# Surface of the Earth

1. Jan 7, 2005

### PhysKid24

Hi, I'm just confused about what is meant when physics talks about the surace of the earth and gravitational acceleration being constant near the surface of the earth. Are we considered to be on the surface of the earth, or is the surface corresponding to the spherical surface of the earth? And if I go higher into the atmosphere, doesn't the gravitational acceleration decrease because of wind forces present. Sorry, it's just been confusing me for a bit. Thanks.

2. Jan 7, 2005

### HallsofIvy

Staff Emeritus
Generally "surface of the earth" is taken to be sea level. Of course, even that varies slightly but is close enough to a sphere that the difference is negligible in most calculations.

Yes, the gravitational acceleration decreases as you go higher but that's because gravitational force (and so acceleration) varies inversely as the distance from the center of the earth. Wind forces are irrelevant to gravitational acceleration but might effect net acceleration.