Carlos Solis
Our planet’s faithful companion has existed for 4.5 billion years. But like everything in the universe, it isn’t static. Dr. Steven Dickey, an astrophysicist at the University of Michigan, says the Moon is drifting away from Earth at about 3.8 centimeters a year.
As a result, he explained, Earth’s rotation is slowing down. That means, over time, our days could become longer.
This discovery helps explain why, around 70 million years ago toward the end of the Cretaceous, a day on Earth lasted only 23.5 hours.
As the Moon continues to drift away, the number of seconds, minutes and eventually hours in a day will gradually increase. But it’s unlikely anyone alive today will notice the change.
“Don’t worry, these effects are very minimal. 3.8 centimeters a year compared to the distance of 384,000 kilometers is just 0.00000001 percent per year,” Dickey reassured.
Dickey explained that tidal forces are behind the Moon’s motion. Earth’s tides depend on the Moon’s gravity, which causes Earth’s oceans to form two bulges. One bulge faces the Moon, where the gravitational force is strongest, while the other bulge faces away from the Moon, where the gravitational force is weakest.
“These tidal bulges slightly ‘lead’ the Moon because the Earth rotates and pulls them forward. The gravitational pull from the nearer tidal bulge accelerates the Moon, increasing the size of its orbit. Thus, the Moon is gradually drifting away from Earth,” Dickey continued. He added that the effect is very gradual and imperceptible.
“If we fast forward billions of years, Earth’s rotation may slow until it becomes tidally locked with the Moon. At that point, the Moon would stop drifting away, and we would see only one face of the Moon from Earth,” Dickey said.
However, future generations will never witness that outcome, the Daily Mail reported.
First, in about a billion years the Sun will brighten and evaporate Earth’s oceans, eliminating the tides that affect the Moon’s orbit, he explained. Second, in a few billion years the Sun will expand into a red giant, which will likely destroy both Earth and the Moon.
Photo: Unsplash
