Why the 2017 total eclipse is a repeat of 1963

DW: Your book "In the Shadow of the Moon" is as much about the science of total solar eclipses as it is about the people who study or like to observe them. And you have yourself made a career out of observing eclipses from diverse places on Earth. So would it be fair to call you an "eclipse chaser"?

Anthony Aveni: Well I wouldn't classify myself among the eclipse chasers like Jay Pasachoff, my astronomy colleague from Williams College who has seen many more total eclipses than I have [Ed.: Pasachoff has witnessed 65 solar eclipses and 33 total eclipses]. I have chased down eight of them. I've done some eclipses on cruise ships and some over land, but my interest is in natural phenomena, and particularly people's reactions to natural phenomena. But I would say I was an eclipse chaser, yes.   

So how does that start? What fascinated you early on for you to want to make a life of this?

What fascinated me and led me into cultural astronomy, a field I helped develop, is that I think we have a problem in Western culture in thinking everybody reacts to nature the same as we do. I get very interesting questions from people, such as "Why, if the Maya were so smart about timing movements in the heavens, didn't they know the world was round? How come they didn't know the Earth orbits the sun or that we're part of a spiral galaxy?"

And my answer is that we only know those things because of the way we, in our Western understanding of nature, which descends from the Babylonians, the Greeks and through the Renaissance, have come to raise those kinds of questions. Circular orbits, for example, come from the Greeks who worshipped the circle, so we still have this divine attachment to the circle. When we deal with the Inca and the Maya, Hinduism and other cultures that were out of contact with the West for a long time, we see a very different perspective on nature. We see a world which is vibrant with life, of which we are a part.

And we in the West don't consider ourselves to be part of the universe. We have us and it. There is nature, which seems to operate on its own, from rocks to stars to galaxies, and then there is us and we probe nature with the idea of trying to control it.

You write about the science of eclipses, and that's interesting. But I'm also interested in this idea that there's a disconnection between people and nature. And you describe how people on these cruises you've been on seem more interested in taking photos, in recording an eclipse event than actually experiencing it.

Yes, and I remember there were many times on these eclipse cruises and doing lectures, I would hear the snaps of the camera shutters, thousands and thousands of clicks, without the people paying attention to what they were looking at.

And what I think is especially interesting is that even though we know what causes an eclipse we still are enthralled by what we see. We abandon our scientific, positivistic attitude about how we know there are equations that explain all this, and there is this contact with the sublime. That's why I entitle my book "In the Shadow of the Moon."

Sublime is a word first used by philosopher Edmund Burke to describe natural phenomena that bring on, at the beginning, a sense of fear, followed by a jaw-dropping awe at the wonder that takes place in nature.

It's a term that one of our presidents, Thomas Jefferson, used, and the writer James Fenimore Cooper used it when he saw the eclipse of 1806. It is subliminal and you are in the shadow, the boundary between light and dark … you could say between good and evil, if we wanted to cast biblical terms, and all of these feelings well up in us regardless of our rational explanations. 

What about the ancestry of eclipses? As we get closer to this next big North American eclipse on August 21, why is the ancestry of this total eclipse important?

Ah, that's a term I invented ... if you're referring to what I think you are … where I talk about an eclipse being the grandparent of another eclipse, is that what you mean?

Yes, exactly.

Yeah, I've gotten some reaction to that. Well, it's well known that the saros cycle is an 18 year or 223 month cycle that we derive from the Babylonians, over which eclipses repeat. They turn out to be the same kind of eclipse – about the same duration of totality, the same approach of the shadow, and so on. And so I call the eclipse of 1999 the father of the eclipse of 2017.

The saros is actually a fractional number of days long – 223 months is 6585 and a third days ... the numbers aren't important … but the third of a day means that this identical eclipse will repeat, but because of the third of a day it will happen 120 degrees West of the location of the first eclipse, because of the rotation of the Earth ... it's an eight hour difference.

If you go back three saroses, that's 54 years, you get an eclipse that is not only seasonal, like the saros comes in the same season of the year, but it also happens in close to the same longitude, albeit a slightly different latitude. That was the 1963 eclipse, the great-grandparent, if you will, of the 2017 eclipse. The 1963 eclipse took place across the United States and Canada but it was farther north. In fact, it's mentioned in a Stephen King novel, and for those who like trivia, it's also portrayed in an episode of Mad Men.

So, yes, there are these families of eclipses that occur at least in the cycles we appreciate in the western tradition. 

But the Maya had a completely different cycle. They were seeking eclipse periodicities that harmonized with periods in nature important to them - one period being the gestation period of the human female, which they accounted for as 260 days. So they cared about eclipses that had a 260 day multiple rhythm. 

It seems now that all our knowledge of the universe, or our planet, is totally limited by the questions we ask. 

Yes, of course it is, absolutely. The Maya posed different questions. So to them the question "Why don't you people know the Earth orbits the sun in an ellipse?" was a stupid idea. They'd say, "Who cares about that?" These were people who cared only about the environment that affected them and that they affected. And you might say that's narrow-minded of them.

I don't want to make moral lessons out of this, but maybe we'd do well to pay more attention to the things that are closer to us in distance, than those that are far away. For us, the center of the universe is a place that's millions of light years away. It's not in our backyard. You learn so much about the diversity of culture, and I think this is a lesson in cultural diversity that comes from science.

Dr. Anthony Aveni is Russell Colgate Distinguished University Professor of Astronomy and Anthropology and Native American Studies, Emeritus. He has written dozens of books and his latest is "In the Shadow of the Moon – the Science, Magic and Mystery of Solar Eclipses," published by Yale University Press (2017).

You can watch a live stream of the 2017 total eclipse via NASA's Eclipse Live.