Earth is spinning faster this summer, making the days marginally shorter and attracting the attention of scientists and ...

At right top (steps 1–2) is the sidereal lunar cycle: The time it takes the Moon to complete an orbit (360°) around Earth is 27 days, 7 hours, 43 minutes, and 11.5 seconds.

Lunar distance is an always-changing thing, with the moon tracing an elliptical orbit around the Earth. At its closest approach—or perigee—the moon is only 224,000 miles distant.