What's the difference between weightlessness and Zero-gravity?

Question

Are they the same thing?

**Lots of questions tonite!!

Thanks Chicken and Abby... that helps!! and everyone else who answered....

Answer 1

Hi Stephanie

My answer from your other question probably answers this one as well:

Generally when people talk about zero gravity what the actually mean is that they feel no accelerating force due to gravity. Gravity can still be there, you just don't feel it.

This requires a quick examination of what we think we know about gravity. According to general relativity (einstein's gravity theory) a state of motion in which you don't feel any external forces is called *inertial motion*. Einstein realised that when you are free-falling in a gravitational field you're actually in inertial motion - you don't feel any net force. You only *feel* gravity when something (eg the surface of the earth) accelerates you out of free fall and makes you be stationary in a gravitational field. Anybody who has been skydiving can confirm this for you - you feel what most people call "weightless" when in freefall, but when you land on earth's surface you feel the acceleration of the ground pushing up against your feet.

This now makes the answer to your question fairly straightforward. If you want to feel no acceleration due to gravity you need to be in freefall. You can achieve this by jumping out of a plane or off a diving tower, or on a roller-coaster. Astronauts can achieve this in short "free-fall" plane flights. An astronaut in orbit around the earth is also in freefall and so feels no acceleration. Note that in each and every one of these examples I've just mentioned gravity is still there - it hasn't been shielded or negated or magicked away - it is the feel of the acceleration that is being avoided.


Hope this helps!
The Chicken

Answer 2

Weightlessness is the absence of weight. Weight is a relative term used to quantify mass (also relative). Any time and object has no mass, it has no weight and no weight means no mass (note the differance between mass and volume). Luna's gravity is 1/6 that of Earth, therefore you would have 1/6 of your mass on Luna as you do on Earth. So yes, weightlessness is essentially the same thing as zero-gravity, in the general sense. Remembering however, that no matter where in the Milky Way you go, you will be under the effects of some gravity (however slight) so you will always have *some* mass.

Answer 3

From a perception point of view, nothing, they are the same - this was what so interested Einstein. How, he postulated, could one tell if he was truly falling, or merely accelerating downward, in, an elevator say.

There is NO way of telling, thus they are essentially the same. In popular culture we use them as essentially interchangeable ideas, but in Scietific terms they can be quite differently interpreted. An object whose orbital velocity and its orbital motion cancel out is experiencing "Weightlessness"; as as it falls toward the planet below it, the planet below rotates away - this is the same "Feeling" that one would experience out in the middle of galactic nowhere, far from any bodies. But the feeling, the effect is the same - Lack of gravity and relative motion simulating lack of gravity are the same.

Answer 4

Weightlessness = when the acceleration due to gravity is 0 (w=mg, where g=0)

Zero Gravity = No gravitational attraction whatsoever.

Answer 5

They are very similar, but Abby has it right... weightlessness just seems like zero-g.

Answer 6

Nothing. They are one and the same.

Answer 7

me