Sun, Shadows and Daylight Lab

A shadow forms when an object blocks sunlight. The sun shines in a straight line, so anything solid casts a dark area behind it.

• Low sun. Long shadows form because the sun's rays hit at a steep angle from the side.
• High sun. Short shadows form because the rays come nearly straight down from above.
• No sun. No shadow forms at night because there is no sunlight to block.

The sun appears to move across the sky each day because Earth rotates. It rises in the east, moves upward until noon, then arcs back down toward the west.

• Morning (east). Sun is low; shadows point west.
• Noon (south). Sun is highest; shadows point north and are shortest.
• Afternoon (west). Sun drops back down; shadows point east and grow longer.

The tilt of Earth changes how high the sun gets and how many hours of daylight each day has.

• Summer. The sun travels a higher arc, daylight lasts about 14 hours, and noon shadows are shorter.
• Winter. The sun travels a lower arc, daylight lasts about 10 hours, and noon shadows are longer.
• In winter the sun may still be below the horizon at 6am and 6pm, so there is no shadow at those times.

Scientists describe shadows using two measurements.

• Length. How long is the shadow? It is compared to the height of the object that made it. Short noon shadows may be less than half the object's height; very long morning shadows can be twice as long.
• Direction. Which way does the shadow point? Morning shadows point west; afternoon shadows point east; noon shadows point north.