Eli5: If millions of years ago a day had only 22 hours, does science count those years differently, or is the standard always 24 hours? Aren’t we then missing a few years which we need to add up?
In: 7
As others have pointed out the time it takes for the earth to complete one rotation (a day) has changed, but that doesn’t effect the time it takes for the earth to go around the sun (one revolution).
But to answer your question, does science count those past years differently? No, and it doesn’t need to. When we talk about millions of years ago we are talking about it relative to our current time. 1 million years ago is 1 million of OUR years ago. We don’t care what the “date” was we are talking about because nothing that happened 1 million years ago has a specific date we care about. If you were magically transported to 1 million years ago you might have to setup a slightly different calendar, but we don’t care about it today.
The speed of the earths orbit around the sun IS slowing, but its on a time scale of roughly 0.0000048 seconds per year. That means in the entire existence of humanity (roughly 300,000 years) the year has gotten about 1.5 seconds slower. Meaning you could more or less use the current calendar even then. Even a million years ago the calendar year would only be 4.8 seconds faster. In the entire existence of the solar system, roughly 4.5 billion years the length of the solar year has changed by 6 hours. If you lived on earth when it was first formed (which would be difficult at best!) that would mean…wait a second, that means no more leap year! A year would be close to exactly 365 days! But wait, thats 365 MODERN days. It would actually be different due to the slowing of the earths rotation due to the moon. So complicated.
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