing with him is pointless.

1. If arguing is pointless then don't argue.
2. Atoms are made of charged particles (or waves if you prefer). The theoretical limit for the range of the electrostatic force is in the billions of light years so I would say that electrostatic force would exist between 2 atoms in an otherwise completely empty universe unless they are very far apart. If the 2 atoms are moving with respect to each other then electrostatic would also imply electromagnetic.
3. In our universe atoms and EM are not the only candidates for occupying a vacuum. How about neutrinos, dark matter, and dark energy for starters.

 

[russ_watters]

I guess what I'm really trying to get at is, if a vacuum is filled with eletromagnetic radiation, can it be classified as a "perfect vacuum"?

Yes - by definition.

Well, I'm way off then.

Apologies russ, seems like you were on the right track.

No worries - I have a seventh sense for this sort of thing.

 

[brainstorm]

I think that when gravitational lensing occurs around a massive gravity-well, spacetime should curve in a way that separates photon paths from one another. If the photon paths are curving around a black hole, there must be some area between the photon paths and the BH with no photons present.

Also, when you consider that photons are discreet packets of EM energy, there must be some moment between photon emission/absorption where an atom is completely free of any contact with either photons or other atoms. So in that moment, the space between that atom and any approaching or departing photons must be a photon-less vacuum, correct? This, of course, assumes that photons are not only discreet in energy-quantity but also discreet in volume, which they may not be.

 

[santhony]

1. If arguing is pointless then don't argue.
2. Atoms are made of charged particles (or waves if you prefer). The theoretical limit for the range of the electrostatic force is in the billions of light years so I would say that electrostatic force would exist between 2 atoms in an otherwise completely empty universe unless they are very far apart. If the 2 atoms are moving with respect to each other then electrostatic would also imply electromagnetic.
3. In our universe atoms and EM are not the only candidates for occupying a vacuum. How about neutrinos, dark matter, and dark energy for starters.

Excuse my ignorance. But, is dark matter and dark energy real? Or, is it theory?

 

[pallidin]

At this time, theory only.
There is no direct evidence.

 

[santhony]

Yes - by definition.

Do you have any references to support your answer?

 

[santhony]

At this time, theory only.

Thanks. I'm not looking to support an argument with theory. I'm learning little by little about physics. My current passion is medicine. Yet, physics has always intrigued me.

 

[pallidin]

Do you have any references to support your answer?

I support your contention in the sense that it seems, intuitively, that a vacuum condition excluding EM would be "more perfect" than one that does not.

Perhaps I'm being overly trivial here. Than again, perhaps not.

 

[JaredJames]

Thanks. I'm not looking to support an argument with theory.

Then you're going to have a hard time debating quite a lot in physics. If this is your attitude, you might want to avoid physics.

Do you have any references to support your answer?

A vacuum is defined as being a place where there is an absence of matter not em radiation. Don't confuse the two.

Pallidin, given that the definition doesn't involve EM radiation, the lack of it doesn't affect change the state of a vacuum. See the bolded portion below:

In everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty". A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in practice.

http://en.wikipedia.org/wiki/Vacuum
http://www.thefreedictionary.com/vacuum
http://dictionary.reference.com/browse/vacuum

 

[brainstorm]

A vacuum is defined as being a place where there is an absence of matter not em radiation. Don't confuse the two.

You should learn the difference between arbitrarily defining something for the sake of making arbitrary claims and actually reasoning about the logic of the concept. A vacuum may be generally viewed as referring to an absence of matter but not energy, but the relevant issue is why. To get into that, you need to reflect on what really constitutes "vacuum" and what its purpose as a descriptive term is in the first place.

My impression (though I'd like to know if others see it differently) is that a vacuum refers not only to the absence of matter but also to the potential for matter and/or EM energy to be present. If there was some possibility for a vacuum to exist in which neither matter nor radiation could be present, would space even exist there?

