Scientists believe collisions create the moon, Mercury, Pluto, etc., how do they become spherical? There is no air or gas that "smooths" them out as they travel through space. Is it gravity pulling it to a central point, making it average across the entire surface?
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If you get a large enough mass of rock together, say about 1000km across, it will naturally crush itself into a spherical shape.  Once you have enough mass for gravitational forces to overcome structural support things becomes spherical.
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Interesting question.  You can extend it - why does the Earth continue to turn on its axis?  And circle the sun?  Why does the sun circle the center of the galaxy?  Why do things keep going, year after year for billions and billions of years?\n\nNewton thought about this and came up with one of his famous laws:  Without an external force, a body in motion stays in motion, a body at rest stays at rest.\n\nThe second half is easy.  Put a rock on the floor and it will stay there forever until you pick it up.  It won't move without an external force.  So what if you shoot a bullet into the air.  We all know it falls back, but why?  Because the force of gravity acts on it.  Take away gravity and it will still stop.  Why?  Because the friction of air on the bullet's surface will slow it down and finally stop it.  Take away air, take away gravity, and the bullet will go on forever.\n\nSo to answer your question:  Simply put, the asteroids have no forces to stop them.  Gravity keeps them trapped around the sun, but they outside of the range where they fall in, so they simply continue to go around, just like the planets such as Earth.  The asteroids started in motion at the formation of the solar system 4.5 billion years ago, and except for random collisions that altered courses and accelerated (or decelerated) the rocks, no force has acted on them to slow them down.  A perfect example of Newton's law, even more amazing because Newton did not know of the existence of asteroids.
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Explain how a 600 yard wide rock could cause the 2,160 mile wide Moon to wobble, without touching it? It'd be like throwing a golf ball at a bus and expecting it to tip it over....\n\nIt doesn't matter what the moon does as far as wobbling and spinning, it's gravity isnt affected (unless it breaks up) and therefore the end result means zip to us. We may just get to see the far side!
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The arrangements in our solar system is(from the Sun):Mercury, Venus, Earth, Mars, Jupiter, Saturn, Neptune, and Pluto.\nNote:Pluto's orbit isn't similar to ours.\nThe solar system also includes an infinite number of stars, whom biggest is the Sun. There are plenty of Black Holes in the solar system. The gravity pull of the Black Holes are so strong, they can suck in nearby stars.\nThere are also plenty of stars bursting. We call the explosions Supernovas. After the Supernova, the star becomes a White Dwarf. There are also plenty of comets around. Among them, Halley's Comet is one example, passing over earth in 76 years at a time. Its orbit is 18 degrees to the ecliptic.\nHope this is useful and answers ur question!:)
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Fussion in the sun is caused by massive gravity well within the sun.  So where is gravity the greatest the center The Center the center   The fussion causes a really big explosion that sends out charage ions flying through space space space space Space in the way of radiation waves.  Interesting eh?
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When the cloud of gas and dust that formed the sun began to gather together to form the sun, some of it didn't get sucked in by the increasing gravity at the center, but gathered together into less-dense "rings" around the newly-formed sun.\n\nThen gravity did its magic on those gases and dust, gathering them together into smaller balls, the planets. Around some of them were still smaller rings, which gathered together into moons, or, in some cases, more widely dispersed rings.\n\nIf you play with water, stirring it with a pencil to create a little whirlpool, then drop little bits of soil or even food coloring into it, you'll get a feel for how it might have happened. It's not the same, but if you watch it and try, you can imagine how it might have happened.\n\nThen, of course, you'll start wondering about hurricanes. <g>
