Does the value of 'g' vary, as we move on the surface of earth?

What will happen to the value of 'g' as we go above the surface of earth?

Is the value of 'g' same everywhere on the surface of earth?

What will happen to the value of 'g' as we go below the surface of the earth?

What is the value of 'g' at a height near the surface of earth?

If g_e and g_p denote the acceleration due to gravity on the surface of earth and another planet whose mass and radius are twice that of earth, then the ratio (g_p)/(g_e) is