Both of these words are made out of Greek and Latin root words, which is one of my favorite aspects of scientific language because it allows you to understand many more words than just the ones you're defining.
"Heliocentric" is a compound of the roots "helio" or "helios" and "centric." Helio refers to the sun, and centric just means "in the center" or "focused upon. In contrast, geocentric uses the root word "geo," which means earth or ground, in the same way that geology or geography use it.
Typically these root word compounds can seem a little awkward if you take their definitions literally, so you have to be slightly liberal in how you interpret them. Heliocentric, in astronomical terms, means moving primarily around the sun, and geocentric means moving primarily around the earth.
This is a little easier to understand through examples. All of the planets exhibit heliocentric motion, and not geocentric motion; the only thing at the "center" of their orbits is the sun. In contrast, our moon and most of our artificial satellites exhibit geocentric motion because their motion can most accurately be described as an orbit around the earth, even though they're also moving around the sun. Likewise, the moons of other planets could be described as having geocentric motion around their respective "earths," or you could be more descriptive by using the roots that are more appropriate for those specific planets. For example, the root word referring to Jupiter is jov or jovi, so an orbit focused on Jupiter would be jovicentric.
No comments:
Post a Comment