Quote:Original post by Max_Payne
I wasn't talking about the mass but the radius.

Scattering experiments doesn't show the electron to have any radius.

Sorry, here:

The diameter of an electron is less than 1/1000 the diameter of a proton. A proton has a diameter of approximately 1/25,000,000,000,000 inch (0.000000000001 mm).

Modern physics is really confusing. In modern models, electrons don't even have a radius, they are treated as a point mass. They don't have a position, they have a function that gives the probability of the electron having a position. Any pictures of nucleuses being clumps of neutrons and protons, or electrons orbiting nuclei, or whatever, these are just illustrations of simpler models of these things.

It depends on what model you are using. The quauntum model is statistical. Other models do not need to be so vague.

Quote:Original post by MooMansun
Sorry, here:

The diameter of an electron is less than 1/1000 the diameter of a proton. A proton has a diameter of approximately 1/25,000,000,000,000 inch (0.000000000001 mm).

Where'd you get this info? In the standard physics model, fundamental particles (of which a proton isn't one, but an electon is), are point particles.

Again, it depends on the model you use. The quantum model is theoretical and thus pointless to refer to, unless you want to work on a theory. For quick computations with a good resolution, the values work best.


"As a physical concept, the classical electron radius has been outdated by the advent of the quantum mechanical description of the electron; however, the value is still useful as a point of reference."
http://en.wikipedia.org/wiki/Classical_electron_radius

Hm. Interesting, I didn't know this. Thanks for the link.

Quote:Original post by MooMansun
Again, it depends on the model you use. The quantum model is theoretical and thus pointless to refer to, unless you want to work on a theory. For quick computations with a good resolution, the values work best.

"As a physical concept, the classical electron radius has been outdated by the advent of the quantum mechanical description of the electron; however, the value is still useful as a point of reference."

Sure, but the "classical electron radius" is 2.8*10^-15 m, so how do you come to the conclusion that its size is 1/1000 of the proton? Scattering experiments show the proton to have a radius of roughly 1.2*10^-15 m, so it is actually smaller than the classical electron radius. On the other hand, like I said before, scattering experiments doesn't show the electron to have any radius at all. That means an electron wave packet can be localized beyond the resolution of todays experimental limits, and they are believed to be a indefinitely localized (or, according to String theory, have a size on the scale of the Planck-length, 10^-35 m).

http://hypertextbook.com/facts/2000/DannyDonohue.shtml

World Book Encyclopedia. Chicago: World Book.

"The diameter of an electron is less than 1/1000 the diameter of a proton. A proton has a diameter of approximately 1/25,000,000,000,000 inch (0.000000000001 mm)."

< 10 -18 m

There's no such thing as "radius of proton" or "radius of electron". There is some effective "radius" that makes some sense, and for electron radius that makes sense is larger than for proton

effective radius of proton, given by how dense protons are packed in the nucleus.
1.2*10-15
classic radius of electron (or rather radius where electromagnetism goes bad)
2.81*10-15
Electron is "bigger" (tho it's of course apple vs orange comparison). It's not size that matters, it's how you use it.[grin][lol]

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Speaking of QM in the simulation: At such scales, classic simulation will not give results anywhere close to real results. Period. Actually it's good thing for you: you could as well make up strong force as you like to, and it'll be as precise as any other classic simulation. Heck, you can aswell use hard balls that are attracting eachother.

But if you want good results, QM simulation is a must. Unfortunately, QM is very computationally expensive, so probably it is not possible to do.

In everyday world, special relativity is also "just matter of precision", but at higher velocities results with relativity and without are drastically different.

Quote:Original post by Eelco

Quote:Original post by Dmytry

Quote:Original post by Eelco
it just seems wrong two phemonena that appearently have completely different roots, like gravity and electromagnetism are so similar at the surface. it does feel like there should be a reason for that.

meh i know too little about all this.

Yes, it seems strange to me too. But on other hand, inverse squares law (at surface) is natural for fields that sorta conserve something. For example, "field" of bullets shot in random direction by the shotgun (in space), assuming bullets don't disappear and no new bullets is created in the space. Number of bullets per squared meter per second decreases as 1/r^2 .
Another example, apply simple "blur filter" to floating point image many times (to all image except some black and some white pixels used as sources as field). Gradient of resulting field will obey 1/r law in 2D and 1/r^2 in 3D. (with certain filters there could be anisotropy, but even in this case law will hold at least for parallel distance vectors) Seems that it doesn't matter what filter is used as long as filter doesn't change "brightness".

edit: another great example is things like deformations. Like heightfield of soap film - gradient obey 1/r law (on surface(pun intended)). I'm is not very sure about small 3D deformations in materials but it seems to me that there is some inverse squares law too.
Or sound, also inverse squares.

yeah well the inverse square law isnt that surprising an analogy, but what about the very concept of force? GR makes it pretty much redundant for gravity, it would seem odd that the concept would hold up for EM.

also, it would seem to me the weak and stong force arnt really forces in the classical sense of the word, they feel more like 'constraints' to me. somehow the notion of a nonconservative field doesnt fit in with the word force imo.

i remember reading about some model that explained the structure of atoms by viewing elementary particles as interlinked circles. it was kindof brief, but it did make a lot of sense inituatively, and was capable of correctly predicting all nuclei and their stability, or so it claimed.

Yes, and it seems to me that force is already sort of obsolete - at deeper level force is transmitted with "force carrier", that changes the impulse when it interacts with particle. I.e. there is impulses , not forces. Or so it seems. There's another question, do gravity and EM change impulse in same way.

[Edited by - Dmytry on October 9, 2005 2:29:16 AM]