Do Atoms Exist in a Perfect Vacuum?

[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...

 

[thopsy]

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.

 

[Drakkith]

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?

 

[thopsy]

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

 

[capanni]

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.

 

[santhony]

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?

 

[JaredJames]

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?

 

[santhony]

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.

 

[JaredJames]

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?

 

[santhony]

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?

 

[JaredJames]

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.

 

[santhony]

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

 

[JaredJames]

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

 

[santhony]

So, between the subatomic particles exists empty space?

 

[JaredJames]

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.

 

[Drakkith]

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.

 

[santhony]

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.

 

[JaredJames]

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.

 

[santhony]

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.

 

[JaredJames]

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.

 

[Matterwave]

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.