Yesterday’s Astronomy Headlines

• The first stars to shine may have been found (National Geographic)

• 4G Coverage bound for Moon in 2019 via a private company (Smithsonian.com)

• A Bus-sized asteroid will whiz past Earth on Friday (Space.com)

• Also, in Medical Science: “Vaccine-Autism Myth started 20 years ago. Here’s why it still endures today.” (Time.com)

On any slide, an asterisk (*) in the lower right corner of a slide indicates there is an entry in the “notes” section for that slide. The color of the asterisk may not always be as shown in this slide.

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Golden Ages of AstronomyPart 1: The Greeks

OLLI Course Presented byDavid LintonMarch, 2018

A Note on Science

I attempt, as much as possible, to examine the world around me through the filter of science. If I am confronted by a claim that something remarkable happened, I choose not to accept that claim without critical analysis. If the analysis is beyond my abilities, I tend to seek the advice of experts in fields of study that are germane to the particular claim.

ScienceIs arguably the greatest invention ever made. It is the process that allows us to determine which ideas are (most likely) correct and which are (most likely) not. Millions of people over thousands of years have contributed to our understanding of the world around us, and to the process by which we will learn more in the future.No one has ever come up with a better way of determining the correctness of an idea. But that has not kept critics from discounting results from Science – examples include astrology, effects of smoking, climate change, and a supposed connection between vaccinations and autism.

It is my hope that:Your understanding and appreciation of the role that Science has played in the long journey of humankind will be increased by examining certain periods in history, within the confines of this one scientific field, Astronomy. Maybe you will be able to transfer an idea encountered here to other areas of Science that you are more familiar with. Perhaps you will come to identify shortcomings and advantages of Science, and characteristics of a society in which Science can thrive. I continue to be amazed by how Science has impacted the way we live - and I enjoy speculating upon how it will do so in the future.

A Note on “Golden Ages”

• Let this not deter us. We have 4 class meetings, and so I have decided to talk with you about 4 of my favorite times during the history of Astronomy.

“A Society’s Golden Age marks that periodin its history having a heightened output

Of art, science, literature, and philosophy.” [citation needed]

From Wikipedia

A Note on “Golden Ages”

• Historians do not agree on how many golden ages there have been in Astronomy, on when a golden age began or ended, nor even what a golden age is.

• Let this not deter us. We have 4 class meetings, and so I have decided to talk with you about 4 of my favorite times during the history of Astronomy.

A Note on “Golden Ages”

• Historians do not agree on how many golden ages there have been in Astronomy, on when a golden age began or ended, nor even what a golden age is.

• Let this not deter us. We have 4 class meetings, so: I shall try to make a case for there having been 4 “Golden Ages of Astronomy”over the course of history.

Regardless of my success or failure in stating my case (that there have been 4 “golden ages” in Astronomy), each of these 4 time periods was an exciting time to be alive. New ideas & new knowledge opened up new possibilities for people to think about or (for some) to base new technologies on.

The first “Golden Age of Astronomy” to consider occurred in Greece, from about 600 BC until about 150 AD.

But first, let’s try a .

Imagine The Year Is NOT 2018

• Instead, imagine that we (everyone in this room) are all members of a tribe of hunters & gatherers, living in Central Europe 10,000 to 15,000 years ago.

• We have no iPhones, cars, paved roads, OLLI, grocery stores, airplanes, radio, TV, wall calendars, internet, guns, schools, agriculture, no domesticated animals (except perhaps dogs).

• We subsist on the nuts, roots and berries we can gather, and on the wild animals we are able to kill.

A Question:

In what ways will the chances for the survival of our tribe be improved by our familiarity with the behavior of objects in

our sky (both nighttime and daytime sky)?

In other words, in what ways can we use our knowledge of the sky to our advantage?

Ways We Might Use the Sky:

To determine:1.2.3.4.

Ways We Might Use the Sky:(My List)

1. To Determine the Time of Day2. To Anticipate the Coming of Seasons

1. Ripening of Fruits & Nuts2. Migration of animal herds3. Relocation of the tribe4. Observation of tribal rituals

3. To Navigate through unfamiliar territory4. To anticipate and prepare for new life

Bighorn Medicine Wheel, Wyoming: almost 10,000 feet above sea level

100-200 of these Native American constructions remain, scattered between Colorado & Central Canada

It appears likelythat at least some of these medicinewheels were used to find bright starsas they rose or set.This could havealerted the NativeAmericans to theseason, and (for example), to theincreased possibilitythat winter snowsmight trap them inthe mountains.

