Our closest neighbor in space, the Moon, is slowly drifting away from us. Researchers have calculated that the Moon’s recession runs at around 1.5 inches (almost 4 centimeters) per year. Even though it’s slow, this drift does impact life on our planet.
Over the centuries, we’ve built up an impressive array of knowledge about our satellite, but how many of us have wondered what would happen if the moon drifted away from Earth? Though it’s unlikely to affect us in our lifetime, there are some major changes to expect with the Moon’s departure.
Lunar Recession History
The Moon was born out of a massive collision of rocky material hurtling into our planet. The Atlantic describes that, when molten debris spun and formed into our satellite, the Moon’s orbit was about 10 times closer, and a day on Earth ran at around four hours. It was also pulling away much faster — at around 8 inches (around 20 centimeters) per year.
From the time it formed to the present day, the Moon has been moving away from Earth. Astronomers suspected this but were able to confirm and measure the rate by bouncing lasers off mirrors installed on the Moon’s surface during the lunar expeditions of the 1960s and 1970s.
The Conversation notes that the current rate is around 1.5 inches (3.8 centimeters) per year. From this rate, scientists initially calculated back to an initial impact date of around 1.5 billion years ago; however, other evidence showed that the Moon is much older with a creation date of around 4.5 billion years ago.
Rather than give in to “alternative” creation theories, the researchers turned to sedimentary rock analysis, which suggested variation in recession rates over the years. For example, around 2.46 billion years ago, the distance between Earth and Moon was 60,000 kilometers less than it is today, which shortened the day to only 17 hours instead of 24 hours.
Why Is the Distance Between the Earth and Moon Increasing?
Before asking what would happen if the moon drifted away from Earth, we first need to understand why this drift is happening. All bodies in space exert a force on each other, and the magnitude depends on a number of factors, including distance and size or mass. Closer objects exert more gravitational pull, and that increases if they are larger. Earth exerts a gravitational pull on the Moon, and vice versa.
The force that the Moon exerts on Earth shows up as our tides, with the oceans ebbing and flowing roughly twice each day. The gravitational pull of the Moon makes our oceans bulge outward along the direction of the pull; however, NASA notes that this pull is out of sync, since it takes some time to move water around. The tidal movements also slow Earth’s rotational spin due to friction. This, in turn, impacts the speed at which the Moon orbits, letting it drift off into space.
What Are the Implications of This Drifting?
So, what would happen if the distance between the Earth and Moon increased? Most of this question can be answered by looking at what influence the Moon exerts on Earth, and as the Royal Museums Greenwich describes, it’s mostly to do with the sea, as this is where lunar gravity has the most effect.
Interestingly, if the Moon was closer, its gravity would start tugging at Earth’s crust. At even half the distance, Live Science describes that, not only would tides be eight times higher and slow down Earth’s spin, but there’d also be more seismic activity and volcanic eruptions.
Increasing distance would also cause extinctions and climate upheaval. A more distant Moon would mean smaller tides, which would affect coastal ecosystems and ocean currents. Loss of coastal ecosystems and habitats for many species would seriously affect animals on land and sea that rely on them as part of the food chain.
Ocean currents drive and stabilize the weather, so we could expect more extremes of temperature and global climate disruption. The Moon’s gravitational pull also helps stabilize Earth’s tilt toward and away from the Sun, which causes the different seasons in each hemisphere. Less stability might completely abolish the seasons or perhaps lead to more extremes.
Being further away would mean less impact on Earth’s rotation, with longer days and nights. There would also be less moonlight, as the Moon would seem smaller in the night sky. Predators that hunt at night wouldn’t be able to locate prey so easily.
And with a “smaller” Moon in the sky, we’d lose an astronomical highlight — in 600 million years, the Moon will be too far away to completely block the Sun in a total eclipse.
Sweet Dreams, Moon
Another reason for the Moon’s drift is tidal locking. On Earth, we only see one side of the Moon, but this wasn’t always the case. Early on in its development, the Moon had its own rotational spin. However, since Earth was also exerting a gravitational pull and distorting its shape, energy dissipated and slowed the Moon’s rotation down. Eventually, one lunar rotation took the same length of time to orbit the Earth, and the Moon became tidally locked with only one face presented to the planet. This energy dissipation also contributes to lunar drift.
As the two drift further apart, Earth will become tidally locked and have its own dark side compared to the Moon. In about 50 billion years, not only will the Moon be further away, but only one half of our planet will be able to see it each night. While that’s quite a bit away, it’s just one more reason to appreciate the Moon in the night sky while we can still see it.
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