Why is gravitational potential negative?

Question

anonymous · Answer

Because it is always calculated from a height above the ground level. And, acceleration due to gravity(g) is taken negative in upward direction.
So, according to formula, 
    U = Mgh, where "g" is negative

sk8teroy · Answer

Why is it calculated above the ground level?

anonymous · Answer

Because potential energy means the energy possessed by a body at a height from the ground level. So, height is a must condition for calculating Potential energy.

sk8teroy · Answer

Where is the ground level?

sk8teroy · Answer

If it's on the Earth, shouldn't the acceleration be taken as positive?

anonymous · Answer

i think it isn't negetive allways it's sign depped on your frame direction

anonymous · Answer

choose of ground level is arbitrary you can take that every where

anonymous · Answer

gravitation is calculated in negative direction as it is acting downwards and perpendicular to a body

anonymous · Answer

yes it's normal to mass but you can get downward positive

mani_jha · Answer

Aadarsh is not wrong, the reason why gravitational potential is negative is purely mathematical. Now, see according to newton, every mass particle creates a field around it, where it affects another mass particle if it is placed in it(i.e. exerts a force). 
The gravitational potential at a point around a mass is the work done to bring a unit mass substance from a random far enough point(infinity) to that point. This is potential at point x:
$$Potential(x)=W(\infty)-W(x)$$ 
Take $$x=\infty$$
$$Potential(\infty)=W(\infty)-W(\infty)=0$$
Thus potential at infinity is zero.
Thus $$Potential(x)=0-W(x)$$ =-W(x)
Thus gravitational potential is always negative.

anonymous · Answer

when we say gravitational potential energy is negative in the physical sense it means that a body having negative gravitational potential energy is BOUND to the earth we all have negative gravitational potential energy(it means we are attracted to the earth's surface and bound to it)
whenever we calculate escape velocity, we equate the final energy at infinity to be equal to 0 as all the negative part of gravitational potential energy has been made positive and that the body acquiring escape velocity is no longer BOUND to the earth and has 0 energy with respect to this regard