Antikythera Device, modelling its elliptical motion

The Antikythera Mechanism is a hunk of metal fragments found in the Mediterranean Sea over 100 years ago. Numerous scholars have demonstrated that it is the corroded remains of a calculator of celestial motions, built around 2000 years ago.

I've dabbled with a few illustrations of the object and its origin in my show The Astro Time Machine. Since creating this show, I've worked a little on my animation of how this device was thought to portray the motion of the moon's elliptical orbit.

The journal Nature published a description of the use of a pin and slot mechanism to create elliptical motion. I've created an animated version of the pin and slot mechanism on my website (Pin and Slot):

My model is simplified. I'm showing only the pinned and slotted gears, which is enough to show how this arrangement produces elliptical motion.  The actual device would have had a minimum of four gears for the same motion, similar to this exploded diagram:

And using four gears would have allowed the modeling of additional motions, such as the change in axis of the moon's orbit.

I don't claim to accurately show the arrangement of gears used in the Antikythera device. My animation is meant only to show how two wheels with a pin and slot produce the motion of an elliptical orbit. My animated model could easily be replicated with real wheels for a classroom project. Gears could be replaced with wheels connected by belts of elastic cord. With the correct tools, I think it would be easier to build a real elliptical motion mechanism than to program a model, at least for me.

jg

Trying not to see stars

I've commented before on Native American artifacts that resemble constellations near my home in Southern California (e.g., cupula rock). My comments weren't original: Ray Williamson, in his book "Living the Sky", refers to constellations in Great Basin petro glyphs. In searching for other examples of constellations in rock art, I found this paper: http://www.uni.edu/earth/rapanui/rapa_nui_journal.html -- but the paper doesn't declare strong support for the constellation hypothesis, and in personal correspondence, the author offered his hindsight that he is now very skeptical of the constellation hypothesis. I've also sent photos of cupula rock to Anthony Aveni (Author of The End of Time: The Maya Mystery of 2010) who saw no reason to interpret the patterns as other than randomly distributed boreholes (see  Ok, I did do the nose).

So it is with caution that I share these photos of a rock at Joshua Tree National Park:

Six, similarly sized depressions, with four in a pretty straight line.

Here is a view of the area. I'm looking approximately South. Center in the photo (and you may need to click the photo to see ths) is the pattern:

 Here is a close up of the depressions, with my size-12 foot for scale:

The depressions look as worn as the surrounding rock and are even in size.

The rock at Joshua Tree is large-grained and crumbly. I believe it erodes quickly, and that people could easily make these depressions (now and thousands of years ago), but I saw no scratches or evidence hinting at human hands at work.

The depressions are in a popular camping and climbing area called Indian Cove. Joshua Tree has other Native American artifacts, so long-term human occupation is not in question. In the following photo, I noticed other patterns. The main group is in the center, but lower to the right you can see an alternating pattern of depressions:

 Here is a zoomed in view showing a right-left stepping pattern:

I see many natural depressions in the rock at Joshua Tree, but I've not seen any that are so consistent in shape as these.

jg

Ok, I Did Do the Nose

In my title I'm alluding to Monty Python and the Holy Grail, the scene where members of the witch hunting crowd admit to adding the nose and hat to their suspected witch. The significance of this will come later.

Some time ago I shared a possible archeoastronomy artifact from my region refered to as cupula rock. A photo is below:

I've hypothesized that this rock contains constellation images that the Native Americans, likely Luisano, thought worthy of representing. My only support for this notion other than the apparent similarity of some patterns to constellations is a mention of this behavior in Ray Williamson's Living the Sky and a fleeting conversation with a local Luisano who said "yes, our ancestors did that [carved constellations]". Verification or refutation has been on my to-do list.

Recently I had the opportunity to see Professor Anthony Aveni of Colgate University and author of many books on archaeology speak on the Maya calendar and the significance of 2012. Professor Aveni is motivated by the anxiety among young people he's met that 2012 bodes ill. His work assures us that there is no reason to believe the Maya made any prediction about 2012 other than it being the time when, like an odometer, their calendar turns over. Since the lecture, I've read his book 2012: The End of Time. A main thrust of this book is that it appears to be an American (U.S., not Native) tradition to project our views onto ancient cultures, and he cites a list of cults and doomsayers from throughout American history.

I sent the photographs displayed here to Professor Aveni. Speaking as someone who has examined countless artifacts and sites, he offers the opinion that there is no compelling reason to see constellations in this rock. He recommended another of his books, Uncommon Sense, in which he argues that maps are a product of western culture. My conjecture on this rock is not too different from projecting my own map of the sky, or of elements of the sky, onto a past culture. Fair criticism. He adds that this is only his opinion, but I went out of my way to get it, so I'm eager to share it here in connection with (or correction to) the previous post I made on this topic.

I would add one update from my previous post. I had thought one star in my proposed Cassiopeia was a natural indentation. I've recently returned to the rock and this indentation looks less natural than I had first thought.

And now my joke: Am I projecting my concept of the stars onto this rock? Here are the photos I sent him and so I have to admit: well, yes, I did draw Cassiopeia:

Cassiopeia traced from a photo and overlaid on the image

Hypothetical Cygnus (also called the Northern Cross):

Ok. I did place the paper circles.

Hypothetical Hercules (butterfly shape on the left):

Yep. My hand was in this one too

(Update, 6 April 2010: I just learned that within the past week, someone of Native American descent, asked at the Reserve to see "the star rock" saying that her grandmother had told her about it. Two possibilities come to mind: one, my sharing of this rock evoked someone's curiousity or influenced a memory; or two, there is some cultural history of this custom or specific rock outside of my influence. Humility suggests the latter, but either are possible.)

jg

Archeo-astronomy, cupula rock

Archeoastronomy is the science of using what we know about astronomy, specifically naked-eye observations, to infer meaning in archeological artifacts. My knowledge of this subject comes mostly from Ray Williamson's book, Living the Sky, and from an inlaw who's contribution is cited within Williamson's book. Living the Sky also mentions constellations in great basin petroglyphs, and a possible example from the Temecula Valley is shown here:




Native americans left at least two records on local rocks: 1) grinding holes used in the preparation of food, and 2) smaller holes such as those you see in the rock above. These holes are about the size of a golf ball split in half, possibly ground with a rock of this size. When the sun is overhead shadows are cast, making the holes look like dark stars on pale rock.



A group of stars in the middle bears a strong resemblance to the constellation Cassiopeia, with one qualification: The hole at the apex of the 90-degree angle in Cassiopea is not like the others; it appears to be natural, suggesting either that the carver exploited a natural nook (quite understandable if you've ever tried to drill rock or scrape out a fossil) or that the excellent match to Cassiopea is a coincidence.
These cupulas can be found throughout the desert of Southern California. Below is an example from Anza-Borrego Desert State Park. Though I can imagine several constellations in the rock shown above, I can't claim to see any in the one below.



In this post, I tried to model the type of language and caveats offered in the primary science literature. Any claim (e.g., in this case, that the holes could be constellations) is offered with any known evidence that would undermine certainty in this conclusion (e.g., not all of the holes in Cassiopea were necessarily drilled by human hands). And so it was when I read an paper in Nature (in 2000?) that claimed the first observational evidence of the greenhouse effect. The authors did not declare themselves right and sceptics wrong. They merely stated something like "should our observations be corroborrated by further research...." They also cited concerns over the field of view and resolution of the instruments used in their analysis. This willingness to expose strengths and weaknesses in our observations and beliefs is a characteristic of good science, and is an attribute we can look for in determining whether we are reading science or propoganda.