It is not clear to the human eye and we can’t feel the change but the day is becoming a bit longer every year and this is caused by the earth’s rotation that is being slowed down by the Moon. Our Moon gains energy from Earth and it slowly drifts away from Earth.
This shift can only be observed and measured thanks to NASA’s Laser Ranging RetroReflector that sends laser signals which bounce back to the satellites within Earth’s atmosphere. Every laser signal seems to take milliseconds longer to come back to earth which indicates that the day is getting longer.
Time on Earth
Time itself is still something quite complex from a scientific perspective and something that we are still having difficulties companding on the more philosophical ground. Time is only a perception by the human mind which is trying to give meaning to life through a timeframe as we like to call it.
Due to a phenomenon called gravitational time dilation, which refers to time moving slower as gravity increases. This means that the closer you are to earth’s core the faster time will pass. This also applies to the hypothesis that every planet within our galaxy can have time move faster or slower depending on the gravitational force presented on that planet.
Our Moon is kept in orbit by Earth’s gravitational force. The Moon also exerts its gravitational force onto Earth which affects its rotation by forcing oceans to form a tidal bulge. However, the moon is absorbing a lot of Earth’s gravitational force which affects our gravity by a very small percentage, therefore slowing Earth rotation, making time on earth to be perceived as longer.
How small you may ask? Well to be precise, based on NASA’s calculations in the last 100 years due to Earth’s rotation being slowed down the day became 1.4 milliseconds longer (0.0014 seconds). If we average Earth’s rotation slowing down in the past 2,000 years based on historical records of solar eclipses, we can average that the day gets longer by 2.5 milliseconds (0.002 seconds) every century.
This brings us to the big question.
How long until a day will be 25 hours?
Let’s first put some things into perspective. Based on the calculations done by NASA it would take 50,000 years to add a second to the length of a day. Our day is counted by hours, each hour has 60 minutes and each minute has 60 seconds.
An hour is 3,600 seconds so if we times that by 50,000 years it will give us the answer we are looking for. To answer the question, it will take another 180 million years until the day will last 25 hours instead of 24.
However, in those 180 million years there can be other major cosmical events taking place which might significantly impact the rotation of Earth, therefore bringing a 25 hour day much quicker than expected. Hopefully, until then no meteorite big enough to destroy Earth will hit our planet.