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Mystery
Class GMT Worksheet
Estimating Approximate Longitude using
GMT Sunrise Times
on the Vernal Equinox
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Step
# 1
Fill in the GMT sunrise time and date for the Mystery Class. This
is the time it is in Greenwich, England when the sun rises at the
Mystery Location. Put in Box A.
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BOX A
_______time______date
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Step
# 2
Fill in the time that the sun rises in Greenwich, England on March
20, the spring Equinox. This year that sunrise time is 06:03
A.M.
Put in Box B.
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BOX B
06:03 A.M. (3/20) |
Step
# 3
Figure out how many hours and minutes there are between the time in
Box A and the time in Box B. Put answer in Box C. This is the difference
in time between sunrise at Greenwich and sunrise at the Mystery Location.
(CAUTION!!! This may not be a simple subtraction or
addition equation. Remember that hours and minutes are not in decimal
form. Be sure to think about your answer!) Put in Box
C.
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BOX C
_______hours______minutes |
Step
# 4
For the next step you'll need to convert hours to minutes. Multiply
each hour in Box C by 60, add the remaining minutes from Box C.
Put the answer in Box D.
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BOX D
________minutes |
Step
# 5
Almost done! You now know how many minutes the earth spins between
the time the sun rises at the Mystery Class location and the time
it rises at Greenwich. Since the earth spins 1 degree longitude every
4 minutes, you must next divide by 4 to get the number of approximate
longitude degrees away from Greenwich. Divide the number of minutes
given in Box D by 4.
Put the answer in Box E.
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BOX E
________degrees |
| Step
# 6
Eastern or Western Hemisphere?
To determine the site's longitude you need to know if it is in the
Eastern or Western Hemisphere (i.e East or West of Greenwich, which
is 0 degrees).
- If
the sunrise time in Box A is later than the sunrise
time in Box B, the Mystery Class is west of Greenwich (Western
Hemisphere).
- If
the sunrise time in Box A is earlier than the sunrise time
in Box B, the Mystery Class is east of Greenwich (Eastern Hemisphere).
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BOX F
East or West? |