PHYS 120 – Assignment 1 Name Average Grade (9.1/10)

We are going to begin this course with a description of the scientific method and then a quick historical review of the Astate of the universe@ from the perspective of intelligent and educated observers starting with the Greeks a few hundred years before the current period, 200 BC or so.

The information that people had about the nature of the “universe” centuries ago was so different than our current view, that it is difficult for us, in the twenty-first century, to put ourselves into the Aproper@ frame of mind to understand the evolution of Astate of the universe@ through time.

As a first step, I would like you to answer the following questions based primarily on information that you have garnered by being an alert, curious person for the last twenty or so years.

1. How big is earth? (What is it=s radius, diameter, or circumference?)

Radius is about 4000 miles and the circumference is about 25,000 miles.

2. What is the distance between earth and sun? Earth and moon?

Earth to sun is 93,000,000 miles and earth to moon is 239,000 miles

3. Describe the relationship between earth, moon, and sun. That is how do they move with respect to one another?

The sun is the local mass that acts as the center of the solar system. Earth orbits the sun once a year and spins around its own axis once a day. The moon orbits earth.

4. What is the Milky Way? What is the relationship between the earth, sun, and moon and the Milky Way?

The Milky Way is the galaxy that houses the solar system. The sun orbits the center of the Milky Way and is about 2/3 of the way out from the center. Of course earth, moon, and all the other planets are carried along by the sun.

5. What is the relationship of the Milky Way to the Auniverse@ as a whole?

The Milky way is one of about 100 billion galaxies (10¹¹ galaxies) and each galaxy has about 100 billion stars!

This last question takes much more imagination. Suppose you were a human living 20,000 years ago as part of a clan that maintained a long oral history of the Astate of the universe@ based on observations of the sun, moon, planets, and stars. For the sake of argument, suppose this group was also involved in rudimentary agriculture. At this time in human history, people=s lives were governed by sunrise and sunset and the only late night viewing was of the heavens above. So it is likely that their practical knowledge of the night sky was much more refined than most of us living now.

6. What sorts of regularities in the “motion” of the stars, moon, planets, and sun would this group have immortalized in their oral history?

The summer and winter solstice (longest day and shortest day) along the equinoxes in fall and spring (days with equal amounts of day and night) would have been important for the development of agriculture. The day (sunrise to sunrise), the month (full moon to full moon) and year (summer solstice to summer solstice) are the obvious time periods connected to the motion of earth, moon, and sun.