An international team of researchers, led by Hisashi Hayakawa from Nagoya University, recently used corrected coordinates for ancient Qufu, China, to refine Earth's rotation speed for a 709 BCE solar eclipse, setting the delta T (ΔT) between 20,264 and 21,204 seconds. This revised calculation resolves a long-standing discrepancy in astronomical records and provides new data for understanding Earth's rotational changes and solar activity over millennia.

What the records show

The timeline

What changed and for whom

What the subject has said publicly

What we could not confirm