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I will state this here, in yet another question: THERE IS NO SUCH THING AS CENTRFUGAL FORCE!! Look it up in a basic physics textbook like Giancoli or Serway. Or even do a google search. You have to understand what reference frame you're talking about. The fact that your body tends to want to move to the outside of the curve when your car goes around in a circle has nothing to do with anything other than the fact that your body wants to keep going along in a straight line (conservation of momentum), but the car gets in front of it at every turn (semi pun intended). What is actually happening is that the car is an accelerating reference frame.\n\nAs for the moon/earth question... imagine a man 6' tall throws a tennis ball horizonatally with respect to the earth's surface. The ball will go forward a certain distance (because of it's velocity tangential to the earth's surface) as it falls the ~6' to the ground (because gravity pulls it down). The faster he throws the ball (horizontally), the further it will go before it hits the ground. If he throws it fast enough then the amount that the ball travels forward and the amount that it drops towards the earth's surface can match the curvature of the earth, and the ball will orbit the planet (neglecting air resistance, as we physicists always do) and come around and bonk the thrower in the back of the head. The moon is just a much larger tennis ball, thrown by a much larger man.\n\nYour eqn. is correct, but it only describes the force acting upon the moon. It is not the equation of motion, which detirmines what actually happens to the moon. The equation of motion is:\n\nF = m * a  (F = force, m = mass of moon, a = acceleration of moon around earth)\n\nIn the case of the circular motion of the moon around the earth, "a" is defined by:\n\na = (v^2)/r (where v is the magnitude of the velocity of the moon and r is the center-to-center distance from the earth to the moon)\n\nPlugging one into the other you get:\n\nG * M * m/r^2 = m * (v^2)/r (where M is the earth's mass)\n--> G * M/r = v^2\n\nSo, as long as the tangential velocity, v = sqrt(G * M/r), the moon falls just enough towards the earth as it travels just enough tangentially second by second, that it continues to orbit around the earth. (Note: there is NO CENTRIFUGAL FORCE anywhere in any of these eqns.!!)
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During my Time Travels I did do some Intergalactic Exploration. When I was in Grid 946 Quadrilateral 47, the solar system was similar to your solar system. Basically we ( my Friends and myself) observed than any planetary structure is protected from outside forces due to Gravity and Atmosphere. Moons, as you are accustomed to calling them lack those two important aspects, thus, any outside forces bombard those structures and they similar to the moon as larger structures with gravity and atmosphere are similar to Earth. It simple Physics according to Earth's Concept. Once your Scientist understand Dimensions, then you understand the many things you now consider mystery.
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all of them have different orbits...and each satellite is bound to its orbit by means of gravitational force...so they dont collide....however if they loose their stability of the orbit they may collide.
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A sphere can be formed by rotating a semi-circle about a diameter. \nLet us consider the circle x^2 + y^2 = r^2. \nIt is a circle with centre at the origin (0,0) and radius 'r'.\nIf the semi-circle of this circle which is above the x-axis is rotated by 360 degree about the x-axis (which is also a diameter) then a sphere of radius 'r' is produced. \n\nThe volume 'V' of any solid produced by revolution of the portion of the curve y=f(x) between x=a and x=b is \nV = pi*I(y)^2*dx in limits x=a to x=b\n[where 'I' denotes the integral sign]\n \n\nIn this case y^2 = r^2 - x^2 and the curve rotated is semicircle above x-axis so a = -r and b = r\n\nSo volume of the sphere is\nV = pi*I(y)^2*dx \n= pi*I[r^2 - x^2]dx in limits x=-r to x=r\n= pi*I[r^2]dx - pi*I[x^2]dx in limits x=-r to x=r\n= pi*r^2*x - pi*x^3/3 in limits x=-r to x=r\n= [pi*r^2*r - pi*r^3/3] - [pi*r^2*(-r) - pi*(-r)^3/3]\n= 4*pi*r^3/3
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Often many people get involved in discovering a "planet" as several observations are required to verify and calculate the orbit.  Exactly what a planet is is subject to debate as even Pluto is not completely accepted as one.  The debate includes the question "how big does a rock have to be for us to call it a planet as opposed to an asteroid?"  Planet X was one possibility that seemed to just fade out of the news.  "Buffy" is the nickname of the latest "unusual" object out there (see my source article).  Heheheh, yes, "Xena" came public a few days before "Buffy."  Both are among the many rocks in the Kuiper Belt, including Pluto.  NASA's launching a probe called "New Horizons" to check out Pluto and the Kuiper Belt.
