Weightlessness due to gravitational field

[scientict]

Astronauts in a space capsule orbiting the Earth at a height of 900km experience weightlessness: hence the gravitational field due to the Earth must be zero at that altitude'.

Can someone please help ?
What does it mean?

 

[rcgldr]

Someone posted that gravity at the space station is about 90% as strong as it is at sea level. The astronauts are in free fall, but moving fast enough perpendicually to the force of gravity that the inwards acceleration from gravity results in their path being an orbit around the Earth at a near constant speed and distance.

 

[scientict]

i still don't get it.. please explain clearly

 

[Doc Al]

Read this: http://75.126.60.30/showpost.php?p=1466077&postcount=2

 

[Troponin]

They're still experiencing gravity in an inverse square relation to their distance from the Earth's center.
However, so is their space capsule...

They're both free-falling back to the Earth with a tangential velocity that prevents them from ever actually reaching the earth.

 

[Topher925]

In a nutshell: Force of gravity = Centrifugal Force from spinning around the earth