When in free fall are you actually weightless or do you just FEEL weightless? Is it the same thing if weight is relative?


When in free fall are you actually weightless or do you just FEEL weightless? Is it the same thing if weight is relative?

In: Physics

You feel because you didn’t just lose all your mass.

If you’re in free fall but inside and thus don’t feel the drag of air, such as on Iss, then it will feel exactly as if you were weightless.

But even on Iss gravity is only around 12% less than on the surface of earth.

You just feel weightless since you are in free fall. We don’t feel speed, we feel acceleration or changes in velocity, so once you get up to speed, you don’t feel the force any more. It’s, to my knowledge at least, not quite the same since gravity is still actually acting on us, we just don’t register it the same way.

‘Weight’ is the sensation of the ground *resisting* your free fall. When you feel weight, what you feel is the ground pushing up against your feet.

Remove the ground, and you no longer have a weight. Objects in free fall are truly weightless. They are not *massless*, which still affects things like inertia, but ‘feeling weightless’ and ‘being weightless’ are the same thing because weight is something you can only *feel* to begin with.

The textbook definition of “weight” is the force that gravity asserts upon you. By this definition, as you free fall, you very much still have weight.

However, in common speech, when we say “weightlessness”, we are referring to those astronauts floating around in the space station. By this definition, the feeling that you get as you free fall and the weightlessness experienced by the astronauts are exactly the same thing — the astronauts are falling towards Earth just like you, except that they are traveling sideways so fast, and because the Earth’s surface is curved, that they never actually hit the ground.

So yes, that is weightlessness that you feel. But it is not because weight is relative. Instead, it’s because “weightlessness” isn’t really related to “weight”.

From a physics standpoint, as shown by Einstein, feeling weightless is the same as being weightless. So, if you have jumped out of an airplane, it is exactly the same as if you are drifting in space. It’s not intuitive, but if you feel weight at all it is because you are actually accelerating upwards against the inwards flow of spacetime, which from a physics standpoint is stationary. It’s complicated, and can’t really be ELI5’ed but it is true nonetheless.