Science. Is this course science? A. Yes B. No

Science

Science Is this course science? A. Yes B. No

Science Is this course science? A. Yes B. No, this course is about the results of science

Science Is this course science? A. Yes B. No, this course is about the results of science But it is not science

Science Is this course science? A. Yes B. No, this course is about the results of science But it is not science Then what is science?

Science Science is a way of explaining the physical world Religion and philosophy offer explanations of the physical world, too You can also consider the arts as explanations explanations of what s going on in someone s mental world The bottom line is that we humans are explanation machines We can t help it We are born that way And our explanations form the basis of our culture

Science The various aspects of our culture help us understand our world Science is no different from the others in this regard But science is unique among them in one very important way: It demands that the world actually be the way it says Understanding this, the basis of the scientific process, is one of the most important things you can take away from this course

Science Believe it or not, science is not contrary to normal human nature In fact, science is everyday human behavior, formalized That formalization has a special name...???... The Scientific Method

The Scientific Method Observation Science

The Scientific Method Observation Hypothesis (model) Science

Science The Scientific Method Observation Hypothesis (model) ==> predictions

Science The Scientific Method Observation Hypothesis (model) ==> predictions More observations or experiments (or both) to test predictions

Science The Scientific Method Observation Hypothesis (model) ==> predictions More observations or experiments (or both) to test predictions If predictions fail, revise hypothesis and continue experimentation and/or observation Hypothesis This may not seem much like everyday human behavior, but It s just the way we humans normally solve problems Granted, scientists do it more methodically and carefully and document what they do But it s really the same thing It s how humans work And it s how scientific theories are created

Science Scientific Theories How many times have you said this to somebody? I ve got a theory about that What you mean is you have an educated guess, which is like a hypothesis Theory in science means something very different from an educated guess

Scientific Theories Science Scientists carefully document how they test their hypotheses Then they publish their results Other scientists can then evaluate them and try to replicate them If a hypothesis is tested by many scientists and found to pass all the tests, then (usually together with other hypotheses) it can become a scientific theory The most successful scientific theories explain things that weren t even on the minds of the scientists who originated them

Science Scientific Theories But even the most strongly supported scientific theory can be disproved! In fact, if a theory cannot be disproved, then it s not a scientific theory at all!

The Process of Science Hypothesis The process of science is a cycle of observation/experimentation, hypothesismaking, and prediction One of the earliest observations to which this process was applied involved the way celestial objects move in the sky People saw the stars and planets apparently moving around the motionless Earth fixed to a nested set of celestial spheres But sometimes planets didn t move in a way that fit this idea

Retrograde Motion The path of Mars through the constellations of the celestial sphere is generally from the west to the east But periodically, it reverses its path and travels backwards toward the west in retrograde motion All the planets show some amount of retrograde motion

Retrograde Motion The ancients came up with elaborate explanations for retrograde motion The most influential was due to Claudius Ptolemy (of horoscope fame)

Retrograde Motion The ancients came up with elaborate explanations for retrograde motion The most influential was due to Claudius Ptolemy (of horoscope fame) Ptolemy s model consisted of a set of nested spheres with the Earth in the center

Retrograde Motion In Ptolemy s model, each planet moved on its own sphere along two circular paths It moved around the Earth on its circular deferent And it moved around a point on the deferent on a circular path called an epicycle

Retrograde Motion The epicycles are necessary to explain retrograde motion The paths of Venus and Jupiter are traced in dashed lines above

Retrograde Motion Ptolemy s model explained two observations: Observation 1: Retrograde motion because planets move backward when on the near side of their epicycles Observation 2: Planets are brighter when they are moving retrograde because they are nearer then and therefore brighter

Retrograde Motion Ptolemy s model also did a decent job of predicting the positions of planets in the sky But it was complicated, with all these epicycles And how to explain epicycles?

Retrograde Motion Enter Occam s Razor A philosophical principle attributed to the 14th century English philosopher William of Ockham In the modern formulation, Occam s Razor says that when comparing two models, the simpler one is usually better

Retrograde Motion There is, in fact, a simpler model that explains planetary motion But it requires a major change in the perspective people had held for thousands of years EARTH IS NOT THE CENTER

Retrograde Motion Once that conceptual leap is made, and the Sun is put in the center, retrograde motion is revealed as just an illusion As planets orbit the Sun, those farther out move slower So the ones closer in catch up and pass them by The consequence is illustrated above

Retrograde Motion So retrograde motion is explained in a simple way by assuming a Suncentered solar system Hundreds of years before Ptolemy (in 260 BCE), a Greek named Aristarchus of Samos suggested that Earth goes around the Sun But the Greeks did not accept Aristarchus s Sun-centered model Why not?

