As the Moon orbits Earth, its gravitational pull creates the ocean tides. As the “bulge” in the water laps against the continents, it creates drag that slows our planet’s rotation. That increases the length of a day by about 2.4 milliseconds per century. That doesn’t sound like much, but over the eons it adds up.

That rate can be affected by big changes in Earth itself, including powerful earthquakes, volcanic eruptions, tropical storms, and more. And over the past few decades, it’s become clear that one of those factors is climate change.

As Earth gets warmer, glaciers and polar ice sheets melt, raising sea level. The extra water increases the power of the tides, slowing Earth’s rotation.

According to a recent study, that’s extending the day by 1.33 milliseconds per century – the highest rate of change over the past 3.6 million years. And the rate could get even bigger by the end of the century. In fact, climate change could add more to the day than the effects of the Moon itself.

As Earth slows down, the Moon moves farther away. Right now, it’s receding at about an inch and a half per year. But climate change could speed things up – pushing the Moon away.

The crescent Moon is low in the west at sunset. And it has a bright companion: Venus, the brilliant “evening star.” They drop from sight a couple of hours later.

Tomorrow: measuring the age of the universe.

Script by Damond Benningfield