Why is our planet round. Why are planets and stars round? Description, photo and video
Can a star as flat as a pancake exist? Maybe if it spins really fast!
The sun and almost all the stars are very close to a ball in shape. Direct observations with small telescopes show that the nine major planets and some of the largest minor planets are also nearly spherical. But why does it happen this way, because during the growth of bodies on the surface of the Earth, for example, crystals, although spherical objects are formed, but very rarely?
Obviously, the growth of large bodies in the Universe is determined by processes different from those that create crystals or other forms of existence of matter on the earth's surface. These and other similar considerations lead us to an understanding of the dominant importance of the force of universal gravitation in astronomy.
Jupiter. If you look closely, you can clearly see that the planet is very strongly flattened from the poles. No wonder, given that the gas giant spins around its axis like a ball
Stars and large planets condensed from interstellar gases and dust under the influence of the gravitational attraction of individual particles to each other.
Since the gravitational force is directed towards the center of the attracting body, all the clumps that occur during compression must be spherical, unless the condensing matter is rotating. In the latter case, the contracting body becomes more or less flattened at the poles.
Since the speed of rotation of the Sun at the equator is very small, its oblateness is too small to be measured. The shape of the Earth is also only slightly different from a sphere, but the disk of Jupiter (this planet is a record holder not only in size, but also in speed - it takes only 10 hours to complete a revolution), when viewed through a telescope, is already noticeably flattened at the poles.
In our sky many round objects. The sun is round. At night, we see a silver ball of the Moon in the sky. We also know about other planets and stars that they have a spherical shape. The sight of numerous balls around us astonishes us, and we involuntarily ask: “Why shouldn't the stars really be small dots in the sky? Or why not be at least one non-circular planet Te? Well, let one, only one, be cubic or pyramidal. Why is it impossible? Here's why. There is a force that in the entire universe turns worlds into smooth balls. This force is gravity, that is, the force of gravity, or, more precisely, the force of gravity.
The force of gravity is the force that attracts any piece of matter to another. This is the force that makes a baseball hit the earth and keeps the planets in their orbits. The greater the mass of an object, the greater its gravitational force, that is, gravity. However, if we compare the force of gravity with electromagnetic forces, then gravity is much weaker. Therefore, we do not notice the forces of gravity between people in a crowd or between a hand and a pencil. A pencil and a person do not have too large masses.
But drop the pencil and see gravity in action. The pencil will not fly up and fly to the side. It will fall straight down towards the ground. The gravitational force of the earth acts on the pencil. Compared to a pencil, the earth is a huge material body, the mass of which is incredibly large in relation to the mass of the pencil. To feel the force of gravity on yourself, just jump. And you will feel with what inexorable force mother earth attracts you.
As the planets grow, gravity turns them into a ball, they become round.
Gravity tends to hold things together, for example, the nine planets of the solar system, which were formed from the collision of small particles of world dust about 4.6 billion years ago. As planets grew, and the force of attraction increased between their parts. They attracted more matter to themselves from space, and their mass grew. A good example of this process is meteorites falling to the Earth.
As the planet grows, gravity tends to turn it into a ball. . The more the planet grows, the stronger its gravity. More and more new parts of matter are added to the planet and spread over its surface. As a result of this process, a round body is formed. Although gravity forms spherical planets, there are still protrusions on their surface. From space, the Earth looks like an almost perfect blue-and-white sphere. But when approaching it, high mountains protruding above the surface of the earth become noticeable. From an even closer distance, buildings and people become visible.
Everything is quite simple: every body in the universe is trying to reduce its potential energy.
Before solidifying and outwardly taking the form of stone, all the planets were assembled from billions of particles under the influence of gravity forces in the cooled dust cloud left after the formation of a star. The collision of these particles with each other, as well as the pressure exerted by the outer layers on the inner ones, led to the formation of a drop of hot stone, rotating around its axis by inertia.
Now about the form. A sphere is a geometric figure that, with the largest volume, has the smallest surface area. The gravitational attraction forces each atom of the planet to be as close to the center as possible, and for each atom the most advantageous position (with minimum potential energy) will be the position in the center. The round shape is ensured by the fact that it can fit the largest number of atoms (due to the largest volume), with the lowest energy, or energy spread (due to the smallest area), this state is the most stable.
And about rotation. Since the future planet in the process of solidification is in motion around its axis, a centrifugal force acts, which causes it to stretch in the equatorial plane. Therefore, it is more correct to speak not of a spherical shape, but of an ellipsoid
No. Everything tends to the shape of a ball, but because of the centrifugal force, the planets stretch a little. This takes some finite time, then the process stops, as the system comes into equilibrium due to the continuously acting gravity.
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You forgot to figure out what turns on this gravity, which begins to act evenly on the interstellar cloud and attract everything to an unknown, arbitrarily taken point in space. I note that no, somewhat massive body has gravity. And even more scattered interstellar dust. So where does it come from?
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Gravity involves movement in space filled with some substance. Imagine if you lower an object into the water and give it a good impulse, then when moving this object will bend the water column, transferring part of its energy (momentum) to it. And space, warping, attracts a loyal environment according to a given trajectory. And so it will continue as long as there is movement. And if we take into account the fact that the Universe is extremely young and is not going to stop, then gravity, having a potential for trillions of trillions to a hundredth degree of years, acts as a fundamental constant.
