A
few weeks ago, we asked you to think about what your photoperiod
graphs would look like on the equinox. It is said that every place
on Earth has the same amount of daylight and night on the equinox,
twelve hours each. Is that what you discovered with this week's
data? As some of you may have observed, many locations do not appear
to have EXACTLY twelve hours of equal day and night on the equinox.
This made us wonder:
Challenge
Question #5:
"Why don't all locations appear to have EXACTLY twelve hours
of day and night on the equinox?"
SEASONAL
Cycles vs. DAILY Cycles
A 5th Grade Class in New Jersey raised a good question. They wondered
if the equinox happens at the same time in New Jersey and California.
Their question points out a very common confusion between Earth's
SEASONAL and DAILY cycles. Let's see if we can explain the difference:
* Moments
in seasonal cycles (e.g., spring and fall equinox, summer and winter
solstice) occur everywhere on Earth at the same time. They relate
to the Earth's location in space as it revolves around the sun.
Everybody is on the same Earth!
* Moments
in daily cycles (e.g., sunrise, noon, sunset) occur at different
moments in different places on Earth. They relate to Earth's spinning
(rotating) on its axis. (As Earth rotates each day, the sun hits
different areas.) Everybody is NOT on the same place on Earth!
Now
try this:
Challenge Question #6:
"Try to explain in your own words or with a diagram why the
equinox occurs everywhere on Earth at the same time. Then explain
why sunrise and sunset happen at different times in different
places on Earth."
To
respond to these Challenge Questions, please follow these instructions
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