Why are all planets circular shaped?

When planets and suns form, they are molten. In this molten state with no gravity influencing it, it will take a state of equilibrium. This cause it to take the smallest volume and it becomes round. Have you ever try this? Try flicking some water droplets in the air. You will notice they become round in mid air. Why? Because in this state of free fall, they clump together in the smallest state to become round.

That's because of the nature of gravity. Gravity forces objects inward toward the center of the planet so that every part of the surface is pulled evenly toward the center, resulting in a spherical shape.

Of course, planets are not perfect spheres because mountains and valleys and even skyscrapers are all deviations from the spherical shape. However, as planets get larger, gravity gets stronger, until eventually large objects on the surface are crushed under their own weight. Planets stay basically spherical because any large deviations get crushed.

Although gravity keeps planets close to spherical, there are other forces that cause deviations from the basic spherical shape. For example, the rotation of the earth once every 24 hours, causes an apparent centrifugal force which creates a bulge at the equator. In fact the earth's diameter at the equator is 7,926 miles while the diameter between the poles is only 7,900.

Not all are circular shaped. It depends on how they were formed. A sphere (3-D circle) is the most stable form, so if a planet is mostly molten at some time in its history or is gaseous it is likely to take that shape. The larger the planet the more likely it is to be spherical due to gravitational forces. Pluto is not spherical although it has recently been downgraded to something less than a planet. Basically gravity is what causes planets to be spherical.

All single bodies in space (not a galaxy, made of lots of small bodies) tend to assume spherical shapes in space because it is the shape in which all forces are balanced and energy is at a minimum.

A glob of orange juice released into the air on board the shuttle will form a ball because it will create a balance of forces of the attraction the molecules have for each other (pulls) and the pressure they exert on one another (pushes) where potential energy will reach a minimum, like a ball rolling to the bottom of a hill will stop and stay there. It will take energy to raise up part of the glob.

Objects in space do the same thing if they have enough mass to have a gravity field strong enough to do this. If I raise a great mountain on a fluid ball, it tends to sink into the rest of the mass. If I carve out a crater, matter flowing "down" will tend to fill the low points as all matter is attracted toward a center of gravity.

This is especially true for bodies that are fluid, like the plasma of stars, or the gases of gas giants, or the molten mass of most of Earth. Even the great asteroid (now dwarf planet) Ceres could have begun as a mass of molten material and flowed into a spherical shape. The small asteroids tend to be more irregular and potato-shaped due to the weak influence of their gravity pulling their mass toward a center.

It has to do with the center of gravity of the mass of the planet. Before it was a nice sphere it was just a bunch of mass in the form of "space dust" circling the sun. What happens is when you have two chunks of mass they pull each other toward and if nothing else is tugging on them harder they'll collide somewhere in the middle. If after the collision they stick together you get two smaller rocks forming a bigger rock. So you've got these rocks joining together as they spin around the star and they attract more and more smaller rocks until you get one rock bigger than the rest. The reason why it is round is that the big rock has a center of mass and all the dust and pebbles and stones that are making up this large planet sized rock want to get as close to the center as possible. The center of mass pulls all directions in equally and eventually (after millions of years for rocky planets like earth) you get a nice round planet as everything settles into place.

Not one of the previous answers is correct. Were there to be a solar mass the size of our sun in form of a cube in outer space, would it remain that shape, and how could that shape be changed?

The answer lies in an everyday occurrence. Were you to place an ice cube (cube of ice) on a plate, the cube would soon melt and no longer be a cube. Were the same act done inside a space station the cube of ice would form into a sphere. That which would cause the change is the heat energy within the mass.

Were a mass the size of our sun to be seen in outer space, what could be determined by its shape is: a. it possessed very little heat energy within b. it would have a very slight to no gravitational field.

Asteroids have a random shape. Were a person to intensely heat one of these masses, the mass would form into the shape of a sphere and it would have an increased gravitational field.

The force of gravity IS what forms a mass into a sphere, and you will notice in the physics trilogy: E = mc2, m = E/c2, and c2 = E/m the a field of gravity is of a particular form of energy. It takes energy to change any value within a mass. The last equation is that of a field of gravity, or that of physical time.

There is a short, easy to read writing at http://360.yahoo.com/noddarc entitled "Earth's (very Own) Black Hole" that may be of interest to you. You'll have to scroll down or go to "list view" to find it.

It is the net result of the forces involved. Gravity pulling everything towards the center of mass, the state of the matter acquired, etc. Keep in mind that the earth is more pear shaped. Some of the bodies are more spherical than others.

Note that spherical is the term you wanted. Circular refers to 2 dimensions.

an ordinary answer: Planets look spheres, no longer cubes or cylinders or oddball rocky shapes. some smaller bodies which includes asteroids or Mars moons Phobos and Deimos, do have unusual shapes, yet larger bodies like the 9 planets and maximum of their moons do look as though spheres. it is by technique of the character of gravity. you could think of of gravity as a tension that factors inward in direction of the middle of the planet so as that each and every area of the exterior is pulled gently in direction of the middle, ensuing in a around shape. of direction, planets are no longer suitable spheres because of the fact mountains and valleys or maybe skyscrapers are all deviations from the around shape. besides the undeniable fact that, as planets get larger, gravity gets better, till ultimately super gadgets on the exterior are overwhelmed under their very own weight. it is why we've not got mountains that are 50 miles severe or skyscrapers that are 2,000 thoughts tall. Planets stay extremely around because of the fact any super deviations get overwhelmed. even in spite of the undeniable fact that gravity keeps planets close to to around, there are different forces that reason deviations from the worry-loose around shape. as an occasion, the rotation of the earth as quickly as each and every 24 hours, reasons an obvious centrifugal tension which creates a bulge on the equator. in certainty the earth's diameter on the equator is 7,926 miles on a similar time as the diameter between the poles is in basic terms 7,900.

Well, not all the planets are circular. But the circular shape is do to materials flying out in all directions as a result of explosion upon impact.

Actually they are spheres, a ball. The most volume with the least surface area, formed by gravity. If they spin, as the earth does, they bulge at the equator, due to inertia and angular momentum.