Frontiers of Space, Time, and Thought by Edward M. Lerner

Author:Edward M. Lerner
Language: eng
Format: epub
Tags: science fiction, aliens, ufos, time travel, ai, nanotech, ftl, gaming, quantum mechanics, science essays, rfids
Publisher: ReAnimus Press

Meteoroids and asteroids and comets (oh, my)

What might smack into Earth?

Many more things than planets (however defined—I won’t go there) whiz about the solar system. We call these sub-planetary objects:

• meteoroids, if boulder-sized or smaller (and meteorites if they survive reentry and reach the Earth’s surface), or

• asteroids, or,

• comets, if they exhibit a coma (gaseous envelope).

Meteoroids, by definition, are too small to endanger many people or any significant area. Only size distinguishes asteroids from meteoroids.

Asteroids mostly orbit between Mars and Jupiter, in the too inclusively named Asteroid Belt, at a distance from the sun of between about two and four astronomical units. (One astronomical unit, or AU, equals the mean distance between the Earth and the sun: about 93 million miles or 150 million kilometers.) Of course if all asteroids orbited in that belt, this would be a short article. And maybe dinosaurs would still rule the Earth.

The threat to Earth comes from Near Earth Objects (NEO). How near? The current standard is approaching within 1.3 AU of the sun. Stated another way, a NEO is anything that comes within 28 million miles of Earth’s orbit.

Astronomers distinguish several populations of near-Earth asteroids. Generally speaking:

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.