Why doesn't the earth fall out of orbit into the sun, just as earth satellites eventually do?

Question

I understand the basic mechanics of orbiting bodies -- they are actually 'falling' around the orbited object. What I don't understand is how the balance could be so perfect that even over billions of years, the earth stays in place. And many meteors and meteorites hit the earth all the time. Wouldn't these impacts eventually alter the orbit enough to doom the earth?

Answer 1

Satellites in low earth orbit are not quite above all of the Earth's atmosphere, so there is some small amount of drag from the extremely thin air. That drag force is constantly taking kinetic energy away from the satellite, so its orbit is constantly getting lower.

It is different for Earth. Earth is not experiencing a continuous drag force. It does sometimes get hit by meteoroids or asteroids, but not always from the same direction, so each impact is not necessarily reducing the Earth's kinetic energy.

An orbit is not a delicate balance between gravity and centrifugal force. It is a sum total of the kinetic and potential energy of the orbiting body. Kinetic energy is energy of motion and potential energy is, in the case of an orbit, energy of height. In a perfectly circular orbit both types of energy would be constant all the time. In an elliptical orbit, the potential energy is larger, at the expense of kinetic energy, at the high point of the ellipse (aphelion for Earth) and at the low point (perihelion for Earth) the kinetic energy is larger at the expense of potential energy. So the speed of Earth in it's elliptical orbit is constantly changing, as is its distance from the Sun, but the total energy is constant. To make to Earth fall into the Sun would require removing all its kinetic and potential energy, which is just so much energy that even a large number of big asteroid impacts are trivial in comparison. And remember, some impacts might actually increase the Earth's orbital energy if they hit from the correct direction.

Answer 2

First of all...the 7 answers before this one are filled with mis-information. (Sorry guys) The Earth will never fall into the sun. The sun will never supernova. Magnetism also has nothing to do with any of the planets orbits although we do have a magnetic field around earth. The truth is hidden in your own question. It is a "balance" of forces at work. We are bound to the Sun by gravity and we are going around it, at a speed which keeps it stable. It's called angular momentum. We are at Equalibrium now. We are also traveling in the gravitational well of the sun. (It's like going in straight line.) If you could somehow stop our rotation around the sun we would then fall into it. (But don't worry about that happening.) As for the impacts from meteors, comets, ect.... What do you think knocked Earth off it's axis? A huge one in the past. It used to be straight up and down. (Now it has a tilt.) Also....a meteor is the name while going through space and once it has touched the Earth it is called a meteorite. One last thing ...The mass of the sun is not big enough to blow up or supernova. It is half way through it's life now and in another 4 or 5 billion years it will swell up to become a red giant which will be so big it should envelope Earth or come close to it. Then it will cool and shrink down to remain a white dwarf. But a billion years before that even happens, Andromeda Galaxy is going to merge with our Milky Way. I hope you find all this helpful and cool to learn. It is all real and true. So now you know.

Answer 3

There is a phenomenon known as centrifugal force that keeps the earth's orbit from decaying and falling into the sun. If the earth or any other planet revolves fast enough the pull of the sun is counter balanced and the distance will not change or change so slightly that there is little or no measurable difference over thousands of years. Considering the mass of our planet it's orbit or rotation is affected little when struck by meteors even of great size as some in the past. It is the same as throwing pebbles at a bowling ball. You can throw a pebble as hard as you can at a bowling ball and it would just bounce off and the bowling ball would not move.

There is nothing about magnetic fields involved in this as others have suggested. It just involves massive amounts of material moving freely through space and the gravital pull of the sun.

Answer 4

Man made satellites fall out of orbit after relatively short times because as high as they are, they are not completely free of the atmosphere. So air drag slows them down and eventually they come down. There are also factors that effect the orbits of celestial bodies, even though there may be no air friction. The most significant is the tidal forces. These cause friction which slows the rotation of the body, changing the overall angular momentum. This will actually cause the orbit diameter to increase. Other effects (meteor impacts, etc) could cause orbits to shrink. I don't know which way the earth vs sun is going. I think the moon's orbit is widening. In any case, these effects act very slowly.

Answer 5

First of all, Earth won't crash in the sun for several reasons....

It has been proven that Earth is slowly getting father from the sun..

Also, a planet, all planets have a difinate orbit and the magnetic field of each planet keep them from ever bumpng into one an other even if 2 were ever on the same course, which will never happen... Like 2 positive magnets repulse one an other...

Meteorites, and meteors are objects that have very little magnetic field an so are simply pulled where ever....
The reason the satellites are pulled towars the SUN, thank God,
is that the little magnetic orbital power they have is limited... like
a small battery(artificial power) an so, they are pulled to the stongest magnetic power around...which is of course the Sun..

Hope this helps a little...

Answer 6

Well, eventually we will-- but I don't know if you'd call it "falling". Anyway, satellites experience a low-grade drag effect from the Earth's upper atmosphere. Also, the Earth is on a whole different size scale than those satellites; it's not directly comparable. (Also, it's not like all those meteors hit us from one side)

Answer 7

that's the thing, it's not perfect. eventually, the earth WILL crash into the sun, assuming the sun doesn't explode first. but it will take like a zillion years, so everyone who's alive at the moment is probably safe from it

and considering that most meteors burn up before they even hit the earth's surface, or are no bigger than a chihuahua's head when they land, they'd have a lot of trouble pushing us to any significant degree

Answer 8

The earth is too large and thus exerts a certain magentic field. Something very freaking large would have to hit the earth to throw it into the sun.

Answer 9

Gravity, vibration and movement.

Answer 10

campbelp2002 has a good answer except it is centripetal force.