Why are planets all spherical?

Hi All

I recently had a thought that i was unable to answer with any reasonable and justifiable means and thought i should share it with you all- Why are all planets round and spherical?

It is really something that i (we?) take for granted in common day analysis of the universe and the planets, so i thought i would do some digging to try and find an answer. For those of you who know the truth already, feel free to chime in with any more detailed information-

I found a few different sites and just wanted to share this interesting info with those of you, who also take this fact for granted like i did.

The shape of small objects (like people and houses and mountains and small asteroids) are determined by their mechanical properties. You can take a rock and cut it into a particular shape and it will pretty much stay that way.

The larger the object, though, the stronger its gravitational field. Imagine that you want to build a really tall building. You have to make sure it has a really strong foundation, or the foundation will be crushed by the weight of the building and the building will fall. If there was anything really big sticking up on a planet or a star, gravity would pull it down.

If a planet was like a cube, the corners of the cube would be higher than the rest of the planet. Since planets and stars are so big, you cannot build a "foundation" strong enough to hold up those corners! Anything you built it out of would be too weak to hold them up. Gravity would eventually pull them down. Even solid rock will flow like a liquid, although very slowly, if it is pulled by a very strong gravitational force for a very long time. Corners on a cubical planet or star would eventually just squish down.

Since gravity pulls toward the center of the planet or star, everything gets pulled down into a sphere. However, planets and stars are not really perfect spheres. They spin, so they bulge out a little around the equator.

Why are planets spherical?

I do hope that this little snippet has been as enlightening for you all as it has for me? Its funny how each little piece of the puzzle we put together, makes us want to keep digging for the rest of the pieces in the set.

Natura non facit saltus

A sphere is the most economical and efficient form of mass.

Second line.

Originally posted by dooper
A sphere is the most economical and efficient form of mass.

Second line.

Right.

Imagine space is a giant rubber sheet, and planets are bowling balls, and how the planets indent that sheet is was gravity and force is all about. A planet has angular momentum that...I am tired, I'm going to bed.

Ya know, I never really thought about it but before I read the excerpt, I came to a exact conclusion.

You have a square spinning around in space, massive amounts of gravitational pull.

Now think about this, you have a square piece of wood, you stick it on a spindle that rotates it horizontally 360 degrees at a controlled revolution.

Now, you bombard that piece of wood with insane amounts of pressurized air for 72 hours, and that wood continues spinning.

Think about it, it's not going to come out perfect, but chunks of it are going to rip away and the center is going to be whats left, formed as a circle.

That's why, it's easiest for a mass to exist in a spherical forum.

Because, it's natural, and economic as the other poster said.

Yes by their definition, planets are spherical.

A planet is a body large enough for gravity to make shperical and it clears its neighborhood of smaller objects.

All planets actually start off as cubes.
It's all the millions of years of traveling through space at super high speeds that cause the edges to get worn off and erode.

[edit on 10-4-2009 by Alxandro]

[edit on 10-4-2009 by Alxandro]

Planets being large conducting capacitors, the sphere is the best form.
There must be a theorem in the electrical universe discourse.
That is the only way to impart momentum electrically.
Don't ask how its done cause I was never taught such things.
Science is silence in these electrical areas.
But since electrical charge can have great force there must be
something to the theories.

Originally posted by Alxandro
All planets actually start off as cubes.
It's all the millions of years of traveling through space at super high speeds that cause the edges to get worn off and erode.

Suppose that only two planets of the solar system changed their shape from cube to sphere. Which planets would be spherical?

The reason for the sphere is gravity and magnetism and our 3 main dimensions, and the pressure of forces invisible to the human eye from all directions.

When you have your x,y,z dimensions, up/down, left/right, forward/backward, and you have a single point in space such as planet Earth, and you have gravity and magnetism, you get an attraction and repulsion force in all directions at once.


So your answer is, the planets are all spherical for the same reason an air bubble under water is spherical. A single point in a 3D space emanating a force in all directions equally.



[edit on 11-4-2009 by l0st0ne]

Because Mass = Gravity and gravity pulls in every direction in space.

2nd line, ^.^

Originally posted by stander

Suppose that only two planets of the solar system changed their shape from cube to sphere. Which planets would be spherical?

I give up.
Can't wait to hear the punch line?

...insert drum roll here...

Originally posted by Alxandro

Originally posted by stander

Suppose that only two planets of the solar system changed their shape from cube to sphere. Which planets would be spherical?

