What the App Knows
1The weather club at Lakeview Middle School keeps a small weather station on the school roof. Its sensors send temperature, wind and sunlight readings to a forecast app the club built with their teacher, Ms. Farah Lindqvist. Lakeview is at 40° north latitude. Besides the forecast, the app shows how high the Sun climbs at noon, the length of the day, Earth's distance from the Sun and the phase of the Moon. Each Friday the club checks the app's forecasts against the station's real readings and posts how often they were right.
2Eighth grader Anouk Brandt pulled four dates from a full year of station data. The table shows them. The station's sunlight sensor also measures how much solar energy reaches each square meter of the flat roof. On a clear day at noon, it reads about twice as much in June as in December. Earth's axis is tilted about 23.5°, and all year the axis points toward the same place in space, close to the North Star.
3To test why the angle of sunlight might matter, the club shined the same flashlight at a sheet of graph paper from the same distance. With the beam pointing straight down, the bright spot covered 20 squares. With the beam tipped low, like a winter Sun, the bright spot covered 40 squares and looked dimmer.
4For the moon phase feature, the club built a model in a dark classroom. A bare lamp stood for the Sun. A student's head stood for Earth, and a foam ball on a stick, held at arm's length, stood for the Moon. The student turned slowly in a circle and watched how much of the ball's lit side faced her. The Moon's path around Earth is tilted about 5° compared with Earth's path around the Sun, so the club sometimes held the ball a little above or below the lamp's height. Over one month, the app showed the dates in the second table. The club also added eclipse dates from a public space agency calendar, and they noticed that only a few full moons each year had a lunar eclipse listed.