Quote:
Originally Posted by ckissick
Astronauts orbiting earth are weightless because they are in free-fall while orbiting earth. The spaceship is also weightless for the same reason. Earth is orbiting the sun, just as a spaceship orbits earth. Therefore, Earth is weightless. So if you can be at the exact center of Earth's mass, you are weightless. I'm ignoring other gravitational "forces" - gravity is not a force - like the pull between Earth and Moon, and the fact that orbits decay.
Is this correct? I just came up with this theory. But it makes sense to me.
|
Weightless is a misnomer
micro gravity is more appropriate
first weight is the pull of gravity, on or near Earth it pulls mass toward the center of Mass for the system,
in orbit that pull still is present it just presents as a constant change in motion(ie acceleration) whose vector carries it in a path around the CoM, In a car going around a corner you inertia wants to keep you and the car in alignment with the motion vector of the car a force applied by the tires to the wheels to the chassis to the seats to your body and eventually to your neck is indistinguishable from the pull of gravity except for it's direction
when falling the same applies, there is a gravitational pull, but here here the motion vector is more closely aligned w/ the acceleration vector, the less alignment the more sideways motion
In a descending elevator the force of gravity is reduced by the acceleration of the elevator, if it accelerated own at 9.8m/s2 then you would feel no weight(till you hit bottom where the neg accel hits all at once making you weigh tons for a micro sec)
similarly when going up on the elevator the acceleration of the elevator adds to the pull of gravity causing increased weight on your legs
These inertial forces are all indistinguishable from the force caused by gravity except for the mechanism and vector