Global Warming and Daylight Savings Time ```Name: Joey Status: student Grade: 6-8 Location: KS Country: USA Date: Winter 2010-11 ``` Question: We were discussing global warming in science, today, and I thought of a great solution! Why not eliminate daylight savings time so that we would get less sunlight and not warm the Earth as much? My teacher said that we would still get as much sunlight. But if the sun sets at 7 instead of 8, wouldn't we have less sunlight? Please let me know if this is a good idea. Replies: Hi Joey I like the way you try to solve a problem! Let's think this one through. Pretend we are in a place on Earth where there is 12 hours of daylight and 12 hours of night. Let's say that the sun rises at 7 AM and sets at 7 PM with standard time. During daylight savings time, you are correct in saying that the sun would set at 8 PM. However, since Earth is still turning at the same rate and that determines when the sun rises and sets, during daylight savings time the sun would rise at 8 AM. So in standard time we have sun from 7 AM to 7 PM, or 12 hours. In daylight savings time, we have sun from 8 AM to 8 PM, also 12 hours. So there really is not any change in the amount of daylight from standard time to daylight savings time. It is just a matter of shifting when daylight happens. Hope this helps. Bob Froehlich Your teacher is correct. "Daylight savings time" has no effect on how long the sun shines. If the sun sets at 7, instead of 8, it rises earlier on 7 day. Daylight savings time is a simple convince to give people more daylight time after work. "the practice of temporarily advancing clocks during the summertime so that afternoons have more daylight and mornings have less" (http://en.wikipedia.org/wiki/Daylight_saving_time) Michael Loop Joey, Here is something I want you to try: get out a ruler that has both the inches and centimeter markings on it. Measure something, say the edge-length of your computer, first in inches, then in centimeters. You will notice that the number in the centimeter measurement is higher than the number you got for the inches measurement. But that did not mean that while you were measuring the length of the object with the centimeter units that the length changed, became longer, did it? Now try this, using the inches measuring unit, measure the object again, but this time, do not put the starting edge at the zero-mark of your ruler. Put the edge at the 1-inch mark and measure the length from there. You should notice that it will appear that the length of the object has increased by one inch. Again, this does not mean that the length of the object changed just because you started at 1-inch and not at zero, did it? It is the same with daylight savings time. How we measure time does not affect time or anything that comes with that time (like the amount of sunlight), the object is still the same regardless of how we measure it. The 24-hour clock is a human invention which only controls when we, humans, are awake, working etc. It does not control the physics of the Earth. Greg (Roberto Gregorius) Canisius College Joey- I think it is wonderful that you are thinking about ways that we can help global warming. To think about your idea, we need to consider a few things: Global warming is something that affects the entire planet, no matter how long the sun shines in a certain place. There are a lot of things involved, such as sunshine, chemicals, and the layers in the atmosphere. Think about what the Earth does 24 hours a day, all year long. It turns on its axis while moving around the sun at the same time and is always going at the same speed. At a given place on the Earth, the sun hits it as Earth turns. Now, imagine a ball turning on a pole always at the same speed. If you shine a light bulb on the ball, it is a bit like the sun shining on Earth. The ball turns in the light at the same speed. If you draw a vertical line on the ball, that line always comes back into the light in the same amount of time. You could time this. Now, let us say that you could draw a line on Earth and stand at a place in space and watch the Earth turn. If you timed the turn from the line passing and then turning around to the line again, it would take 24 hours. No matter what time the clock on the wall says, it would take the same time for the line to turn back into the light. So, the total amount of light hitting the Earth over the course of the 24 hours is the same no matter what time it is. So, stopping Daylight Saving Time would not help global warming. Patricia Rowe Joey: Unfortunately, how we set clocks does not affect how much sunlight we get, just when we get up and go to bed. Under daylight savings time the sun goes down an hour "later". But it also gets up (rises) an hour later. The time the sun is in the sky is the same the day before and the day after we mess with