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.
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.
