NAME__________________________________________ PER______
Earth's Revolution and its Seasons
PART 1 - Earth's Revolution:
Examine the Figure 1 above. Answer these questions. ________
1. True/False: As Earth revolves around the Sun it is always tilted toward the Sun.
2. The Labeled dates in the picture are for the [Northern, Southern] Hemisphere
3. The winter solstice occurs on what date in the Northern Hemisphere? DEC 21
4. The vernal equinox occurs on what date in the Southern Hemisphere? March 21
5. The winter solstice occurs on what date in the Southern Hemisphere? June 21
6. Earth's rotation around the Sun is [circular, elliptical]. The sun is positioned in such a way, though slightly
wrong in this diagram, to generally show Earth's distance from the sun. Interestingly Earth is closer to the Sun
during the [Equinoxes; solstices] and furthest on the first day of the Northern Hemisphere [summer, winter].
7. So, the seasons are controlled by the [tilt of the Earth; distance from the Sun] and NOT [tilt of the Earth;
distance from the Sun].
PART 2 - The Solstices and Equinoxes
Examine these Figures. The arrows refer to the source of
light from the sun
Fig 2A
1. Figure 2A shows the first day of northern hemisphere
[summer, winter, spring, autumn].
(a) How many hours of daylight are received at the equator?
12 hr
(b) Latitudes north of the equator have [longer, shorter]
days and therefore receive [more, less, the same amount
of] sunlight during one rotation.
(c) Latitudes south of the equator have [longer, shorter]
days and therefore receive [more, less, the same amount
of] sunlight during one rotation.
(d) How many hours of daylight are received at the North Pole? 24 hours
(e) How many hours of daylight are received at the South Pole? 0 months
2. Figure 2B shows the first day of northern hemisphere [summer, winter, spring, autumn].
(a) How many hours of daylight are received at the equator?
12 hr.
(b) Latitudes north of the equator have [longer, shorter]
days and therefore receive [more, less, the same amount
of] sunlight during one rotation.
(c) Latitudes south of the equator have [longer, shorter]
days and therefore receive [more, less, the same amount
of] sunlight during one rotation.
(d) How many hours of daylight are received at the North
Pole? 0
(e) How many hours of daylight are received at the South
Pole? 24 hours
Fig 2B
Fig 2C
3. Figure 2C shows the first day of northern hemisphere [summer or winter,
spring or autumn].
(a) How many hours of daylight are received at the equator? 12
(b) How many at the other latitudes? all
(c) However, all areas [do, do not] receive the same amount of energy from the
Sun because the energy [is, is not] directly perpendicular to the surface at all
latitudes.
Part 3 - Energy From the Sun.
Analyze the graph below and follow the directions
1. There are three sets of data plotted below. To the right of the key, label each of the cities as either
equatorial, mid-latitude, polar based on the latitude that is given.
2. Construct an annual solar radiation curve for each of the three locations. Do this by drawing smooth curved
lines connecting the radiation values that are already plotted. Use three different colors.
winter
spring
summer
autumn
equatorial
Mid latitude
polar
3. Look at the quantity and units given on the Y-axis: Average Daily Radiation in "Calories per square inch per
day". Calorie is a unit of [energy, force], square cm is a unit of [distance, area] and day is a unit of time.
Combined they represent the total amount of radiation that Earth receives at these different latitudes; because
they are real measurements of energy they take into account that not all light strikes the Earth perpendicularly
because the Earth is [circular; spherical] and its axis of rotation is [vertical; tilted].
4. According to the curves, at which latitude region shown does average daily solar radiation vary the least?
[equatorial latitudes, mid-latitude, polar latitudes]
5. The variation in average daily solar radiation in #4 is primarily due to slight changes in [length of day; path of
sunlight through the atmosphere]
6. The pattern of sunlight received near the equator over the course of a year indicates that the seasonal
differences there are [similar to, less than] those seen for the mid-latitudes.
7. The graph shows that there is a 6-month period during which there is no sunlight at the [equatorial, midlatitude, polar] location.
8. According to the graph, there are months when both the mid-latitude and polar regions receive more solar
radiation that the equator. The major factor that causes this to happen is the greater [length of daylight each
day; height of the sun in the sky].
9. Comparison of the three curves' indicates that the annual range (i.e., difference between minimum and
maximum) [increases, decrease] as latitude increases.
Now, go back to the graph and add VERTICAL LINES AT THE APPROXIMATE DATES OF THE EQUINOX ES AND
SOLSTICES WITH BLACK OR GRAY COLORED PENCIL. These dates can be found in the previous parts of the
activity. You should have four vertical lines. Label the intervals between the lines you just drew spring,
summer, autumn, winter in the Northern Hemisphere.
10. First consider the equatorial curve. Two equal maximum points and two equal minimum points normally
occur in the solar radiation curve if sky were always clear (which is never the case). This curve shows something
close to this, and it is evident that the maxima occur near the [solstices, equinoxes].
11. The area under the curves for a season can be thought of as a total solar radiation for that season. Which
region has similar total radiation that is about the same for each season? [equatorial latitudes, mid-latitude,
polar latitudes]
12. At the mid-latitude location, the season of Spring and Summer receive the most solar radiation per day.
13. At the mid-latitude location, the season of Autumn and Winter receive the least solar radiation per day.
14. During spring and summer in the Northern Hemisphere, the south pole receives [its maximum, zero] solar
radiation. In the Southern Hemisphere, these are the seasons of Autumn and Winter
Equator
Part 4 - Sun's Position in the Sky (Solar Altitude)
Use the figure to the right to answer questions that follow. It shows a
person (you?) standing on the ground and the Sun's position in the sky
at solar noon. LABEL THE DIAGRAMS AS FOLLOWS: Fig A = Equator,
Fig B = New Jersey (mid-latitude), and Fig C = North Pole
1. At the equator, the sun is directly overhead on the [equinoxes,
solstices] at noon.
2. At the equator, the sun would appear in the [northern, southern]
sky at noon on the first day of northern hemisphere summer.
NJ Midlatitudes
3. At the equator, the sun would appear in the [northern, southern]
sky at noon on the first day of southern hemisphere summer.
4. At the equator, the sun would appear to set exactly [due east, due
west] on the first days of both spring and autumn.
5. In New Jersey, the sun is closest to directly overhead at noon on
the first day of [spring, summer, autumn, winter], but it is never truly
directly overhead.
North Pole
6. In New Jersey, the sun is lowest in the sky on at noon of the first
day of [spring, summer, autumn, winter].
7. Imagine the Sun following the path indicated as you watched it
move across the sky in New Jersey...
Which date's path is the longest? June 21
Which date's path is the shortest? Dec 21
Which is the longest day of the year? June 21
Which is the shortest day of the year? Dec 21
On which dates does the Sun set due west in the horizon no matter where you are? March 21 & Sept 23
8. At the North Pole, what would the sun appear to do on a daily basis around the time of June 21?
Circle the sky, but not set
9. In your own words, why is the Sun high in the sky on June 21st at the North Pole, but not the other days?
Each day after June 21, the sun “moves” south and is less and less visible for the north pole.
10. December 21st is not shown for the North Pole because the sun appears to circle the Earth far [above,
below] the horizon.
Try these:
Suppose you are standing at 40˚N latitude on the first day of spring. How many degrees from the
vertical is the sun in the sky? (Hint: it has to do with latitude and the sun's direct rays on that day).
Suppose you are standing at 40˚N latitude on the first day of summer. How many degrees from the
vertical is the sun in the sky? (Hint: it has to do with latitude and the sun's direct rays on that day).