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I thought every day was shorter then 24 hours, and that is why we have leap year.
A leap year is because 1 year isn’t exactly 365 days. It’s something like 365.24.
You may be thinking of a sidereal day which is around 23 hours 56 minutes. That’s the time it takes the Earth to complete a rotation, but since the Earth orbits the sun it isn’t long enough to put the sun at the same spot in the sky.
From the article:
The Earth’s rotation is influenced by the core and the atmosphere, according to Scientific American.
The science magazine says that the core’s spin has been slowing, though for unknown reasons, meaning that the rest of the planet must speed up to compensate.
“The core is what changes how fast the Earth rotates on periods of 10 years to hundreds of years,” Duncan Agnew, a geophysicist at the Scripps Institution of Oceanography, told the magazine. “The core has been slowing down for the last 50 years, and as a result, the Earth has been speeding up.”
Atmospheric forces cause the rotation rate of the Earth to speed up in the summer of the Northern Hemisphere, according to Scientific American. Forces caused by the moon also affect the rate the Earth spins.
The magazine notes that on the geologic timescale, the Earth has been slowing, with the rotation taking half an hour less 70 million years ago.
August 5th is predicted to be more than a millisecond shorter than 24 hours this year, although that’s just a prediction and it also may not be.
