Why are stadium lights on during the day?

Answer 1

ANSWER:It is because of shadow. A stadium floor usually isn't at ground level. It can sometimes be 30-60 feet lower. If the sun isn't directly overhead then the field can be in shadow making it difficult to see if you are standing in the sun. You can try this by standing in a well lit room and look out a window at night. You cant see anything outside unless that area is lit as well. Many teams practice in the daytime, thus the lights are on.