Bok’s team developed an alternative approach. Even though it is thin and lightweight, their membrane transmits sound as well as the thick layer of material.

One group of 16 volunteers got a normal amount of sleep — seven to nine hours a night. The other two groups of 20 people each were kept sleep deprived. They got only two hours of sleep a night, for three nights in a row. To stay awake, the volunteers were asked to do things such as walk, play video games, watch TV, sit on an exercise ball or play ping-pong. Throughout the experiment, one of the sleep-deprived groups got a nutritional drink with extra protein and vitamins. The other group got a placebo drink: It looked and tasted the same but had no extra nutrition.

She and her team studied three groups of healthy people who came to their laboratory to take part in tests. They gave each recruit small skin wounds. Applying gentle suction on their forearms, they created blisters. Then they removed the tops of these blisters. (The procedure doesn’t hurt, although it can be itchy, Smith says.)

MacGregor’s team took a second look at these data. And it found that all the excess light came from a two-minute period on March 24. A massive flare explains all the extra light, MacGregor now says.