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Dark Skies: From the eyes of
Eratosthenes, to our eyes
Introductory section and preparatory phase• Short Description: Studying Ancient Astronomers especially in Greece,
Egypt, and Middle East we are astonished by the detailed descriptions of the Constellations and Stars. Eratosthenes is describing in full detail the Hydra constellation, while Aratus described the constellations of Orion, Ursa Minor and Major, Draco and Cepheus. Their ability to observe a wide number of stars was mainly due to low “light pollution”. Nowadays, stars are almost out of sight especially in cities due to high levels of “light pollution”. We will compare the number of stars observed by ancient astronomers to the number of stars we can observe nowadays, revealing information about “light pollution” through centuries. We will use the Stellarium application and a Google plug-in for light pollution for each place.
• Keywords: Light pollution, Constellations, Stars, Ancient Astronomers.
• Target audience: Students studying Physics and Astronomy.
• Age range: 14-18 years old
• Context: Natural Sciences School Lab, Computer School Lab, Internet Connection.
• Time required: 6 hours
Introductory section and preparatory phase• Technical Requirements: Internet connection, appropriate software: Stellarium,
Google Earth plug-in, Microsoft Office, Microsoft Windows, Computers, video projector could be useful.
• Author’s background: Knowledge of Physics, knowledge of Astronomy, Constellations, stars. Stellarium, Google+, internet, Google Earth plug-in. Ancient astronomers descriptions of stars and constellations (use of Wikipedia can be useful).
• Connection with the curriculum: Strongly related with Astronomy (Second Class of Greek High School), Physics (First, Second and Third Class of Greek High School). Partly related with Philosophy and ideas of ancient astronomers and philosophers (Eratosthenes, Hipparchus, Aratos).
• Learning Objectives: Hands on learning, Inquiry based learning, ICT in education, use of Open Science Resources, learn students to cooperate and act as researchers.
• Guidance for preparation: Search in literature, bibliography, internet and other sources, about detailed descriptions of stars and constellations developed by ancient astronomers. Download the plug-in GaN2013.kmz for Google Earth. Download Stellarium. Both Stellarium and Google Earth GaN2013.kmz are free in internet.
Pre-Experiment / Observation– Teaching Phase 1:Questions Eliciting Activities – PROVOKE CURIOSITY
Teacher introduces students in “Eratosthenica”, book written by Eratosthenes describing in detail the constellation of Hydra.
http://www.wilbourhall.org/pdfs/Eratosthenica.pdf Then asks students to find how many stars Eratosthenes was able to observe and describe.
Teacher also presents to students the book of Aratus, “Phaenomena” referring also to descriptions of constellations:http://www.theoi.com/Text/AratusPhaenomena.html Then he asks question about the detailed reference to the stars of the constellations.
Finally teacher asks from students to find and collect descriptions of constellations from astronomers during centuries, mainly focusing on the number of mentioned stars (Wikipedia).
Pre-Experiment / Observation– Teaching Phase 1:Questions Eliciting Activities – DEFINE QUESTIONS FROM CURRENT KNOWLEDGE
• How many stars can you see from your house? Match your night sky view with one of the images beside.
• Visit the site “Globe at Night” http://www.globeatnight.org/ and find out the complete scale of “light pollution”.
• Would you see more stars at countryside, away from city lights?
• Why this happens? • Which is the main reason for “light
pollution”?• Search in Wikipedia about light pollution,
reasons, consequences, effects in Astronomy: http://en.wikipedia.org/wiki/Light_pollution
Pre-Experiment / Observation– Teaching Phase 2: Active Investigation – PROPOSE PRELIMINARY EXPLANATION OR HYPOTHESES
• Students are asked to use the Stellarium software and test different values of light pollution as shown in figure.
• Also students are asked to count the influence of the atmosphere to our observations, as shown in the image.
Light pollution
Atmosphere
Pre-Experiment / Observation– Teaching Phase 2: Active Investigation – PLAN AND CONDUCT SIMPLE INVESTIGATION
• Students then asked to find the constellation of Hydra and the description of this constellation by Eratosthenes. They also asked to observe the constellation at night by their own.
• We ask students to record how many stars they observe from their places and compare the number of observed stars to the number of observed stars by Eratosthenes.
• We then encourage students to find constellation descriptions of other ancient astronomers and compare again their findings.
Pre-Experiment / Observation– Teaching Phase 2: Active Investigation – PLAN AND CONDUCT SIMPLE INVESTIGATION
• We download the special plug-in for Google-Earth GaN2013 that provides information about light pollution of each place (yellow dots on the above map).
• Students are encourage to find the original places of primary observation by ancient astronomers. Then they set at Stellarium the representative values of light pollution and play the role of the ancient astronomers.
Experiment / Observation– Teaching Phase 3: Creation – GATHER EVIDENCE FROM OBSERVATION• If all those ancient astronomers were observing nowadays the night
sky how many stars would have they seen?• Students are recording the original places of early observations and
how precise were their observations (how many stars per constellation):
Year of observation
Name of ancient Astronomer
Number of stars observed per
constellation by ancient
astronomers
Number of stars
observed per
constellation now
Nowadays light
pollution at specific place
(by plug-in)
• Then, students are asked to make assumptions about light pollution at ancient times, and how light pollution is changing our view of sky.
Experiment / Observation– Teaching Phase 4: Discussion – EXPLANATION BASED ON EVIDENCE
• Students are asked to confirm or revise their initial ideas about light pollution. We ask them if they have initially considered how critical, light pollution is for sky observations.
• Because, many ancient astronomers have observed night sky from different places (Greece, Egypt, Italy) we ask students to record locally the values of light pollution:
Place of ancient
observation
Light pollution at ancient
timesLight pollution nowadays
• We ask students to relate light pollution to geographic factors. For instance: light pollution at developed and developing countries.
Experiment / Observation– Teaching Phase 4: Discussion – CONSIDER OTHER EXPLANATIONS
Furthermore we ask students to observe the traffic lambs during the night. We encourage then to combine the light diffusion with light pollution and how “clear” the night sky is.
Students are asked to predict light pollution and number of observed stars just by looking at the road lambs.
Post-Experiment / Observation– Teaching Phase 5:Reflection – COMMUNICATE EXPLANATION
• Students can now explain why stars are not any more visible from large cities.
• Even more students can combine “light pollution” with atmospheric pollution by gases such as CO2. A polluted atmosphere further
intensifies the problem. The diffused light into the atmosphere expands the problem far away from the light sources.
• As follow up activities, students can continue recording the light pollution of the Globe.
Post-Experiment / Observation– Teaching Phase 5:Reflection – FOLLOW UP ACTIVITIES AND MATERIALS
• We will encourage them to join the “Globe at Night” project and be a part of a global research community.
Contact Information
• Name Surname: Chiotelis Ioannis• Affiliation: Model Experimental High School of
University of Patras• Address: Arakinthou 20, 26226, Patras, Greece• Telephone: +306948372341• Email: [email protected]
