The Rooftop Garden Sky Journal

Nia's Sky Notes

Nia keeps a field journal for the science club's garden on a city rooftop. The club wants to explain why the Sun looks much brighter in the daytime than other stars look at night. They never look directly at the Sun. Instead, they use a light sensor and a safe model made with two identical, low-power lights. The lights have the same setting. A sensor measures how much light reaches it.

On the first day, Nia places one light at several distances from the sensor. She keeps the sensor pointed at the light and changes the distance between them. The light, its setting, the sensor, and the rooftop location stay the same. The readings are recorded in relative brightness units. A higher reading means more light reached the sensor.

On the next day, the club checks an astronomy reference card. It lists the distance from Earth to the Sun and to several stars. A light-year is a distance of about 9.5 trillion kilometers. The card also gives an apparent-brightness score made for this journal. The score compares how bright each object looks from Earth; it does not tell how much light an object produces in total. The club uses the model and the space records together because a model can show a useful pattern, while the records show the very different distances in space.