... Also introduces systems of time-keeping, e.g. local solar time, time zones, universal time and the international date line. ... This lesson plan supplements: "Latitude and Longitude," section #5: on disk Slatlong.htm , on the web . ... Declination is measured from the north pole, not from the equator (the way co-latitude is defined) . ... In this case, it is the line of latitude 49 degrees. ... How long is one minute of arc along a line from the pole to the equator (line of longitude)? . ...

... Concerning those theories, Tycho believed that all planets revolved around the Sun, but the Sun circled Earth. ... That was when he published his first two laws of planetary motion: . ... Kepler's 3rd Law . ... Earth . ... Not only were Kepler's laws confirmed and explained by later scientists, but they apply to any orbital system of two bodies--even artificial satellites in orbit around the Earth. ... By Kepler's formula . ... More will be said about Kepler's first two laws in the next two sections...

Comet Shoemaker-Levy 9 was discovered photographically by the husband and wife scientific team of Carolyn S. and Eugene M. Shoemaker and David H. Levy on March 24, 1993, using the 0.46-m (18-in.) ... Its discovery was a serendipitous product of their continuing search for near-Earth objects , and the 9 indicates that it was the ninth short-period comet (period less than 200 years) discovered by this team. ... In other words, the comet, or at least parts of it, could very well hit Jupiter. ...