Physics PHYS 102
General Astronomy

Problem Set #1

After you finish this problem set, you should be familiar with:

 angular measurements rotation of the Earth scientific notation revolution of the Earth light years seasons parsecs sidereal time astronomical units calendars metric system precession celestial sphere latitude constellations longitude

1.       When Voyager 2 sent back pictures of Neptune during its historic flyby of that planet in 1989, the spacecraft’s radio signals traveled for four hours to reach the Earth.

a.       How far away was the spacecraft? Remember, radio waves are a form of electromagnetic radiation, just like visible light, and therefore travel at the same speed as visible light, $d=v&space;\cdot&space;t$

b.      Express this distance in centimeters using scientific (powers-of-ten) notation.

c.       In "Star Trek, the Motion Picture", Voyager 6 collided with an alien probe and had its programming altered. This altered spacecraft, which was encountered in deep space by the crew of the U.S.S. Enterprise, changed its course and returned to Earth. In the movie, the altered Voyager traveled from the orbit of Neptune to the orbit of Earth in approximately 5 minutes. How fast was the probe traveling? Is this speed possible according to our current understanding of physics?

2.       Explain why constellations are useful to astronomers.

3.       What is the celestial sphere, and why is it useful?

4.       What is the ecliptic, and why is it tilted with respect to the celestial equator?

5.       At what places on earth is Polaris seen on the horizon?  Explain why.

6.       Start up the Java Planetarium at http://www.skyviewcafe.com/skyview.php . You may get a message like “Java needs your permission to run.” If so, give it permission. You may also be asked to update or install the Java Runtime Environment at http://java.com/en/download/index.jsp.

Now you should see something like the screen shot at right.  Click on the "Find" button under location, and type in the area code for Houghton, 14744.  This will set your location and should show you the sky as it would look right now from Houghton. You may want to check the "constellation" box, and show the names of the right stars and planets.  You might also want to make sure “sky color” is set to black.

a.          Highlight the ten-minute position of the time in the upper left hand corner.

b.         Now, by using the up and down arrow keys on your computer you can make time move forward or backward in tem minute increments. Describe the motion of the stars. Can you explain why are they moving this way?

c.          Now highlight the day position, and use the up and down arrow keys to show the sky as it is each day at the same time. How are the stars moving? Why are they moving this way?

d.         Change the latitude to 90° N and answer the same questions.Change the latitude to 0° and answer the same questions.

7.       What causes precession of the equinoxes? How long does it take the vernal equinox to move one degree along the ecliptic?

8.       Using a diagram, explain why the tilt of the Earth's axis relative to the Earth's orbit causes the seasons as we orbit the Sun.

9.       Since God created the Universe, shouldn't its observable characteristics reveal information about the nature of God and his creation? Some people say that the Bible reveals the great "Whys" of the Universe, whereas the sciences, to some extent, reveal the "Hows". Do you agree or disagree with this statement?  Explain why/why not.

Here are some hard practice "figure it out rather than memorize" type questions.  They will not be graded as part of the homework (so don't turn them in), but they may be useful as you prepare for the test.  More questions like these can be found in the test practice folder at the library.

1.   When do you expect to observe the north celestial pole near the zodiac?
1.   During the winter solstice
2.   During the summer solstice
3.   During the equinoxes
4.   Not in the foreseeable future.

1.   What would be the position and motion of the Sun on December 21st from the South Pole on Antarctica?
1.   It would pass across the sky from the horizon at midnight to reach an angle of 23.5° above the horizon at midday and then return to the horizon.
2.   It would move completely around the sky in 24 hours while maintaining an angle of 23.5° above the horizon.
3.   It would rise in the east at 6 A.M. and set in the west at 6 P.M., reaching 47° above the horizon at midday.
4.   It would remain below the horizon for the whole 24 hours.

1.   An observer on the equator, in a period of one year, would be able to see what fraction of the overall sky?
1.   a variable amount, depending upon which year
2.  50%
3.   100%
4.   a variable amount, depending upon the person's longitude