This change is minuscule and hardly noticeable to the naked eye, but it will continue incessantly and never come to a halt. Invisible and inescapable gravitational forces will persistently influence the Moon, and after millions of years, a separation between the Moon and Earth will inevitably occur.
In the past, around 4.5 billion years ago, when the Moon was newly formed, it was much closer to Earth than it is today. The estimated distance between Earth and the Moon at that time was nearly ten times smaller than it is now. Scientists have noted that the Moon was shifting at a rate of about 20 cm per year during this period.
Our planet Earth and the Moon are destined to slowly part ways. While the gravitational pull of the Moon is typically weak, it can still impact its host planets. In Earth’s case, being an ocean-covered planet, the gravitational force from the Moon manifests in the changing tides. The Moon tugs at our oceans, but is also pulled by them, causing an acceleration in the Moon’s orbit. As explained by planetary scientist James O’Donoghue of the Japanese space agency JAXA, “if you speed up while going around Earth, you are going to escape from Earth more easily, so the distance will increase.”
Scientists refer to this phenomenon as the “moon’s recession.” They have measured this retreat by projecting laser beams onto the reflectors left on the Moon’s surface by Apollo astronauts, utilizing that data alongside other sources to estimate the ongoing shifts.
Researchers have discovered that the pace of the Moon’s recession has varied over the years, coinciding with significant events like asteroid impacts on the Moon or Earth’s changing ice ages. This lunar retreat has had far-reaching effects, both on Earth and in terms of tidal impacts.
The Moon’s gravitational forces pulling away from us are also slowing Earth’s rotation, lengthening our days. Initially, with the Moon closer, Earth spun faster, leading to days lasting just five hours. Over 4.5 billion years, under the influence of the Moon, Earth’s rotation slowed to 24 hours. With the current rate of recession, the Moon will take a century to add an additional 2 milliseconds to a day on Earth or even longer.
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When it was first formed, the Moon was closer to Earth than ever before. Image: NASA
In scientific theory, the Moon is expected to continue its journey away from Earth, and in about 600 million years, it will reach an orbit far enough that humans will no longer experience a captivating astronomical event: a total solar eclipse. This is because the Moon will be positioned where it cannot cast a shadow on Earth from the Sun. Yet, the Moon will remain tied to Earth – a much hotter version as the oceans begin to evaporate. Billions of years later, a fuel-depleted Sun will transform into a dead star, engulfing the entire Solar System in a massive explosion and, of course, leading to the permanent disappearance of the Moon and Earth.