Module 2 Activity: Part 1

Apparent Diurnal Motion: Northern vs. Southern Hemisphere

Here in Part 1 of the Module 2 Activity, you'll start to become familiar with what the sky looks like as a result of the Earth's rotation - we call this the apparent diurnal motion of the sky.

To start with, you'll work with this sky simulator, which shows the sky as seen from Lick Observatory, California, near where De Anza College is located. (Note that California is in the Earth's northern hemisphere.) Instructions for what to do are directly below the simulator.

Instructions: Put your mouse cursor over the picture of the sky and do these two things:

1. Change your direction of view: Use your left mouse button to drag the sky to the left and right. Practice looking towards the South (S), East (E), North (N), and West (W).
2. Speed up time and stop it again: Press the "L" key several times to speed up the flow of time. Press "K" to freeze time. Practice making time flow fast enough for you to see the stars seeming to move, then stopping, then starting again. (I find that if from a stop, it works well if I press "L" about 7 or 8 times to get a good, fast time flow.)

Now that you've gotten used to doing these two things, answer Question 1.

Having answered Question 1, let's go to the Earth's southern hemisphere. Here's a map of the sky as seen from a point in the Pacific Ocean, about 4700 miles south of California. We've gone directly south from Lick Observatory, into the southern hemisphere.

Now answer Question 2.

Okay, now we've seen the sky from the Earth's northern hemisphere, and from its southern hemisphere. Here's your next challenge:

What if someone took one of your friends, blindfolded them, flew them around in an airplane for many hours, and then dropped them off somewhere under a clear, starry sky, with a phone so they could call you?

Your challenge: How would you help your friend figure out which hemisphere they're in?

Let's assume they have 88 charts with them, showing what each of the 88 constellations looks like. (Here's an example. If you want to see a full set, here they are...scroll down on that page for the charts.) That way, you don't have to try and describe what Orion or Leo (or whatever) looks like.

Write your answer in the text box for Question 3.

Here are some tips to get full points:

When you scroll back up, to look at the sky maps again, consider making the sky (in each map) appear to rotate until it's gone through a full cycle. You wouldn't want to miss anything that's below the horizon.

Talking about which constellations are visible is helpful, but it's a good idea to be more specific: What about how a constellation appears to move? What about where certain constellations appear in the sky?

The best answers will attack the problem in multiple ways, not just by saying "Can you see such-and-such constellation?" There are many ways to write a good answer!