# What was the rotational velocity of Earth on Dec 31, 1899

I ask because time is defined with reference to this day (the SI second is based on a caesium clock is calibrated with reference to the 1952 ephemeris time standard, which was based on a second being 1/86 400th of Jan 0, 1900 (with Jan 0 being Dec 31 of 1899).

So... how do I calculate the rotational velocity of Earth on that day?

russ_watters
Mentor
Divide the length of the day by how far Earth rotated.

(hint: it isn't 360 degrees)

Right- of course! that's embarrassing - thanks!

360.9856° / 86400 s = 0.004178°/s or 15.041°/hr

Thank you Russ

russ_watters