why all planets are almost round ?

Answer 1

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.

Answer 2

Maybe I can help explain why the planets are round. It basically has to do with gravity. Gravity is pulling all parts of the Earth toward the center as close as they can get, and the best way for this to happen is for the Earth to be a sphere because all points on the surface of a sphere are the same distance from the center. In other words, on the surface of a sphere there are no points that are winning over other points on the Earth's surface in getting close to the center. If the Earth were a cube, then the corners would be sticking far out compared to the centers of the sides and the Earth's gravity would pull on the corners and flatten them out so that the corners were no farther away from the center than the sides.

Even mountains that stick up a few miles higher than the surrounding surface of the Earth are constantly feeling the pull of Earth's gravity, and this keeps them from getting too high. Parts of the Himalayas are still growing because of tremendous forces acting to push them up, but other parts of the Himalayas are collapsing under their own weight because the Earth's gravity is pulling them down. This may be hard to imagine when mountains are made of solid rock, but solid rock is not very strong compared to the force of gravity when you are talking about very heavy things like a whole mountain range.

OK, now here is something to think about. In fact, the Earth is not a sphere (although it is close). This is because the Earth rotates around an axis that goes through the north and south poles. Think of a merry-go-round and the force you feel when you are near the outer edge of the merry-go-round. You tend to get thrown off the merry-go-round. In the same way, the part of the Earth that is at the equater and that is farthest from its center axis feels a greater outward pull than parts that are closer to the poles. This force counteracts gravity, and since this counteracting force (centrifugal force) is greater at the equator than at the poles, the Earth is not a perfect sphere. Can you figure out whether the centrifugal force would make the Earth more like a bagel or more like a hotdog?..

Answer 3

a sphere is the most natural body. A drop of water, if not ditracted by gravity forms a small ball.
A sphere is natural because it has the lowest energy level meaning that all points of it's surface have the same distance to the center. THis forms a kind of equilibrium.
When you take a mountain on earth, this would be a small but still exemption of the spherical shape. take a ball and let it roll downhill. If you do this over and over again from every montain on earth, eventually your balls (not YOUR balls;-) will have filled up every valley and TAMTAM-TAM earth is round. This is what happened when planets formed (being it either the idea of liquid magma leveling or objects hitting it and rolling "downhill")
In fact, the planets are not round but almost. Most planets, including our earth are a little flat on the poles. So going around the world North-South is s shorter walk that East-West on the Equator.
The flatness comes from the centrifugal force due to the earth's rotation.
To put it short: Its their own gravitational force which forces everything towards their centers.

Answer 4

The planets' central gravity pulls from all directions, making the planets round

Answer 5

All planets are moving in circular motion .thereis an experiment for proving this quitions answer . take a substance made of flour.
hang it on a stick then move it in circular motion in speed. then it gets round shape.therefore because of planets circular motion planets are almost round.

Answer 6

The answer to this is the gravitational pull each planetary body has. The highly gravitational centre holds them together and it was this force that is responsible for the almost spherical shape of the planetary bodies as they started cooling down after the BIG BANG.

Answer 7

Gravity like all other forces tries to minimize the total energy of the constituents it acts upon. This is possible in a sphere.

Answer 8

The ball shape has the smallest surface area for any specified volume.All planets started as fluids, and that's what fluids do if left alone.Its caused by surface tension. Matter attracts matter,if you think it matters.

Answer 9

yo foooooooooooooooooooooooooooooooool who told you that planets are round

Answer 10

It is because of their centripetal acceleration around their center for millions of years that has given them this shape. They first got this shape when they were young i.e. in molten form.