The Moon has been our celestial companion for about 4.5 billion years, forming after a massive collision between Earth and a planet-sized body called Theia. Over time, its orbit has changed, and it’s slowly drifting away from us—about 3.8 centimeters every year. This journey means that one day, humanity might witness the last total solar eclipse.
Scientists have used the Lunar Laser Ranging Experiment, set up during the Apollo missions, to measure the Moon’s distance with impressive accuracy. By bouncing lasers off retroreflectors left on the Moon, they’ve been able to track its movement almost precisely.
Interestingly, if we rewind the clock based on its current distance, the Moon would have been much closer to Earth about 1.5 billion years ago—an odd figure since the Moon is actually older than that. Instead of relying solely on this backward calculation, researchers look at evidence from Earth’s geology. For instance, fossilized coral can give insights into how long a day was in the past and how distant the Moon was at various times.
Looking ahead, eclipses will become less frequent. Richard Vondrak from NASA predicts that about 600 million years from now, we will witness the last total solar eclipse. Right now, the Moon and Sun look similar in size from our perspective, making total eclipses possible. This is a happy coincidence: the Sun is about 400 times larger and farther away than the Moon.
Historically, the Moon’s size in our sky has changed significantly. Four billion years ago, it appeared about three times larger than it does now. As it continues to drift, it will seem smaller over time, but it will never fully escape Earth’s gravity.
Eventually, in around 5 billion years, the Sun will enter its red giant phase and could engulf the Earth. By then, the Moon will still be gravitationally bound to Earth, indicating our celestial bond will continue until much later than any physical separation.
As we observe and study these celestial movements, it’s fascinating to think about the unique dance between Earth and the Moon, reminding us of the transient nature of our universe.
For more insights on the Moon’s movements, you can check NASA’s detailed reports here and the fascinating findings from the Lunar Laser Ranging Experiment here.
