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Planning Brannock's Power: An Eclipse and a Year of Seasons

Grade 8 Earth-Sun-Moon practice: use a city solar farm's eclipse forecast, monthly energy and water data, and a lamp model to explain eclipses and seasons.

Grade 8ScienceInteractive · Printable

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11 questions
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Format: Interactive · Printable
Grade: Grade 8
Subject: Science
Question types: Fill in the blank, Multiple choice, Sorting, Short answer

About this worksheet

What students practice

Students use a lamp, globe and ball model to explain where the Moon is during solar and lunar eclipses.
Students use energy and day-length data to explain that Earth's tilt, not its distance, causes seasons.

How to use

If you can, act out the lamp, globe and ball model before students read Part 1. Students answer Parts 1 and 2 on their own, then share their open responses in pairs.

Curriculum

NGSS standard covered

MS-ESS1-1

Model the Earth-Sun-Moon system to explain moon phases, eclipses and seasons.

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Planning Brannock's Power: An Eclipse and a Year of Seasons

Use a city's solar farm data and a lamp-and-globe model to explain eclipses and seasons.

Part 1: The eclipse forecast

Read the passage and Table 1, then answer questions 1–5.

Junior Interns at the Planning Office

1Every summer, the planning office in the city of Brannock, at 40° north latitude, hires two eighth graders as junior interns. This year Dashiell Mbeki joined the team that writes the city's water and energy plan. Much of the city's daytime electricity comes from a large solar farm on the east side. The pumps that move water from the river to the treatment plant use a lot of that electricity.

2Next spring, a solar eclipse will cross the region on a weekday afternoon. The narrow path where the eclipse is total passes about 300 km south of Brannock. In Brannock itself, the Moon will cover about 80% of the Sun's disk at the peak. The office's planner, Ms. Ilse Varga-Bello, showed Dashiell a forecast of the solar farm's output for a clear eclipse day (Table 1). On a clear afternoon without an eclipse, the farm makes about 100 megawatts (MW) at each of those times.

3To explain the forecast at a council meeting, Dashiell built a model in a dark room. A lamp stood for the Sun, a globe for Earth and a table tennis ball on a stick for the Moon. When he held the ball between the lamp and the globe, the ball cast a small, very dark spot on the globe, surrounded by a much wider, paler shadow. When he moved the ball to the far side of the globe, the ball slipped into the globe's shadow.

4For the yearly plan, Dashiell also compared the solar farm's monthly energy with the water the city pumps (Part 2). He learned that Earth is closest to the Sun in early January, about 147 million km away, and farthest in early July, about 152 million km away. Then he taped a tiny solar cell to the globe at Brannock's latitude, kept the globe's axis tilted toward the same wall of the room, and carried the globe around the lamp. At each stop he turned the globe so the cell faced the lamp, as it does at noon. With the north end of the axis leaning toward the lamp, the cell's meter read 41 mA. With it leaning away, the meter read 18 mA. At the two positions where the axis leaned to the side, it read 30 mA.

Table 1: Solar Farm Forecast for a Clear Eclipse Afternoon
Time	Sun's disk covered (%)	Farm output (MW)
12:40 PM	0	100
1:10 PM	30	72
1:40 PM	65	37
1:55 PM (peak)	80	22
2:10 PM	70	32
2:40 PM	35	67
3:10 PM	5	96

Use Table 1 and paragraph 2.

At the peak of the eclipse, the farm is forecast to make MW less than it makes at that time on a clear afternoon without an eclipse.

Which statement best describes the pattern in Table 1?

A. The more of the Sun's disk is covered, the lower the output, by about 1 MW per percent.
B. Output drops to about half at the peak, then climbs back to 100 MW by 2:10 PM.
C. Output is lowest at 3:10 PM, when the afternoon Sun is lower in the sky.
D. The more of the Sun's disk is covered, the higher the output, since the panels cool down.

Use the model in paragraph 3. In what phase is the Moon on the day of the solar eclipse?

A. Full moon, with Earth between the Sun and the Moon
B. First quarter, a quarter turn from the Sun
C. New moon, between the Sun and Earth
D. Third quarter, three quarters of the way around

Use paragraphs 2 and 3. Why will people 300 km south of Brannock see a total eclipse while Brannock sees only part of the Sun covered?

A. Earth's shadow falls across the south first and reaches Brannock later in the afternoon.
B. The Moon's darkest shadow covers only a small area, and Brannock lies in the wider, paler shadow.
C. Brannock is farther north, so the Moon passes in front of the Sun there after dark.
D. The Sun is closer to places in the south, so the Moon blocks all of its light there.

A total lunar eclipse is also forecast for next year. A council member asks whether the solar farm should plan for an output drop that day. Based on the model, what is the best answer?

A. No plan is needed: Earth's shadow falls on the Moon, so sunlight still reaches the farm.
B. A plan is needed: the Moon's shadow falls on the city, so the farm's output drops by about 80%.
C. No plan is needed: the lunar eclipse will happen in winter, when the farm is shut down for repairs.
D. A plan is needed: the full moon passes in front of the Sun and blocks it for about an hour.

Part 2: Energy and water through the year

Use the bar graph, Table 2 and paragraph 4 to answer questions 6–11.

Table 2: Brannock Day Length and Water Pumped (mid-month)
Month	Day length (h)	Water (million L/day)
January	9.4	60
March	11.9	65
May	14.3	90
July	14.8	120
September	12.5	95
November	9.9	62

Use the bar graph. Round to the nearest tenth.

The solar farm made times as much energy in July as in January.

Use Table 2.

Brannock's mid-July day is h longer than its mid-January day.

Which pair of facts from this page best shows that Earth's distance from the Sun does not explain Brannock's seasons?

A. July has the longest days in Table 2, and July has the most solar energy.
B. Earth is farthest from the Sun in early July, and July has the most solar energy.
C. January has the shortest days in Table 2, and January has the least water pumped.
D. Earth is closest to the Sun in early January, and March has more energy than November.

Use the globe test in paragraph 4. Which explanation of why the farm makes so much more energy in July than in January fits the data best?

A. In July Earth's axis turns to point straight at the Sun, so the poles get the most light.
B. In July Earth is closer to the Sun, so each square meter of the farm gets stronger light.
C. In July the Sun gives off more energy than in January, so the cell's meter reads higher.
D. In July the north half of Earth leans toward the Sun, so sunlight is more direct and days are longer.

10.

Sort each observation by what mainly causes it.

The farm makes 15 GWh in July but 6 GWh in January.Next spring the Moon will cover 80% of the Sun's disk over Brannock.Brannock's mid-July day lasts 14.8 h, but its mid-January day lasts 9.4 h.The full moon turns dark red-orange during a total lunar eclipse.The globe's solar cell read 41 mA in one position and 18 mA in another.

Earth's tilted axis as Earth orbits the Sun	Where the Moon is in its orbit

11.

A council member says, "Our solar farm should make the most energy in January, because that is when Earth is closest to the Sun." Make a claim about this idea. Use at least two numbers from the bar graph or Table 2, the distances in paragraph 4 and the globe test as evidence, and explain your reasoning.