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Earth and Space 6-8 / Week 04 / Wednesday
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Week 04 · Seasons

Wednesday

Sky Deck Lab: Light on grid paper
// A tilted axis that always points the same way
⏱ about 20 min

Wednesday: Sky Deck Lab: Light on Grid Paper

Rocket tapes a sheet of grid paper to the Sky Deck floor. Raven holds the flashlight straight above it.

"Count the squares in the bright spot," she says. Rocket counts fast. "Twelve!" He counts again, slowly. "Fourteen."

"Now the slant," Raven says. She tips the flashlight, same height. The light stretches across the paper.

Rocket counts. "Thirty-one squares. The same light on more than twice the paper."

Nova hovers above the grid. "What do you notice about how bright each square is now?"

"Dimmer," Rocket says. "Each square gets a smaller share."

"That is winter sunlight," Raven says. Nova hums. "Now write it down before you forget your numbers."

Your mission

Today you measure the flashlight effect from Tuesday. The same light spread over more squares means less light per square.

This is the first of the two effects of the tilt: direct sunlight in summer, slanted sunlight in winter.

You will shine straight down, count squares, shine at a slant from the same height, and count again.

  • A flashlight, the same one for every trial
  • A sheet of grid paper, or plain paper with a grid of 1-centimeter squares drawn on it
  • Tape to hold the paper flat, a ruler to keep the same height, a pencil
  • A dim room and your Sky Log
Safety first
Never shine the flashlight into anyone's eyes, including your own.
Use a flashlight or an LED lamp, never a hot bulb near paper.
Keep the floor clear so nobody trips in the dim light.
The flashlight stands for the Sun. Never look at the real Sun to compare.
  1. Tape the grid paper flat on the floor or a table. Dim the room lights.
  2. Hold the flashlight pointing straight down, one ruler length above the paper.
  3. Trace the edge of the bright spot with a pencil. Count the squares inside. Record the number.
  4. Keep the flashlight at the same height. Tilt it so the beam hits the paper at a slant.
  5. Trace the new lit shape. Count the squares inside, including partly lit squares. Record the number.
  6. Tilt even more, still at the same height, and count once more.
  7. Repeat all three trials a second time and fill in the data table.
PREDICT BEFORE YOU SHINE
  • Read the question.
  • Tap your answer.
Which position will light more squares?
Which position will make each square brighter?
Flashlight angleSquares lit, trial 1Squares lit, trial 2Brightness of each square (bright, medium, dim)
Straight down
Slanted
Slanted more

Reading the model

The flashlight gave off the same light every time. Only the angle changed. More squares lit meant less light for each square.

That is why slanted winter sunlight heats the ground less than direct summer sunlight. The energy is spread thinner.

The straight-down beam stands for the high summer Sun. The slanted beam stands for the low winter Sun.

What the model gets wrong: the real Sun lights a whole hemisphere at once, and its height changes slowly over months.

What the model showsTrue or false?
The slanted beam lit more squares.?
The slanted beam made each square brighter.?
The flashlight gave off more light when it was slanted.?
The straight-down beam stands for the summer Sun.?
WHY THIS EXERCISEThe standard asks you to model how the tilt changes the intensity of sunlight on different areas.
Which beam stands for the winter Sun: straight or slanted? Type one word.
WHY THIS EXERCISEThe low Sun spreads its energy over more ground, and that is why winter is cold.
Sketch your grid paper twice: the small straight-down spot and the long slanted shape. Write the square counts beside each.

A model that measures. Tomorrow you read a Naval Observatory table of the longest and shortest days.

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