^{Danny Kane, age 13, of Red Bud, I11., for his question:}

^{WHAT IS GRAVITY?}

^{Sir Isaac Newton, the story goes, was lying on the grass under an apple tree and he saw an apple drop near him. "Why did the apple come down and not go up?'' it is said that he asked himself.}

^{Newton's investigations led to his famous law of motion}

^{that proved that the paths of the planets and moon in their orbits could be. explained by some invisible force of gravity. In 1672 or 1687  historians aren't sure which year—Sir Isaac Newton came up with a statement called Newton's Law of Universal Gravitation. He stated that the same force that kept the planets in their orbits also made objects fall to the ground. He added that this attraction exists between any two masses regardless of their position. The attraction occurs to both masses equally because the first mass attracts the second mass with the same force as the second attracts the first.}

^{In other words, gravity is the force of attraction by which an object tends to fall toward the center of the earth.}

^{The force of gravity which earth exerts on a body is called weight. Because the surface of the earth is farther from the center at the equator,. the force exerted on a body is smaller and weighs less there than at the poles. A 180 pound man would weigh one pound less at the poles than he does at the equator.}

^{Gravity's pull is stronger at low altitudes than it is higher up. If you weigh 100 pounds at sea level, your weight four miles up would be only 99.8 pounds. Although this weight difference isn't much, it shows scientists the power of gravitational pull.}

^{You can also see the action of gravitational attraction by the tides in lakes and oceans. They are caused by the attraction of the sun and moon acting.on the earth.}

^{Gravity also pulls on air as it pulls on water and solid objects. It keeps air near the earth and gives us an atmosphere. It draws heavier cold air down from the mountains into the valleys and thus is one of the things that causes the movements of air or winds.}

^{The pull of the earth's gravity squeezes the atmosphere into all the hollows on the earth's surface. If you open a can or bottle, air immediately is drawn in by gravity.}

^{Air also rushes into our lungs when we breathe in. Gravity plays a most important part in our breathing procedure.}