Long-term Slowdown:
- Earth's rotation is slowing down over time. This is mainly due to the Moon's gravitational pull on Earth's oceans, creating friction that gradually slows the spin.
- Millions of years ago, days were significantly shorter. Studies suggest a day was only 18 hours and 41 minutes around 1.4 billion years ago!
- Even today, the day is slowly lengthening by about 1.7 milliseconds per century according to atomic clocks. This gradual change is accounted for by occasional "leap seconds" added to Coordinated Universal Time (UTC).
Recent Oddities:
Interestingly, scientists recently observed Earth spinning a bit faster than usual, particularly in 2020. The 28 shortest days on record all occurred during that year.
Melting ice caps due to climate change redistribute mass on Earth. This counteracts the usual slowing trend to some degree, potentially delaying the need for future leap seconds.
Other Factors Affecting Rotation:
- Earth's rotation isn't perfectly uniform. Earthquakes, volcanoes, tidal forces, and wind patterns can cause slight variations in speed.
- The Earth's liquid outer core also influences rotation. Its movement can actually speed things up to an extent.
Overall:
- Earth's rotation is a complex system affected by multiple factors.
- The long-term trend is a slow down, but there are variations and recent observations suggest a more nuanced picture.
The changes are minuscule in our daily lives, but scientists continue to monitor and understand them.