For centuries, a setting sun has signaled the end of fasting rituals on holidays such as Ramadan and Yom Kippur, a cue to tuck into a delicious meal after a full day of abstaining from food and drink. But what if the sun's clockwork were to suddenly change, as it does for astronauts riding aboard the International Space Station? The orbiting laboratory whips around the Earth at about 17,000 miles per hour (27,600 kilometers per hour), giving passengers 16 sunrises and sunsets each day.
