Is weightlessness just an illusion of free fall?

Question

Of course, I am talking about weightlessness in a gravitational well, such as Earth's. When astronauts are in orbit, they are essentially high above the earth. Without propulsion, they'd ultimately fall back through the atmosphere. With propulsion, they are able to keep their altitude. Does this continous free fall create the illusion of weightlessness?

I know this might be a stupid question. This is just out of curiosity.

Answer 1

The way you actually feel your weight is the normal force of the ground on your feet or the seat of your chair on your rear end. So if you are in a swing (at the top when you're just barely hanging) or a freefalling elevator or an orbiting spacecraft or deep space far away from any significant gravity, you aren't going to feel weight. Weightlessness gives you a funny feeling in your gut at first since you are used to having something supporting you.

As for the astronauts in orbit, you are wrong on something. They do NOT need propulsion to stay in orbit. Once you get above the air resistance of the atmosphere, you can travel so fast that gravity doesn't actually decrease your altitude--it just pulls you around in a circle. So the astronauts are in perpetual freefall. If they fire their thrusters, THEN they feel weight--not from gravity, but from the acceleration on their spacecraft. Weather or not you consider weightlessness an illusion is a question of semantics. You aren't really weightless (as defined in the earth's reference frame), since gravity is still pulling on you. But you are weightless in your own tiny little reference frame where you can just float free.

Answer 2

Yes. The space shuttle is falling around the Earth all the time. It just keeps missing the ground because its high forward speed takes it over the curved horizon before it can fall all the way to the ground. The feeling you get on one of those free fall thrill rides is exactly the same as the astronauts feel in space. But they don't have an open chair with a tower and air whizzing by to accentuate the feeling. But I have done weightless maneuvers in a small plane, and it is exactly the same as falling. Just like the coyote falling from a high cliff with the rock falling right above his head all the way down.

Answer 3

Yes, the speed of the object determines its altitude. The faster it is going, the lower the altitudes. If you were on any artificial satellite above Earth, you would feel weightless. There is also a point where a satellite takes exactly one day to orbit the Earth. It's called geo-synchronous orbit, and is about 23000 miles above us. That's how satellite TV and Radio antennas can always be pointed the same way.

Answer 4

The only stupid question is the one you DON'T ask! So, no, this is by no means a stupid question at all.

One needs to remember what "weight" actually is. Most people incorrectly consider weight as the force due to gravity. It isn't at all. It is the Newtonian reaction force to gravity. So, when you are standing on the ground, your weight is the force with which the Earth is pushing on you, not the force that you are imparting on the Earth.

Therefore, "weightlessness" is what we experience when there is no apparent force opposing gravity. Neglecting air friction, this is the case in freefall, and of course the force opposing gravity in orbit is the centrifugal force of circular motion.

Hope this helps.

Answer 5

yes, it's just a illusion, Weightless can't exist in the presence of gravity. it's a illusion because the gravitational pull is being altered by the propulsion. it's not a stupid question, it's food for thought.

Answer 6

Yes. The propulsion isn't away from the earth, it's around the earth, where centripital force of gravity keeps things in orbit from leaving.

A great example of this is the freefall thingy at your local theme park. Put a penny on your knee before it goes, it will seem to float in air for a moment before it starts bouncing around.

Answer 7

It isn't an illusion. Anyone in free fall, whether in orbit or headed straight toward the ground, will show no weight on a scale -- the scale is falling at the same speed and acceleration as the person standing on it. But free fall does not, of course, obviate mass.

Answer 8

There is a point in space there the gravity pull of the earth and moon cancel each other out. There, is almost true weightlessness. I say almost because there is still the sun's gravity, and as theory says a gravity wave from the latest big bang.

Answer 9

I'm adding on to gintable, because gravity is not the only force acting on you during freefall. The other significant force acting on you is air resistance (the friction of the air on your body.) This accounts for the limit in possible speed (terminal velocity.) At terminal velocity, the gravitational acceleration and the air resistance are equal. The weight you are talking about in W=mg is the weight of something at a constant altitude. The actual definition of weight (actually, the correct term is force) is F=ma. This is the total mass and the total acceleration. With a constant mass, and an acceleration of zero, the force is (duh!) zero. No force, no weight. Weightlessness.

Answer 10

Yep. A rocket launches you, and you fall in a ballistic path. If you launch high enough and fast enough, the curve of your fall matches the curve of the earth itself -- orbit.