From the shadow of a stick to the ....circumference of earth

Category 12 years to 15 years : 1

From the shadow of a stick to the ....circumference of earth

Repetition of Eratosthenes Experiment

4th junior High School in Petroupoli, Greece

On the 20th of March 2015, the closest to the vernal equinox date, our school had calculated the circumference of Earth. What we had done is use a cylinder of a map case (we call this a “gnomon”), measure its length, hold it vertical to the ground and measure its shadow at solar noontime, when the shadow is the shortest. Then we calculated the angle that sunrays hit the ground.

 Other schools that date, had the same procedure of measurements, too. We exchanged data with those schools and using in a method of three the difference of the angles of the sunrays to the ground, we calculated the circumference of earth.

We did this, because of the participation of our school in etwinning project Eratosthenes 2015, an ongoing etwinning project that celebrates its ten years of life.

On March the 20th, 16 schools of this project had also measured their gnomons and shadows.	Matching our data with theirs, the most accurate calculation for our school, came from matching those of the French college Antonin Perbosc in Lafrancaice, France.

 The circumference of earth calculated as 39954 Km.

This is a repetition of Eratosthenes experiment, which originally took place 2200 years ago. Watching this video you'll get a description of it (click on the following picture):	And more vividly and precisely the mathematician’s part is explained in this one (click on the following picture):

 You can also repeat this experiment!

We are looking forward to exchange measurements with you!

4th Junior High School in Petroupoli, Greece: Light, color and heat

Imagine that it is 40 degrees outside. How do you stay cool? What kind of clothing do you wear?

Can you think of any instances that the color of an object makes a difference in how hot it gets in the sun?

In 4th Junior High School in Petroupoli, we tried to approach

How the color of an object

affects

heat absorption

of light

Do you want to try our crossword?

Thinking of the light ...brainstorming activity

from 4th Junior High School in Petroupoli

 Click on a word to start

Across

1. Light .... is 300.000 km/s

5. There is a great variety of them that  produce light

8. A ...... is a region where light from a light source is obstructed by an opaque object

12. ....... is when light hits an object and part of its energy goes into the material of the object

13. The main source of light on Earth

Down

2. Duality of light means that it exhibits properties of both wave and....

3. Direction that light travels

4.   ......... is an instrument that aids in the observation of remote objects

6.  .... happens for the part of the light that doesnt "stay" into an object when light hits the object

7.  Light is seen as ... and simultanously as consisted of particles

9.  The study of light,......, is an important research area in modern physics

10.  The subject of our etwinning project

11. .... reflect light and also are used for personal grooming

Looking for answers?  Click here