There Are Times Gravity Can Lighten Your Load
Posted on: Tuesday, 7 March 2006, 12:00 CST
By Walter itschey
The force of gravity, like the oxygen in the air, is easy to ignore. Gravity is the force that draws objects with mass together.
We think of gravity as the force that draws us toward the ground. It keeps us from flying off the Earth - and it makes all of us, whether at the North Pole, the South Pole or Richmond, feel like we are standing right side up.
Any two things with mass will tend to pull toward each other. The bigger their mass, the harder the pull. The farther apart they
are, the less the pull.
Our Earth and moon have a gravitational attraction for each other. This holds the two embraced in a revolving dance. The gravity acts on the oceans.
The Earth's gravity keeps the water in our oceans from flying off into space. The gravity of the moon has a different effect. It attracts ocean water toward it, producing a bulge in oceans that we call high tide.
The moon's gravity also pulls the Earth's rocks slightly out of shape, but the effect is much less noticeable than the tides.
The sun and the Earth have a gravitational attraction for each other, and that pull keeps the Earth in orbit around the sun. There is also a tidal effect on the oceans from the sun's mass, but it is much smaller than the tides the moon causes. This is because the sun, though larger, is much farther away.
And what about the gravity diet?
We go to the Dead Sea - the lowest spot on Earth - and weigh ourselves. If we then go to a higher elevation - a point farther from the center of the Earth - we will weigh less. If we traveled to the top of Mount Everest, we would weigh about one-half percent less.
We can do the same between Richmond and the top of Afton Mountain, but our weight loss will be much smaller.
Virginia's science Standards of Learning deal with gravity and tides in 3.8, 6.8, ES-4, and ES-11.
Walter Witschey is director of the Science Museum of Virginia.
MEMO: SCI-KIDS
Source: Richmond Times - Dispatch
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