# Empty space of Atoms

1. Mar 16, 2012

### Allojubrious

I've always heard that atoms are 99.9999996% empty space, now I am wondering is the empty space between the orbiting electrons and the nuclei just empty; a vacuum...?? My question is: What is in the empty space of the atom?(for I doubt it is actually purely empty) What is in the space between the electrons and the nuclei??
So if one could answer these questions it would be of great help.

Thanks,
Allojubrious

2. Mar 16, 2012

Staff Emeritus
It's empty. That's what empty means.

3. Mar 16, 2012

### Allojubrious

So you're saying its truly a vacuum?? There's no energy fluctuations within it or some such, its just a blank vacuum? (And yes I know what "empty" means, no need to be condescending.)

Last edited: Mar 16, 2012
4. Mar 16, 2012

Staff Emeritus
Apparently not.

Energy is not "stuff". It doesn't have a position. It is a property of a configuration of objects, and is not a material.

5. Mar 16, 2012

### Allojubrious

Oh, well is it true to say that there is no real empty space, because quantum field theory suggests that there are quantum fields that pervade the universe, the vacuum is just a place where the fields and their particles are at rest, no?

6. Mar 16, 2012

### A. Neumaier

The electromagnetic field and the gravitational field.

Commonly one calls a region of space empty if there is no matter in it, though an empty region is still filled with non-matter fields. A mathematical vacuum (ground state of a quantum field theory) doesn't exist in Nature.

7. Mar 16, 2012

Staff Emeritus
A. Neumaier has given what is, in my view, a terrible answer.

A field is a mathematical quantity with a defined value for all space and time. You can have an electric field, a magnetic field, even a field that describes the price per kg of bananas. Specifically mentioning "The electromagnetic field and the gravitational field" and not mentioning the banana-price field is profoundly misleading, because it leads you to believe there is something special in there.

8. Mar 16, 2012

### Allojubrious

So the vacuum is actually filled with certain mathematical and quantum fields, vacuum energy, and possibly dark matter and dark energy, no?

9. Mar 16, 2012

### steve watson

Why is it called "space" if it's not empty? What is the point of the meanings of words if they have no relationship to relaity? If there was no space, i.e., no emptiness how could you ever know one thing from another?

10. Mar 16, 2012

### Allojubrious

Alright well thank you for your help all, I now understand that the space in the atoms is actually not purely empty, nor is there a purely empty area.

Thanks,
Al

11. Mar 16, 2012

### steve watson

Al, seems to me that "space" is empty or not, but not "purely" empty. What do you mean when you say "purely empty". Why isn't "empty" descriptive enough? Just curious.
Tks ...

12. Mar 17, 2012

### Allojubrious

I say "purely empty" because "empty" has been used to describe a vacuum and yet the vacuum is not empty, like purely empty. There are some things inside, so I see that writing "purely empty" is showing that something is or might be purely empty and not used lightly as "empty" has been used. But all in all, it's not that important to this discussion.

13. Mar 18, 2012

### A. Neumaier

One can measure the response to electromagnetic field and the gravitational field at every point in space. Thus the fields must be there, with as much justification as one can say that a material object is somewhere, because I can see its color.

But one cannot measure the banana price at every point in space. Thus it is not at par with the electromagnetic field and the gravitational field.

14. Mar 18, 2012

### dtyarbrough

Imagine that the atom is 500 times larger than it is thought to be. It is vibrating within an area almost twice that diameter. Only a minute area within this sphere will always block background light or reflect foreground light. It will appear to be 1/1000 of the diameter of the area it occupies.

15. Mar 18, 2012

### A. Neumaier

It is just for these situations that scattering theory was developped. One doesn't measure a scattering cross section (and from that get a charge radius) by one single experiment, but by making statistics over many. And the charge radius is defined (roughly) as the radius of a classical charge that would give a scattering cross section with the same mean behavior as observed.

Almost everything we measure in a repeatable fashion is such a statistical average.

16. Mar 18, 2012

### kurros

These discussions about whether there is "empty space" in there are a bit silly I think. In the Standard Model all fundamental particles are point-like, so there is no space that is NOT "empty". Of course, that doesn't mean that everything can just move through each other freely, of course there are interactions which limit where you can move. Atoms are pretty solid in the sense that they are full of electrons and you encounter a rather strong resisting force if you try to push more electrons in there. The electrons "fill up" the whole space around the nucleus, and try as you might you will not be able to fit any more in there. The nucleus itself is not really more solid than that, in that you will not be able to crush the thing any smaller. It is still just a bunch of quarks with "empty space" between them though.

17. Mar 18, 2012

### Hypatio

Energy doesn't have a position? How is that possible? Wouldn't it then be meaningless to talk about a photon moving through space?

18. Mar 18, 2012

### Allojubrious

I disagree, from what I've read currently, it looks like there is NO SPACE that is empty. There's always some minute factor or field within it, either at rest or active. This would be where dark matter and dark energy come into play.

19. Mar 19, 2012

### kurros

Dark matter has nothing to do with it, although dark energy might. Anyway, that's beside the point, I was just saying that this is just a semantics game about what one really means by "empty", and that this concept needs adjusting in the quantum world. If by empty you mean "the values of the quantum fields in this given space are zero", then no, no space is empty. If you mean "the expectation values of the quantum fields in this given space are zero" then space is mostly empty, except for the Higgs field, but the space "inside" atoms is certainly nothing like empty.

20. Mar 19, 2012

### Allojubrious

Oh well that answers my question! So the space inside atoms is not empty, excellent.

Thanks,
Al