Cumberland-Times Sky Columns
June 2005

June 5 - Spotting Space Station
June 12 - Interplanetary Travel
June 19 - Good Space Books in Libraries
June 26 - Planets Mingle

June 5th - SPOTTING SPACE STATION

The International Space Station is now in a tight orbit about the Earth, about 220 miles altitude. Every month, the Space Station drops about 2 kilometers (1.24 miles) in altitude. The Space Station relies on the Space Shuttle to keep it at its intended altitude of 250 miles. The closer the Space Station is to the Earth, the faster its orbit shrinks. The Space Shuttle is tenatively scheduled to be launched in mid July, to elevate the Space Station into a higher orbit and provide supplies needed to continue station construction. By the time the Space Shuttle is terminated (2010), the Station should be finished.

To find when you can see the Space Station from our area, visit the website www.heavens-above.com . You have to specify your location. One option is to type in your home town and select the right state. (There are a number of Cumberlands across the U.S. ) Then select ISS (International Space Station) and you will be given a schedule of when the ISS can be seen locally over the next 10 days. It will be either in the dawn (before sunrise) or at dusk (after sunset). The Spapce Station looks like a bright star that noticeably creeps across the sky. If its maximum altitude is over 50 degrees, it will be very bright, rivalling any stars and most planets as it flies over. Typically, the ISS is in view for about 5 minutes from its first appearance to its disappearance (usually in the Earth's shadow). We can see the Space Station because the sunlight is reflecting off its solar panels.

June 12th - INTERPLANETARY TRAVEL

This summer I will be writing some columns about how to use ordinary math and a basic calculator to solve some interesting space problems. This is to provide some practice to both adults and students to keep their math skills sharp. So many students and adults make comments such as "Math is not my thing" or "I was never good at math" to avoid having to make even a modest effort. As a result many students and adults slowly lose their math skills (students during summer and adults for year after year). But space offers many interesting problems that can be solved in a number of minutes (not hours).

Nearly 400 years ago, a German scientist named Kepler discovered the relation between the average distance of a planet from the sun and the time for a planet to orbit the sun. Kepler found that the bigger the orbit, the longer it takes to orbit the sun. Kepler's finding was unique because he found a mathematical relation between the average distance from the sun and the planet's year. This can be stated with words as: if you cube the average distance from the sun, you get a number that tells you the orbital period squared. If one uses algebra, then each word or phrase has a letter. Kepler's Law is A cubed = P squared where A is the average solar distance in Earth-sun distance units and P is the orbital period in Earth years. For example, Mars has a distance that is 1.52 times from the sun as the Earth. Then 1.52 x 1.52 x 1.52 = 3.512 which is Mars' orbital period squared. By using the square root key (present on most calculators), one can find that the square root of 3.512 = 1.87. So Mars takes 1.87 Earth years, about 22.5 Earth months to orbit the sun.

But what does Kepler's Law have to do with interplanetary travel? The most energy efficient path from planet to planet is an elliptical path whose minimum distance is the orbit of one planet and the maximum distance is the other planet's orbit. Then the average solar distance of the flight path is the average solar distance of both planets. For instance for a trip to Mars from Earth, we first find the average distance of the two planets. This would be (1 (for Earth) and 1.52 (for Mars)) divided by 2. This operation yields an average distance of 1.26 x the Earth's distance from the sun. Then if we cube 1.26 (multiply 1.26 x 1.26 x 1.26), we get 2.0. The square root of 2 is 1.414. This is the time for a flight from the Earth to Mars and then back to Earth's orbit. Then the actual time to fly from Earth to Mars would half of 1.414 years or 0.707 years, or about 8.5 Earth months!

Another example would be a flight from the Earth to Pluto. As before Earth's distance is 1 unit while Pluto's average distance is 39.2 Earth units. Then the average distance of 20.1 Earth units. This number cubed is 8121, whose square root is 90.1 Earth years. Then the actual flight time from Earth to Pluto would be about 45 years.

For any other interplanetary flights, you need all the sun-planet distances. They are: 0.39 (Mercury), 0.72 (Venus), 1.0 (Earth), 1.52 (Mars), 5.2 (Jupiter), 9.58 (Saturn), 19.2 (Uranus), 30.0 (Neptune) and 39.2 (Pluto).

June 19th - Good Space Books in Libraries

Each month, I review one or two space books available in our local libraries in my column. During the summer, students have more time for reading and it's important to maintain or improve their reading comprehension. The books mentioned are also good for adult or senior novices.

A wonderful book filled with many activities (for both young and old) is "how the Universe Works", a Reader's Digest book by Heather Couper and Nigel Henbest. The Introduction gives photographs of the items used for activities, how to set up a home observatory and make your own telescope. (You might have an easier time by purchasing a low powered toy telescope or modestly priced ($20) binoculars.) The major headings in this book's table of contents are: Spaceship Earth, The Moon, The Solar System, The Sun, The Stars and The Cosmos. "Spaceship Earth" features a homemade sundial using a pickle jar, a knotting needle and other homemade items. "The Moon" features a moondial that you can use to predict the moon's direction by consulting the moon's prinicipal phase dates in the newspaper. "The Solar System" features an activity showing the approach used to look for life on Mars' surface that you can do in a kitchen. "The Stars" features how to make a star theater, an interesting way to learn the constellations on a clouy night! "The Cosmos" has an activity explaining spiral arms using cream and black coffee (not to be consumed by youngster). "How the Universe Works" ends with an nice set of sky maps and a glossary of terms.

Another Reader's Digest book is "The Universe and How to See It" by Giles Sparrow. The subtitle is "A practical guide to viewing and understanding the night sky." This book is at higher reading level (middle school and beyond) than "How the Universe Works" and can be found in the regular (non juvenile) section of the library. "The Universe" is more suited for someone who already knows the basics of science. The major sections of the table of contents are: Getting Started, The Solar System, Stars and the galaxy, Beyond the Milky Way and Foundations. "The Universe" is beautifully illustrated with about half text and half photos/diagrams on most pages. As well as introducing unusual objects (ex. dwarf stars and supermassive stars), this book tells you where in the sky these objects may be found. Someone who reads through "The Universe" will have a good introduction to most of the big concepts in Astronomy as well as an idea of where to look in the evening sky. The book finishes with a nice set of tables on the stars and planets. In addition to a glossary, there is an index based on sky location.

June 26 - PLANETS MINGLE

The next few nights will offer a good view of three planets tightly bunched low in the western dusk. The three planets are brilliant Venus, bright Saturn and Mercury. These planets are merely in the same direction as we see them. But from somewhere else in the solar system, Mercury, Venus and Saturn wouldn't even look close. Closest of the three is Mercury at about 95 million miles from Earth. (Mercury is now about 38 million miles from the sun.) The next closest planet to us is Venus at 142 million miles, on the far side of its orbit. (Venus is now 67 million miles from the sun.) Saturn is a remote third, at a distance of 931 million miles from Earth (and 845 million miles from the sun). Tonight the three planets will appear within a circle that's three moon widths (1.5 degrees) across.
Why all three planets seem to be lined up is primarily due to the rapid motion of Mercury, Venus and Earth about the sun. (Mercury orbits the sun 4.15 times a year, Venus 1.62 times a year and the Earth once a year.) Mercury and Venus will appear close through mid July, while Saturn will be lost in the sun's glare in a few weeks.
The next good line up the planets will be on September 2nd when Venus and Jupiter will appear about two moon widths apart. This will be an easier event to observe due to the brightness of the two planets and their greater height above the horizon.