Earth’s days are slowly getting longer which means one day we could technically end up with 25-hour days
Earth’s rotation is slowly slowing down. Not enough for anyone to notice in everyday life, but enough that scientists can measure it incredibly precisely.
Over millions of years, those tiny changes add up to noticeably longer days.
The main reason comes down to the relationship between Earth and the Moon. The Moon’s gravity pulls on Earth’s oceans, creating tides.
Because Earth rotates faster than the Moon orbits us, those tidal bulges sit slightly ahead of the Moon’s position, creating what scientists call tidal friction.
That friction acts like a very slow brake on Earth’s rotation.
At the same time, the Moon gains a small amount of energy from the process and slowly drifts further away from Earth – currently by around 3.8 centimetres per year.
Scientists estimate Earth’s day lengthens by roughly 1.7 to 2 milliseconds every century.
That sounds tiny, but over geological timescales it becomes much more noticeable.
Around 100 million years ago, a full day lasted about 23 hours, while some estimates suggest Earth’s days may have been closer to 18 hours around 1.4 billion years ago.
Earth’s rotation also changes slightly for other reasons.
Melting glaciers, rising sea levels, weather systems and movement inside Earth’s core can all subtly affect the planet’s spin.
In recent years, researchers have even found climate change is contributing to measurable changes in Earth’s day length.
Even these tiny shifts matter because modern systems like GPS, satellites and internet infrastructure rely on extremely precise timing.
Since Earth’s physical rotation doesn’t perfectly match atomic clocks, scientists have occasionally added “leap seconds” to keep global time aligned.
For now, Earth slowing down is more scientific curiosity than real-world problem – but it’s still strange to think that even something as familiar as a 24-hour day is slowly changing over time.
