Ó2000 Mike Dowling, All Rights Reserved. Page 1 of 4

The Electronic Passport to Time and Space

A Look at the Stars

Late one night, when I was almost four years old, I remember laying in bed, listening to my father downstairs in the living room. “I want to wake him up to see this. He’ll probably never have a chance to see something like this again.” My mother wanted me to stay in bed. If I got up, I wouldn’t go back to sleep.

A few minutes later, my father looked into my room. I sat up in bed to let him know that I was awake. “Shhhhh,” he said, “don’t wake your brother.” My brother was only one, and too young for whatever we were about to do. “Put on your shoes and your coat, let’s go outside.”

The sky was filled with stars. Beautiful bright stars set off against a black winter night. It was November 9, 1965, the night of the Great Blackout. There was no electricity anywhere in New York or most of the New England states. We lived in Waterbury, Connecticut, and on this night, without any lights to spoil the view, we looked at the stars.

My dad and I got to see what people through most of history saw when the sun set. A beautiful sky filled with stars. If you looked, you could see the stars arranged in patterns that told wonderful stories from the heavens.

Today, we live in a great world with huge cities and instant communication. I think it’s the best time in history to be alive, but it’s very different from the way people lived for almost all of history. Its hard for kids today to understand how people could imagine a storybook in the sky.

Last July I went on vacation. I stayed in northern Vermont, high on a mountain. Even there, the small town of St. Johnsbury, twenty miles away, gave off too much light to see sky the way I saw it almost 35 years ago. My father was right; I’ll probably never have the chance to see something like that again.

Aristotle

Aristotle lived in Greece more than three hundred years before the Common Era (or before Jesus). In Aristotle’s time, most people believed the anger or the pleasure of gods caused events. Aristotle decided he could understand the world by using logic and reason. This is why Aristotle is remembered as the Father of Natural Science.

Shortly after Aristotle, another Greek named Aristarchus reasoned that the earth traveled around the sun. Almost everyone believed that the earth was the center of the universe, in fact, Cleanthes the Stoic declared that he ought to be arrested for challenging the beliefs of the Greek people.

Most people in Aristotle’s time believed the earth was flat, but Aristotle concluded that the earth was a round sphere. He realized that a lunar eclipse happened when the earth came between the sun and the moon. He saw that the shape of the earth’s shadow was round. If the earth was flat, it would have a much different shape. Next, he considered the position of the North Star. The further north you were, the closer it was to the middle of the sky. If you were south of what we now call the equator, you could not see the star at all. Finally, Aristotle watched ships sailing into port. He noticed that at a distance, he could see the tops of their sails before he saw the rest of the ship. Aristotle deduced that this was because of the curvature of the earth. We know today that Aristotle’s conclusions were correct, because humans have traveled around the earth and we have seen pictures of the earth from space.

Like most people of his time, Aristotle believed that the earth was the center of the universe, and the sun and other heavenly bodies moved in circles around the earth. In 1514, a Polish priest named Nicholas Copernicus suggested that the earth revolved around the sun. Copernicus feared what he would face mistreatment if he made a statement that went against popular opinion of the day, so he circulated his statement anonymously. A legend about Copernicus says that a book he wrote about the sun-centered universe was placed in his hands a few days after he lost consciousness from a stroke. He awoke to see that his work had been published, then died peacefully. We don’t know if that story is true, but it shows how fearful people at that time were of challenging long held beliefs, even if they were wrong.

Galileo proved Copernicus right in 1609 when he observed the heavens with a telescope, which had just been invented. Galileo observed that Jupiter had several moons orbiting around it. This proved that not every heavenly body had to revolve around the earth.

The Random House College Dictionary definition of time:

“Time is the system of sequential relations that any event has to any other, as past, present or future; indefinite continuous duration regarded as that in which events succeed one another.”

Scientists understood the world was round, but Isaac Newton explained why people did not fall off the earth. Newton realized that everything in the universe was attracted to everything else, and that the greater and closer the object, the greater its gravitational pull. We call this force gravity, which comes from a Latin word meaning heaviness. The earth is very large, so people and objects were attracted to it. The earth had just enough attraction to the sun to keep it in orbit.

Longitude and Latitude

The ancient Babylonians originally divided any circle or sphere into 360 degrees. Ptolemy was a Greek thinker who borrowed their ideas as he wrote his book on Geography. The furthest point at the right or left side of a circle is 90 degrees from the top of the circle. There are 180 degrees between any two sides of a circle or sphere. The north and south poles are 180 degrees apart from one another, and both are 90 degrees from the equator, which is the imaginary line that is as far from the north pole as it is from the south pole.

The horizontal lines that circle the globe are called Lines of Latitude. Lines of Latitude are known as parallels because they parallel, or run in the same direction as, the Equator. The lines that run between the North and the South Poles are Lines of Longitude, also known as meridians. The line at 0 degrees longitude runs through the Royal Observatory in Greenwich, England. Meridians are counted east and west from the Prime Meridian, which is numbered 0 degrees longitude. The International Date Line is located 180 degrees, or as far away as possible, from the Prime Meridian. When it is noon along the Prime Meridian, it is midnight along the International Date Line.

