The original question was: What exactly causes the Earth’s rotation and revolution? Does this occur due to centripetal force and the lack of friction to stop the Earth from spinning? IE- Newton’s First Law? If so, where did this centripetal force come from? Was it a product of this rock being hurled through space and stuck in the Sun’s pull? As for the rotation, I don’t even have a guess. Are there planets that don’t revolve at all, or is that a necessity?
Physicist: I’ll break this down into two questions: “Where does the rotation originally come from?” and “Once the a planet is in orbit, what keeps it there?”
Where does the rotation originally come from?: The original yearly rotation of the Earth around the Sun (orbital rotation), as well the daily rotation of the Earth about it’s own axis (just “rotation”) is essentially dumb luck.
If you hold out any object and toss it in the air, you’ll find that it’s almost impossible to toss it in such a way that it doesn’t turn at all. The same is true of stellar nebulae (the gigantic clouds of gas and dust that condense to form stars and planets). They always have at least a little bit of swirl and spin.
As the cloud that became our solar system collapsed inward, the mass settled into a spinning disc with a big bump in the middle (the Sun), and that disk began collapsing even more to form the planets. This process is called accretion, and you can see it at work over and over again.
When stuff collapses it tends to form a central ball and a disk.
There aren’t any non-spinning planets, but the speed that they spin varies widely. Jupiter’s day is only 10 hours long, while Venus’ is around 240 Earth days long. How fast and in exactly what direction a planet will end up spinning is a fiendishly complicated problem. Some of it is determined by the flow of the gas and dust of the “proto-planetary disk” (which is fairly simple), which is why the orbits and rotations of every planet in the solar system orbits and rotates in roughly the same direction.
Since the Earth orbits the sun in the same direction that it rotates, when it's morning (6 am) you're standing on the "front side" of the Earth.
But once the ball gets rolling (so to speak) you find yourself with a solar system full of big rocks on slightly different orbits slamming into each other, and changing each others rotations. For example, the Earth’s moon was (most likely) created by a stupendous collision with something Mars-sized that “splashed” the moon into orbit. That impact, as well as tidal effects from the moon itself, have radically changed the length of the day on Earth. Uranus is also believed to be the victim of an even bigger collision that tilted it’s rotation axis around 98° from it’s orbital axis (the direction perpendicular to its orbit), and dramatically changed the length of it’s day. We can’t say by how much; no one saw what it was like before.
So, in general, things spin because they collapse from very large clouds of stuff that were spinning (just a little) already. If the cloud hadn’t been spinning, then all of the mass in the solar system would have fallen all the way into the Sun. Instead, a mere 99.86% of the solar system’s mass is in the Sun.
Once a planet is in orbit, what keeps it there?: Gravity pulls the Earth in, and centrifugal force holds it out.* The centrifugal force on the Earth is just a result of the Earth moving in a curved path around the Sun. It doesn’t slow down because there isn’t any friction. After all, in space, there’s nothing to have friction with. Why exactly an orbit is stable involves a short romp in math town.
Gravitational force, Fg, is given by 
Centrifugal force, Fc, is given by 
Looking at the total potential, U=Ug+Uc, it becomes clear why orbits can be stable. In order to picture forces better physicists will sometimes draw “potential diagrams”. A potential diagram is just an intuitive way of describing energy and, in turn, forces. To understand it, imagine putting a marble on the line and think about how it will roll. In the picture below the marble will roll to the left, but no too far.
The total potential curve in terms of distance to the Sun. When a planet gets too close to the Sun the centrifugal force "rolls it away", and when it gets too far away the gravitational force "rolls it back". A stable or "bound" orbit is one without enough energy to roll out of the pit. This diagram helps explain why it's so hard to fall into orbit around something: If you start from far away, you have enough energy to get back there.
An orbit is stable when the energy of a planet is “cupped” by the total potential. If it gets too far out the gravity pulls it back, and if it gets too close the centrifugal force pushes it back out.
Also, as if you needed another reason to be excited about living in this universe, orbits are only stable in two and three dimensions. The force of gravity drops in the same way that the intensity of light or sound drops off (in our case: 1/R2), so if the dimension of your space is D, then the force of gravity is 
Gravity gets weaker, faster, the higher the dimension. In 1 dimension there's no circular movement and no orbits. In 2 and 3 dimensions the forces balance such that there are stable orbits. In 4 dimensions an object will either fall directly in or fly away forever (depending on its angular momentum). And in 5 or more dimensions gravity wins if an object is too close and centrifugal force wins if it's too far.
For small dimensions (2 and 3) the centrifugal force is stronger for small R and gravity is stronger for large R, which yields stable orbits. For large dimensions (5 and up) gravity is stronger for small R and centrifugal force is stronger for large R, so the orbit is always trying to fly apart, one way or another. In 4 dimensions the forces get stronger and weaker at the same rate (~1/R3), so if one is stronger than the other it’s always stronger.