I suppose you could go on to ask the question that if it was possible to have a vacuum devoid of both matter and radiation, would gravitational force still be present? How would it be possible to have a vacuum devoid of all matter, energy, and force? How would that even be measurable/observable at all?

 

[f95toli]

You should learn the difference between arbitrarily defining something for the sake of making arbitrary claims and actually reasoning about the logic of the concept. A vacuum may be generally viewed as referring to an absence of matter but not energy, but the relevant issue is why.

The answer to "why" is that this is how people communicate, words are "arbitrary" and mean what we (by consensus) want them to mean.
The word "vacuum" simply mean absence of matter, and the reason for this is that it is how the word has been used for the part 200 years or so. This is a question of etymology; not philosophy. As far as I know there is no word that means "absence of EM radiation", but of course there is nothing that prevents you from making one up.

 

[JaredJames]

You should learn the difference between arbitrarily defining something for the sake of making arbitrary claims and actually reasoning about the logic of the concept. A vacuum may be generally viewed as referring to an absence of matter but not energy, but the relevant issue is why. To get into that, you need to reflect on what really constitutes "vacuum" and what its purpose as a descriptive term is in the first place.

My impression (though I'd like to know if others see it differently) is that a vacuum refers not only to the absence of matter but also to the potential for matter and/or EM energy to be present. If there was some possibility for a vacuum to exist in which neither matter nor radiation could be present, would space even exist there?

I suppose you could go on to ask the question that if it was possible to have a vacuum devoid of both matter and radiation, would gravitational force still be present? How would it be possible to have a vacuum devoid of all matter, energy, and force? How would that even be measurable/observable at all?

I gave you the definition from three sources. It does not involve EM radiation.

Now if you want to give me another source that shows a vacuum is connected to radiation levels I will happily consider your above statement.

Until then, we'll stick with the agreed upon definition.

The "relevant issue" as you put it is not why, that question has never been raised. Besides, a vacuum is simply a way of describing a system where there is no / little matter - it doesn't need to mention radiation because that isn't what is being described.

 

[abhishek ghos]

cut short, you can't have vaccum(no presence of anything )cause you never know what are the particles you can't measure.
just as in "Does GOD exists?"

 

[santhony]

So, given the definition, as meaning, the absence of matter but not necessarily the absence of electromagnetic radiation, can eletromagnetism have any affect on the velocity of light?

 

[JaredJames]

So, given the definition, as meaning, the absence of matter but not necessarily the absence of electromagnetic radiation, can eletromagnetism have any affect on the velocity of light?

So let me get this straight, if I'm following this thread correctly your question is actually:

"Is the speed of light constant wrong because we can never measure it in a perfect vacuum?"

An identical question to one we had only a few days ago regarding dark matter.

I say this because your initial question really has no bearing on where this thread has evolved.

Can I confirm that you understand light is EM radiation? And that all EM radiation travels at that constant speed?

 

[brainstorm]

The answer to "why" is that this is how people communicate, words are "arbitrary" and mean what we (by consensus) want them to mean.
The word "vacuum" simply mean absence of matter, and the reason for this is that it is how the word has been used for the part 200 years or so. This is a question of etymology; not philosophy. As far as I know there is no word that means "absence of EM radiation", but of course there is nothing that prevents you from making one up.

I gave you the definition from three sources. It does not involve EM radiation.

This is essentially the issue of whether scientific terminology and concepts are (or should be) based on traditional authority or rational authority. If there is no basis except tradition for scientific terms and concepts, why should anyone ever subject them to critical rigor in any form. Shouldn't theories then simply be accepted by definition and contradictions and other problems within them ignored?

If vacuum is traditionally defined as the absence of matter, fine, but why would that be the end of the story? Vacuum is not an arbitrary concept. It has specific analytical uses that make it relevant. If you aren't open to understanding and discussing these, what kind of science are you really engaged in?

Now if you want to give me another source that shows a vacuum is connected to radiation levels I will happily consider your above statement.

This isn't a contest of proving one definition is more established than another. It is about dissecting the concept of "vacuum" to understand it better, why or why not radiation and/or force should be considered in terms of vacuum-analysis, and why.

