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In my last two columns, I have dealt with fireflies and alien invasion. Well this Friday morning (August 12th), we will be attacked, but not by aliens! The Earth will then be crossing the orbit of Comet Swift-Tuttle. Comets are huge frozen masses of water and grit, formed in the early days of the solar system. As a comet travels near the sun, its outer layers vaporize and much loose grit is shucked off. This grit, mostly about the size of a pea, is rather crumbly. So when the Earth crosses a comet's orbit, it collides with this cast off comet debris. Our upper atmosphere acts as shield where the grit is incinerated due to air friction. Since there is then no moon in the predawn sky, conditions are great this year for a good display. Up to 100 meteors may be seen per hour in the last few hours before dawn. (Sunrise is about 6:20 a.m.)
a meteor look like? If you have seen a firefly, then a meteor looks like
a streaking firefly in the sky, being visible typically for less than
a second. Meteors are often called 'falling stars' or 'shooting stars'.
The Earth travels about the sun at 66,700 miles an hour (covered in an
earlier column last month). So a typical piece of grit from this shower
will be impacting the Earth in the vicinity of 30,000 miles an hour! From
100 to 50 miles above Earth's surface, these fast moving particles are
heated to thousands of degrees due to air friction. The ball of heated
glowing gases around the grit is about the size of a house. In a fraction
of a second, the grit is blasted into tiny pieces and the hot gases quickly
disperse. This is what causes a meteor or shooting star. Each day, about
ten tons of meteoric dust reach the Earth's surface after falling for
days from the upper atmosphere where the grit is incinerated.
Why watch meteors in the A.M. hours when evening P.M. are much more covenient? In the hours before dawn, we are on the advancing side of the Earth; the meteors are nearly hitting us head on and appear brighter. In the evening hours, the meteors are catching up to the receding side of the Earth; they don't appear as bright.
one look to see the most meteors? The meteors can be seen in all directions.
The meteors can be traced back to the head of Perseus, a star group then
high in the northern sky. So the best way to see the meteors is lay back
in a lounge chair and look at the top of the sky. Then you will have a
chance to see meteors in any direction. If 100 meteors are seen in an
hour, then you have a chance of seeing several meteors each minute that
you watch. Several minutes may go by without a meteor; then you may see
several meteors in quick succession.
There are two interesting ways to learn the constellations or star groups. One way is to recount the fascinating myths behind the groups, that were told around the community fire by the elders or traveling bards. Then the community members could look up in the sky and trace out the constellation outlines of the Hunter, the Queen, the Lion, etc. Another way is to have a book that tells you each month or even each day, what is worth watching in the evening sky. The key to these calendar books is that you find he material so interesting that you will tend to read ahead in anticipation of what the next season's evening skies will bring.
The myth approach is done superbly by "Dot to Dot In the Sky: Stories in the Stars" by Joan Marie Galat. Galat has selected 15 star groups or constellations. Each group is covered in two or three pages, with simple but effective charts of that group as well as charming versions of that group's myths. Interspersed with the text are boxes of "space notes", interesting tidbits about astronomy that relate to that group. I also like the pronounciation aids to help you say each group (for example, Aquila, the Eagle is pronounced "ah-KWILL-uh"). The reading level is suited for middle school students and up; bright primary students should enjoy it as well. There is a fine glossary of terms and an index that also mentions the pages of any accompanying figures. Galat is a Canadian who regularly visits the schools and gives writing workshops. Her previous pen name was Joan Hinz. She has a website www.joanhinz.com with more information about astronomy as well as astronomy links. "Dot to Dot In the Sky: Stories in the Stars" has an ISBN 1-55285-182-6, published by Whitecap in 2001 and retails at $13. It can be ordered through your local book store or over the Internet.
approach is best done by Chet Raymo's "365 Starry Nights" available
in the Allegany County Library System. Chet Raymo is a college teacher,
philosopher and avid sky observer. Starting in January, Raymo tells you
what to look for each evening, using effective charts and light sprinklings
of astronomy, history, mythology and physics. In July, Raymo focuses on
Hercules, Ophiuchus (off-ih-YOU-cus), Kepler's Star (last supernova in
our galaxy seen from Earth), Sagittarius and our Galaxy. At the end of
each month, there is a sketch showing the Earth's edge of night, which
changes noticeably from month to month. Just by reading through "365
Starry Nights" on our frequent hazy nights, you can learn the basics
of astronomy as well as key sky objects visible to either the eye and
through small telescopes. For finding this books in the libary stacks,
the Dewey Decimal Number for this book is 523.19 R. "365 Starry Nights"
has a ISBN of 0-13-920570-5 and was published by Fireside Books in 1982.
Have you ever heard the phrase "like a drop in the ocean"? Is there any way to estimate the number of drops of water in the ocean? The way to get an approximate answer is by a 'back of envelope' approach. We will use rough estimates to make the calculation possible. The final answer will be probably be within 30-50% of the real number. If you have a scientific calculator, use it to check my numbers.
It's easiest if you break this problem into two stages. In the first stage we will find how many raindrops will fit in a liter. (A liter = 1.06 quarts; most of us occasionally buy 2 liter bottles of soda.) In the second stage, we will find how many liters of water there are in the oceans. Then to find the number of raindrops in the ocean, we multiply the number of raindrops in a liter by the number of liters in the ocean. Expect this number to be far larger than any of the giant numbers we read in the newspapers, such as the annual U.S. government budget (about 2,500,000,000,000 dollars) or the U.S. national debt (about 3 times bigger than U.S. government annual budget). (It will be helpful to know that: a million is a thousand x a thousand with 6 zeroes; a billion is a thousand x a million with 9 zeroes and a trillion is a million x a million with 12 zeroes.)
