RANDY L. PHELPS
This is the "How Big,
How Far?" Module
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Procedure
1. For this module, please look through the
"lecture" notes for "How Big, How Far?".
These notes contain the material, in condensed form, that I will expect you to become
familiar with. I am sure you will have questions about the material, especially
since it is presented in the form of lecture notes. To help you fill in the blanks,
I have added web links that you can follow, in order to gain further insight into the
material.
2. Additionally, you should complete the
following exercises to help you understand the material, and reinforce the concepts:
Exercise 1: Aristarchus and the Scale of the
Solar System
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Upon completing
this and previous assignments, you should be comfortable with the following material:
- The calibration of the astronomical unit
- The relationship between intrinsic size, angular
size and distance
- Determining an object's mass
- Determining an object's density
- Determining an object's surface gravity
- Determining the escape velocity from an object
Upon completing
this and previous assignments, you should be able to answer these, and similar questions
General
Concepts
- What are the relative distances of the planets from the Sun, in
Astronomical Units?
- How many miles in an astronomical unit? How many kilometers?
- How far is the Moon from the Earth?
- How massive are the planets in the Solar System, compared to the Earth?
Applications
- Conceptually, how can one determine how many miles/km/etc. there are in
an Astronomical Unit?
- A radar beam, traveling at 186,000 miles/sec, is sent toward an asteroid.
The signal returns after 20 seconds. How far away is the asteroid in
miles? How far away is the asteroid compared to the Moon (note: this question
assumes a familiarity, however rough, of the distance from the Earth to the Moon).
- If two objects subtend the same angle on the sky, but object #1 is
intrinsically twice the diameter of object #2, what are the relative distances of the
objects?
- If two objects subtend the same angle on the sky, but object #1 is
intrinsically five times the diameter of object #2, what are the relative distances of the
objects?
- If two objects are intrinsically the same size, but object #1 subtends
and angle that is three times greater than object #2, what are the relative distances of
the objects?
- Describe, in sufficient detail, how the mass of the Sun can be estimated
using Newton's version of Kepler's 3rd Law.
- Describe, in sufficient detail, how the mass of Mars can be determined.
- Describe, in sufficient detail, how the mass of Venus can be determined.
- The planet Mercury has no moons orbiting it. Can the mass of
Mercury be determined, and if so, how?
- Two spherical objects have the same masses, and the same radii. How
do their densities compare?
- Two spherical objects have the same masses, but the radius of object #1
is three times greater than that for object #2. How do their densities compare?
- Two spherical objects have the same radii, but the mass of object #1 is
five times greater than that for object #2. How do their densities compare?
- Two spherical objects have the same masses, and the same radii. How
do their surface gravities compare?
- The surface gravity of the Moon is 1/6 that of the Earth. How much
would you weigh on the Moon?
- Two spherical objects have the same masses, and the same radii. How
do their escape velocities compare?
These questions, and similar ones, will form the basis of the exam
material for this section of the course. If you have problems with the material,
please see me. If you are unable to answer some of the questions, I will help
you before the date specified on the syllabus, provided you show me the results of your
inquiry into the material.
That is, you must provide me the answers you
we able to obtain for all questions, including your attempts at problem questions, before
I will help you with any of them!
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