# Free fall in deep space

I realize that microgravity is really free fall due to falling around the earth while in orbit, similar to the down side of a roller coaster hill. It’s my understanding that if I were standing on a 200 mile tall ladder I would actually weigh around 90% of my surface weight. Knowing this, how is it that on the way to the Moon, or Mars while not in orbit around the earth, or free fall, we would still experience the same amount of free fall? Is it because we’d be falling around the sun? Or are we still in earth orbit? The earth still has a gravitational effect up to 1 million miles out.

“Free fall” is exactly what the words say. It’s fall; that is, being pulled by gravity so you are falling towards something. And it’s free; that is there is nothing like a floor under you that is preventing you from falling.

When you are in space and not under power, then you and your rocket are in free fall where you are falling in the direction the net effect of the mass of the Sun, the Earth, and everything else is pulling you by it’s gravity. You feel weightless not because there is no gravity, but because everything around you is free falling together so nothing like the floor is pressing against you.

And no the Earth does not have an effect out to 1 million miles. It’s effect is unlimited in distance. It’s just that the force falls off like the square of the distance. That means if you’re a million miles from the center of the Earth you are 250 times as far from the center as when you’re standing on the surface so the force of gravity is only 1/62,500 times as much.

Sliiiight nitpick. Included in the equation of where you are falling is the sum of previous accelerations. These could include rocket power, jumping or even having an asteroid carom off you. But it’s all part of the equation with gravity.

Free fall in this context simply means “no force acting on us other than gravity”. The gravity in question doesn’t have to be associated with any nearby large object (e.g. Earth) - it could be faint forces from enormously distant objects.

No , not only that. Its any time that either
*there literally is no gravity there
OR

• you accelerate as per the force of gravity - there’s nothing providing reaction force against gravity . Ah actually Newton’s 2nd law doesn’t help clear this up. In freefall, there is no reaction force, there is the reaction of acceleration… its like Newton’s 2nd should end with “Except where accelerating due to the force”.

On the ways to Mars ? well in between there is true micro-gravity… no gravity to feel. And anyway what gravity there is, you are in freefall - unless you feel the thrust of your rocket…

What do you mean by “experience the same amount of free fall”? Free fall is, by definition, something you don’t experience. Zero is the same amount anywhere.

The simplest quick answer is that unless a rocket engine is firing and producing thrust, any such spacecraft is on a ballistic trajectory. This is the key concept here. An orbit is just a special case of a ballistic path, but a spacecraft that’s headed toward the moon, or reached escape velocity and is on its way to Mars or Jupiter, or anywhere else, is always on a ballistic path unless rocket engines are burning and applying an accelerating force, so everything in it is executing the same ballistic path and is therefore under zero-g. It’s no different on earth, either. A baseball in flight or a zero-g training flight (which accelerates to high speed in a power dive and then travels on a ballistic arc under zero power) are all examples of the same thing.

There is always a reaction, just like the law says. This is also known as conservation of momentum. While you are falling toward the Earth, the Earth is falling toward you. The force that is accelerating you is equal and opposite to the force accelerating the Earth. Of course the Earth weighs a lot more than you do, so it’s acceleration is minuscule.