Workshop on Venus and Eclipses

for Astronomy with Stars, Sky, and Culture, spring 1998

by E.J. Zita with LLyn DeDanaan, 7 May 1998
 

This workshop is designed to help you understand the cycles of Venus and eclipse prediction. It builds on the workshops from week 1, on cycles of the sun, phases of the moon, and eclipses. Bring your celestial sphere and your notes from related workshops.

TO PREPARE FOR THIS WORKSHOP: REVIEW the week 1 workshops. Re-read Chapters 2 (The Naked Sky) and 4 (Power from the Sky: Ancient Maya Astronomy and the Cult of Venus) of Anthony Aveni's Stairways to the Stars (pub. Wiley, 1997), and try Aveni's workshops in Appendix A for Ch.2 (P.195) and ch.4 (pp.200-201).

DURING THE WORKSHOP:  Do part 1 (Venus cycles);  leave part 2 (eclipses) for the very end in case you have extra time, maybe design some investigations of your own... and turn in the survey before you leave. Have fun!

Questions    Equipment    Overview    Details    Using Redshift    Mayan ref. info

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QUESTIONS:

1.a) How could Mayan astronomers, with observations, reason, and models, understand and predict the cycles of Venus?

1.b) How do modern models help us understand and predict the cycles of Venus?

2.a) How could Mayan astronomers, with observations, reason, and models, understand and predict solar and lunar eclipses?

2.b) How do modern models help us understand and predict solar and lunar eclipses?
 
 

Equipment:

OVERVIEW:

1.a) Use Redshift to observe Venus cycles as the Mayans did (standing on the Earth), but with time speeded up. Each team should investigate one of the five cycles and then share their results with the class.

1.b) Use Redshift to observe Venus cycles from outside the solar system. Compare your observations with the cycles you saw from Earth's surface.

2.a) Use Redshift to observe eclipses as the Mayans did, but with time speeded up.

2.b) Use celestial spheres and moons-on-sticks to remember how modern models explain eclipses.

3.  How do Venus cycles compare to Moon cycles? 
 

DETAILS:

1.a) Use Redshift to observe Venus cycles as the Mayans did (standing on the Earth), but with time speeded up. Each team should investigate one of the five cycles and then share their results with the class.
. Summarize key aspects of the cycle you observed.

Hypothesize what motions might account for your unique pattern.

Show your results and explain your hypothesis to the rest of the class. If you decide to create a movie of your Venus cycle, be sure to test the technique out by making a small movie first.

Combine eveyone's results to create a table of Mayan numbers that represent the 5 cycles observed by the 5 class teams.

EXTRA:  You could also note the directions of Venus' appearances and motions and recreate a table like Fig.4.9 on p.120.

1.b) Use Redshift to observe Venus cycles from outside the solar system. Compare your observations with the cycles you saw from Earth's surface.

Explain in your own words what actual motions correspond to they key aspects of your cycle, as you identified in (1.a) above.

Why are the patterns (on Aveni p.44) not symmetric in space and time?
 
2.a) Use Redshift to observe eclipses as the Mayans did, but with time speeded up.

At latitude 14.8 degrees N and longitude 89.10 degrees W is the classic Mayan site of Copan (in present-day Honduras, from Malmstrom p.51 and Terry Hubbard,the reference librarian.)

Starting from 1 A.D., how much time do you find between lunar eclipses at Copan? Are they full or partial eclipses? Do the time intervals change? Note the days (in the modern calendar) of each eclipse, and represent these intervals with numbers in Mayan glyphs.
2.b) Use celestial spheres and moons-on-sticks to remember how the modern model explains eclipses.

3.  EXTRA:  How do Venus cycles compare to Moon cycles?  How can they be used to predict eclipses?  How can Moon phases be used to predict Venus' heliacal risings?
 

USING the REDSHIFT planetarium software in the CAL

Setup        Start Redshift        Set Location        Set Time         Move from sunrise to sunset

Watch from outside the solar system

Can you figure out how to keep the sun right on the horizon, as Venus rises (or sets) through its cycle? The only way I see to do that is to fine-tune the time intervals between "days", but that makes it difficult to create a movie quickly. If you figure out an easy way, please let the rest of the class know - thanks.

SETUP:  RedShift needs to run in Windows 95, but the default system on the CAL computers is NT.  So before you can start RedShift:

To start RedShift: MENUS run horizontally on the top of your screen.

PANELS run vertically - move them to the right side and resize your screen so it's not obscured.

To see Venus rising from the horizon:

  To control time: To move from sunrise (east) to sunset (west): To watch Venus and Earth cycle from outside the solar system:
 

Appendix on Mayan numbering system:  why 260 days?

 

From Malmstrom (Cycles of the Sun, Mysteries of the Moon, p.51) the Olmac people started the new year at zenith on 13.August. At latitude14.8 degrees is the classic Mayan site of Copan . Since this site is within 23.5 degrees of the equator, the Sun reaches zenith twice a year - again on 13.April. This is probably the origin of the sacred 260-day year.