<grizzled_prospector_voice> Well, back in the day (late Cretaceous)...days were shorter because the Earth rotated faster. About 16 minutes shorter, by my numbers. </voice> (based on An average Earth day used to be less than 19 hours long and assuming a linear rate of change, which is about as accurate as assuming that cows are spherical) So rather than the current 365.2422 days per year*, there were back then 369.34 days per year. So that poster refers to a period of about 70,555,800 years without a dinosaur incident.
* specifically, per tropical year; that is, the length of all four seasons. (Though the length of the sidereal year likely would be a bit more stable than the length of the tropical year.) At the rate of change noted in that article, the length of the tropical year was 366 days about 17,900 years ago, so 365-day tropical years (with many leap years at the start) would have been appropriate only since then.
25,915,000,000 / 365 equals 71 million years.
ReplyDeleteIt would have been less than 71 million if Leap years had been introduced earlier.
<grizzled_prospector_voice> Well, back in the day (late Cretaceous)...days were shorter because the Earth rotated faster. About 16 minutes shorter, by my numbers. </voice> (based on An average Earth day used to be less than 19 hours long and assuming a linear rate of change, which is about as accurate as assuming that cows are spherical) So rather than the current 365.2422 days per year*, there were back then 369.34 days per year. So that poster refers to a period of about 70,555,800 years without a dinosaur incident.
ReplyDelete* specifically, per tropical year; that is, the length of all four seasons. (Though the length of the sidereal year likely would be a bit more stable than the length of the tropical year.) At the rate of change noted in that article, the length of the tropical year was 366 days about 17,900 years ago, so 365-day tropical years (with many leap years at the start) would have been appropriate only since then.