This Friday, I will begin my Friday visits of Allegany County elementary schools with a portable planetarium.

The planetarium system that belongs to the board of education is called Star Lab. This will be my 31st year of doing Star Lab presentations, having started in 1981.

I use two projection cylinders, one for the night sky and the other showing the major features of Earth’s surface. Last year, I started using the Earth cylinder; I hope to break up my fall 2012 presentations in half, one of the night sky and the other on the Earth’s surface.

I have prepared a one page file called “Key Earth Facts,” which can be downloaded from the teacher’s resource area of //www.frostburg.edu/planetarium .

Using this file, here are some questions about our planet. Near the bottom of this column, I will reveal the correct answers. I hope you find these questions interesting and useful; you are welcome to try them on your friends.

1. How far does the Earth travel around the sun each day? Of course, we make one complete orbit each year. Knowing the Earth-sun distance and the number of days in a year is essential. Is this daily distance: A)25,000 miles? B)238,000 miles? or C) 1.6 million miles?

2. How fast does the Earth rotate in our area in miles/hour? Knowing the circumference of the Earth, the time it takes the Earth to rotate and allowing for our latitude are all needed. Is our rotation speed? A) about 600 mph? B) about 800 mph?  C) about 1024 mph.

There are four major oceans. Here are the oceans in alphabetical order:  Arctic, Atlantic, Indian and Pacific.

3. Arrange the oceans with the largest first, the next largest second, and so on.

4. What ocean covers more area than all seven continents combined?

There are seven continents: In alphabetic order the continents are: Africa, Antarctica, Asia, Australia, Europe, North America and South America.

5. Which two continents have had rock bands named after them? (Hint: You have to go back to the 1980s.)

6. In which continent do over 60 percent of humans dwell?

7. Which continent has the lowest population density? Population density is the number of people per square mile.

(Antarctica doesn’t count as it has no permanent residents, just visiting scientists.)

8. After China, India and the United States, what is the fourth most populous country in the world?

9. Which major country has two of the six most populous urban areas in the world?

10. In North and South America, which are the two most populous urban areas? (Hint: People of these two urban areas tend not to speak in English.)

  Here are the answers to above questions:

1. The Earth’s average distance from the sun is 93 million miles. The circumference of the Earth’s orbit (being nearly circular) is about 584 million miles. 584 million miles/365.25 days = 1.6 million miles/day. Answer C)

2. The Earth rotates every 23 hours and 56 minutes or 23.93 hours. The Earth’s circumference = 25,000 miles.

  We are about 40 degrees latitude north so our rotation speed is about Cos(40 degrees) = 0.766 as fast as at the equator. This yields a local rotation speed of 798 miles per hour. Answer B)

3. The size order of the 4 oceans are: Pacific (largest), Atlantic, Indian and Arctic (smallest).

4. The Pacific Ocean covers an area of 64 million square miles. The 7 continents cover an area of 57.3 million sq. mi.

5. The two continents that have had rock bands named after them are Asia and Europe.

6. 60 percent of humans (now over 7 billion) dwell in Asia, which has 30 percent of the land area. Answer = Asia

7. Which continent has the lowest population density? Australia with a population 21.8 million (0.3 percent of humans) has an area of 3.036 million square miles (5.3 percent of world’s land). Australia is considered to be both a continent and an island.

8. After China, India and the United States, the fourth most populous country in the world is Indonesia.

9. India has the second most populous urban area (Delhi, India with over 24 million people) and the fourth most populous urban area (Mumbai, formerly Bombay with 21.8 million people).

10. The two most populous America urban areas are Sao Paulo, Brazil with 21.3 million people and Mexico City, Mexico with 20.5 million people.

SKY SIGHTS THIS WEEK Last month’s moon (full on Aug. 31) is still prominent in the late evening sky.

On Sept. 6, the moon will appear close to the Seven Sisters star cluster in the late evening northeastern sky.

On the morning of (Sept. 8), the moon will appear close to the planet Jupiter in the southern dawn sky. The moon’s phase is then half full with the curved side facing to the left.

Bob Doyle invites any readers comments and questions. E-mail him at rdoyle@frostburg.edu . He is available as a speaker on his column topics.