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A100 -- Dan Swearingen
Homework 1 -- Due by the beginning of class on Tuesday September 10:

Part 1. E-mail a message to me. This is to demonstrate that you have an email account and know how to use email. The email must come from your own account, not a friend's.

If, and only if, you are a Continuing Education student: you may satisfy this assignment by writing a complete description (one you could give your grandparents and they would be able to use it as an instruction manual) of how an IU student gets an account and uses E-mail.

(2 points) I had to recieve your email message by class time on September 10.

Part 2. From the text:

(1 point) Page 14 Questions For Review 2: What force holds the different astronomical systems described in this section together?

Gravity keeps the crust of the Earth, where we live, attached to the planet. Gravity keeps the planets, comets, and asteroids of the solar system bound in orbit around the Sun. Gravity keeps the Sun in orbit around the center of the Milky Way. Gravity keeps the Local Group of galaxies together.

(1 point) Page 14 Questions For Review 3: About how much bigger in radius is the Sun than the Earth?

(1 point) Page 14 Questions For Review 5: How big is an astronomical unit?

The Astronomical Unit (or AU) is defined as the average distance between the Earth and the Sun. This has been measured to be about 93 million miles or 150 million kilometers.

(1 point) Page 14 Questions For Review 6: How is the light-year defined?

The light year (or ly) is defined as the distance light travels in one year. So if light travels 3 x 105 kilometers each second then light can travel about 10 trillion kilometers in a year. Therefore a light year is about 1012 kilometers.

(9 + 9 points) Page 14 Thought Questions and Problems 4: Imagine building a model of the Solar System on your campus. Work out the diameter and spacings of the planets in millimeters and meters, respectively (use 1 AU = 1 meter as a scale).

For the planets this means that they are one meter from our model Sun for every AU they are from the real Sun:

AU Meters Feet from sun
Sun 0 0 0
Mercury 0.4 0.4 1
Venus 0.7 0.7 2
Earth 1 1 3
Mars 1.5 1.5 5
Jupiter 5 5 16
Saturn 10 10 33
Uranus 20 20 66
Neptune 30 30 98
Pluto 40 40 131

For the sizes of the planets we must first calculate how much smaller the model solar system is than the real solar system.

This gives us:

R in km R in Model (km) R in mm
Sun 700,000 4.67E-06 5
Mercury 2,439 1.63E-08 0.02
Venus 6,051 4.03E-08 0.04
Earth 6,378 4.25E-08 0.04
Mars 3,397 2.26E-08 0.02
Jupiter 71,492 4.77E-07 0.5
Saturn 60,268 4.02E-07 0.4
Uranus 25,559 1.70E-07 0.2
Neptune 24,764 1.65E-07 0.2
Pluto 1,123 7.49E-09 0.01

The point here is that on this scale where we have pluto 130 feet from the Sun, all the planets are too small to draw except for the gas giants (which are dots!).

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