EXERCISE FOR SCHOOLS: MEASURE THE SIZE OF THE EARTH!

by Knut Jørgen Røed Ødegaard

INFORMATION FOR TEACHERS:
Let your school and its students join the project of measuring the size of the Earth!

You must register here.
The form asks for the geographical position of your school (latitude and longitude). You should try to this as accurately as possible. The GPS system gives perfect data, but that level of precision is not necessary. A position accurate to one tenth of a degree should suffice. More accurate numbers may give more accurate values for the size of the Earth.

Then you should select a school from the list. list of participants that will be available here from April 15. Choose a school as far away from you (to the south or to the north) as possible. A school in Finnmark would be ideal for a school in Southern Norway. Schools in southern parts of Norway should select schools in Northern Norway. Non-Norwegian schools should have even better possibilities to select schools far away.

The classes (or even whole schools if the schools choose to do this together) must then agree on a date to make the exercise. It must be done at a very specific time on that date (read more below).

It would be simplest if the schools are at exactly the same longitude, but that is generally impossible. In order to compensate for different longitudes the measurements must be done a slightly different times.

MEASURE WHEN SUN IS TO THE SOUTH

It is very important that the measurements are done exactly (within a few minutes) when the Sun in the South. At that time it has its highest position in the sky (northern hemisphere) that day.

How do we find this time? In Norway it is easy because "Almanakk for Norge" can be used. In other countries there probably are national almanacs available. If you have a tabulated value for a city not too far away, you can find the exact time at your location:

Time difference measured in hours = (difference in longitude)/15

If the difference in longitude between the locations are 15 degrees, the location to the east shall do the measurements exactly one hour before the location to the west.

The time can also be found from this link:

"Data for all countries in the world"
- Choose your country
- Write the name of the nearest city
- Click on the name when the web site has located it
- On the page that comes up, choose "Sun" under "Astronomy".

Note that these times are valid for the day you check them.

HOW TO SET UP EXPERIMENT AND TRAINING

You should practice how to set up the experiment and how to read the angle before the day you have agreed on. This is important so that you are able to read the angle accurately on exactly the right time.

During the exercise the weather must be good enough that the Sun is visible on both locations (this also means that it cannot be done in Northern Norway in the middle of the winter).

Read description of method and how the size of the Earth is calculated.

CONTACT INFORMATION - PRESS CONTACT