(no subject)

[abigailbrady]

Happy solstice everyone!

Random fact: sunrise has already started getting later each day, a few days ago, but sunsets won't start getting earlier for a few days yet [1]. Wonder if those two days (earliest sunrise, latest sunset) have actual names?


1. This may not apply to readers in the southern hemisphere.

Comments

[hairyears.livejournal.com]

Tidal drag from the moon slows the Earth's rotation by 16 seconds per million years... But that's nonlinear and it does not imply a four-hour day length four billion years ago! Fossil evidence suggests that in the middle Devonian period, about 375 million years ago, days were about 21.9 hours long, and there were about 400 days in a year. But beyond that I have no idea: ask a geologist.

However, if that calculation is difficult, day length prior to the collision which is believed to have ejected the Moon and given the Earth it's current 24-ish hour day is a matter of speculation.

The year, surprisingly enough, was pretty much what it is today, plus or minus ten percent. At least, since the end of the 'Hadean' era 3.8 Billion years ago, when the planetary bombardment had died down and no further significant exchanges of angular momentum took place.