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 Sun Rise and Sun Set
Name: Billy C.
Status: educator
Age: 60s
Location: N/A
Country: N/A
Date: 1999 - 2000


Question:
I teach the dual credit courses in science and my colleague (same age and training)teaches science also. We would like to know why the evenings started getting shorter going from sun set at 4:48 to now 5:08 while the mornings are also shortening going from 7:20 to 7:26 as the sun is rising later. It would appear the tilt of the earth would cause equal time for the shortening and lengthing for morning and evening .


Replies:
This is an EXCELLENT question, and usually occurs with another question (discussed below). The reason why the daylight time is advancing is because of the elliptical orbit of the earth about the sun. We reach the closest approach on January 4th. If you note, the amount of daylight has continued to increase, as the days are becoming longer.

The other question that usually accompanies this is, why on the equinox is there more that 12 hours of daylight? This is due to the refraction of light through the atmosphere, causing our real days to be longer than what geometry would dictate.

Thanks for using NEWTON

---Nathan A. Unterman



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 (help@newton.dep.anl.gov), or at Argonne's Educational Programs

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

Argonne National Laboratory