A piece of bone from 32,000 years

ago, showing lunarphases.

This could have served as a pocket calendar

Tonight, 8 PM in Champaign

Some of the 88 constellations made by connecting the dots.

The Sky could have been used to illustrate stories told around campfires.

I find constellation images in many places, like this tattoo of the Southern CrossOn the leg of a Cruise Line crew member from New Zealand.

Tonight, 8 PM

Star Motions as seen from Champaign:

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Tonight, 9 PM

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Tonight, 10 PM

The stars are moving from East to West (or at least are appearing to do so). *

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Tonight, 8 PM

Star Motions as seen from Champaign (looking North):

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Tonight, 9 PM

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Tonight, 10 PM

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The Sun’s daily motion changes with the seasons.

The Sun reaches its highest point at Noon. It NEVER reaches the zenith.

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Tonight, 8 PM

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Tonight, 8 PM + 1 Day

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Tonight, 8 PM + 10 Days

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So, the Sun moves with respect to the stars

• Only a few brightobjects do this:

• Sun• Moon• Mars• Mercury• Venus• Jupiter• Saturn

So, the Sun moves with respect to the stars

• Only a few brightobjects do this:

• Sun• Moon• Mars• Mercury• Venus• Jupiter• Saturn

The word planet derivesfrom a Greek word meaning

“wanderer”.

These 7 wanderers were called planets. They are all bright, and were considered important. Their names are used to create the following:SundayMoondayMardi (Fr) Martes (Sp)Mercredi (Fr) Miercoles (Sp)Jeudi (Fr) Jueves (Sp)Vendredi (Fr)Viernes (Sp)Saturnday

The Domestication of Plants

The invention of Agriculture required attention to the calendar to identify proper planting and harvesting dates, and to properly schedule

religious rituals associated with planting time, harvest time, and the coming of rain.

Agriculture also spurred the invention of writing –Examples: for inventory and bills of sale

Sumerians Invented Cuneiform Writing between 3500 BC and 3200 BC

• Many Babylonian observations of the sky still exist on clay tablets from as early as 1650 BC.

• Babylonian efforts to watch and record the sky were motivated by the belief that happenings in the heavens above could be used to foretell Earthly happenings as related to the kingdom, its King, and royal family. [Astrology for the State]

• Babylonian sky-watchers were searching for correlations using numerical techniques. They appear to have never sought explanations or causes of the observations they made.

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The Celestial Sphere

Stars at different distances all appear to lie on the celestial sphere.

The ecliptic is the Sun’s apparent path through the celestial sphere.

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The Celestial Sphere

The 88 official constellations cover the celestial sphere.

Many constellation namesdate back at least to theSumerians.

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Something Very Important to Science Happened 26 Centuries Ago

In a small city on the eastern coast of the Mediterranean Sea, Nature began to be approached in a whole new way.The city was Miletus, and what took place there and in the next few centuries in Greece would play a big part in turning Science into “the greatest invention of all time.”

The Sky Was Common Knowledge• The sky was at once a calendar and a clock. A

quick glance at the constellation visible in the east at dawn would reveal the time of year.

• In The Odyssey, Homer writes that Odysseus is given instructions to return to Ithaca. “Keep the Great Bear on your left, and steer toward the rising point of the Pleiades.” That would send Odysseus on a course due east.

Carlo Rovelli Comments:

At a certain point in humanity’s history, the idea came into being that it was possible to understand these phenomena – their interrelation, causes, and connections –without recourse to the caprices of gods. This immense turning point took place in Greek thought of the 6th century BCE, and it is consistently attributed to Anaximander in all of the ancient texts.

Rovelli Comments:

When he “opened the doors of nature”, Anaximander ignited a conflict between two profoundly different ways of thinking. On the one hand, there was the dominant mythical and religious way of thinking, based in large measure on the existence of certainties that, by their very nature, could not be called into question.

