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Daylight Savings No matter what its orientation, only half the Earth gets sunlight at any given time. But the amount of sunlight, in terms of the length.

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Presentation on theme: "Daylight Savings No matter what its orientation, only half the Earth gets sunlight at any given time. But the amount of sunlight, in terms of the length."— Presentation transcript:

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2 Daylight Savings No matter what its orientation, only half the Earth gets sunlight at any given time. But the amount of sunlight, in terms of the length of the day, depends on your latitude.

3 Daylight Savings The equator, which is along the great circle relative to the sun, has a constant amount of sunlight throughout the year.

4 Daylight Savings This table shows the number of hours of daylight throughout the year. DateNumber of Hours of Daylight/Day 1-Jan Jan 12 1-Feb Feb 12 1-Mar Mar 12 1-Apr Apr 12 1-May May 12 1-Jun Jun 12 1-Jul Jul 12 1-Aug Aug 12 1-Sep Sep 12 1-Oct Oct 12 1-Nov Nov 12 1-Dec Dec 12

5 Daylight Savings This is a graph of the data.

6 Daylight Savings The situation is different for different latitudes. This is because the Earth’s axis is at a 23° angle relative to the plane of the ecliptic.

7 Daylight Savings During spring and summer, the 23° tilt of the Earth is oriented toward the sun.

8 Daylight Savings During fall and winter, the 23° tilt of the Earth is oriented away from the sun.

9 Daylight Savings As a result, depending on your latitude, the amount of daylight varies throughout the year. This table shows the number of hours of daylight for regions located at 40°N latitude. DateNumber of Hours of Daylight/Day 1-Jan Jan Feb Feb Mar Mar Apr Apr May May Jun Jun Jul Jul Aug Aug Sep Sep Oct Oct Nov Nov Dec Dec 9.17

10 Daylight Savings This is a graph of the data. Note that it is the graph of a periodic function. A graph of several years worth of data would also show a sine curve.

11 Daylight Savings This table shows the number of hours of daylight for regions located at 60°N latitude. DateNumber of Hours of Daylight/Day 1-Jan Jan Feb Feb Mar Mar Apr Apr May May Jun Jun Jul Jul Aug Aug Sep Sep Oct Oct Nov Nov Dec Dec 5.56

12 Daylight Savings This is a graph of the data. This is also a sine curve, but notice that it has a higher amplitude than the 40°N data.

13 Daylight Savings This graph shows the three data sets for the equator, 40°N, and 60°N. The farther away from the equator the more variance there is in the length of daylight throughout the year.

14 Daylight Savings When there are12 hours of daylight, then sunrise and sunset occur at times that don’t cause any inconvenience.

15 Daylight Savings But as the number of hours of daylight shrink, then, without daylight savings time, sunrise could occur later in the morning. This would cause an inconvenience, since going to school or work would happen in the dark.

16 Daylight Savings Daylight savings time is meant to compensate for the decreased number of hours of daylight. This way, going to school or work in the morning doesn’t happen in the dark.

17 Daylight Savings But as spring returns and the number of hours of daylight increase, then during this period, daylight savings time isn’t necessary.


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