Measuring the Solar System: A Collaborative Global Student Program

SUMMARY

The transit of Venus on 5 June, 2012 provides the opportunity to

replicate an entire chain of solar system measurements from the

ancient Greeks’ determination of the Earth’s diameter to the Sun-

Earth distance in kilometers. A yearlong program of simple hands-on

classroom projects, culminating with Venus transit, will be organized,

disseminated and managed by Astronomers Without Borders.

INTRODUCTION

Measurements of the dimensions of the Earth and inner solar system

began in Greece 2300 years ago when Eratosthenes noted the Sun’s

shadow at different latitudes, from which he determined the Earth’s diameter. By the 17th century the invention of the telescope

permitted measurements to be made during planetary transits of the

Sun, giving a relative scale to the inner solar system. Transits of

Venus, occurring only six times in the 400 years since the telescope’s

invention, allowed for the scale of the solar system to be measured in

terrestrial units, prompting observing expeditions to sites around the

world during the 18th and 19th century events in order to obtain the

most precise results possible.

These historic observations are recreated in some classrooms. The

transit of Venus on 5 June, 2012 – the last such event until the 22nd

century – provides the opportunity to replicate this entire chain of

measurements. New technologies available for the first time during

this rare event provide an unparalleled opportunity for worldwide

education. Students in different locations can collaborate to obtain

the multiple, widely-separated observations needed for many of these

measurements without the travel required earlier. Real-time

communication between classrooms provides a unique opportunity for first-hand experience of the Earth’s shape and size through

shared observations. Attention from science organizations and

media assure that the Venus transit will be a high-profile event.

PROGRAM DESCRIPTION

A yearlong program of classroom projects, culminating with the Venus transit, will be organized, disseminated and managed by

Astronomers Without Borders. Classrooms worldwide will be

engaged in these measurements and encouraged to collaborate with

other classrooms in distant locations. The program consists of a

series of simple, hands-on projects making measurements of the size

of the Earth and inner solar system using instrumentation created

with common, easily obtained materials augmented by instructional

materials disseminated by Astronomers Without Borders and others.

This program will be the first to bring together all of these projects

under a single program open and readily available to classrooms

anywhere in the world where an Internet connection is available. The

program will continue with all the experiments except the Venus

transit observation, with the network and infrastructure created in the

run-up to the transit remaining in place to serve an ever-increasing

number of schools as the Internet reaches more sites. The program

will also be expanded to create international observing programs in

education at all levels, and including amateur astronomers, as Astronomers Without Borders has been doing. These observational

programs will include not only the objects and phenomena that are

always available (stars, planetary motion, solar motion, etc.) but also

transient events such as lunar occultations, variable stars, meteor

showers, comets, near-Earth asteroids, solar phenomena and other

transient events.

OUTCOME

The Venus transit and the expanding use of online communications

technologies combine to provide a unique opportunity to engage

classrooms around the world without regard to location or cultural

differences. Students will gain not only scientific knowledge and an

understanding of simple scientific methodology through inquiry-based

learning, but also knowledge of the wider world, and the Universe, in

which they live.

1. Measuring the size of Earth and one’s location on it• Measure the radius of the Earth by observing the minimum gnomon

shadow on the same day at various latitudes.

• Classes at the same longitude work together on the same day, sharing

observations in real time.

• Observation of the disappearance of a gnomon’s shadow on “zero

shadow day” (tropical locations only).

• Measurement of the minimum length of a gnomon’s shadow on the

dates of the solstices and equinoxes to determine locaion.

• Cardinal points of the compass.

Astronomers Without Borders

www.astronomerswithoutborders.org

Mike Simmons

mikes@astronomerswithoutborders.org

(or mikes@astrowb.org )

FURTHER INFORMATION

2. Measuring the relative scale of the solar system

• Measurement of the ratio of the orbital radii of Earth and Venus.

• Method 1, measure the maximum angular separation of Venus and the

Sun.

• Method 2, measure the parallax of Venus as observed from different

locations on Earth.

• Simplest with schools on the same latitude or longitude but more

advanced classes can adjust for differences on both coordinates.

• Classes at different locations work together, combining their

measurements to obtain the results.

INITIAL PROJECTS

3. Measuring the relative size of the Sun and observing its

phenomena

• Angular diameter of the Sun measured directly.

• Solar phenomena observed including sunspots, solar rotation, limb darkening.

• Prominences and flares observed in H-alpha light, where possible.

• Solar constant measured directly.

• Simple spectrographs made in the classroom from paper and a CD to

observe the solar spectrum.

4. The Venus transit: Measuring the absolute size of the solar system

• Two steps

1. Measure the Earth-Sun distance relative to Earth’s diameter by making

observations from two or more locations

2. Calculate the actual distances between the Earth, Venus and the Sun

in kilometers.

• Two methods

1. Time the contacts of the Venus transit from different locations on Earth

2. Measuring the angular velocity of Venus during transit (Halley's

method).

• Classes at different locations work together, combining their measurements

to obtain the results.

• A phone app and website applet for use in making timing measurements

and sending them to a central site is being developed (see below).

Students in Poland taking part

in the Eratosthenes Project of

Ellinogermaniki Agogi.

Calculating the difference in

latitude based on shadow

observations.

Schoolgirls observing the

Sun in H-alpha light in Iraq

(R) and directly with solar

filters in Afghanistan (L).

Venus before and after greatest elongation

when the relative scale of the solar system can

be measured.

© Tunc Tezel / TWAN

The Venus Transit Phone AppDeveloped by Steven Van Roode

This app will be used by classrooms as well as amateur astronomers

and others worldwide contributing to a global project.

Additional projects based on multiple observations by collaborating

classrooms will be added beginning with the 2012-13 school year.

PARTICIPANTS

Galileo Teacher Training Program

Rosa Doran

Portugal

Global Hands-On Universe

USA

Sofoklis Sotiriou

Ellinogermaniki Agogi

Research and Development Department

Greece

The Inter-University Centre for

Astronomy and Astrophysics

India

Michael Zeiler

ESRI

USA

ESRI Geographic Information Systems (GIS) online tools will be used to manage, display and analyze data.

These new interactive web-based tools will provide real-time access to all participating classrooms.

REAL-TIME, INTERACTIVE GIS DATA SYSTEM

(1) Astronomers Without Borders, California, USA, (2) Inter-University Centre for Astronomy and Astrophysics, Pune, India, (3) Galileo Teacher

Training Program, Lisbon, Portugal, (4) Núcleo Interactivo de Astronomia, Lisbon, Portugal, (5) Global Hands-On Universe, California, USA

Mike Simmons1, Arvind Paranjpye2, Rosa Doran3,4,5, Manoj Pai

This program is a global, collaborative project open to

institutions worldwide. Significant exposure for

appropriate institutional and corporate sponsors is

available. For information on participation contact AWB

President Mike Simmons.

Steven van Roode

www.transitofvenus.nl

Example of GIS map of communities including data

on each, interactive (clickable) and updated in real

time on the website as data is added and modified by the users. A map of classrooms will be similar.