What causes weightlessness in a free fall?

In summary, Einstein realized that a person in free fall would feel weightless due to the cancelation of forces. This realization was inspired by a man who fell 60ft and survived. However, Newton did not have this same understanding. Furthermore, Einstein used this concept to develop his theory of general relativity, where gravitation is not considered a force and free fall conditions are indistinguishable from force-free conditions. Therefore, in general relativity, a person in free fall would actually be weightless.
  • #1
chaszz
59
2
Einstein said one his happiest realizations was that a person in free fall would feel no weight. Unless I am mistaken he said this. But didn't Newton realize this?
 
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  • #2
I don't think Newton did realize this. Einstein was given a huge hint by a guy fell 60ft and lived to tell the tale. He is reported to have said he felt 'weightless' whilst falling.
 
  • #3
It depends on the definition of 'weight', 'weightless', and 'felt'.
 
  • #4
You wouldn't actually be weightless in a freefall, but you would feel like it because the forces are canceled out.

Einstein did realize that an observer accelerating due to a rocket or other force is analogous to an observer accelerating due to gravity: http://www.astronomynotes.com/relativity/s3.htm he used this to formulate general relativity from special relativity
 
  • #5
Viracocha said:
You wouldn't actually be weightless in a freefall, but you would feel like it because the forces are canceled out.
What forces are canceled out? In Newtonian physics there is no cancelation of forces for an object in free fall. There is only one force acting on such an object, and that force is gravity.

There is no cancelation of forces in general relativity, either. There is no force acting on an object in free fall in general relativity. Gravitation is not a force in general relativity. There is no local experiment that can distinguish free fall conditions from force-free conditions far removed from any gravitational source. The two situations are identical as far as general relativity is concerned.

Bottom line: You actually are weightless in a free fall in general relativity.
 

1. What is free fall weightlessness?

Free fall weightlessness is a phenomenon experienced by an object or person when they are falling towards the Earth without any external forces acting upon them. This creates a feeling of weightlessness because there is no force pushing back against the object's weight.

2. How is free fall weightlessness different from being in space?

In free fall weightlessness, an object is still within the Earth's gravitational field and is accelerating towards the surface, while in space, an object is in a state of constant motion at a certain velocity. Additionally, in free fall, an object is subject to atmospheric drag and will eventually hit the ground, while in space, there is no atmosphere to slow an object down.

3. Why do astronauts experience free fall weightlessness in space?

Astronauts experience free fall weightlessness in space because they are constantly falling towards the Earth, but their horizontal velocity is fast enough that they keep missing the Earth. This creates a state of perpetual free fall, giving the sensation of weightlessness.

4. Can free fall weightlessness be simulated on Earth?

Yes, free fall weightlessness can be simulated on Earth through parabolic flights, where an aircraft follows a parabolic path and creates brief periods of weightlessness for passengers on board. This is also how astronauts train for the feeling of weightlessness before going to space.

5. Are there any negative effects of experiencing free fall weightlessness?

Although it may feel like a fun and weightless experience, free fall weightlessness can actually have negative effects on the body, such as dizziness, disorientation, and nausea. This is because our bodies are used to the constant force of gravity and can become confused when that force is suddenly removed.

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