This may be a very simple question to answer....?

Question

....but it's something I never learned before.

How do the planets stay on a constant orbit around the Sun, rather than being sucked straight in to it or, conversely, drifting out in to space? How do they remain at a largely constant distance from the Sun?

Answer 1

Why do the planets rotate around the sun?

The basic reason why the planets revolve around, or orbit the sun (rotate actually is used to describe their spin, for example, the Earth completes one rotation about its axis every 24 hours, but it completes one revolution around the Sun every 365 days), is that the gravity of the Sun keeps them in their orbits. Just as the Moon orbits the Earth because of the pull of Earth's gravity, the Earth orbits the Sun because of the pull of the Sun's gravity.

Why, then, does it travel in an elliptical orbit around the Sun, rather than just getting pulled in all the way? This happens because the Earth has a velocity in the direction perpendicular to the force of the Sun's pull. If the Sun weren't there, the Earth would travel in a straight line. But the gravity of the Sun alters its course, causing it to travel around the Sun, in a shape very near to a circle. This is a little hard to visualize, so let me give you an example of how to visualize an object in orbit around the Earth, and it's analogous to what happens with the Earth and the Sun.

Imagine Superman is standing on Mt. Everest holding a football. He throws it as hard as he can, which is incredibly hard because he's Superman. Just like if you threw a football, eventually it will fall back down and hit the ground. But because he threw it so hard, it goes past the horizon before it can fall. And because the Earth is curved, it just keeps on going, constantly "falling," but not hitting the ground because the ground curves away before it can. Eventually the football will come around and smack Superman in the back of the head, which of course won't hurt him at all because he's Superman. That is how orbits work, but objects like spaceships and moons are much farther from the Earth than the football that Superman threw. This same situation can be applied to the Earth orbiting the Sun - except now Superman is standing on the Sun (which he can do because he's Superman) and he throws the Earth.

The next question, then, is how did Earth get that velocity, since in real life there's no Superman throwing it. For that, you need to go way back to when the Solar System formed.

xxFJ

Answer 2

They remain in a constant orbit because they are traveling around the Sun at "fantastic rates of speed."

Take the Moon for example...In round numbers, the Moon is 239,000 Miles from the Earth, and the Earth has a radius of 4000 miles. So, 2 Pi R is the circumference of the Moon's orbit around the Earth, or:

243,000 Miles x 2 x 3.14 =
243,000 Miles x 6.28 = 1, 526,040 Miles.

Now...The Moon travels once around the Earth in about 30 days. 30 days = 30 x 24 Hours per Day = 720 hours.

So 1,526,040 divided by 720 = 21,195 Miles per Hour

And now we know the flight velocity of the Moon is about 21,000 Miles per hour...that is why it stays up there and does not fall down crashing into the Earth.

You can do the same math to figure out the velocity of any of the other planets. Take the distance of the planet to the Sun and add the radius of the Sun to get the total radius of the circle and multiply it by 6.28. Then divide the circumference by the number of hours it takes for the planet to make one complete orbit of the Sun (remember days x 24 hours)...
some of the numbers get pretty big, but the velocities will be amazing if you take the time to calculate them.

Nothing is sitting still in space.

Answer 3

They are effectively falling around the Sun rather than towards it. If you imagine shoving an object sideways off a cliff, it will fall downwards and sideways at the same time. If you shoved it sideways fast enough, it would fall "downwards" at the same rate as the Earth curves away from it, so it would never actually fall down to the ground. The planets are doing the same thing with the Sun. The further away they are, the weaker the Sun's gravity and the more slowly they need to move to avoid falling into it. Most things moving fast enough would either have moved further away or escaped completely, and most things moving slowly enough to fall all the way would either have fallen into it or have reached a speed and an angle where they can stay in an orbit long term. This would have happened billions of years ago as a rule, so most of what is left is in stable orbits.

Answer 4

1.they dont stay at a constant distance from the sun, all planets travel round the sun in an elipse.

2. if a planet comes towards the sun very fast and very close, it will make a very long thin eliptical orbit, these are like asteroids.
if it come past far away then it will make a bigger rounder orbit.

3.also, all planets that are in orbit are either very slowly getting futher away, or closer in, but because it is so slow, in most cases the sun will have burnt out by the time a planet will hit it. also, because a gravitational feild is infititely big, nomatter how fast an object goes past the sun, it will almost always eventualy stop and come back, unless it is attracted by a different star somewhere elce in the galaxy.

hope that aswers it...

Answer 5

The planets stay in their orbits for the same reasons as you stay on the Earth's surface. The force of gravity keeps us on the ground - it also keeps the planets orbiting the Sun. This formula:F =GMm
_____
2
1
is a universal formula which allows us to calculate the gravitational force between any two objects. In this formula, F is the force between the two objects, G is the value 6.67/1011 (this can also be written as 6.67 x 10-11), M and m are the masses of the two objects, and r is the distance between them. You can see that this formula is very similar to the one you used earlier to calculate g. Newton's second law tells us that force = mass x acceleration. Since the acceleration due to gravity is g, you can use this to show that these two formulae are really saying the same thing.

Use the formula for the gravitational force between two objects to work out the force between: * two people standing 1 metre apart
* you and the Earth when you are standing on the surface of the Earth (so r is the distance between the centre of the Earth and its surface)
* you and the Sun
* each of the planets and the Sun

If you use masses in kg and distances in m, then the force will be given in newtons (N). How much bigger is the force between the Earth and the Sun than between you and the Earth or you and the Sun?

Answer 6

I Think the constant orbit of all planet is created by a large magnetic gravitational field.

Answer 7

Simply put: they fall into the sun at the same rate that they fall from the sun unless their orbits are elliptical. Then its the same but at different times. Ugh. Same for the moons and satalites. Same for stars about the centers of their galaxies.

Answer 8

because of two factors inertia and gravity. inertia is a objects tendency to maintain its motion. gravity is a pull that everything in the universe has. so the suns gravity pules the earth towards it but the earths inertia resists ans this gives the earth a curved orbit .

Answer 9

They stay in their constant orbits becos of the gravitational pull they exert on each other.

Eg. the earth stays in its orbit becos of the pulls by Venus, Mars, Jupiter etc... so I pull u here, he pulls you in the other direction, she pulls you yet from another.. and then there is an equilibrium...

Answer 10

The centrifugal force (out ward) is in balance with gravitational force between two planet so there is no acceleration to achieve any speed or suck in the absence of external forces......... be it a planet or satellite