Until then, we'll stick with the agreed upon definition.

How about "we" stick with discussing the topic and avoid making statements that imply collective domination, like "we vs. others." This is an aggressive discussion style.

The "relevant issue" as you put it is not why, that question has never been raised. Besides, a vacuum is simply a way of describing a system where there is no / little matter - it doesn't need to mention radiation because that isn't what is being described.

Now you're saying that it is irrelevant for someone to ask a scientific question about vacuum-operationalization because of definitional traditions? Why shouldn't Galileo have just submitted to the traditional definition of the heavens as being all massive bodies surrounding the Earth and therefore continued to analyze the heavens as centered around the Earth? His science was to explore reasons that it might make analytical sense to define planetary-motion in another way. Even if he would have been wrong, there was no reason to chastize him for exploring the issue.

 

[brainstorm]

So, given the definition, as meaning, the absence of matter but not necessarily the absence of electromagnetic radiation, can eletromagnetism have any affect on the velocity of light?

I'm not claiming to be able to answer this but I want to add something to your question because I think it is interesting. If electromagnetism wouldn't have any effect on the speed of light, how could light slow down in a medium whose volume primarily consists of atomic/molecular electrons?

 

[JaredJames]

Brainstorm, a vacuum is an area devoid of matter. That's it. That's why it's the end of the story.

It's not meant to describe the radiation content. It deals purely with matter.

The scientific label for an area that lacks matter is a vacuum.

If you want to create a word to deal with the lack of radiation then go ahead.

Please take your philosophical questions to the philosophy section. Stick to the scientifically accepted definitions here.

 

[JaredJames]

I'm not claiming to be able to answer this but I want to add something to your question because I think it is interesting. If electromagnetism wouldn't have any effect on the speed of light, how could light slow down in a medium whose volume primarily consists of atomic/molecular electrons?

Because electrons have mass. They are, matter.

 

[brainstorm]

Brainstorm, a vacuum is an area devoid of matter. That's it. That's why it's the end of the story.

It's not meant to describe the radiation content. It deals purely with matter.

The scientific label for an area that lacks matter is a vacuum.

If you want to create a word to deal with the lack of radiation then go ahead.

Please take your philosophical questions to the philosophy section. Stick to the scientifically accepted definitions here.

Wouldn't insisting on definitions and the reasons for accepting them also belong in the philosophy section then? If someone in the thread brings up the issue of whether a vacuum can or should also be free of radiation and/or force, why shouldn't the scientific issues related to that be discussed? You avert this discussion by making it purely about definitions. This is obstructing scientific discussion, isn't it?

 

[brainstorm]

Because electrons have mass. They are, matter.

So what's your point? You make statements without grounds or reasons. Do you think discussion is about establishing definitions and other labels? If electrons have mass and are matter, how does that relate to the question of whether they affect the speed of light? You need to address that specifically. If you are trying to say that their electromagnetism is irrelevant to the speed of light, then say that and explain why. Stop just making insistent statements that assert your point of view without reasonable grounds.

 

[JaredJames]

So what's your point? You make statements without grounds or reasons. Do you think discussion is about establishing definitions and other labels? If electrons have mass and are matter, how does that relate to the question of whether they affect the speed of light? You need to address that specifically. If you are trying to say that their electromagnetism is irrelevant to the speed of light, then say that and explain why. Stop just making insistent statements that assert your point of view without reasonable grounds.

You said: "If electromagnetism wouldn't have any effect on the speed of light, how could light slow down in a medium whose volume primarily consists of atomic/molecular electrons?"

Light slowing through a medium made of electrons has nothing to do with their EM properties, only the fact they are matter.

My post responded to your question.

 

[JaredJames]

Wouldn't insisting on definitions and the reasons for accepting them also belong in the philosophy section then?

Yes it should, but I'm not debating whether they should be accepted. Only that they are what they are and for the purpose of this discussion that's what matters.

