why all planet orbiting sun. Not falling into it same with iss in outer space of earth .

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why all planet orbiting sun. Not falling into it same with iss in outer space of earth .

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They are, basically, but they’re moving perpendicular to the sun’s gravity at roughly the same speed as they’re falling. So instead of falling right in, or flying past the sun into interstellar space, they maintain a mostly consistent distance from it.

It’s kind of hard to picture, but there are two main points to this; space is really, really big and everything in it is, relatively, really small. It’s actually really hard to get something to fall into the Sun; it’s just too far away to hit unless you are really, really accurate.
And if by a one in a million chance you were a floating mass in space with a perfect trajectory into the sun, you would’ve crashed into it hundreds of millions of years ago.

To get something in orbit, you need to have a high tangential velocity. That is, it has to be moving sideways so fast that by the time it “falls,” the curvature of whatever is being orbited is such that the orbiting object never hits it. Without that tangential velocity, the thing would indeed just fall right back down.

I’ve always pictured it like throwing a ball. Throw it, it arcs a bit as it falls to the ground. Throw it harder, it travels further but eventually curves to the ground. Now picture throwing it really hard. The surface of Earth isn’t a plane, so you can throw it so hard that but the time it falls, the curvature of the Earth starts to come into play and the ball has to fall a little more before it lands. Expanding on this, you can theoretically throw something so hard that, if it didn’t slow down, that by the time it fell, the Earth would have curved completely out from under it. In this case, the object could keep falling but never hit the Earth. This is essentially what an orbit is. You need to be in space so you don’t have air slowing you down, but the idea is the same.

relevant xkcd: https://what-if.xkcd.com/58/

Orbiting *is* falling.

If the planets *weren’t* falling towards the sun, they’d move in a straight line forever, the same way a ball would move if you kicked it on a soccer field.

But the planets *are* falling towards the sun; imagine kicking a ball off a cliff, it’s going to go straight ahead still… but it’s also going to go *down.* You’ll get a curved shape as the ball goes forward and down off the cliff.

What makes orbiting so special is that as the planet is falling, the *direction* it’s falling is changing. Imagine you kick that same ball off the same cliff… but you kick it *so hard* that the curve is big enough to follow the curve of the Earth. The ball will go forward and down… but as it does, the direction that “down” is changes, because it’s always towards the center of the Earth. So it keeps falling in new directions, which ends up making it fall in a circle around and around and around.

Orbiting is constant falling.

To add to the other answers.

The ISS isn’t in pure vacuum. It’s still close enough that it experiences drag from the very thin atmosphere which slows it down, making it need to correct periodically.

Everything orbiting the Sun is moving too fast sideways to hit it. And everything that didn’t move fast enough has plunged into the Sun long ago.

Think about spinning a ball on a rope quickly. As long as you spin it quickly enough, it will spin around in a circle. The rope is like the force of gravity pulling it into the center, and stopping it from flying away. But if it didn’t have that momentum, the gravity would just suck it in. Basically, for any given distance from an object there’s a certain speed where gravity will keep it in orbit. If it goes faster, it will fly away; if it goes slower, it will get sucked in.

For ISS or any satellite, if you launch it too slowly, it falls back to Earth, launch it too fast, it flies away. Launch it just right and it goes into orbit.

Edit: I realize that this explanation makes it sound like orbits are circles. They’re actually ellipses, but the math behind why that is is more complicated.