# Why most particles are spherical?

## Main Question or Discussion Point

why most particles are spherical??

Hi

I was just wondering why most of the objects (such as planets, drop of water, atomic and subatomic particles) are spherical in shape..is there a primary shape that particles tend to take up??

thanks

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Who said subatomic particles are spheres?

Pictures in high school text books :D

For water drop, it's because of the surface tension. At the spherical shape, the drop has smallest surface area so its tension energy is at the lowest of all.
For atronomical objects, the cause is nearly the same: At spherical shapes, they all have smallest gravitational potential. But for those too small (severall hundred km in diameter), the gravitational force is not strong enough to win the hardness of the material. So they often appear in irregular shapes.

hi

i knew i was going to be in trouble over that statement(sub atomic and atomic particles are spherical)..i am sorry for that...
well still my question remains is there a basic shape that most particle or object tends to achieve...???

Andy Resnick
Well, liquid drops, when gravitational effects are not important, will tend to form spheres due to surface tension- least surface area. Larger planetary and stellar bodies form spheres due to gravitation.

Astronuc
Staff Emeritus
A sphere would equalize energy/stress in a substance. In a liquid the intermolecular forces produce tension, and this is minimized in a circular (2D) or spherical (3D) form.

Large masses under gravity tend to form spherical shape, but rotation will cause the mass to assume a shape known as an oblate spheroid.

I think it has mostly to do with minimization of potential energy in an isotropic universe.

The potential energy can be due to force fields like gravitational or electromagnetic or surface forces like surface tension etc.

hi

well thank you all for ur response...
well i have one more question....
i would really like to know what is the shape of subatomic/atomic particles??? and what is the reason for "that" particular shape??

malawi_glenn
Homework Helper
hi

well thank you all for ur response...
well i have one more question....
i would really like to know what is the shape of subatomic/atomic particles??? and what is the reason for "that" particular shape??
elementary particles have no shape, they are point-like as we know today.

atoms and atomic nuclei have spatial probability distrubution functions (called wavefunctions), they dont have a definite shape by themselves, but their spatial distribution functions may have certain symmetries.

elementary particles have no shape, they are point-like as we know today.
That is not entirelly true. I know, that at least the electron has been "assigned" a radius (somehing about $$10^{-15}$$ m) How this is messured/calculated/whatever or if it even make sence I don't know.

malawi_glenn
Homework Helper
That is not entirelly true. I know, that at least the electron has been "assigned" a radius (somehing about $$10^{-15}$$ m) How this is messured/calculated/whatever or if it even make sence I don't know.

Source please, you are talking to a guy who are majoring in subatomic physics ;-)

This is the only radius I am aware of, and it is not a measure of an electrons 'real' radius:

Here are some lecture notes on scattering, see slide #3
http://www4.tsl.uu.se/~tord/KP/Material/KP08_material/K2.pdf [Broken]

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neu
A large amount of progress was made in the early days of nuclear physics using a liquid drop model of the nucleus, albeit for heavy (many nucleon) nuclei.

I believe John Wheeler who died this week, along with Bohr were those who first proposed the model.

Subatomic particles (like electrons and photons) don't have any shape analogs in 3D world.

Lied to have you been.

Source please, you are talking to a guy who are majoring in subatomic physics ;-)
As a major in nanophysics, Elementary particles have never been my strong subject. Just stumbled upon it some time ago and though it made no sence at all in a QM perspective I had not the leisure to pursue the matter furhter

But yes it would be the classical -and apparently obsolute - radius I was thinkin about - Crud, so much for having a Human Resource department doing physics :grumpy:. (Ask if you would like the story)