One of the major reasons was that they could not detect stellar parallax The parallax for the nearest star is only 0.75 (1" = 1 arcsecond = 1/3600 degree) 0.75 < the width of a dime at 1 mile On the scale of our model solar system, it s the width of a dinner plate in St Augustine viewed from UNF It s only detectable with telescopes, which the Greeks did not have So without that evidence they were satisfied with the Ptolemaic model

The Greek failure to accept Aristarchus ideas illustrates that scientific advances depend not only on ideas but also on technology Greek technology was not advanced enough to see stellar parallax or any other evidence for errors in their cosmology So the Ptolemaic model was the accepted one for ~1500 years But then technology advanced And advances in astronomy gave birth to the scientific revolution Now we ll look at some of the scientists involved in the development of astronomy and the scientific revolution

Nicolaus Copernicus (1473-1543) Formulated heliocentric model Scientists in Astronomy On the Revolutions of the Celestial Spheres published in 1543, described it Still had epicycles Practically, not much (if any) better than Ptolemy s But it turned out to be more correct Forensic reconstruction of Copernicus head

Scientists in Astronomy Tycho Brahe (1546-1601) The best naked-eye observer ever? Had his own model of the solar system Check out the nose A man of varied interests In his household a dwarf and a moose A party animal, but minded his manners Death by politeness? Or poisoning? Who did it? Kepler? Christian IV of Denmark? Tycho? Most likely his lifestyle PLOS ONE 13, no. 4 (April 19, 2018)

Scientists in Astronomy Johannes Kepler (1571-1630) Profoundly religious Excellent mathematician Published a book on planetary motion, The Mystery of the Cosmos, in 1596 Sent Tycho a copy of the book, and became Tycho s assistant in 1600, hoping for full access to Tycho s data Tycho didn t want to give him full access, so he set him to work on the orbit of Mars But using circular orbits, there was an 8 discrepancy between Kepler s model of Mars and Tycho s observations

Scientists in Astronomy Johannes Kepler (1571-1630) So Kepler made a bold move He tried elliptical orbits instead of circles He didn t want to after all, the orbits ought to be circular But they weren t: With ellipses, the 8 discrepancy to which most might have said that s good enough was gone When Tycho died, Kepler got his data And by 1605, Kepler had arrived at the two of the three of what are now called Kepler s Laws of Planetary Motion

Kepler s First Law Planets move in elliptical orbits with the Sun at one focus

Kepler s Second Law Planets in orbit sweep out equal areas in equal times

It took Kepler nearly ten more years to arrive at his third law of planetary motion

Kepler s Third Law More distant planets orbit the Sun at slower average speeds, obeying the relationship p 2 = a 3 p = orbital period in years a = average distance from Sun in AU

Summary of Kepler s Laws 1. Planets move in elliptical orbits with the Sun at one focus 2. Planets in orbit sweep out equal areas in equal times 3. More distant planets orbit the Sun at slower average speeds, obeying the relationship p 2 = a 3 p = orbital period in years a = average distance from Sun in AU

Kepler s Laws Kepler developed his laws of planetary motion by Making a model of the solar system Using his model to make predictions Comparing those predictions to Tycho s observations Adjusting his model as necessary Making more predictions Etc Does this process look familiar? It s the Scientific Method in action

Kepler s Laws Kepler s Laws explained Tycho s observations better than any previous model But he had no idea why the planets moved this way And that s what scientists really want: a model that explains why But that would have to await the arrival on the scene of Sir Isaac Newton We ll get to him later But first, we need to travel south to Italy

Galileo Galilei (1564-1642) Scientists in Astronomy

Scientists in Astronomy Galileo Galilei (1564-1642) Mathematician

Scientists in Astronomy Galileo Galilei (1564-1642) Mathematician Astronomer

Scientists in Astronomy Galileo Galilei (1564-1642) Mathematician Astronomer Physicist

Scientists in Astronomy Galileo Galilei (1564-1642) Mathematician Astronomer Physicist Lute player

Scientists in Astronomy Galileo Galilei (1564-1642) Mathematician Astronomer Physicist Lute player Not the inventor of the telescope, but greatly improved on the invention And then he put it to use to put to rest certain misconceptions that could be traced back nearly 2000 years

Ancient Errors Ptolemy s model was based on the Greek view of the universe This was largely due to Aristotle (384-322 BCE)

Ancient Errors Ptolemy s model was based on the Greek view of the universe This was largely due to Aristotle (384-322 BCE): Ancient Error #1 - The Earth is in the center of the Universe Ancient Error #2 - The heavens and the Earth are distinct realms, with the heavens being perfect and the Earth imperfect That s what most people believed for 1500 years Then, in the sixteenth century, this view began to change

