Why are planets round?
463058
Planets aren't directly formed from explosions and whatnot, they are formed from gravitational accumulation of mass in dust clouds. They are approximately round for the same reason anything that is approximately fluid that experiences a central force is round. Central forces have circular potential energy wells.\nConsider a cubic planet. A mass on the face of such a planet would be experiencing less force than a mass near a corner of such a planet (The corner has a greater amount of non-cancelling mass "behind" it. If you know the divergence theorem, this can be seen as well.). Since less force is exerted on points on the faces than points near the vertex, the vertex will slowly collapse if the mass is great enough, easily pushing the points on the faces outwards until an equilibrium is reached. This thought experiment works for any polyhedron, with the sphere being the limiting shape. Once the shape is approximately spherical, it is a well known proof that the force experienced by a particle outside the sphere will be the same as the force if the sphere was a point mass at the center of the central force, giving us back the circular potential energy map.
510338
Every body like to kick around, whether on the ground or out of it.You, must have observed it when the match is over.This is true in general life also.\n\nyou see there is another reason also ,earth is round,pizza is round, coin is round. Can I say boobs are round, hips are round------your EYES ARE ROUND ---when you say oooh, your mouth is round ----JUST LIKE FOOTBALL IS.
309717
All, well most physical bodies with substantial mass would be pulled into an orb shape by its own gravity, since all planets started out molten, they were easily molded. And why would gravity pull something into an orb shape? This is because everything is attracted to the body's center and the solid with the biggest volume to surface area ratio is the sphere.
457528
It is not just round or oval. It is elliptical. One side is close to the sun and one side is closer to the Oort Cloud, or Kuiper Belt, or maybe the heliosphere, the end of the sun's influence to the galaxy.
524282
There are two possible reasons:\n1. A non-round object has higher surface area than a round object for same volume. This in turn could lead to higher reaction rates in portions that are not round (projections etc), finally leading to the element appearing round.\n2. The surface tension of water and buoyancy keep the element on the surface at the cost of local depression in the surface of water. Surface tension tends to make the depression round, which could make the element appear round.
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.
184588
we know the shape of the solar system because we know from tracking the movement of planets that they orbit the sun, as they orbit the sun they must be going round it, so that is a slightly stretched oval shape. We can estimate where planets are (i.e. how far away they are) by using stars that we know are different distances away and measuring or by using the Hubble Telescope that can see all the way to Pluto and further and measure the distance.
47522
In a nutshell, planets are round because they are sufficiently massive to attract all of the material towards the centre.  When a planet forms, it is made of molten rock, that is very much like a liquid.  This liquid rock will try to take the path of least resistence (the shortest path) to the centre.  The only shape that would allow liquid on every spot of the surface the same ammount of effort is a sphere. Today, rocky planets still have molten cores and this shaping process continues.
69949
The earth is round because matter attracts other matter, and when they get close they compact together to form spherical objects.\n\nPeople created computers because they kept asking why.\n\nEinstein created an atom bomb because he kept asking why.\n\npeople believe in god because they couldn't figure out why any other way.\n\nThere is music becuase people created it.\n\nPeople have brain because our genetic makeup conducts brain building and reconstruction for our entire lives.\n\nHope that answered your questions
341419
Yes, Planets are generally spheres, not cubes or cylinders or odd shapes. Some small galactic bodies such as asteroids comets do have odd shapes, but planets, suns and stars and even moons look like spheres. That's because, when they were formed millions of years ago, they were essentially molten liquid.  Gravity and meniscus forces (surface tension) cause the object to take on a rounded shape--and it cools in that position.  In addition, the nature of gravity will pull uniformily toward the center--as the distance from the center increases, so does the gravitational force. You can think of gravity as a force that points inward toward the center of all things that have mass-- so that every part of the surface (especially liquids)is pulled evenly toward the center, resulting in a spherical shape.\n\nPlanets are not perfect spheres because there are other forces acting on the planets too which are trying to stretch them.  Because they were once hot moltent liquid, they buldge in the middle.  Earth and the moon reflect this phenomina.   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. \n\nNote that planets and moons had to be a liquid or they would not have been able to escape the gravitational force of the nearest larger body.  Remember that liquid will seek the path of least resistance as it moves.  In otherwords, an impact on the earth would cause a splash of moltent material that could escape the earth's atmosphere at the exact angle (path of least resistance) to be able to exit the planet's atmosphere without burning up.  Once it exits into space, the gravitational pull of the larger body will pull it into orbit. It will stay in orbit until it is acted upon by a larger force.   Fortunately, we haven't seen any larger forces since the earth was created and therefore, the conditions will remain for millions of years into the future.