the clocks. Under regular time, the sun sets earlier but rises an hour earlier in the morning, too. Next time we switch, look in the local newspaper at the sunrise and sunset times for before and after the switch. The clock times change with the clocks, but the time the sun is up [sunset time - sunrise time] will no change. It is kind of fun to think about what would happen if the clocks really did control the amount of daylight. Arizona, which does NOT go on daylight savings time, would be cooler than New Mexico next door. As soon as you crossed the boarder from New Mexico the temperature would drop several degrees. And, what if we pushed our clocks back 10 hours? Would we start another ice age? (That might make a neat science fiction story!) Hope this helps R. W. "Bob" Avakian Hi Joey Sorry but, yours is not a good idea because It will not have any effect on how much sunlight reaches the earth during any day. The hours that we set here on Earth, whether it be Daylight Savings Time or Standard time is just the human way of measuring what happens naturally. So we set noon (Standard Time) to be when the Sun is directly overhead and midnight to be when the Sun is directly overhead on the other side of the world. The universe does not care if we move the clock up an hour or back an hour, so changing our clocks will not have an impact on global warming. Here is another question you might ask: Why are there 12 hours in the day and not 10 or some other number (after all it is irrelevant to what nature actually does)? The answer to this interesting question can be found at this URL: http://en.wikipedia.org/wiki/12-hour_clock Sincere regards, Mike Stewart Nice try! But there are still the same number of hours of day and night no matter what time you call it. The earth does not know what time it is; humans define the rules for telling the time. So, if we call 8 oclock, 7 oclock all we have done is change what we are calling it. It does not change the hours of daylight. Van Hoeck Joey, When we set the clocks back one hour the sun sets one hour earlier. But guess what… it also rises one hour earlier, so, the length of the day remains the same (it just starts earlier and ends earlier). Earth still receives the same amount of incoming solar energy, it just starts and ends earlier. One reason why we use daylight saving time (not savings) is to take advantage of the sun lit part of the day and avoid working when it’s dark outside. We are now (January) in standard time; daylight saving time resumes when we set our clocks forward on the second Sunday of March. In March, when we set our clocks ahead, we will have sunlight later into the evening (saving daylight) and therefore we may not use as much energy for lighting because it will still be light outside! If we save energy, and burn fewer fossil fuels, we might reduce the amount of carbon dioxide in the atmosphere, and thus slow down global warming. There have been numerous studies that have tried to figure out if we are saving energy (or not) by implementing daylight saving time. It is not a simple answer, but it is nice to have light later in the evening, on summer nights, to play outside later and enjoy the beautiful summer weather. Can you come up with ideas for global cooling? We sure could use some new ideas… Leslie Kanat, Ph.D. Professor of Geology Department of Environmental Sciences Your teacher is correct. The amount of light that the Sun shines depends upon where you are on the Earth's surface at a given season of the year. For example, if you are at the North pole in the SUMMER, the Sun never "sets". It's light for the whole day, but at the South pole at the SAME TIME, the Sun never "rises". It is dark the whole day. The number of hours of sunlight varies between these two extremes at intermediate latitudes. The number we assign on the clock doesn't change the rotation or the tilt of the Earth. That number makes no difference. It helps to understand, if you remember that we use a 12 hour clock AM and PM. But the military and other technical applications use a 24 hour clock, starting at midnight (time is 00:00 hours/minutes) turning to noon at (time is 12:00 hours/minutes) returning to midnight 24 hours later at (time = 23:60 = 00:00 hours/minutes). Vince Calder Joey, The best way to understand daylight savings time is to think about what happens at noon. Noon is the point in the day when the sun is at the highest point in the sky. When daylight savings time is NOT in effect, we call this time of day 12 o'clock (assuming you are in the middle of your time zone). During the time of year when DST is in use, we call noon 1 o'clock instead. Whether DST is in use does not change how the earth moves, just what numbers we see on our clocks. - Isaac Tamblyn Click here to return to the General Topics Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs