Originally the idea of noon was when the sun was directly overhead. When high speed transportation and communication (the train and the telegraph) became available the idea of time that was set to the sun being directly overhead didn’t work so well. I could be in one town and they would call it 5 o’clock and the very next town may have decided to call it 5 o’clock 30 minutes later. So, they made time zones so that people would know what time it was in different locations. So, from the east coast to a standard point would all be 5 o’clock. The next zone had not had the sun move that far so they would be an hour earlier so that the sun would pass over head “near” noon for them as well. That way, people could know what time to expect it to be from town to town when they were sending telegraphs and creating train schedules.

Well, first make sure you understand how “solar” time works. The Earth revolves around the sun…but the Earth is also turning on its axis (spinning like a top as it goes around the sun). Because the Earth is like a ball (not exactly a sphere, but very close to it), only 1/2 of the Earth has sunlight shining on it at any one time…with the side facing away from the sun in darkness.

So, if you have a flashlight and a basketball…turn out the room lights…stand and shine the flashlight on the basketball, you can see for yourself that only 1/2 of the basketball is in light and the opposite side is dark. The lighted part is in daylight and the dark part is night.

Now, the Earth is rotating (turning on its axis, spinning like a top). It’s nearly a circle, and a circle has 360 degrees in it. It takes about 24 hours to make one complete rotation….and we call that a full day. So generally, there are 12 hours of daylight and 12 hours of night (but more about that later).

The Earth is about 93 million miles from the sun….so all of the light rays are assumed to be parallel to one another by the time they reach Earth. So, if you take some graph paper and use a drawing compass to make a circle to represent the Earth, you can use some of the graph paper grid lines to be the parallel rays of light coming to the Earth. Whether you look at the Earth from above (so the center of the circle is the North or South pole) of from the side (so you can imagine the North pole at the top and South pole at the bottom) , there is one and only one of the parallel lines that will be perpendicular to the circumference of the circle. This is what we call the vertical ray of the sun and also represent 12 noon…which divides the daylight part of the Earth in half…hence we call noon, mid-day.

The direction the Earth rotates on its axis does not change. If you look down on the Earth so you see the North pole, the Earth will be turning in a anti-clockwise direction. So if you lay a stick lined up with the vertical ray and then turn the paper…but don’t let the stick turn with the paper…you can see that the vertical ray (noon hour) points to a different part of the Earth’s circumference. Standing on Earth, most of us don’t feel the Earth turning…instead, we think the Sun is moving across the sky. Hence, we have the terms sunrise and sunset because humans actually see the sun rising in the East and setting in the West.

So if you watch carefully as you turn the paper and hold the stick in place….only one place on the circumference will be under the noon day stick…and all other places will be either before noon or afternoon.

In the old days, people tended to get born in one place, live there, and die there…so telling time by the sun was OK. But as others pointed out, when traveling faster (e.g. train, car, plane, etc) people need to know the what time it was in different places. So time zones were created.

But it still goes back to the Earth, a 360 degree circle, and the 24 hours needed to make 1 full rotation. Divide 360 by 24 and you get 15 degrees of the circle equal to 1 hour of time. So, its quite logical to have 24 time zones 1 hour wide…just because 1 hour is a convenient time unit. But wait, it gets a bit complicated.

The standard time meridians (a meridian is an imaginary line going from one pole to the other….creating lines of longitude) are all multiples of 15 degrees of arc. But they are numbered starting as zero (0) at Greenwich, England..and go up to 180 degrees to the International Date Line (which is another long tale in the time story).

The actual time zone is 15 degrees of longitude wide…but it is centered on a standard time meridian (the longitude lines that are all multiples of 15). So if we start at the zero meridian, the Greenwich time zone goes 7 1/2 degrees East and 7 1/2 degrees West of the zero line. Add them together and you get 15 degrees…or 1 hour of time.

Back to the noon day sun. When the vertical ray of the sun point exactly on the zero meridian…ALL the cities and towns in the zone…7 1/2 degrees E and W…set their clocks to 12 noon. Without the standard time zones, each town would have to wait until the vertical ray was directly overhead before they could say it was 12 noon. Technically, this means that if you and I were standing 100 feet away from each other (on a line extending East and West) one of us would get to eat lunch when the sun was directly overhead and the other would have to wait until the sun was directly overhead to eat.

Now if this isn’t confusing enough, some countries don’t agree to follow the geometry, math, and astronomy involved in this time zone game….and they set their own rules because it is their country and they can do what they like.

Go back to the Greenwich time zone…zero longitude. Then look at France…2 degrees East of Greenwich…well within the Greenwich standard time zone (remember it goes to 7 1/2 E) and the French government passed a law to set the official time in France to be 1 hour earlier than Greenwich! See how much the French didn’t like the British?!?!

No wonder you have trouble understanding time zones!

I know this was a bit long….but I hope it helps. And maybe if you take a look at this website you can see it and understand it easier http://geoclock.home.att.net/

Best wishes in your studies.

Time zones were created when they built the Transcontinental Railroad. It was used to help schedule trains.