🚀 go-pugleaf

Date: Thu, 15 Sep 1994 22:42:18 -0400
From: aj860@cleveland.Freenet.Edu (James D. Meinke)

          ATTENTION - SEPTEMBER 24, 1994 IS THE EQUINOX

             A WORLDWIDE SCIENCE AND MATH EXPERIMENT

                     ERATOSTHENES EXPERIMENT

Eratosthenes, a Greek geographer (about 276 to 194 B.C.), made  a
surprisingly accurate estimate of the earth's circumference.   In
the great library in Alexandria he read that a deep vertical well
near Syene, in southern Egypt, was entirely lit up by the sun  at
noon  once a year.  Eratosthenes reasoned that at this  time  sun
must  be directly overhead, with its rays shining  directly  into
the well.  In Alexandria, almost due north of Syene, he knew that
the sun was not directly overhead at noon on the same day because
a vertical object cast a shadow.  Eratosthenes could now  measure
the  circumference  of the earth (sorry Columbus) by  making  two
assumptions - that the earth is round and that the sun's rays are
essentially  parallel.  He set up a vertical post  at  Alexandria
and  measured the angle of its shadow when the well at Syene  was
completely sunlit.  Eratosthenes knew from geometry that the size
of  the  measured  angle equaled the size of  the  angle  at  the
earth's  center between Syene and Alexandria.  Knowing also  that
the arc of an angle this size was 1/50 of a circle, and that  the
distance between Syene and Alexandria was 5000 stadia, he  multi-
plied 5000 by 50 to find the earth's circumference.  His result,
250,000  stadia (about 46,250 km) is quite close to modern  meas-
urements.   Investigating the Earth, AGI, l970, Chapter 3, p. 66.

The formula Eratosthenes used is:


     D         A        d=distance between Syene and Alexandria
   _____  =  _____      A=360 degrees assumption of round earth
                        a=shadow angle of vertical stick
     d         a        D=to be determined (circumference)

----------------------------------------------------------------
Are you interested in participating?

All you need to do is place a vertical stick (shaft) into the
ground at your school and when the sun reaches it's highest
vertical  assent  for the day (solar noon  therefore  the  shadow
length will be the shortest), measure the angle of the shadow  of
the stick (a).

                            -\
                            - \
                  stick ->  -  \
                            - a \    a=shadow angle
                            -    \
                            -     \
   ground___________________-______\shadow_______________________

By doing this experiment on the equinox we all know that the
vertical rays of the sun are directly over the equator, like the
well  at Syene.  Using a globe or an atlas the  distance  between
your location and the equator ( d in equation) can be  determined
and the circumference can be calculated.
*****************************************************************

But how about sharing your shadow angle measurement with others
around the real globe.

******************************************************************

Send your measurement of the shadow angle____________degrees

Send your location city ____________________________________

Send your location country _________________________________

Send your latitude _________________________________________

Send your longitude ________________________________________

To Lakewood High School Earth Science Class, Lakewood, Ohio
               bd765@cleveland.freenet.edu

We  will compile all the data and send you a copy to use in  your
classroom  to compare the various locations and angles.

If your interested send us your data.  We will compile and return
it  to you by September 30, 1994.  Chances are your lesson  plans
will  not  be able to fit this in on Friday, September  24,  l994
(the equinox).  Most any day plus or minus 2-4 days of the  equi-
nox will give fairly good data (like Wednesday through Friday  or
Monday or Tuesday).

Jim Meinke - Lakewood High School bd765@cleveland.freenet.edu

******************************************************************

            INTERESTED IN A NEW WORLDWIDE EXPERIMENT

          MAPPING THE EARTH'S MAGNETIC FIELD (ISOGONIC)

This experiment can involve many classrooms around the globe in:
     communications
     measurement
     mapping skills
     calculations

It would involve a minimum of equipment at each school (or home)
to conduct the experiment.
     world map
     compass(es)
     night observation of Polaris (North Star), Southern Cross
         for our southern neighbors

The  experiment would involve many schools or homes  involved  in
gathering the data from their latitude and longitude. How far off
is your magnetic data from true north or south in your location?
This data would be transmitted to us here at Lakewood High School
and  we  would send out a summary so that you could  construct  a
worldwide  magnetic map in your classroom.  This would also  lead
to discussions on the locations of the magnetic poles as well  as
how to draw iso or (equal) lines.  It might also lead to  discus-
sions of night sky movements around the constellations or how the
magnetic field is thought to be created.

                       ARE YOU INTERESTED?

If  you  are interested in trying such an experiment, drop  me  a
quick note at the address below.

Jim Meinke -         Lakewood High School
                     bd765@cleveland.freenet.edu
                               or
personal account  -  aj860@cleveland.freenet.edu
personal account  -  meinke@freenet.lorain.oberlin.edu


********************************************************************************
Richard Lee Holbert '85                          g_holbertrl@titan.sfasu.edu
210 West Austin, #204                            rlh@tenet.edu
Nacogdoches, Texas 75961                         rholbert@cap.gwu.edu
AGGIE '85, Cooking/Eating, Genealogy, Alternative Medicine/Health Care
K-12 Computing/Networking, INTERNET Surfing, and other stuff

"If you think Education is Expensive, consider the Alternative "
                          - cannot remember author -