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2 weeks ago
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Look up at the Moon tonight. Really look at it. That silvery disc has been humanity’s constant companion since before we were human, before we were even mammals. It’s watched over dinosaurs, trilobites, and the very first creatures to crawl onto land. But here’s something that might blow your mind: the Moon you’re looking at isn’t where it used to be. And it’s not staying put.
Right now, at this very moment, the Moon is drifting away from us at about 3.8 centimeters per year. That’s roughly the same rate your fingernails grow. We know this with incredible precision because astronauts left mirrors on the lunar surface, and scientists bounce lasers off them to measure the distance. Every year, those laser beams have to travel a little bit farther.
Now, before you panic about losing our cosmic companion, let me put this in perspective. At this rate, it would take about 25 million years for the Moon to move just 1,000 kilometers farther away. We’re talking about geological timescales here, not something you need to worry about for dinner plans next week.
But here’s where it gets wild. If we could rewind time like a cosmic movie, we’d see something absolutely spectacular. Four and a half billion years ago, when the Moon was newly born, probably from the debris of a catastrophic collision between Earth and a Mars-sized object, it was so close you could almost reach up and touch it. Well, not really, but it was only about 15,000 to 25,000 kilometers away, compared to the 384,400 kilometers that separate us today.
Imagine standing on that ancient Earth. The Moon would have dominated the sky, appearing fifteen to twenty times larger than what we see now. It would have been terrifying and beautiful in equal measure. And the tides? Forget the gentle lapping of waves we’re used to. We’re talking about tidal forces that could create waves hundreds of meters high, reshaping coastlines twice a day with the power of a geological bulldozer.
Earth itself was a different beast back then. Our planet spun like a top, completing a full day in just five or six hours. You could have watched the sun rise and set four times in what we now call a single day. The Moon’s gravity was so much stronger that it was literally grabbing hold of Earth’s rotation and slowly, inexorably, putting on the brakes.
And that’s exactly what’s still happening today. The Moon creates bulges in Earth’s oceans, the famous tides. But because Earth is spinning faster than the Moon orbits, these tidal bulges get dragged ahead of the Moon. The Moon’s gravity pulls back on these bulges, which slows Earth’s rotation. At the same time, the bulges pull the Moon forward in its orbit, giving it more energy and causing it to drift outward. It’s like a cosmic dance where one partner keeps backing away while the other spins slower and slower.
This has real consequences. Every century, Earth’s day gets about two milliseconds longer. It doesn’t sound like much, but add it up over billions of years and you get the 24-hour days we enjoy now, up from those frantic five-hour days of our planet’s youth.
The Moon’s gradual retreat also means something bittersweet for the distant future. You know those spectacular total solar eclipses, where the Moon slides perfectly in front of the Sun and day turns to night? That only works because, by cosmic coincidence, the Moon appears almost exactly the same size as the Sun in our sky. But as the Moon continues its slow journey away from us, it will appear smaller and smaller. In about 600 million years, give or take, the Moon will be too far away to completely cover the Sun. Total solar eclipses will become a thing of the past.
But let’s not get too melancholy about the far future. The Moon’s current position has been a gift to Earth. Its gravitational influence helps stabilize our planet’s axial tilt at a comfortable 23.5 degrees, which gives us our reliable seasons. Without the Moon, Earth’s tilt could wobble wildly over millions of years, causing chaotic climate swings that would make life much more difficult. The Moon has been our planetary stabilizer, our night light, our tide maker, and our calendar keeper.
So tonight, when you look up at that familiar face in the sky, remember: you’re looking at a world in motion, slowly spiraling away on a journey that began when Earth was young and molten. The Moon has been leaving us since the moment it arrived, and yet it’s still close enough to light our nights, pull our oceans, and fill us with wonder.
It’s a slow goodbye that will take billions of years. We might as well enjoy the view while it lasts.