In other words, gravity is a property, not an object or an independent phenomenon. This is the property of objects to bend space, and the greater the mass and speed (including rotation along its axis), the greater the force of attraction.
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Chown Marcus universe tweets
46. Why are the planets round?
46. Why are the planets round?
Gravity is the universal force of attraction between all masses, so that each fragment of a large body tries to attract every other fragment to itself.
If the material can flow, the body forms a sphere. This shape ensures that each constituent piece is as close as possible to any other.
Giant planets like Jupiter and Saturn are formed from gas (and liquid deep inside, it's where the gas is compressed) that flows. That's why they are round.
In fact, Jupiter and Saturn have convex waists. Because they spin fast, the gas at their equators tends to be pushed outward.
Rocky and icy bodies have a different shape. Gravity can't compress the inside enough to make it flow. Therefore, they have an irregular shape, similar to potatoes.
But the more massive the body, the greater the force of gravity that unites and compresses its substance.
At a certain size of a body, the force of gravity is sufficient to make its core fluid. For stony bodies, the threshold size is ~400 km; for ice ~600 km.
Accordingly, all rocky bodies in the Solar System are larger than ~400 km in diameter, and all icy bodies are larger than ~600 km.
Thus, it is a struggle between gravity, which compresses matter, and electromagnetic (EM) force, which makes matter rigid and opposes gravity.
The EM force, due to which the electrons of neighboring atoms repel each other, is more than 1000 trillion trillion trillion times greater than gravity ...
So, it is necessary that a huge number of atoms unite together, that is, that the astronomical body be large for the victory of gravity.
Of course, if there is enough mass, then gravity is an overwhelming force and nothing in the universe can challenge it. Result: black hole. But that is another story!
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Why are planets and stars round? and got the best answer
Answer from V and x r y[guru]
Hello!
The surface of equal gravitational force around the center of the masses united together will be a sphere in weightlessness, therefore all large celestial bodies - planets, stars (with the exception of small planetoids, meteors and meteorites) acquire the shape of a ball, similar to a huge "drop". This happens because their gravitational force is great and the forces of attraction are so powerful that they exceed the forces of mutual friction of individual elements, therefore, all masses, when striving for the center, turn into a large common ball. Therefore, "gas giants" such as stars, and planets such as Jupiter, Uranus and Neptune, etc. have little internal friction of the elements and therefore they "easily" take the form of a ball. This happens in the same way as a drop of any liquid, which has little internal friction compared to the surface tension force, acquires the shape of a ball! And for large stone planets (and a number of satellites), such as the Earth, Venus, Mars, etc., which have reached a sufficient size, the mutual gravitational force is quite large and they also acquire a rounded shape, and in addition, for some of them, due to the pressure force from the weight of the upper layers, the temperature in the deep layers of the planet rises so much, cm
that, starting from a certain depth, plastic and "fluid" magma (creating volcanism) also appears, in connection with which the inner layers of the planet become even more plastic, which also acts to reduce the friction of the inner layers among themselves and additionally contributes to the acquisition of the planet's "sphericity » . And the earthquakes that occur all the time on Earth are nothing more than a constant, as it were, “self-tamping” of the Earth inside to take on a “more rounded” general shape outside due to the constant increase in the mass of the Earth from the surface due to the “collection” by the Earth and space dust, and falling meteorites:
Therefore, and often and constantly the Earth pulsates to take on a more rounded shape:
And besides, the expansion of the Earth along the equator by 21 km compared to the axis of the poles occurs due to the centrifugal force of the Earth's rotation around its own axis, and therefore the Earth is not quite a ball, but the geoid is a ball slightly flattened along the axis of rotation; similar phenomena are observed on other planets of the solar system and on stars.
For small cosmic bodies (such as planetoids, asteroids, meteorites, etc.), their mutual attraction of internal masses to each other is so small that it does not exceed the friction force between the particles of this cosmic body, therefore it does not take the form of a ball! And besides, again, because of their small size, the weight of the upper layers is insufficient for the occurrence of “warming up” of the inner layers to a plastic state and the occurrence of volcanism, and these small bodies remain very diverse in shape, like the above photo of a small asteroid.
All the best!
The sun
This is how our mother Earth looks from space from the height of a geostationary satellite, cm 
And this is a small Asteroid three dozen kilometers in size, photographed from a close distance by a spacecraft flying near it. 
Source: Astrophysics and Cosmology
Answer from HelioZoa[guru]
Ideal shape.
Answer from white rabbit[guru]
Minimum energy in a gravitational field... that is, simply because the gravitational field is centrally symmetrical (also round) And the stars and planets are so large that their material is not able to withstand their gravity (small mountains like NixOlympica do not count 🙂
Answer from White and fluffy. Almost[guru]
gravity compresses any large body into a ball, if the body is small it can have any shape. And liquid bodies become balls having a small weight
Answer from Doctor[guru]
Circle and sphere are the most energetically favorable states. Massive bodies tend to minimize their energy level - for example, at the expense of potential energy.