why are planets has around shaped?
114224
Only bodies with a large gravitational mass are round. There is enough gravity to pack it more tightly and this combined with roation of the object forms a round shape. Smaller objects like asteroids, comets and small moons often have irregular shape because there was not enough gravitational mass to compress the object into a round shape
862988
Earth and the other planets were formed from a giant cloud of gas and dust revolving around the primitive sun. As in any other moving fluid, local whirlpools kept appearing and disappearing all the time. \nAs the cloud started to cool, local perturbations caused density variations : some whirlpools got lumpier than others, just as in a bowl of porridge when it cools off. They thus grew more stable and accumulated more matter because of their increasing gravity. On further cooling, these separated out as planets, molten globes of matter still spinning furiously.\nEven when the planets solidified at last, they retained a part of their original spin. That's why the Earth and the other planets are still spinning around their axes. That's what, thankfully for us, creates days and nights.
231608
If the planets started out in a liquid shape, they would naturally want to try to assume a spherical shape due to their own gravitational forces.  A sphere is the most compact shape, with every point on its surface equidistant from the center, so as the mass settles, it slowly becomes spherical.
120267
Or to give the same answer another way, a cubic planet would be exactly the same as a round planet with 6 humungous mountains on it. Those mountains would form the corners of our cube. And they would be huge mountains, many thousands of times taller than the Himalyas.\n\nEvery time the planet experienced even a minor earthquake bits of those mountains would fall of towards the non-mountain areas. Even if the planet has no atmosphere to assist erosion within a few billion years at most the mountains would have eroded away to nothing and the planet would be round again.\n\nSo even if it were possible for a square planet to form in the first place it couldn’t stay in that shape for very long.
337086
The planets are actually trying to move in a straight line at a high speed due to the intertia from some force long ago.  When two objects are moving by each other, their gravity interacts and pulls them toward each other, bending the path that would otherwise be a straight line.  If they are too massive and too close, the gravity pulls them so much that they collide.  If things are balanced just right, the path is bent into a complete ellipse.  It's an ellipse instead of a circle because the sun is actually also being pulled a tiny bit toward the earth, as well.\n\nYou could consider gravity to be sort of a "perpendicular inertia", and the planets would revolve around the sun FOREVER if there were no other forces involved.
991215
Because the sun has a gravitational pull on all objects that rotate around it. The earth, like all the other planets revolving around the sun, is pulled toward it to a certain extent, which keeps the earth from floating away into outer space.
572633
Aren't the rings about planets just the debris that is spinning around them? If so, then not every planet has a ring because they don't all have space junk that is part of their gravitational field.
884879
Because the earth is round, and if you made your flat map a oval(circle), the oceans would connect and become one!
1069514
By Newton's law of graitation any mass is attracted by another mass. Since the planets are matter like our Earth, the pull of gravity in all directrion make the planet spherical.\n\nThe spin of the planets about their axes actually make them close to  ellipsoid of revolution and not spherical. Our earth is also  close to ellipsoid of revolution.
285187
The are round, in short, because it takes the least enegry to do it.\n\nGravity pulls the matter that will make up the planets/sun/... together.  All the forces are pointed towards to the objects center of mass, everything is being pulled inward toward the center.  With everything trying to get as close as possible to the same center of mass, the object develops a round/sphereical shape.  This shape minimizes the amount of potential energy the matter has above the center of mass.\n\nThe reason why some objects (like the Earth for example) as not totally sphereical is because they are roating around an axis.  Since the Earth is rotating on its axis (causing our days and nights), there is a bulge around the equator as the matter located there is rotating faster [tangential speed] than the matter located at the poles.  This faster tangential speed requires more centripetal force [not to be confused with the fictional "centrifugal" force] or order to keep it rotating.  In order to lessen the required force, the matter bulges out a little bid, increasing its radius away from the axis.\nCentripetal force = m(v^2/r),\nyou can see that a larger radius (r) away from the center means a smaller centripetal force is needed.
520855
We think that the planets all formed pretty much at the same time. However the sun probably formed first. The leftover gas and dust remained in a disk around the sun. In this disk, stuff began to clump and form "planetesimals" (pronounced pla-ne-TE-si-mals). These are small rocky bodies, something like asteroids. They crashed into each other and eventually formed the inner planets. At the same time, planetesimals formed the cores of the outer planets Jupiter and Saturn. Because of their strong gravity, they swept up a lot of gas. Uranus and Neptune did this too, but there was less gas around because Jupiter and Saturn got it first. The asteroid belt may be left-over planetesimals that never formed a planet because Jupiter's strong gravity nearby kept it from forming.
859287
I'm certainly no expert, but from my high school physics days I recall something about Bode's law.  You might be able to Google or Wikipedia it.  It was an explanation, in Newtonian physics terms, of why the planets are where they are.
75988
A planet is a mass that orbits a central star, is massive enough to 'press' itself into a spherical shape but is not massive enough for nuclear fusion to take place.  In simpler terms, a planet is a large, usually rocky, rock that rotates around a star, like the sun.  Sometimes planets can be giant balls of gas (like Jupiter), but they still rotate none the less.
25445
The earth is APPROXIMATELY round due to gravitational forces.
262021
As the mass increases so does the gravity. A spherical object is shaped this way because of its gravity. The larger the sphere gets the smaller the curvature of its surface becomes. It is related but curvature is more of a side effect of a large rotating object. Gravity is dependant upon the mass of the object not the curvature of it.
1103870
Planets do not twinkle the way stars do. In fact, this is a good way of figuring out if a particular object you see in the sky is a planet or a star. The reason is that stars are so far away that they are essentially points of light on the sky, while planets actually have finite size. The size of a planet on the sky in a sense "averages out" the turbulent effects of the atmosphere, presenting a relatively stable image to the eye.
9937
It's because the world in question is ruled by unicorns and merry elves. In "that" world it's only natural that everything is either square or circle. Here of course we have irregular shapes and other geometrical figures like triangles, trapezoids and such. Must sound very strange to you I believe.\n\nUs earthlings, we have strange ways.