Ancient Errors The paradigm shift began with Copernicus s heliocentric model But his model didn t work any better than Ptolemy s geocentric model, and he had no direct evidence that his model was right and Ptolemy s wrong Kepler s heliocentric model, based on Copernicus s ideas, explained the observed motions of the planets much better than Ptolemy s But Kepler didn t know why, and he had no more direct evidence than Copernicus that Earth was not the center of everything Then Galileo and his telescope came along, and provided the direct evidence that had been missing

Ancient Error #1 - Earth is the Center Galileo turned his telescope on Jupiter He saw that there were several objects that looked like stars always associated with it

Ancient Error #1 - Earth is the Center Galileo turned his telescope on Jupiter He saw that there were several objects that looked like stars always associated with it He figured out that the stars were actually moons orbiting around Jupiter In the strictest geocentric model, everything was supposed to orbit around the Earth, and not around anything else So Galileo s observation of moons orbiting Jupiter was inconsistent with the geocentric model Celestial objects could orbit around things other than the Earth

Ancient Error #1 - Earth is the Center Then Galileo turned his telescope to Venus, and found his most convincing proof that Ptolemy s model could not be correct

Ancient Error #1 - Earth is the Center Then Galileo turned his telescope to Venus, and found his most convincing proof that Ptolemy s model could not be correct Ptolemy s model had Venus on an epicycle that was always between Earth and the Sun to explain its location in the sky So a full Venus should never occur, because the Sun would always be behind Venus But with his telescope, Galileo observed Venus go through a complete set of phases, just like the Moon This meant that Venus must sometimes be on the other side of the Sun

Ancient Error #1 - Earth is the Center Aristotle and the Greeks had claimed that the Earth was the center of the universe

Ancient Error #1 - Earth is the Center Aristotle and the Greeks had claimed that the Earth was the center of the universe But with his studies of the moons of Jupiter and the phases of Venus, Galileo showed that this could not be the case Or did it? It still didn t feel like Earth was moving no evidence for Earth s rotation no evidence for stellar parallax and there was a competing geocentric model that also explained Galileo s observations

Ancient Error #1 - Earth is the Center It was due to Tycho Brahe Moon, Sun, and stars went around Earth The 5 known planets went around the Sun Convincing evidence for heliocentrism appeared in the late 18 th and 19 th century New technology (Foucault pendulum, better telescopes, etc) solidified it Another example of how better technology is often needed to support a better idea But Galileo showed that Ptolemy s geocentric model could not be correct, even if he didn t prove heliocentrism correct

Ancient Error #2 Earth and the heavens are distinct realms But what about the Greek idea that the heavens were perfect and the Earth imperfect? Heavenly bodies like the Moon were supposed to be perfectly smooth spheres The dark spots on the Moon were explained as perfectly smooth patches that absorbed or emitted light differently than the rest of the Moon s surface

Ancient Error #2 Earth and the heavens are distinct realms With his telescope, Galileo observed the dark splotches and lines on the Moon By looking carefully at different times, he noticed that the dark lines near the terminator changed size with the angle of the Sun s rays He concluded that these dark lines were not merely variations in the properties of the perfectly smooth surface They were mountains sticking up off the surface, just like we have here on Earth Heavenly bodies were not perfect after all

Ancient Error #2 Earth and the heavens are distinct realms But it was Newton and his apple who demonstrated most elegantly that Earth and the heavens are not distinct realms We ll get to that But first, a bit about Sir Isaac From University of Tennessee Astronomy 161 web site http://csep10.phys.utk.edu/astr161/index.html

Isaac Newton (1642-1727)

Isaac Newton (1642-1727) Arguably the smartest person who ever lived

Isaac Newton (1642-1727) Arguably the smartest person who ever lived certainly one of them

Isaac Newton (1642-1727) Arguably the smartest person who ever lived certainly one of them (IQ has somehow been estimated at ~180-190)

Isaac Newton (1642-1727) Arguably the smartest person who ever lived certainly one of them (IQ has somehow been estimated at ~180-190) Scientist

Isaac Newton (1642-1727) Arguably the smartest person who ever lived certainly one of them (IQ has somehow been estimated at ~180-190) Scientist Alchemist

Isaac Newton (1642-1727) Arguably the smartest person who ever lived certainly one of them (IQ has somehow been estimated at ~180-190) Scientist Alchemist Bible scholar

Isaac Newton (1642-1727) Arguably the smartest person who ever lived certainly one of them (IQ has somehow been estimated at ~180-190) Scientist Alchemist Bible scholar Warden and Master of the Royal Mint President of the Royal Society

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