Let's start with something that I find fascinating:
The ecliptic.
In astronomy, the ecliptic is basically the line that the Earth follows around the sun. Roughly every 365 days the earth goes once around the sun and returns to about the same position it was in a year ago.
Now, the planets also orbit the sun just like Earth does. Each planet has a different mass and is at a different distance from the sun so logically each one shoots around the sun at a different rate. The smaller and closer it is, the faster it goes. The bigger and further it is, the slower it goes.
Okay, so far so good, right?
What I find fascinating is the fact that all of the planets in our solar system follow the same line around the sun. Why, with all the space in, well, space, do the planets all go the same way? This is an interesting question in Astrology also, because the ecliptic equates to the zodiac.
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| Here we can see four planets in the night sky. Notice the line that they are in? That's the ecliptic! |
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| An example of the plane of the ecliptic. The sun, the moon and all the planets follow this visible path through our sky. |
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| Here you can see the differences in the orbit rates of each of the smaller planets. |
The zodiac is nothing more than the group of constellations that the planets and moon and sun follow through the sky. With all those different, relatively unrelated objects zooming around up there, why would they all just spin around the same way? There are so many constellations in the sky: Pegasus, Triangulum, Orion, Ursa Major, etc. Why don't the planets ever move through them?
The answer to that is something that I found out only recently when I read Stephen Hawking's A Brief History of Time. He says that our entire solar system was once part of a single star! The sun, the moon, the earth and all the planets in our solar system once made up the core of a very large star that eventually exploded. The hydrogen core moved back together to form our sun and the other elements continued outward to form the planets and moons and things within our solar system. The force of that initial explosion set the stage for the ecliptic.
To me, it's amazing to think that in some way, I was once part of a star! Pretty cool, huh?