*This isn’t technically true. Technically the planet is moving in a straight line through curved spacetime, and experiences no centrifugal acceleration. But whatevs.
Is centrifugal force real? http://xkcd.com/123/
Real enough.
It depends on your perspective. In a non-rotating frame you’d describe the “force” as the object being accelerated around a curved path (any path that isn’t a straight line with constant speed requires acceleration). When you’re the object doing the spinning, however, it’s hard to keep that in mind.
Right, and so the next question is, “What is the best way to explain this situation?” It does indeed depend on perspective, and if we adopt the perspective of an observer outside the earth (let’s say looking “down” on the solar system, for example), then there is an argument to be made that it is preferable to avoid discussing centrifugal forces. (They are perhaps more useful when adopting the perspective of an observer on earth.)
From the perspective of an “outside” observer, an alternative explanation is along these lines: If there were no acceleration, the earth would just carry on in a straight line at a constant speed (by Newton’s first law of motion). But the earth moves in (approximately) a circle. Why? There must be a reason … and the reason is that the sun exerts a force on it. OK, but the force had better be just the right size to account for the acceleration, according to Newton’s second law of motion, F = ma. Because the earth goes in a circle (approximately),
. (This is the centripetal acceleration.) Thus
From this perspective, nothing keeps the earth out, and nothing is needed to keep the earth out. There is no balance of forces, one inwards and one outwards. The earth goes in the circle, therefore there must be a force acting on it towards the centre of the circle, and that is the only force needed for the explanation. The sun provides the force.
For my preference, this is a simpler explanation, especially for a beginner. But the author’s explanation is also good; to each his own.
What I’m really missing here in the answer to the first question is conservation of angular momentum, and how it makes the inner planets orbit the sun faster than the outer ones!
A single planet must always have the same angular momentum, but different planets are free to have different angular momenta. So, angular momentum isn’t the best way to explain why different planets in different orbits have different speeds.
. “GM” (the gravitational constant and the mass of the Sun) aren’t going to change. So if R gets small, v has to get bigger to compensate. That is; if you orbit closer to the Sun, you have to orbit faster.
The last equation in Santo D’Agostino’s comment (two comments up) is probably a better approach. If you multiply both sides by R2 and divide by m you get
If you don’t trust the math: the Sun pulls more when you’re close, so you have to spin faster to stay away.
Why does earth is orbiting around the sun and spinning on its axis?
There are thousands of thousands answers but none will statisfy you if you use your common sense.
OK the law of gravity is playing a big role in this rotating and spinning. But where does this gravity come from? Who ordered or set it there so precisely. If speed of spinning rate faster than whatever is now….. say 2000 km per hour….. then we have two dawns and two dusks in 24 hours instead of ALMOST equal period of day and night.
As one physcist answered “Is essentially dumb luck ” Is this you call sciense?
Absolutely!
Science does try to explain as much as possible about the universe around us, but part of that is knowing why there are some things that can’t be known. For example; using mighty science we can predict weather, with fair accuracy, several days in advance. But (again, with science) we also know why we can’t do much better (see: “chaos theory”).
In this case we know that planets can form with a wide range of rotation speeds, because we’ve got 8 planets (9 if you were born in the ’90s or earlier) to take data from. The lengths of their days are all over the place.
I am a person with no education but I read much and try to understand things. I deeply respect learned and people of knowledge and understanding, like you. Through such people human race had achieved a lot of comfort and left behind most suffering and misery. My argument is not leading to persuade you towards any faith or belief. Planets can form with a wide range of rotation speeds. But why our planet earth is so unique? Suitable for life! Why there is a tilt of 23 degree? So we can have seasons! Why the atmosphere with 78% and 21% of nitrogen and oxygen? Why with seventy percent liquid water? Why the full sky become dark at night and bright at day? From where the first life or first cell come from? Science cannot answer all these questions and a lot many. They can speculate. Based on your argument that the planet formed through gravity’s rotation of dust and gas. They are still trying, in Cern, Switzerland, since 1992 a project named (Large Hadron Collider), to create the basic particles of the earlier universe, after Big Bang. The result was very embrassing for science community. Also more than ten Billion $ bill to be paid. Common sense and reason tell us to accept all these happening are the result of Divine Intervention. The One God! Yours and mine.
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Hi,
Why full sky is dark at night and the same time other side of the globe (which facing the sun) is full bright? Please do not explain to me through Olber’s night sky Paradox.
what is the variable in the earth orbit ellipse
What do you mean?
why doplanets have names?
That’s kinda profound!