What Took Us So Long?

A few years ago I had taken my family on vacation to a cabin by a lake in Maine. The mid August weather was perfect for a lakeside retreat with cool nights and dry sunlit days. Finding myself awake at midnight one night, I got up and slipped outside into the pines and walked the short distance to the shore of the lake. Out of the corner of my eye, I saw a flash in sky, looking up quickly enough to see the transient streak of a meteor before it flared out. Recalling that it was the time of year for the Perseids meteor shower, I decided to take a canoe out into the middle of the cove to see if I could catch more of the show.

I pushed the canoe into the water as smoothly as possible, not wanting to disturb the complete silence of the night. The water was so still that it reflected constellations like a mirror. A couple of quiet paddles and the wide bottom canoe slid across the surface like a skater on ice. I stopped in the middle of the cove, placed the seat cushions on the floor of the canoe and slipped down to lie on my back and gaze at the sky.

Drifting and turning very slowly and silently, with the sides of the canoe blocking any presence of the shore, it gave the illusion that I was floating in space. With my eyes adjusted for pitch blackness, it was only me and the astonishing beauty the night sky. I lost count of the number of meteors I observed that night, so I figured my plan was vindicated.

If you have ever seen the night sky on a dry clear night, undiminished by the lights of civilization, you can understand how the Milky Way got its name. The Milky Way is our view into our own galaxy, the immense cluster of stars that make up the cosmic neighborhood of our own Sun. In conditions like I described above, the visible stars are so numerous that it looks more like a milky fog than it does a collection of individual stars. And it stretches across the sky in a band from horizon to horizon that looks very much like a celestial highway.

If you have learned to recognize some of the constellations and the names of some of the stars they contain, you can often pick them out just about anywhere where you can see the night sky. But on that particular night, they seemed so close that I felt I could reach up and touch them. Rather than being “way up there”, they seemed very up close and personal like longtime faithful friends.

It is easy to forget that for the last hundred of thousands of years, up until the advent of outdoor artificial lighting, people moved about with the constant presence of this up close and personal canopy of the night sky, not simply seeing it as the rare treat that I did that August night on the lake.

In times past we conducted our affairs with the features of the night sky looming large and prominent in our field of vision. The constellations and stars surely must have felt like faithful companions that accompanied us wherever we went. It is no surprise that many of the names of stars and constellations come down to the present day from a time since before the birth of Christ. Those names have outlasted many of the civilizations that created them.

More than just names, many cultures created entire stories to go with constellations, partly for entertainment and partly as religious belief.  Some cultures considered the stars themselves as deities. One thing they would not fail to notice is that none of the stars move in respect to each other.  Where on Earth kingdoms rise and fall, rivers flood, forests burn, and every living thing flares up only to burn out in a short time, the heavens would seem to be immutable and eternal to people in ancient cultures.  If it were not for the effect of the Sun and Moon, the constellations would seem to simply rotate around the Earth.  Its no surprise that some cosmologies had the stars affixed to the inside surface of a hollow sphere, rotating around with a stationary Earth at the center.

So in one sense, the stars themselves seem boring.  Or better said, they seem bored with us. By that I mean that if the stars are deities or not, they seem completely disinterested in the affairs of man and the natural events on Earth.  Wars, famine, fires, floods, good harvest or bad all happen with no correlation to the constant deliberate rotation of that celestial sphere.  If you need a calendar for planting or harvesting, don’t bother with the stars since one day/night rotation of the sphere is no different than the next.  It’s like trying to tell time with just a clockface but no hands.

And so ancient observers who took to their watchtowers at night to record the celestial events had no reason to record over and over again the position of the stars in regard to each other.  The answer was always the same.

(What about astrology, you might ask?  Didn’t astrologers believe that our destiny was in the stars, and can be forecast by their motion?  Yes, but not the stars that make up the constellations.  Up until the invention of the telescope (and for some time after for many) the planets were considered as wandering stars. They are the exception to the rest of the stars that seemed glued permamently to the inside of that celestial sphere.  (But more on planets later.)

If the stars are cold, distant, unchanging, and disinterested, the Sun, on the other hand is close, warm, and obviously life-giving.   Ancient cultures could not fail to notice that their very existence was tied to the presence of the Sun.  The Sun was something to be reckoned with whether they though it was divine or not.

More than just giving light and heat during each day, the motion of the Sun is not as featureless as the stars.  The Sun rises and sets in a different spot on the horizon each day. The point on the eastern horizon where the Sun rises, and the point on the western horizon where it sets moves slowly southward as winter approaches, comes to a stop at mid winter (the winter solstice) and then starts moving north again as summer approaches only to turn around again at midsummer (the summer solstice).and start back southward.

