about gravity

[no idea]

is the gravity above the ground 8000km is less gravity from the ground than on the ground?because i think that the distance will affect the attraction

[LURCH]

Yes, the attraction of gravity decreases as one gets further from the central sourxce of gravitational influence. It is a function of the sqaure of the distance, meaning that if you get twice as far away, gravity is 1/4 as strong, three times the distance and gravity's pull is 1/9, etc.

[no idea]

but why the thing still drop

[Gokul43201]

No matter how far you go from the source (in this case, the center of the earth) there will still be a gravitational attraction, only it will be weaker. If you go into space though, there are other planets/stars that start attracting you towards them.

[mathman]

Gravity gets weaker with distance, but it doesn't go away until it is neutralized by something else in the opposite direction. For example, going from earth to moon there is a point where the effects cancel.

[Moe]

Actually, it never goes away, it just becomes infinitely small. If you were to hurl a ball upwards at sufficient speed, it would keep slowing down forever, although the rate of deceleration will decrease. Of course, the gravitational fields of other bodies (in your example the moon) would influence the ball's flight path as well, so if you launch it at the sun, the ball would be pulled into it. But on a stricly theoretical level, the earths grav field is pretty much infinitely large.

The fact that astronauts are "weightless" in a space shuttle is due to the fact that they are in a constant free fall around the earth. There still is gravity, but they don't feel it. It's an effect fairly similar to that what you feel in an elevator when it starts to descend.