The paths which the earth follows around the sun

Since he knew that the pendulum could not change its motion, he concluded that the Earth, underneath the pendulum was moving. An observer in space will see that Earth requires 23 hours, 56 minutes, and 4 seconds to make one complete rotation on its axis.

But because Earth moves around the Sun at the same time that it is rotating, the planet must turn just a little bit more to reach the same place relative to the Sun. Hence the length of a day on Earth is actually 24 hours. At the equator, the Earth rotates at a speed of about 1, km per hour, but at the poles the movement speed is nearly nothing. For Earth to make one complete revolution around the Sun takes This amount of time is the definition of one year.

At the top of each chart is an arrow pointing toward the North celestial pole. Finally, the three small crosses on each chart show the positions of Jupiter and Saturn during the first three classes of this semester. Your assignment is to plot Jupiter and Saturn on these charts every time we observe. This should be pretty routine after a few weeks, and a reasonably complete set of plotted positions will nicely show the tracks of both planets as they end their retrograde phases and resume normal West to East motion along the ecliptic.

Here's how to plot planetary positions:. The point of this exercise is to track the planets over the entire semester as they switch back from retrograde to normal motion. Don't worry if we miss a few observations due to bad weather; we can just pick up again when the weather improves. If you want, you can make additional observations whenever you have the chance.

For example, if we miss an observation due to bad weather on Tuesday, you can go out the next clear night and fill in the gap of course, always write the current date next to your mark.

This report is due on May 6th the last class of the semester ; if the weather is good that night, we won't collect the reports until you've had a chance to make one final observation. Your report should include, in order,. In more detail, here are several things you should be sure to do in your lab report:.

These charts show If printed at a resolution of dpi, the GIF images have an scale of 2 cm per degree; the Postscript plots should automatically print at this scale. The faintest stars shown are magnitude 8. Paths of the Planets This Fall we will be able to observe just one bright planets. T he reasons for this yearly variation in the apparent motion of the Sun are twofold. The first reason has to do with the fact that the Earth's orbit is not a perfect circle, but is elliptical with the Sun being nearer one end of the ellipse.

The speed of the Earth in this elliptical orbit varies from a minimum at the farthest distance to a maximum at the closest distance of the Earth to the Sun. The second reason for the yearly variation has to do with the fact that the Earth's equator is inclined to the plane of the Earth's orbit around the Sun.

These two effects are explained in the following paragraphs. Elliptical Orbit. While the Earth is rotating upon its axis, it is also moving around the Sun in the same sense, or direction, as its rotation.