Anatomy of Earth Help (page 2)

Anatomy of Earth

The Earth has a slightly larger diameter at the equator than at the poles. This oblateness , or flattening, is caused by the rotation of the planet. The effect is too small to be visually apparent as the planet is seen from space; the outer planets, especially Jupiter and Saturn, are much more oblate than is the Earth and actually look that way. The Earth’s diameter is 12,756 km (7,926 mi) in the plane of the equator and 12,714 km (7,900 mi) as measured along the rotational axis from pole to pole.

The Power Of Time

Time is one of the most powerful forces in the Cosmos. The Earth-dwelling two-legged creatures who call themselves Homo sapiens have not developed a mature concept of this power and how it can be harnessed. If they had a better understanding of time and how things happen in the long term—millions upon millions of their years—many of the mysteries that befuddle them would become clear and simple in their minds.

Suppose it were possible to look at time so that a year seemed to pass in a fraction of a second? How would Earth look when beheld from such a perspective? The precession of the axis would be apparent; Earth would look like a furiously spinning top. The continents would drift around like ice floes on an Arctic lake during the springtime thaw. In some places large chunks of land would break away from continents. In other places islands would bump into continents and join up with them. Crumpling of the crust, caused by the drifting of land masses, would create mountain ranges. The Hawaiian Islands would drift toward the northwest, eroding down into the ocean at the northwestern end and being born anew in continuous volcanic eruptions at the southeastern end. The sea level would rise and fall periodically; glaciers would advance and retreat. The Earth, which seems like a stable place on a day-to-day scale, would be revealed as dynamic, fluid orb. One might be tempted to suppose that Earth has a life of its own, that it is a gigantic biological cell. An idea of this sort has been posed by some respected Earth scientists. It is called the Gaia hypothesis . However, this notion has not been proven true, and many academics have dismissed it as unscientific.

Given sufficient time, rivers cut canyons hundreds of meters deep. One of the best-known examples is the Grand Canyon in the southwestern United States. It is hard to imagine, on an hour-by-hour or day-by-day scale, how the little Colorado River could have gouged out such a ravine, but time is patient beyond all human understanding. Time has unlimited endurance. It works day and night; it never rests. It carves and chips and grinds, builds new structures atom by atom or cell by cell, and keeps on doing its work for human lifetime after human lifetime, generation after generation, age after age. Time has been at work on Earth for more than 4 billion human-defined years and will continue to mold and change the planet for at least that many years yet to come.