The Wobbling Earth Earth not only spins, it wobbles. Today, the sun is in Pisces at the vernal equinox and in Taurus at the summer solstice.
Precession is caused by the constant pull of the sun and moon on the bulge of the Earth s equator.
It s a slow wobble, however, taking nearly 26,000 years to complete. Listed here are things that not everyone knows, but basics that every new astronomy student will eventually know, and will benefit from knowing now. Charon Physical Constants and Astronomical Data with a JavaScript calculator with all of the constants programmed into it. To get a sense of size in our galaxy, imagine the Sun to be the size of a dime. Then our closest star system, Alpha Centauri, would be about 325 miles away.