Here’s How the Moon Is Actually Making the Days Longer Each Year

published Mar 7, 2023
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We’re on the brink of Daylight Saving Time, which means later sunsets for the spring and summer season ahead. But, even without DST shifting into gear, the days on Earth are actually getting longer every year, and we have the moon to thank for that.

According to a report from BBC, the average day on Earth billions of years ago only lasted about 13 hours. But because the moon has been tiptoeing away from Earth between then and now, the days have gotten longer and will continue to do so, due to friction caused by tides. 

Using lasers, astronauts have found that “lunar recession” is happening at a rate of about 1.5 inches each year. As the moon grows more distant, and therefore its orbital path around the Earther becomes longer, it causes a tidal drag here on Earth that slows the Earth’s rotation on its axis and creates longer days.

Since the late 17th century, scientists have estimated that we’ve gained about 1.09 milliseconds per day. 

However, lunar recession isn’t constant, and scientists say that the moon could actually move closer to Earth in the future. One study suggests that at one point around 550 to 625 million years ago, the moon was retreating about 2.8 inches per year. But, for most of its history, the moon has retreated far slower than it has in recent years.

Tidal drag and length of days are also affected by factors here on Earth, too. Because the Atlantic Ocean is larger than it was millions of years ago, and the continents are positioned in their specific spots, Earth is experiencing a tidal drag that is three times larger than expected. And of course, climate change and melting glaciers have an impact on tidal drag, too.

So…does lunar recession mean that Earth may lose its moon altogether? Experts say that’s unlikely. At least, not in the next 10 billion years or so.

Do something fun with that extra millisecond — it may not be much, but it’s something!