The moon is drifting away from us.
Each year, our moon moves farther away from Earth—it’s just a tiny drift, about an inch and a half, a hardly noticeable change.
The forces of gravity are invisible and unshakable, and no matter what, they will keep nudging the moon further away.
Over many millions of years, we’ll continue to grow apart.
The moon used to be closer.
When it first formed, about 4.5 billion years ago, molded out of space rock that had been floating around Earth, the moon orbited 10 times nearer to the planet than it does today.
Our planet and the moon were always going to grow apart like this.
The moon pulls at our oceans, but those oceans pull back, making the moon speed up in its orbit. And “if you speed up while orbiting Earth, you are escaping Earth more successfully, so you orbit from a farther distance,” James O’Donoghue, a planetary scientist at JAXA, Japan’s space agency says.
The constant retreat has influenced Earth beyond the ebb and flow of its tides.
The forces that draw the moon away from us are also slowing down the planet’s rotation, stretching out the length of our days.
In the beginning, when the moon was closer, the Earth spun faster, a day lasted just four hours.
At the current rate of lunar retreat we are looking at 24 hours.
The moon is expected to continue drifting this way for the very scientific measure of forever.
Someday, about 600 million years from now, the moon will orbit far enough away that humankind will lose one of its oldest cosmic sights: total solar eclipses.
The moon won’t be able to block the sun’s light and cast its own shadow onto Earth.
But the moon will still remain bound to Earth, looking out onto a very different, much hotter version of the planet, as oceans start to evaporate.
Of course, a few billion years after that, the sun will derail the moon entirely, and Earth too, when it runs out of fuel, expands, and engulfs the inner solar system in a spectacular act of star death.
But not to worry, we still have a few billion years to cross that bridge.
