Its always interesting how things that dominate our life can often be overlooked, misunderstood or taken for granted. Gravity is one of these. The nature of gravity is to this day still being decoded and it was not until the day so Newton that is nature could be expressed mathematically. On that note we will consider a little about gravity now.
First interesting facts:
At an altitude of 100km which is the edge the atmosphere the force of gravity is only decreased by 3%.
If the sun where instantly turned into an infinitely small black hole and its mass didn’t change the earths orbit would not change.
If one weighs in at 150lbs and is sitting from another person of approximately the same weight the force of gravity would cause an attraction between the two individuals that equates to about the weight of a flea.
Pounds are a measurement of weight; Kilograms are a measurement of mass. So if one weighed 150 pounds on earth they would weigh approximately 63 pounds on the moon, but if they weighed 75 kilograms on earth they would also weigh 75 kilograms on the moon.
Astronauts are not weightless in space. An astronauts weighing 150 pounds on the surface of earth would weigh only 8lbs less in orbit at 200kilometers, they would not be weightless despite appearing to float around.
A satellite in low earth orbit (LEO) or a few hundred miles above the earth must travel at a pace of 8 km/s to maintain its altitude. At this speed it takes only 1.5 hours to orbit the earth.
Oil companies use gravity to search for Oil. How so? Oil is less dense then rock. Because of this when one is standing above an oil field they actually weigh less then on typical land since the material below them is less dense and exerts less of a gravitational force. Companies have exploited this fact and measured the discrepancy in gravitational pull over large areas of the planet, there by creating gravitational maps in an attempt to find fields of oil in areas of less gravity.
Examples of these maps can be seen here:
More later on Gravity and acceleration.