993320
Planets are not "round" but in fact "spherical".  Planets are spherical because gravity acts upon each part of the planet, pulling it closer to the center.  A sphere is the most efficient shape to contain the greatest volume with the smallest dimensions.  In the case of a sphere, the radius is a smaller distance from the center of the planet than any other shape could manage, thus, matter naturally forms this shape in the absence of other factors.\n\nIt is important to note that the planets were not always as cool and ridged as they are now.  When the planets were born, they were made of molten elements, and did not solidify until their shape had already taken.  In some other cases, where planets were formed through the collision of multiple bodies, the heat generated by the impact liquified sufficient amounts of the bodies for a spherical shape to form.
455949
everything in this universe moves. stars are parts of galaxies. for example our sun is a part of the milky way galaxy. we are in the sagittarius arm of our galaxy which rotates about its centre and as we are in one of the outer arms as the galaxy seems to rotate the sun along with its nine planets revolves around the centre of the galaxy. this is exactly what happens in other stars and star systems. secondly  all stars are round not to mention, every heavenly body is round because gravity makes them round. and the shape we concieve is just because of the phenomenon of scattering of light as the light from the stars passes through various layers of the atmospheres of different densities
266634
yeap, the gravity force and centrifugal force on liquid or molten object (early planets) and gasous objects.\n\nNotice many asteroids are not spherical. They were chunks formed from a solid state already\n\nP.S. I'm afraid I gave a wrong account why many asteriods are oddly shaped. Sorry! Here's the explanation:\n\n"Derek Sears, professor of cosmochemistry at the University of Arkansas and editor of the journal Meteoritics and Planetary Science, provides the following explanation: \n\nPlanets are round because their gravitational field acts as though it originates from the center of the body and pulls everything toward it. With its large body and internal heating from radioactive elements, a planet behaves like a fluid, and over long periods of time succumbs to the gravitational pull from its center of gravity. The only way to get all the mass as close to planet's center of gravity as possible is to form a sphere. The technical name for this process is "isostatic adjustment." \n\nWith much smaller bodies, such as the 20-kilometer asteroids we have seen in recent spacecraft images, the gravitational pull is too weak to overcome the asteroid's mechanical strength. As a result, these bodies do not form spheres. Rather they maintain irregular, fragmentary shapes."
462097
"The equatorial diameter is c.7,926 mi (12,760 km) and the polar diameter 7,900 mi (12,720 km)"\nThe Earth is the fifth largest planet of the solar system. The reason why earth is in a spherical shape, is because of the gravitational pull. The number that appeared most often in my sources was 12,756 km. There are actually two diameters of Earths: equatorial and polar. One of my sources stated that the equatorial diameter is 40 kilometers wider than the polar diameter. The Earth is not a perfect sphere because of a bulge in the equator. Most of the current knowledge of the Earth has been collected in three methods, through satellites, telescopes and outer space exploration.
80
Largely because of the massive amounts of gravitational force involved.  A sphere is the only sustainable shape when talking about forces of that magnitude.  Stars are incredibly dense towards their core, and over billions of years the matter will coalesce in a sphere like shape.
308046
Gravity. A sphere is the shape which allows every part of the planet to be as close as possible to the centre. Planets which spin are flattened slightly, so that they are not exact spheres, the faster the spin the more they are flattened. Earth is slightly flattened at the poles. If a planet was not a sphere, the parts which stuck out further than average would effectively be "mountans" and any loose parts would roll down under gravity, thus the planet becomes more spherical
1069004
For the most part, the atmosphere moves along with the surface of the earth. On the other hand, winds going in any direction tend to grind down mountain peaks.\n\nHowever, if the Earth were not fairly close to round, then the molten lava inside the earth would rupture the crust and deform the earth into a round shape. The main reason the Earth is round is gravity, not wind.