The average radius of a raindrop is 0.1 cm or about 1/25th inch. (A centimeter is roughly the width across your index finger nail; there are 2.5 centimeters in an inch.) Using the formula for the volume of a sphere (4*Pi*radius cubed), we find that each raindrop has a volume of 0.0042 cubic centimeters (to check multiply 4 x 3.142 x (0.1 * 0.1 * 0.1) / 3 ). (A cubic centimeter has a volume of a small thimble used in sewing.) Now a liter has a volume of 1000 cubic centimeters. So to find the number of raindrops in a liter, we divide 1000 cubic centimeters (a liter) by 0.0042 cubic centimeters (volume of a raindrop). Our answer is 238,800 raindrops in a liter. (This number is very close to the average distance from the Earth to the moon in miles. (No connection, of course.)
Now we will find how many liters in the world's oceans. Let's start by finding the surface area of the Earth. The Earth's average radius is 6370 kilometers or 6.37 million meters. The formula for the surface area of a sphere is 4 * Pi * Radius squared. So if we plug the Earth's radius in meters into this formula, we get 509.9 trillion meters squared.
Now what part of this surface area are the oceans? Presently, about 70% of the Earth's surface is covered by oceans. So to get the ocean surface in square meters, multiply the total surface area by 0.7 (or 70%). This gives us 357 trillion square meters of global oceans. The oceans average 3700 meters deep. (3700 meters = 2.3 miles) Then the volume of the oceans will be the surface area x depth. The product of these two numbers = 1.32 million trillion cubic meters. Now each cubic meter contains 1,000 liters. So the total number of ocean liters will be 1.32 billion trillion liters. (This number in scientific notation is 1.32 x 10 to the 21st.)
get our final answer to the question of how many raindrops are there in
the oceans, we multiply 238,800 (raindrops in a liter) by 1.32 billion
trillion liters (liters of water in the oceans). The answer is: 315 trillion
trillion raindrops. (In scientific notation, this is 3.15 x 10 to the
26th power.) A number that is close to this number is the number of atoms
in a 3 liter bottle of pop. Each liter of water has about 10 to the 26th
atoms. So a 3 liter bottle of pop (mostly water, some sugar, a little
bit of fizz (carbon dioxide gas) and the plastic bottle itself) has about
as many atoms as the number of raindrops in the ocean!
Now that the schools, primary, secondary and colleges have begun, I feel a need to present some of my ideas about the importance of reading. Despite emphases on critical thinking, discovery and hands-on activities, reading remains the most essential skill for students and learners. All the other approaches to education are heavily reliant on good reading skills.
Consider the state of reading in this country. Have you noticed the occasional report on how our elementary students have good reading skills while secondary student reading skills are in decline? As students get older, they begin to use cell phones, i-Pod/MP-3 players and computer/game machines as well as hanging out with their friends in cars, at snack shops, on skateboards, in malls and the associated parking areas on the edge of malls. The time each day teen students spend reading goes down markedly while the amount of time watching TV or computer monitors and talking/messaging to friends grows. Many college students don't read newspapers or magazines. Surveys show more young adults get their news from comedic late night TV shows rather than 'straight' news magazines or TV/radio news. This is why many students and young adults shy away from reading in contrast to their usual social/electronic activities.
Many secondary and college teachers find that few students read their text assignments prior to class coverage. This puts more burden on many teachers, who then try to cover ideas in class using techniques based on students being unacquainted with the text material. A few teachers start each class with a quiz based on what the students are supposed to have read. (This approach demands that teachers spend a large amount of time outside of class grading every week. Also students resent this practice; cheating on daily quizzes is widespread.)
What can be done to promote reading in a positive way that rewards rather than punishes students? It's important for every individual and their parents (if students) to know their reading level. It's no disgrace if you don't read at your grade level. What's injurious is to pretend that you are reading at grade level (when you are not) and adopt techniques to obscure this. Good cover up comments include "the book is so boring" or "I can't relate to the material". If you are confronting a tough text that seems impenetrable, the most productive remedy is to find a text at a lower reading level that you can grasp. Find related chapters to the assigned text chapter and read these chapters in the lower level text. Then return to the tougher text chapter and try to read them again. Taking reading notes is also a must; these notes state the key ideas in your own words. Make use of text features such as summaries, end of chapter review questions and explanatory diagrams. Some texts give you web addresses of sites where the material is explained using animations. If you have an encyclopedia either as a book or a CD-ROM, refer to the key ideas there as well.
There are a lot of possibilities for acquiring lower level texts. First is your public library, including the juvenile area. Another is to scour the budget/clearance bins at discount stores. Acquiring a lower level book is a MUST if school textbooks can't be taken home. In many subjects (ex. math, chemistry, physics, history, English literature, etc.), an old book will do nearly as well as current books. Then a trip to a used book store may be in order.
The more you read each day, the higher your reading level climbs. Besides your textbooks, read about other subjects. Go to your public library and look through the variety of newspapers and magazines on display. I enjoy looking at the reading material in the waiting rooms of doctors/dentists and where I get my car serviced. Read about several different subjects; for reading is like eating. (You wouldn't want to just eat French fries three meals every day.)
In a future column, I'll mention practices that I use in my own classes to improve reading. I also produce a nice summary and questions for each of our public planetarium programs that helps improve reading comprehension.
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