Kids
Calculating Photoperiods
Here are
three ways in which students can calculate the photoperiod of a location
from sunrise and sunset data.
1.
Use noon as a pivot point.
If the sunrise is at 6:14 a.m. and the sunset is at 9: 36 p.m., you would
divide the photoperiod into two parts: the amount of time before noon
and the amount of time after noon. Most students would work it through
like this: from sunrise (6:14) to 6:30 is 16 minutes, from 6:30 to noon
is 5 hours and 30 minutes, so from sunrise to noon is 5 hours and 46 minutes.
From noon to sunset is 9 hours and 36 minutes so the total would be 14
hours and 82 minutes. Since they know that there are only 60 minutes in
an hour, it becomes 15 hours and 22 minutes. It may help to state it visually:
sunrise 

noon 

sunset 
6:14 
morning
photoperiod 
12:00 
afternoon
photoperiod 
9:36 
2.
Convert sunrise and sunset numbers to a 24hour clock and subtract sunrise
from sunset.
sunset
9:36 
convert
to 24 hour clock 
21:36


sunrise
6:14 


6:14 

photoperiod


15:22

15
hours and 22 minutes 
This can
be challenging when one of the hours has to be converted to 60 minutes
to enable proper subtraction. For example:
sunset
9:08 
converted
21:08 
rename

20:68 

sunrise 5:52 
5:52 

5:52 
photoperiod



15
hours and 16 minutes 
3.
Mystery Class veteran teacher, Jo Leland offered this helpful Teacher
Tip for calculating photoperiod too:
Students
may also come up with their own methods that come out correctly. Let them
use whichever method they feel comfortable with as long as it works consistently.
National
Science Education Standards
Science
as Inquiry
Use math in all aspects of scientific inquiry. (58)
Earth
and Space Science
Most objects in the solar system are in regular and predictable motion.
Those motions explain phenomena such as the day, the year, phases of the
moon, and eclipses. (58)
National
Math Standards
Numbers
& Operations
Understand numbers, ways of representing numbers, relationships among
numbers, and number systems.
Compute fluently
and make reasonable estimates.
Problem
Solving
Build new mathematical knowledge through problem solving.
Connections
Recognize and apply mathematics in contexts outside of mathematics.