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hi, \n\nas i understand it, jupiter (and all the other gas giants, saturn uranus and neptune) don't really have a clear phase-separated surface, in the sense that earth/mars/moon do.\n\nthe interior structure of the planet is not well known, but it is believed that the atmosphere simply gets denser and denser as you go lower and lower, like fog that gets thicker and thicker until it's essentially liquid.  similarly as you go deeper yet, a smooth boundary between the liquid and solid is encountered.  however this has not really been directly confirmed.\n\nthe galileo mission to jupiter released a small probe, which descended into jupiter for 150 kilometers, until it was crushed by the high pressure of the atmosphere.\n\nhere are some resources that might help you out:\nhttp://nssdc.gsfc.nasa.gov/planetary/planets/jupiterpage.html\nhttp://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=1989-084E\n\ncheers!
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No, planets and stars are round because of gravity (to be more accurate, gravity is the curvature of space-time). This is a caused by a different phenomena than surface tension, which is due to the electromagnetic attraction between water molecules. The force of gravity and the electromagetic force are two different forces.  \n\nSurface tension does not actually make the drop round; air pressure does that.  Surface tension simply gives the drop an outer wall like the wall of a balloon.  \n\nThe reason that water drops form into spheres is the need to equalize the pressure inside the drop. Air pressure tries to squeeze the drop, and the internal pressure inside the drop pushes back  - creating the internal pressure of the drop. This puts tension on the wall of the drop (Where the wall of the drop is caused by surface tension.). The geometric shape of the sphere minimizes the wall tension (http://hyperphysics.phy-astr.gsu.edu/Hbase/surten2.html).  A shape with corners, such as a cube, would allow forces to be concentrated at the corner, which would smash the corner flat, or else cause the area around the corner to expand. A sphere allows for an even pressure distribution.\n\nThe pressure on a planet is caused by its own weight pulling its own matter inward.  A sphere allows for an even distribution of gravational 'pressure'.  \n\nIn other words, a sphere resists being crushed better than any other shape, so objects under internal or external pressure tend to become round (irregardless of what is causing the pressure).
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gravity.\n\nany shape of mass that is not spherical is gravitationally unstable
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A little more specifically, meteorites contain little inclusions called "chondrules" which have not been melted and reformed since they first formed in the proto-planetary disk around our sun.  All rocks we find on Earth or any other world have been formed since that time; the "fingerprint" of what conditions were like in space before becoming part of a planet is lost. This is not the case for chondrules in meteorites.\n\nChondrules give us insight into the sorts of particles that were available for larger bodies (and eventually planets) to form from.\n\nYou can read about chondrules on wikipedia.\nhttp://en.wikipedia.org/wiki/Chondrule\n\nAsteroids are examples of the smallest gravitationally bound objects in the solar system.  These are possible building blocks of protoplanets (enough of them stick together and you can have enough gravity to start pulling dust and even gas right out of the proto-solar disk).  By understanding their characteristics, we can more accurately model the formation of protoplanets.
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The Earth is in receivership of the energy of the Sun. No one thing such as a planet can generate Gravity. Gravity is the product of a transmitter (Sun), a receiver (Earth) and an object on or about the receiver. All planets rotate about the strongest electro-magnetic generator along a predictable plane. Electricity flows in a path of a helix as in $ our dollar sign. The helix is doubled and at the null or the point of crossing is where the dust accumulates and forms planets. Thus we are fixed within the boundaries established when the first two particles of dust magnetically aligned N & S and bonded. We are fixed in position therefore we can not be the hitter. We could be hit by a comet or other foriegn body that are in orbit by another cosmic energy beyond our solar system. Astroids that are dust fragments adrift as a result of other cosmic collisions. Particles adrift will be attracted by like elements which follow magntic trails of moving celestrial bodies in search of a home.
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P1 & P2 are pre-existing moons, not the results of recent impacts.  There are a number of indicators as to this.\n\nThe first, to rule out a meteor impact in the past year, is that after the moons were noticed in 2005, photographs taken by Hubble from June 2002 - May 2003 showed the moons.\n\nAnother indicator that they have been there for a long time is their orbital stability.  They are in circular orbits in the same plane and direction as Charon, the previously known moon of Pluto.\n\nThere have also been no disturbances in Charon's orbit which would likely be the case if two new bodies were introduced into the Pluto system.  If they were recently introduced into Pluto's orbit, they would show a more erratic orbit, most likely not in the same plane as Charon and in a more eccentric orbit, moving closer and further from Pluto throughout their orbits.