1. Dark Skies: From the eyes of
Eratosthenes, to our eyes

2. 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

3. 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.

4. 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/Eratosth
enica.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/AratusPhaenomen
a.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).

5. 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

6. 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

7. 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.

8. 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.

9. 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.

10. 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
times
Light pollution nowadays
• We ask students to relate light pollution to geographic factors.
For instance: light pollution at developed and developing
countries.

11. 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.

12. 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.

13. • 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.

14. Contact Information
• Name Surname: Chiotelis Ioannis
• Affiliation: Model Experimental High School of
University of Patras
• Address: Arakinthou 20, 26226, Patras, Greece
• Telephone: +306948372341
• Email: johnchiotelis@yahoo.gr
johnchiotelis@gmail.com
johnchiotelis@icloud.com