text: what is the easiest way to calculate gravity pressure on the surface of the earth mass.? without using general relativity? i don't know if any of the below will help you, but here goes nothing:  "&#92;item{&#92;itemc.} gravitation acceleration near the surface of the earth.           the force of gravity near the surface of the earth on any small           object of mass $m$ is           $$  f= {gm_{&#92;oplus}m&#92;over r_{&#92;oplus}^{2}}    &#92;,&#92;, ,  &#92;eqno(&#92;eqn)$$           where $m_{&#92;oplus}$ is the earth's mass and            $r_{&#92;oplus}$ is the earth's radius.           the acceleration effect of this force on the small object can be           learnt from substituting from $f=ma$:           $$  ma={gm_{&#92;oplus}m&#92;over r_{&#92;oplus}^{2}}    &#92;eqno(&#92;eqn)$$           or           $$  a={gm_{&#92;oplus}&#92;over r_{&#92;oplus}^{2}}&#92;approx 9.8&#92;,{m&#92;,s^{-2}}                                                        &#92;,&#92;,  .  &#92;eqno(&#92;eqn)$$           thus, the acceleration of a body due to gravity alone near the           earth's surface is independent of the body's mass.           because of its great utility this acceleration is given a special           name $g$.           and in rocketry, one often measures accelerations in units of           $g$.           equation~(&#92;showeqn -0) is result that is famously evidenced by            galileo's           dropping of different mass balls from the leaning tower of pisa           circa 1590.           the dropped balls start from rest and have the same acceleration           all the way and reach the ground virtually simultaneously            it seems to be a myth that these demonstrations are myth (fa57).           they were probably demonstrations for students rather than formal           experiments.           in aristotelian physics, more massive objects reached the ground           first, but there was no quantitative mathematical rule describing           their motion."