Geographers also divide the earth into hemispheres. Everything north of the equator is in the Northern Hemisphere, while everything south of the equator is in the Southern Hemisphere. The Western Hemisphere is west of the Prime Meridian, while the Eastern Hemisphere is east of the Prime Meridian. The hemispheres both end at the International Date Line. The United States is in the Northern and Western Hemispheres. West Palm Beach, is 80 degrees west of the equator and 27 degrees north of the equator. This is commonly expressed as 27oN,80oW.

We measure the hours of the day by the turning of the earth. The time of day at any particular moment depends on where you are. When it is noon in Greenwich, England, it is midnight along the International Date Line.

Time

Days and nights occur because the earth is spinning on an axis and a different part of the planet faces the sun. Time changes as you move east or west, so the earth is divided into twenty-four time zones, one for each hour of the day. Some time zone boundaries zigzag so that people living in one region or country can have the same time.

The time along the Prime Meridian in Greenwich, England is known as Greenwich Mean Time, or GMT. People communicating across two different parts of the globe often use Greenwich Mean Time. Palm Beach County, Florida is five time zones behind GMT.

There are four time zones in the continental United States. They are Eastern, Central, Mountain, and Pacific. You might notice that live television programs might begin at 8:00 Eastern Time, 7:00 Central Time, 6:00 Mountain Time and 5:00 Pacific Time. Alaska is an hour behind Pacific Time and Hawaii is two hours behind Pacific Time.

Almost every nation uses this system of measuring time, but China does not have time zones. China extends across five times zones, but the country has a single time zone. If you live in western or eastern China, the sun will not be directly overhead at noon.

Most western nations advance the clock ahead one-hour during the summer months. We call this period Daylight Saving Time. Benjamin Franklin originally suggested the idea. He wanted to take advantage of the additional daylight time in the summer when many people were sleeping. The United States did not adopt Daylight Saving Time until World War I, and today every state but Arizona, Hawaii, and part of Indiana observe Daylight Savings Time.

Daylight Saving Time lasts from the first Sunday in April to the last Sunday in October in the United States. It begins one week later in Canada and Mexico, except in Saskatchewan, Canada, which does not observe the period. The nations of the European Union observe Daylight Saving Time, but they call it the “summer time period.”

Years

The earth travels completely around the sun about every 365.242199 days, or what we call a “solar year.” The Romans devised our calendar. They created years that lasted 365.25 days. In 1582, most western nations began using the Gregorian calendar, named for Pope Gregory. This calendar synchronized the calendar year with the solar year.

Most of our calendar years last 365 days. Every four years we add one day to the last day of February. February usually has only 28 days, but the month lasts a day longer in what we call “leap years.”

Think about this:

· Children born on February 29, 1988 have only had two birthdays. Their tenth birthday will be on February 28, 2028. That’s a long time between birthday presents!

· Astronomers developed the modern calendar in 1582. They found that the calendar year was ten days behind the solar year, so they just skipped the next ten days. The day after October 4, 1582 was October 15, 1582. You can actually say that between October 4 and October 15, 1582, absolutely nothing happened!

· Pope Gregory ordered the calendar we now use, which is why we call it the Gregorian calendar. England did not follow the teachings of the pope, so they did not adjust their calendar – or the calendar in their American colonies – for almost another two hundred years. This is why George Washington was actually born on February 11, 1732, but the date was later adjusted to February 22. We don’t know if the Father of Our Country celebrated both birthdays and received twice as many presents!

Years divisible by four are leap years. The last four leap years were 1996, 1992, 1988 1984, and 1980. We have to make another adjustment to the calendar because leap years would make the calendar year last 365.25 days, and the solar year is .007801 shorter, so we have to make further changes. Centennial years are years that end in 00, or at the end of a century. Centennial years are not leap years unless they are divisible by 400. This means that 1700, 1800, and 1900 were not leap years, but 2000 will be. The next time someone says that there are 365 days in a year; you’ll have a lot of corrections to offer!

Seasons

The earth rotates on its axis, an imaginary line that runs through the middle of the earth from the North Pole to the South Pole. The revolution of the earth around the sun and the tilt of the earth cause the seasons. The axis of the earth is tilted about 23 degrees, and that tilt never changes.

In June, the Northern Hemisphere is tilted toward the sun, so the people in the Northern Hemisphere have longer and warmer days. The days are shorter and colder in the Southern Hemisphere in June, because the earth is tilted away from the sun. The days start getting shorter in the Northern Hemisphere and longer in the Southern Hemisphere after June 21. Daytime lasts exactly as long as nighttime on the first day of spring and the first day of autumn. The first day of winter in the Northern Hemisphere, on December 21 is the shortest day of the year in the Northern Hemisphere and the longest day of the year in the Southern Hemisphere.

The days are longer in summer and shorter in winter the further you move from the equator. It’s generally dark on a summer night in Florida by 8:30 p.m., but in Vermont, there will still be some light at 10:00 p.m. The situation is reversed in the winter, where the sun will go down in Vermont by 3:45 while it remains light in Florida until 5:15.