This motion is also perfectly correlated with the hours of daylight each day and roughly correlated with the seasons. As most humans populations had switched from hunter-gatherer to agrarian lifestyles by about 10,000 years ago, this correlation was important to them.  It is no surprise that cultures built stone structure that were aligned with the sunrise at winter solstice and no surprise that they were eager to see that important “turn-around” meaning that another cycle of seasons was beginning.

With something to observe to indicate the annual cycle of the seasons, there is still not enough information to know week by week when to plant crops and when to harvest them for maximum production.  Fortunately, there is another celestial body that cycles faster than the Sun’s equinox.  The Moon makes a revolution around the Earth about every 28 days. And it does so independently of the Sun’s motion.  By observing both the motion of the Sun and the motion of the Moon, one can get a pretty good estimate of what week of the year is the current week and use that to make decisions about planting, harvesting, breeding of livestock and so on.

Consider what Genesis says about the purpose of the Sun and the Moon:

14 And God said, “Let there be lights in the vault of the sky to separate the day from the night, and let them serve as signs to mark sacred times, and days and years, 15 and let them be lights in the vault of the sky to give light on the earth.” – Genesis 1:14-15 

Holy days scheduled to celestial events are still with us.  Easter might be the most important holiday for Christians.  Easter is a “moveable feast”, that occurs on the first Sunday after the first full Moon after the vernal (spring) equinox.

 

But if you are scanning the heavens for signs and portents instead of keeping a calendar, the motion of the Sun, Moon, and stars are not very helpful. Imagine the court astrologer telling his patron that today would be a good day to go to war because the Sun rose this morning as expected.  Or the stars stayed in their constellations last night as they have done since recorded history.  Divining your destiny by the Sun, Moon, or stars is much like waiting for a clock to do something unexpected.

Now notice what Genesis has to say about the stars:

“…he made the stars also.” – Genesis 1:16

I love how that is tossed off as if they almost forgot to mention the stars. The authors of Genesis seem to find no purpose for stars.

Fortunately for astrologers there are a few strange stars that wander around moving through the constellations like lost sheep.  These are the planets, of course.  The name itself means “wanderers”.  While the clockwork rotation of the Sun, Moon, and stars make them ideal for calendar keeping, the motion of the planets seem so arbitrary that they are useless for that.

What the Sun, Moon, and planets have in common is that they all drift through a narrow band of twelve constellations we call the Zodiac.  What is unique about the planets is that they speed up and slow down dramatically, and at some points they appear to stop, reverse direction around a loop and then continuing on in the original direction.  The loops are referred to as retrograde motion.  The reason for this strange apparent motion is the shifting perspective we have as our own planet orbits the Sun, compared to the different rates that the other planets have as they orbit the Sun.  The different orbital rates of the planets, including the Earth, means that these retrogrades are not going to happen for a given planet in the same Zodiac constellation each time.

Consider that major life and death decisions were made on the basis of astrological deliberations.  If you are in the astrology business no one is going to pay you for telling them that the Sun rose on time, or that anyone can see that Mars was in Capricorn last night.  The big money is not in knowing where every planet was last night but knowing where precisely the Sun, Moon, and planets were on the day the king was born some 3o years go (even if some of the planets were not visible on those nights because they were on the other side of the Earth in daylight.)

Herein lies the big problem.  Putting up some sighting stones to pin down the solstice is one thing. That is going to happen like clockwork year after year.  Predicting or “post-dicting” where the planets will be in the sky on a date decades into the future or a date decades in the past is another thing altogether. And that “other thing” is the impetus or driving force behind what ultimately established modern science.

We stared at planets for thousands of years, carefully recording their strange but fascinating motion through the Zodiac.  We built crude geometric models to predict where they were in the sky on any particular night in history.  And we moved armies and chose spouses based on what we thought the positions of the planets told us about our destinies.

But with all that serious life and death planet-gazing, we never in thousands of years figured out that the Earth is also a planet and they all orbit the Sun.  The questions I would like to answer for you is

  1. Why and how did we suddenly develop dead certainty about the Sun-centered makeup of the solar system about 250 years ago?
  2. What took us so long to get there?

Answering the first question will tell us why we can develop dead certainty about any scientific theory.  Answering the second question helps us answer the first, because if there was a scientific revolution, what was it revolting from?  (Hint: The answer to question #1 is not the telescope or Galileo’s testimony, or even Copernicus’s work).

 

I have been involved in science and engineering since probably before you were born. I am interested in writing about science, its conceptions and misconceptions.

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