Evolution of Concept of

“Interest” part of fc Requires the following: 1. Understand the size and nature of Universe Cultural Evolution, II 2. Understand our place in Universe (not the center) 3. Optimistic Drake Equation

Are ability and interest linked? Both are very recent developments Is this a coincidence?

Evolution of Worldview Oyster World

• Early astronomy had dual nature • Flat – Calendar Astronomy (observations) • Dome of Heavens • Waters above • Precise calendars in agricultural societies • Waters below • Dates back to at least 3800 BCE • Stars fixed to the dome • Mayans: length of year to 0.001% accuracy • moves across the – Cosmic Myth (theory) sky • Tied to religion, origin stories • Earth is fixed

1 Late Babylonian World Egyptian World

• Three heavens • God of the Air (Shu) • Underworld • Separated his parents • Babylon is center • Sky and Earth • Created by Marduk • Mother was sky – City god of Babylon – Unusual choice – Sliced up Tiamat – Separated waters above and waters below

One group of Greek philosophers (the Atomists) believed in other worlds. Origin of Natural Philosophy Epicurus 4th Century BCE Infinite atoms implies infinite worlds, living • Around 500 BCE, Greeks on Ionian islands creatures • Thales and others In contrast: Aristotle • Search for universal substance “The world must be unique” – Tried water, air, earth, fire Lucretius (Roman poet and philosopher) “It is in the highest degree unlikely that this • Key feature is search for natural explanation Earth and sky is the only one to have been • Distinguished planets from stars created…” • Began to think about larger Universe But even the Atomists did not have a correct vision of the nature of the Universe, stars

2 Plato and the dominance of the circle Aristotle and the two spheres

• Plato chose the circle – the most symmetric • Aristotle distinguished the two spheres – Sub-lunary – “And he gave the universe the figure which • Four elements, natural motion dictated by nature is proper and natural…” • Unnatural motion requires constant force – “… he made it move with circular rotation” – Celestial • Both from Timaeus • Quintessence • Eternal, uniform, circular motion • Crystalline spheres • Moved by Prime Mover • All motion centered on Earth • No empty space

Saving the phenomena Ptolemyʼs model

• Ptolemyʼs Earth Centered model – Size: 19,865 Earth Radii • No voids (but cheated) – To match observed motions of planets, • Eccentrics, epicycles, equants • Extremely contrived

For moving models, check http://faculty.fullerton.edu/cmcconnell/Planets.html - 7

3 Astronomy & Religion Model showing Ptolemyʼs “tricks” Augustine (420 CE) Neo-platonism incorporated into Christianity Ignore Observation World-view regressed

Aquinas (13th Century) Aristotle incorporated into Christianity Ptolemaic system

Heretics e.g. Giordano, Bruno Stars are with Planets, Life Images and Animated Prepared by Tommy Huerta and Craig McConnell

Two Thousand Years of Error Copernican Model (1540)

• Sun at center • All planets orbit around Sun • Circular motion “There is perhaps no other example in the history of thought of • Uniform speed such dogged, obsessional persistence in error, as the circular • To explain planets: fallacy which bedevilled astronomy for two millennia.” – Still need: – Epicycles Arthur Koestler, in The Sleepwalkers, pg. 58) • To avoid apparent motion of stars Example: the of 1054 was recorded in China, American – Much bigger universe – 7,850,000 Earth radii southwest, …, but NOT in Europe. It did not fit the theory. – voids

4 Tycho Brahe (late 1500s) Braheʼs Compromise World View

• Before the telescope • Very large circles for sighting positions of planets • Observed supernova • Careful records • Hired Kepler • Compromise world view

Kepler Elliptical Orbits

• Worked with Braheʼs data • Found that he could fit the Mars data if – 1. Planets moved in elliptical orbits – 2. At different speeds at different places – 3. P2 = a3 • P is period (how many years to complete orbit) • a is semi-major axis ~ radius of orbit • P in Earth years, a in earth orbit radii (AU) This would be an extremely elliptical orbit. In fact, orbits in are nearly circles.

5 400 Years from Galileo Galileo

Clarified dynamical laws Applied the telescope to the sky • Used telescope (recently invented) Discovered “new planets” (moons – New “planets” (moons of Jupiter) of Jupiter), craters on the Moon, – Sunspots confirmed phases of Venus. – Craters on Moon Endorsed Copernicanism… – Many more stars And paid a price! • New physics New observational tools drive – No force needed to keep a body in motion progress in astronomy Portrait of Galileo Galilei by Giusto Sustermans

Conflicts with Religion and Philosophy Newton completes the revolution

• Copernicus was careful about his “model” • Newton (1687, Principia) • Galileo relations with church hierarchy varied – Unifies celestial and sublunary physics – Accepted by some, but ran into trouble – Questioned by inquisition – Newtonʼs Laws of motion – Forced to recant idea that Earth moves – Theory of Universal Gravitation – Excommunicated and placed under house arrest – Together these explain both – That was corrected in 1992 (359 years later) • Motion of planets – Now a statue of Galileo in Vatican courtyard • Motion on Earth • Even stronger objections from the natural philosophers than from the Church

6 Newtonʼs Laws of Motion Newtonʼs Law of Gravity

• 1. A body in motion tends to remain in motion unless • Every object with mass exerts a force on acted upon by external forces. every other object with mass. . Momentum (p = m v) remains constant . The force is proportional to the product of • 2. The rate of change of momentum with time is the two masses equal to the force. . F = (dp/dt) = m (dv/dt) = m a, if m constant . The force is inversely proportional to the • 3. An object exerting a force on a second object square of the distance between the two experiences an equal and opposite force. masses. 2 . F12 = – F21 . F = (GM1M2)/r

Pause for Demo The

• Galileo and the leaning tower story • Copernicus (heliocentric but circular) • Squash ball about 1 ounce • Tycho Brahe (meticulous observations) • Basketball about 20 ounces • Kepler (ellipses, not circles!) • Which falls faster? • Galileo (constant motion needs no force) – The Earth can move but we donʼt feel it. – The inquisition was not persuaded. – “eppur, si muove” • Newton (unified physics)

7 Copernican Principle The Universe as we see it now

• Removal from the center • The Observable Universe (Horizon) • Very large (about 48 billion light years) – geocentric before 1543 (Copernicus) • Very clumpy on “small” scales – heliocentric 1543 to 1915 (Shapley) – planets, stars, galaxies, clusters, – galactocentric 1915 to 1923 (Hubble) • Very empty on average – nowherecentric 1923 to present (Einstein, – about one atom every 40 cubic meters …) • Expanding (galaxies moving apart) – velocity proportional to distance • Nothing special about us • No “fine-tuning” to allow us

Evolution of World View Evolution in other fields

• Need for a correct world view • Geology – If solar system is whole Universe – Earth much older than 4500 yrs – No possibility of other civilizations • Lyell (1860s) – Radioactive dating – Need to learn how big is • Biology – (Note that we consider only the Milky Way) – Species all evolved from common ancestor • Time to communicate with other galaxies is too • Darwin (1859) long – Natural origin of life • Miller Urey experiment (1953)

8 Connections How to Estimate fc Consider both “capability” & “interest” Are these coupled?

Yes - Science and Technology closely linked No - Technology without Astronomy? Cloudy planet?…

Does correct worldview favor a civilization?

Yes - European domination No - Germs more important than weapons?

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