If someone in the thread brings up the issue of whether a vacuum can or should also be free of radiation and/or force, why shouldn't the scientific issues related to that be discussed?

Because once again, a vacuum does not deal with EM radiation.

You avert this discussion by making it purely about definitions. This is obstructing scientific discussion, isn't it?

Scientific definitions.

Do you accept that the word vacuum only deals with the lack of matter? Do you accept it is a way of describing a system that lacks / or has little matter?

EM radiation is irrelevant when it comes to vacuums. The 'why' of that is simply because it is the accepted scientific definition.

 

[santhony]

Can I confirm that you understand light is EM radiation? And that all EM radiation travels at that constant speed?

As I said before, physics is not my expertise. But, I do find it fascinating. I am aware of the fact, that, all electromagnetic radiation is light vibrating at various frequencies; so, it would make sense to say all electromagnetic radiation shares a constant speed. So, I guess my question, in that regard, is nonsensical.

 

[Drakkith]

I'm not claiming to be able to answer this but I want to add something to your question because I think it is interesting. If electromagnetism wouldn't have any effect on the speed of light, how could light slow down in a medium whose volume primarily consists of atomic/molecular electrons?

I've read that this is because the photons are continually absorbed and re-emitted, which takes a small amount of time, thus making the average velocity throughout the material slower than c. The light still travels at full speed between the time it is emitted and the time it is reabsorbed.

 

[mheslep]

I've read that this is because the photons are continually absorbed and re-emitted, which takes a small amount of time, thus making the average velocity throughout the material slower than c. The light still travels at full speed between the time it is emitted and the time it is reabsorbed.

Common mistake.

This explanation is incorrect and inconsistent with empirical observations.

https://www.physicsforums.com/showpost.php?p=899393&postcount=4

 

[Drakkith]

Mheslep, from the post you linked:

So the lattice does not absorb this photon and it is re-emitted but with a very slight delay.

So isn't this the same thing as I said above, but instead of the individual atoms absorbing the photons it's the lattice? Or am I not understanding something?

 

[mheslep]

Mheslep, from the post you linked:
So isn't this the same thing as I said above, but instead of the individual atoms absorbing the photons it's the lattice? Or am I not understanding something?

I would not attempt to elaborate on the clear and precise FAQ article by ZapperZ, Gokul43201 and inha. You might PM one of the authors if you don't see further response in thread.

 

[thopsy]

A perfect vacuum is a finite area with zero mass (no atoms, or other massive particles, protons, neutrons, electrons, positrons, etc...).

Electromagnetic radiation is composed of photons, which, to my understanding, have zero mass. Therefore, you certainly can have electromagnetic radiation in a vacuum.

Additionally, photons like vacuums the best. That's where they travel at the speed of light!

 

[Drakkith]

I would not attempt to elaborate on the clear and precise FAQ article by ZapperZ, Gokul43201 and inha. You might PM one of the authors if you don't see further response in thread.

Alright, thanks for the link!

A perfect vacuum is a finite area with zero mass (no atoms, or other massive particles, protons, neutrons, electrons, positrons, etc...).

Electromagnetic radiation is composed of photons, which, to my understanding, have zero mass. Therefore, you certainly can have electromagnetic radiation in a vacuum.

Additionally, photons like vacuums the best. That's where they travel at the speed of light!

So do you think photons prefer Hoover or Oreck vacuums better? =)

 

[thopsy]

Let's be clear on something...electromagnetic radiation, i.e. electromagnetic waves, is composed of photons (no mass), not electrons (which have mass).

 

[thopsy]

@Drakkith...neither. Photons like Dyson all the way.

 

[JaredJames]

So do you think photons prefer Hoover or Oreck vacuums better? =)

Dyson, any day of the week!

 

[JaredJames]

@Drakkith...neither. Photons like Dyson all the way.

Dyson, any day of the week!

It's unanimous.

 

[Drakkith]

@Drakkith...neither. Photons like Dyson all the way.

Touche...