I give up.
Can't wait to hear the punch line?

...insert drum roll here...

The punch line proved to be a mental terror for a university assistant professor who couldn't figure out why 93% of students answered the question with Earth and Mars. The real and science fictitious existence of the earthlings and the Martians was a weak common denominator to put both planets into one bag with the sphere criterion nowhere in sight -- unless you decide to compute the volume of both planets. In that case you employ this formula:

Volume = 4/3 * pi * radius * radius * radius

The fraction 4/3 tells you to compute the volume of the 4th and the 3rd planet from the sun which is Mars and Earth -- if you feel like computing a volume of two spheres and don't want to take a random choice.

And that's why only Mars and Earth turned from being cubes to spheres.

And that's why Pluto was taken off the list of the planets.


Well, a cube has 6 facets, which agrees with the 6 planets of the solar system that remained cubes.

[edit on 4/12/2009 by stander]

I think the real question is:

Why dont planets look like this?

[atsimg]http://files.abovetopsecret.com/images/member/69cf548a9bc0.jpg[/atsimg]

Originally posted by Tentickles
I think the real question is:

Why dont planets look like this?

[atsimg]http://files.abovetopsecret.com/images/member/69cf548a9bc0.jpg[/atsimg]

Why don't planets look like that?
I think it has something to do with self-esteem.

A Gas Planet would be more spherical an orb than a rocky planet.

the Earth is actually more fatter at the equator than it should be (geometrically)
so Earth would be better described as 'round' or even 'ovoid' rather than spherical
I guess because it has a hot, molten core... whereas Mercury/Venus/Mars/
have long since cooled their insides & their rotation does not fling their equatorial mass away from the center ...as in centrafugal force


when space explorers type planets, those with a 'bulge' like Earth's,
will hold special consideration....


[whew... the 500 character button must have been turned off for the time being.)
Or is this 500 character reply criteria a 'test' or the sign-of-things-to come??


thanks,
___________________________________________________________
__________________________________________________________-_


Ah Ha... i just received the NEW U-2-U... about 'minimum character replies'

2:39 pm, Easter Sunday.... gotta be something significant with the new rule
Arising on Easter Sunday !!

[edit on 12-4-2009 by St Udio]

If gravity was the force created by electromagnetic energy curving into the event horizon of the singularitys contained within every particle. Then a sphere would be the final form of that process. Of course to look out into the universe and see ALL spherical planets and planetoids is strange. It most likely lends to the thought that a time scale of infinity for our universe would not be to far fetched.

Small particles are absorbed by planets... planets are absorbed by stars and then their particles become a part of the larger plasma dynamics of a galaxy with the final form of a double torus, or a spiral galaxy.

whatever all that means lol.

A celestial body that is (a) in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.


A planet's defining physical characteristic is that it is massive enough for the force of its own gravity to dominate over the electromagnetic forces binding its physical structure, leading to a state of hydrostatic equilibrium. This effectively means that all planets are spherical or spheroidal. Up to a certain mass, an object can be irregular in shape, but beyond that point, which varies depending on the chemical makeup of the object, gravity begins to pull an object towards its own centre of mass until the object collapses into a sphere.[95]

en.wikipedia.org...


not to be a prick or anything.. but why go through all the trouble to ask the question on ATS when you could have just typed it into google.. found out.. then maybe shared your findings on ATS in a thread ABOUT hydrostatic equilibrium?

this is the second time in one week i've seen this question asked..

-

Originally posted by prevenge
not to be a prick or anything.. but why go through all the trouble to ask the question on ATS when you could have just typed it into google.. found out.. then maybe shared your findings on ATS in a thread ABOUT hydrostatic equilibrium?

this is the second time in one week i've seen this question asked..

That's because not all questions regarding the spherical shape of the planets are answered by surfing the net. Here is an example: In 2012, God decided to reshape planet Venus into a cube. How much time would be required for Venus to resume her spherical shape?

(Remember that terrestial planets assumed their spherical shape when they were made of hot, molten rock thereby lacking the hard crust.)

Originally posted by Tentickles
I think the real question is:

Why dont planets look like this?

[atsimg]http://files.abovetopsecret.com/images/member/69cf548a9bc0.jpg[/atsimg]

Hey, that planet looks like a swastika with a head.
Are you that's not bacteria? Maybe that's the missing link.

Oh my god I have discovered the meaning of life! All praise be to the Tentickles and her horrible MSPaint picture!