TRANSIT OF VENUS: SCHOOL ACTIVITIES

by Knut Jørgen Røed Ødegaard

How do we measure the distances in space? Several hundred years ago, the transits of Venus were used to determine the dimensions of our Solar system. Here you can find out how this was done and how you can do this yourself!

Below we present two practical exercises aimed at schools and others with an interest in this subject. The first exercise is to measure the size of the Earth and this you can do at any time. The second one can only be done on the 8th of June: it involves measuring the distances in space!

The two problems provide an insight into the unique effort that made it possible to determine the scale of our Solar system. In the following presentation, little knowledge of mathematics is assumed. For those specially interested, there are links below to a range of background material.

Through these exercises the student will - in a new and unique way - learn about space and the sizes and distances to our neighboring celestial objects. We hope that everyone takes advantage of this a-once-in-a-lifetime opportunity.

To carry out the calculations you need to compare your measurements with those obtained at a different location on the Earth. Thus it is important to register as soon as possible. See the link "Registration" in the exercise sections below.

Exercise 1: HOW TO MEASURE THE CIRCUMFERENCE OF THE EARTH
	EQUIPMENT AND HOW TO MEASURE You can easily make the equipment you need yourself. A long straight tube and a spirit level are the most important things. Collaborate with a school far away and measure the size of our planet! The method was used for the first time in Egypt almost 2500 years ago. More.
	CALCULATING THE SIZE OF THE EARTH You have now measured the altitude (elevation above the horizon) of the Sun (link above). Before you continue, you or your teacher must exchange results with the co-observing school. More.
	REGISTRATION: IMPORTANT INFORMATION FOR TEACHERS In order to estimate the size of the Earth you need to exchange results with the school you are collaborating with. Find a partner school.

MORE INFORMATION / BACKGROUND MATERIAL:
	HOW THE EARTH WAS MEASURED Almost 2500 years ago an Egyptian managed to calculate the circumference of the Earth! It was a major achievement. Here you can find out how he did it. More.

Exercise 2: HOW TO MEASURE THE DISTANCE TO THE SUN
	METHOD 1: TIMING THE CONTACTS BETWEEN VENUS AND THE SOLAR DISK This method is based on the fact that the entrance and exit times will be slightly different when observed from different parts of the world. One can use this principle to find the distance from the Earth to the Sun. More.
	METHOD 2: MEASURING THE PATH OF VENUS ACROSS THE SOLAR DISK This method is based on the fact that Venus will move along two slightly different paths across the solar disk if the transit is observed from two different locations on Earth. One can utilize this to find the distance from the Earth to the Sun. More.
	REGISTRATION Once you have made the observations you are invited to register the measurements on this registration form.
	INTERNATIONAL SCHOOL CAMPAIGN Since a transit of Venus is a truly historic event, an international school campaign has been organized. Students - and others - from the whole world are encouraged to participate and make as accurate measurements as possible. More.

MORE INFORMATION / BACKGROUND MATERIAL:
	PARALLAX AND THE DISTANCE TO THE SUN What is parallax, how is it measured and how can we use it to determine the distance to the Sun? More.
	DETERMINATION OF THE SUN-EARTH DISTANCE USING THE PATH OF VENUS ACROSS THE SOLAR DISK (METHOD 2) A transit of Venus offers a unique possibility for us to measure the actual distance to the Sun. Once this quantity is determined, we can easily compute the other distances in the Solar system by using Kepler laws. More.
	THE POSITIONS OF THE PLANETS RELATIVE TO THE EARTH AND THE SUN The inner planets of the Solar system, Mercury and Venus, can never be very far away from the Sun in the sky. Here you will find the reason why, and you will also understand other concepts related to planetary orbits and why Venus only covers a small fraction of the Sun during a transit. More.
	THE EARTH'S AND VENUS' RELATIVE DISTANCE TO THE SUN With the transit of Venus in 1769, astronomers for the first time managed to determine a rather accurate distance to the Sun. However, the relative distances between several objects in the Solar System were already known. In 1543 Nicholas Copernicus published a work describing the workings of the Solar system. It also gave a determination of the relative distances between the Earth and the Sun and between Venus and the Sun. More.
	KEPLER'S LAWS DESCRIBE THE MOTION OF THE PLANETS For hundreds of years astronomers studied the movements of the planets with increasing accuracy. But it was hard to describe their orbits mathematically. We only see the planets projected onto the sky, so we can only study their apparent motion against the stars. It is not trivial to observe how the planets really move around in space - towards us or away from us. More.

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