A Children's Guide to Daylight Savings Time
Turning clocks ahead or back one hour is a ritual every year for many people. You've probably heard the saying “spring forward, fall back.” It means that you turn your clock one hour ahead in the spring, while turning your clock back one hour in the fall. This process is referred to as “Daylight Savings Time” or “DST.”
You may wonder what the reason for changing time every spring and fall is, and how it began. Benjamin Franklin was the U.S. Ambassador to France when he thought that people could make better use of daylight hours in terms of electricity and lighting use. He didn't know how to go about it though, and the idea did not become further developed. Germany was the first country to use DST. It was during World War I, and Germans were trying to decrease artificial lighting use and save the use of coal for the war. In 1918, federal law in the United States standardized the yearly beginning and ending times for daylight savings time for the states who chose to take advantage of it. Throughout the years, daylight savings time beginning and ending times have changed and sometimes gone away altogether. Sometimes daylight savings time is extended.
The use of electricity and energy corresponds to when we go to sleep and when we arise in the morning. During the summer months, the sun rises very early before the majority of people even wake up. When the sun has risen and is shining, people don't need many, if any, lights on in their homes. People tend to use less energy in the morning. The sun sets an hour later during summer so there is less electricity needed or appliances and lighting. When winter comes, we need to use more electricity because it is darker as well as cooler in the morning. At this time, the clock is set back one hour.
The Earth's Spheres
Scientists have separated the Earth into various spheres. Each sphere differs by its physical characteristics. All of the air and gases of Earth are considered part of the “atmosphere.” The atmosphere extends from less than one meter below the surface of the Earth to more than 10,000 kilometers above the surface of the Earth. There are many different layers that are part of the atmosphere, and they vary by temperature and chemical composition. The second of Earth's spheres is the “lithosphere.” The lithosphere includes the physical materials of Earth such as soil and rocks. It is all Earth's land from the hard surface to the liquid center. It encompasses mountain ranges, plains and deep valleys that comprise the ocean floor. The third sphere is the “hydrosphere” which, naturally, involves all the water on Earth (even solid liquid and gaseous water). The majority of Earth's water is actually frozen such as icebergs, polar icecaps and glaciers. The Earth's water is comprised of both salt and fresh water. Ninety-seven percent of water on Earth is salt water which is the oceans. When referring to water as “gaseous water” it means that when temperatures are very high water turns into a gas and evaporates (especially at the equator).
Maps are always a useful tool. It you are on a road trip, maps help you find your way. Lots of valuable information can be found on a map such as lakes, mountain ranges, campgrounds, tourist attractions and even time zones. Maps are made up of symbols, which are pictures that stand for a particular item in the real world. For example, a picture of a fire could represent a campground or a tree picture could represent a park. You need a key in order to know what the various symbols stand for. A key (sometimes referred to as a legend) explains what all the map symbols represent. A picture of the symbol is followed by a brief, written explanation of what it stands for.
A map is a miniaturized version of a large land area. You have to “scale” down a map in order to make it fit onto a piece of paper or a screen of some sort. Every part of a map must be scaled by the exact same amount to achieve the greatest amount of accuracy. The Earth is round and maps are flat. This makes it impossible to perfectly scale it. Scale distortions will be greater when the territory is bigger. For example, on a map one inch could equal 10 miles in the real world.
Three methods exist for the representation of scale. The “graphic method” uses a “graphic scale” which is a line separated by smaller lines that intersect it (just like on the side of a ruler). On one side of the line distance on the map is represented, while on the other side of the line real world distances are represented. You can measure the distance between two objects on your map, and then use the graphic scale to figure out what the distance equals in the real world. If one map inch equals 10 miles and the distance between two objects on the map measures two map inches, then that means that the two objects are 20 miles apart in the real world. This is a very quick and easy method for figuring out distances in real life.
The second method is very similar to the first in terms of calculations. When using the “verbal method” instead of the graphic method, written words are used to describe the scale. For example, your instructions could be stated as “one inch equals 10 miles.” As with the graphic method, you then measure the distance between two points on the map and use the word scale to determine the actual distance.
