Why is the Moon moving away from Earth?
We have seen Moon shining over us, as a calm beautiful presence in the sky since the day we were born. Countless poets and authors have written their best work while being moved by the beauty and serenity of the Moon. We expect the Moon to be the forever companion to Earth.
But sadly that is not the case. Our dear Moon is moving away from us. And this descent started much before social distancing became the norm for us on Earth.
You might be surprised to know that billions of years ago Moon used to be very close to us. Around 4.5 Billion years ago when the early Earth collided with a proto-planet the size of Mars a large amount of matter was ejected out of Earth’s surface. These shards of rocks and debris then coalesced together to form the Moon we see today. After its formation, Moon was only 22,500 km away from us, orbiting around the Earth at a distance more than 10 times closer than what we see today.
Then why did the Moon start moving away from us?
Scientists have deduced that the Moon’s descent away from Earth happens at a rate of 3.78 cm per year. Scientists have measured this movement using laser beams that they reflect over the mirrors left by astronomers over there courtesy of various Moon Missions.
As we all know objects in space are held together by forces of gravity. Earth being the larger of the two exerts tremendous amounts of gravitational pull on the Moon. Similarly, Moon also exerts a gravitational force on Earth but it’s relatively weak.
It is this force that makes our oceans bulge creating the tides that we see today. The “tidal bulge” here creates enough friction with the surface of the Earth to reduce the speed at which Earth spins on its orbit. In other words, Moon’s gravity acts as a break to Earth’s spin.
The is breaking effect has been happening for so long and the evidence for it can be seen by studying the daily growth bands of corals. Earth days have gotten longer over the years and the 24 hours that we experience today is a direct result of this slowdown. Scientists estimate that Earth days will continue getting longer at a rate of 19 hours every 4.5Bn years.
The tidal bulge also exerts a pull over the Moon which causes it to speed up in orbit. It is this speed up that pushes the Moon outward making Moon escape from Earth’s gravitational influence easy thereby letting the Moon depart from us.
What happens if Moon leaves us like this?
Well, the Moon can never fully leave us, but as it moves farther apart there will be dramatic changes to Earth as a planet.
The departure of the Moon will wobble the planet creating instability. Seasons will get altered, causing extreme temperature swings causing a wide range of ecological problems. While humans like us may be able to adjust to these changes, a large number of plants and animals cannot. This will gradually create ecological breakdowns whose net effect we can’t even foresee. It is safe to say it would not leave a pretty picture behind.
Should we be worried?
It will take around 50 Billion years for Earth to completely stop spinning and by that time our tides would have stopped and the Moon will also have stopped moving away from us. It will take another 600 million years or so for Moon to move enough distance to create any of these problems and there is no guarantee that we will be around here to watch these events unfold anyway. So keep enjoying your Moonlight like you always do.