Day 3 Homework

I'm not sure if this is exactly what I'm supposed to do, but here it goes.

Day 3 Recap

We began by talking about extraterrestrial life in the universe. The original search for life was Europeans traveling the ocean and happening upon the new world. They brought war and disease, and set up exploitative institutions. This is rather frightening to compare to if Earth was vised by aliens. Would they wage war and enslave us? Would they carry bacteria and viruses that are nothing to them but create widespread devastation on earth?

In the 60's the US and Russia studied life outside earth. In 1975 Alan Boss and Stanton Peale started Theoretical Planetology, which became the study of life outside Earth. In 1993 Michel Mayor and Didier Queloz discovered the first extraterrestrial planet, and the Kepler spacecraft was sent to find more planets in 2009.

Chapter 2.1 was about patterns. There are 88 constellations, which are human conventions to region and map the sky. An object in the sky is referred to by altitude and direction. Altitude is 0deg at the horizon and straight up is 90deg. Direction is the cardinal directions, so an object may be referred to as “60deg SE.” The meridian is north and south straight through Earth.

We measure the sky using angles. A stretched hand is 20deg, a fist is 10deg and one finger is 1deg. The sun and moon both measure 1/2deg. A circle is 360deg, 1deg is 60 arc-minutes, 1 arc-minute is 60 arc-seconds 1Deg is 3600 arc-seconds Angular size=physical size*360deg/ 2pi*distance.

The Earth rotates, so the stars rise and set east to west. The constellations visible depend on your latitude and the season. Latitude determines the slice you can see and the season varies with the tilt of the earth's axis.

Chapter 2.2 Was about the seasons. The Earth's tilted axis causes the seasons. The Sun's position is higher in the summer and lower in the winter, this affects the directness or flux of incoming sunlight and heat. The earth's distance from the sun varies only 3% and is overwhelmed by the effect of axis tilt. There are summer and winter solstices and spring and fall equinoxes. The solstices mark the farthest extremes, when we get the most or least direct sunlight and when the days are longest or shortest. The equinoxes mark the middle points when the day and night are of equal length. The axis of the earth processes every 26,000 years like the wobbling of a top.

Chapter 2.3 was about the moon. The lunar phases are part of the moon;s 27.3 day orbit around earth. The phases are caused by out view of the moon's reflecting sunlight, not shadows cast upon the moon. The moon has a synchronous orbit, only one side of it is visible from earth.

When the earth blocks the sun from the moon it is a lunar eclipse. It must be a full moon and there are two periods per year. When the moon blocks the sun from the earth it is a solar eclipse. It must be a new moon and follows 18 year and 11.3 day soros cycles.

Chapter 2.4 was about the ancient mysteries of the sky. We only covered retrograde orbit which is best described by a diagram. A planet appears to stop in the sky, reverse, reverse again to its original direction, and continue on its way. This is because the earth “catches up” with the other planet's orbit and overtakes it.