On the other hand, there was the new way of looking at the world, based on curiosity, rejection of certainties, and change. This conflict has run through the history of Western civilizations, century after century, with alternating outcomes. It is still an open conflict.

Science does not reject religion or God. It merely assumes that no supernatural intervention has occurred, and therefore seeks natural explanations. This approach has been very successful, and has driven (together with resultant technology) our economy for the past several centuries.

Many scientists are religious. Many are not. Science deals with how things happen, while religion deals with why things happen. Unless one accepts the inerrancy of a religious authority (the Bible, the Koran, the Torah, for example), the discoveries of Science seem to be compatible with religious beliefs.

Dirk Couprie, Anaximander Biographer:

“We are convinced that Anaximander was one of the greatest minds that has ever lived. . . I do not hesitate to put him on a par with Newton”

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At Anaximander’s Birth in 610 BCE:

Humans had been living in cities for at least 10,000 years.

The Great Kingdom of Egypt had been in existence for 26 centuries, the same time period that separates Anaximander from us.

Babylon, with 200,000 inhabitants, was the largest city in the world.

The Babylonians had developed the concepts that, in our time, are studied by seven-year-olds.

Thales of Miletus (635-543 BCE)

• Commonly referred to as “The First Scientist”• Anaximander studied under him.• Is said to have predicted a solar eclipse.• Believed the Universe came from water.• Introduced Deductive Logic• Used Geometry to find the distance to a

ship at sea & the height of a pyramid• Held that Earth is flat and floats in water

Then why the Emphasis on Anaximander?

• Anaximander’s contributions were far more wide-ranging – from meteorology and geology to astronomy and biological evolution

• Anaximander was a student of Thales but did not feel compelled to support his worldview.

• It is worth noting that Nobel Prize Winner Richard Feynman once defined Science as “not trusting your parents” or any other authority figure. Re-testing our understanding of the past is an essential aspect of increasing our understanding of nature.

Anaximander reasoned that nothing supports the Earth –anything underneath it would block the stars in their daily paths.

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It is said that Anaximander of Miletus first opened thedoors of nature.

Pliny, Natural History 2

Pythagoras of Samos (572-492 BCE)

• Held that the Earth is spherical – noted that ships disappeared hull first, sails last, as they traveled into the distance.

• First to suggest that the Sun, Moon & planets could be described by numbers and mathematical precision.

• Discovered that the morning and evening star are the same thing, the planet Venus. This was also known to the Babylonians.

Plato: The Heavens Are Perfect

• The only permissible path must be the circle.• Solid bodies must be spheres.• Changes do not occur – comets & meteors

must be atmospheric phenomena.• Heavens are composed of a 5th Element –

quintessence or ether. It is a “perfect, invisible crystalline material.

• Aristotle (~350 BC) A student of Plato, he was a “polymath,”and one of the greatest geniuses ever. He argued that the Earth was a sphere, in part because those who traveled N or S reported the stars in front of them became higher in the sky. He also felt that Earth cannot move, because of its great size. The next two slides illustrate his model of the Universe.

• Aristarchus of Samos (~250 BC)

• Eratosthenes (~200 BC)

• Claudius Ptolemy (~150 AD)

It’s all Greek to Me:

Aristotle’s Universe

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The Ptolemaic SystemGave a mathematical basis to the best ideas of earlier Greeks

• Is all done with Circles and Spheres.• Earth is a sphere, and does not move in any way.• The Celestial Sphere is real and it rotates. It marks the

limits of the Cosmos, and is only slightly further than Saturn.

• The 7 wanderers (planets) move with the stars, but each also has additional motion. Each moves on the surface of a sphere centered on Earth. Five of the planets also have secondary circles, called epicycles. These are used to model retrograde motion. The spheres are invisible, made of the 5th element, “quintessence”, or “ether”.

Planets occasionally change direction.

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Ptolemy: The Almagest

Epicycles and Deferents

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The Ptolemaic System

• Went largely unchallenged for the next 14 Centuries – in this sense, it was the most successful scientific theory of all time.

• Was accepted by the Roman Catholic Church as an article of faith, thereby greatly discouraging scientific inquiry. It became frozen in place –but it helped to provide a sense of “certainty” to the lives of individuals of those times.

Next Time:

The Second Golden Age of Astronomy:

The Age of Galileo