The final method is probably the more complicated of the three. It is called the “fractional method,” and uses a fraction to calculate distance on the map versus real life. For example, 1:100,000 or 1/100,000 could mean that a distance of one inch on the map equals 100,000 inches in the real world. The same units must be used with both numbers such as inches or feet.
Globes Help Us Understand Our Planet
Globes are a great way to see how Earth really looks from space. Globes are round just like Earth, which means that you don't get the large distortions that come from trying to put a round area onto a flat piece of paper as with a map. Globes are more accurate than maps, but require a very small scale so you can't show as much detail on them such as a small river or lake. Yet you can show these smaller items on a map. A globe can only have larger objects shown on it. It can also be difficult to transport. Can you imagine bringing a globe in the car to help figure out where you're going' Globes do help us though to view our world as it truly exists.
Projecting an image involves a projector of some sort to display or show the original image on another object. For example, when you are at a movie theater a movie projector projects the movie onto a large screen. There are four projection methods that exist in order to project a globe onto a piece of paper or a flat screen. The first method is referred to as “cylindrical projection.” Using this method is similar to trying to put a movie screen on a globe. You cannot get the movie screen to be flat, so distortions result. The closer you are to the equator, the smaller the amount of distortion. The closer you are to the north and south poles, the greater the amount of distortion. This method is the most common method used on maps. The “conic projection” method is like taking a cone shaped screen and covering the globe with it. This method is more accurate than the cylindrical method, but the further down the map you go, the more distorted and less accurate the map becomes. A “plane projection” is like placing the movie screen directly above or below the globe, but isn't used very often. The final projection method for map-making is “interrupted projection.” There are a variety of types of interrupted projections maps which attempt to show the continents as realistically as possible. Blank spaces are used in the less important map areas such as in oceans.
Shape vs. Size
When working with map projections, there are two essential factors that must be considered. You cannot create a map with accurate projections of both size and shape. If you choose to depict size accurately, shapes will become less accurate and vice-versa. A conformed map focuses on the accurate portrayal of the shapes of objects. Users can understand how objects are realistically shaped. Unfortunately things become very distorted the closer they are to both the top and bottom of the map. Scale is much more accurate near the equator, while becoming more distorted as you get further away from it. An equivalent map focuses on size instead of shape. These types of maps are accurate regarding the size of objects no matter where you look on the map. Yet the shapes of objects are distorted on this type of map. There are hybrid maps, which are neither entirely conformed nor equivalent. The two types are combined to create a distortion in balance for both shape and size.
A person who creates maps is referred to as a “cartographer.” In order to create relatively accurate and precise maps, cartographers use something called “remote sensing” to measure Earth. There are several different remote sensing technologies that are used in the creation of maps. With these technologies, you don't need to physically touch territory on Earth in order to measure it. Planes and satellites are often used to deploy these sensing technologies. Different types of sensing include: aerial photographs, infrared sensing (which shows temperatures of ground objects), microwave sensing (electromagnetic waves that scan Earth), radar sensing (shows the terrain of an area) and sonar sensing (sound waves used in water).
Not everyone in the world adheres to Daylight Savings Time, yet the majority of the states in America choose to participate except Hawaii and Arizona. Daylight Savings Time is exactly what the phrase “spring ahead, fall back” states. Sometime during spring you turn your clocks ahead one hour, and during the fall you turn your clocks back one hour. For the current year, 2011, clocks were moved ahead one hour on Sunday, March 13 as of 2:00 a.m. Clocks will soon be turned backed on Sunday, November 6, at 2:00 a.m. There is links listed below that shows the world time zones for more information. Daylight Savings Time was created as a way to help reduce lighting and electricity consumption. The following links provide you with more information on daylight savings time and the other topics that were briefly discussed such as maps and globes.
- Pitara Kids Network
- Kid's Geo
- Center for Educational Technologies
- National Geographic
- World Time Zone
- Kidz World
- Time and Date
- Science Time
- Maps 4 Kids
- Jacksonville State University-Alabama
- Science Kids
- Enchanted Learning
- Google Earth
- Maps of World
- Remote Sensing Tutorial-NASA
- Britannica Kids
- Academic Kids
- National Atlas