Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Rate of Change of Day Length
Name: Reginald
Status: other
Grade: other
Location: NV
Country: N/A
Date: N/A

Hello there, This question is regards to changes in sunrise/sunset times. I understand how they work, but surely the amounts by which the times differ on a day to day basis depend on the time of year. I would expect for the greatest change to be around March 21st and September 21st as they are the opposite days from the solstices. Does the rate of change of time depend on what rate the angle is changing between the earth's tilt and the sun?

Dear Reginald.

You got that right! the greatest change in daily sunset and sunrise times is around the equinoxes each year. However the tilt angle changes from 22.1 to 24.1 over many thousands of years, very slowly indeed! For all practical purposes it is constant.

David H. Levy

Click here to return to the Astronomy Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (, or at Argonne's Educational Programs

Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory