Models of the Solar System, Gravitation and the motion of the Planets – A.K.A DEAD WHITE GUYS

Cosmogony A cosmogony is theory about ones place in the universe. A geocentric cosmogony is a theory that proposes Earth to be at the center of the universe. A heliocentric cosmogony is a theory that proposes the Sun to be at the center of the universe.

Which is the geocentric cosmogony and which is the heliocentric cosmogony? geocentric (Earth-centered)heliocentric (Sun-centered)

Pythagorean Universe time: about 550 bc first recorded attempt at rational explanation of heavens formed foundation for Greek astronomy

Philosophical Ideas The heavens represent perfection. The heavens are immutable. The circle is the perfect shape. All heavenly motions must be circular.

Pythagorean Model stars reside on stellar sphere stellar sphere rotates about axis in 23 hours 56 minutes Sun follows path called ecliptic going around Earth once in one year accounts for most observations!!

Axis of Rotation North Star Stellar Sphere How the Greeks modeled the heavens

Polaris NORTHERN HORIZON

BUT - THERE WAS A COMPLICATION …. There were stars that appeared to move across the sky without staying in their respective constellations WANDERING STARS – (Greek word for wanderer is planete`)

Prograde and Retrograde Motion Prograde Motion (normal motion) – The apparent West to East motion of objects (over many nights) as compared to the stationary background stars. Retrograde Motion - The apparent East to West motion of objects (over many nights) as compared to the stationary background stars.

Planets were often called wandering stars because they seem to slowly move from one constellation to the next. West East South

Retrograde motion Models of the universe MUST adequately describe this retrograde motion!!!

Philosophical Ideas The heavens represent perfection. The heavens are immutable. The circle is the perfect shape. All heavenly motions must be circular.

The astronomer must try his utmost to explain celestial motions by the simplest possible hypothesis; but if he fails to do so, he must choose whatever other hypotheses meet the case. -Ptolemy of Alexandria (140 A.D.)

Ptolemy was : 1.Polish 2.Danish 3.Italian 4.German 5.Greek

Ptolemy tried to crate a model that would account for retrograde motion. He placed the planets in orbits (deferments) on orbits (epicycles) all around the Earth

Ptolemy’s Epicycles Epicycle Deferent Earth

Ptolemy’s Epicycles

Where is retrograde motion occurring? Planet’s Path

Ptolemy’s Epicycles Where is retrograde motion? Planet’s Path

For most of human history, we have thought the universe was geocentric

“A system of this sort seemed neither sufficiently absolute nor sufficiently pleasing to the mind.” --Copernicus On the Ptolemaic system:

Why heliocentric NOW?? Renaissance art literature medicine exploration

Copernicus (1473 – 1543 AD) was : 1.Polish 2.Danish 3.Italian 4.German 5.Greek

Copernicus (1473 – 1543 AD) is known for : 1.First observations of the sun 2.First sun centered model of the solar system or universe 3.The world’s best naked-eye astronomical observations in history 4.Creating first a theoretical model to explain planetary motions 5.Creating first a theoretical model for explaining gravity

Copernicus (1473 – 1543 AD) is known for - 1.First observations of the sun 2.First sun centered model of the solar system or universe 3.The world’s best naked-eye astronomical observations in history 4.Creating first a theoretical model to explain planetary motions 5.Creating first a theoretical model for explaining gravity

Copernicus (1473 – 1543 AD) - 1.Probably died a virgin 2.Was a priest and Lawyer 3.Had artificial wooden and silver noses 4.Probably died of Mercury poising 5.Rumored to have died of a bladder burst 6.Was blind at the time of his death 7.Was labeled a heretic by the church

Copernicus (1473 – 1543 AD) - 1.Probably died a virgin 2.Was a priest and Lawyer 3.Had artificial wooden and silver noses 4.Probably died of Mercury poising 5.Rumored to have died of a bladder burst 6.Was blind at the time of his death 7.Was labeled a heretic by the church

Copernicus devised the first comprehensive heliocentric cosmogony to successfully explain retrograde motion Retrograde motion is an apparent motion caused when one planets moves from being behind another planet to being in front of the other planet.

Copernicus devised the first comprehensive heliocentric cosmogony to successfully explain retrograde motion Let’s watch a movie of this motion.

To demonstrate that the appearances are saved by assuming the Sun at the center and the Earth in the heavens is not the same thing as to demonstrate that in fact the Sun is in the center and the Earth in the heavens. I believe that the first demonstration may exist, but I have grave doubts about the second. --Cardinal Bellarmine (1615)

Tycho Brahe ( )

Cross-Tab Label Tycho Brahe ( ) was - 1.Polish 2.Danish 3.Italian 4.German 5.Greek

Tycho Brahe ( ) - 1.Probably died a virgin 2.Was a priest and Lawyer 3.Had artificial wooden and silver noses 4.Probably died of Mercury poising 5.Rumored to have died of a bladder burst 6.Was blind at the time of his death 7.Was labeled a heretic by the church

Tycho Brahe ( ) - 1.Probably died a virgin 2.Was a priest and Lawyer 3.Had artificial wooden and silver noses 4.Probably died of Mercury poising 5.Rumored to have died when his bladder burst 6.Was blind at the time of his death 7.Was labeled a heretic by the church

Tycho Brahe ( ) is known for - 1.First telescope observations of the sun 2.First sun centered scientific model of the solar system or universe 3.Being the world’s best naked- eye astronomer 4.Creating first a theoretical model to explain planetary motions 5.Creating first a theoretical model for explaining gravity

Tycho Brahe ( ) is known for - 1.First telescope observations of the sun 2.First sun centered scientific model of the solar system or universe 3.Being the world’s best naked- eye astronomer 4.Creating first a theoretical model to explain planetary motions 5.Creating first a theoretical model for explaining gravity

Tycho Brahe ( ) What do we mean by “Greatest Naked-eye Astronomer?”

No telescope!!

Scientists use parallax to measure distances.

Tycho Brahe measured distances using parallax that disproved ancient ideas about the heavens He observed a supernova in 1572 and with this showed that the heavens were both changing and had a dimension of distance; this troubled scholars who previously thought the heavens were unchanging. He showed that comets were objects that occurred in the region of the planets, not in Earth’s atmosphere.

Johannes Kepler

Cross-Tab Label Johannes Kepler was : 1.Polish 2.Danish 3.Italian 4.German 5.Greek

Johannes Kepler Probably died a virgin 2.Was a priest and Lawyer 3.Had artificial wooden and silver noses 4.Probably died of Mercury poising 5.Rumored to have died when his bladder burst 6.Was blind at the time of his death 7.Was labeled a heretic by the church

Johannes Kepler None of these. He was a deeply religious man and a family man. He was rumored to have hated Tycho Brahe and was in the relationship for the data. With that data he changed the understanding of motion of heavenly bodies forever. He was also a writer, who wrote children stories about the heavens.

Cross-Tab Label Johannes Kepler is Known for - 1.First telescope observations of the sun 2.First sun centered scientific model of the solar system or universe 3.Being the world’s best naked-eye astronomer 4.Creating first a theoretical model to explain planetary motions 5.Creating first a theoretical model for explaining gravity

Johannes Kepler is Known for - 1.First telescope observations of the sun 2.First sun centered scientific model of the solar system or universe 3.Being the world’s best naked-eye astronomer 4.Creating first a theoretical model to explain planetary motions 5.Creating first a theoretical model for explaining gravity

Johannes Kepler 1571 – 1630 Kepler’s Three Laws of Planetary Motion

Eccentricity, e how squashed or out of round the ellipse is a number ranging from 0 for a circle to 1 for a straight line e = 0.02 e = 0.7 e = 0.9

Kepler’s First Law: The orbit of a planet about the Sun is an ellipse with the Sun at one focus.

What is the shape of Earth’s orbit around the Sun? Earth, e = 0.016

SECOND LAW A line drawn from the planet to the Sun sweeps out equal areas in equal times

Kepler’s Second Law: A line joining a planet and the Sun sweeps out equal areas in equal intervals of time.

Kepler's Second Law Movie

SECOND LAW A line drawn from the planet to the Sun sweeps out equal areas in equal times orbital speed is not constant for an ellipse only for a circle planets move faster when near the Sun (perihelion) planets move slower when they are far from the Sun (aphelion)

THIRD LAW The size of the orbit determines the orbital period –planets that orbit near the Sun orbit with shorter periods than planets that are far from the Sun a 3 AU = P 2 years

THIRD LAW The size of the orbit determines the orbital period –planets that orbit near the Sun orbit with shorter periods than planets that are far from the Sun

Kepler’s Third Law: The square of a planet’s sidereal (orbital) period is proportional to the cube of the length of its orbit’s semimajor axis (p 2  a 3 ).

The Second and Third Laws The Second Law tells us what a particular planet does when it orbits a Star –The planet will move faster when it is close to the Sun and slower when it is farther from the Sun The Third Law how the orbital periods are related to the orbital distances for all the planets in the Solar System –planets that are in an orbit located near the Sun have short orbital periods –planets that are in an orbit located far from the Sun have long orbital periods

SECOND LAW The speed a planet travels during its orbit is related to the distance from the star –When the planet is near the sun the planet goes faster than when the planet is farther from the sun Planet travels fast here Planet travels slow here

THIRD LAW The size of the orbit determines the orbital period –planets that orbit near the Sun orbit with shorter periods than planets that are far from the Sun p = 1 year p = ~ 12 years

THIRD LAW The size of the orbit determines the orbital period –planets that orbit near the Sun orbit with shorter periods than planets that are far from the Sun –MASS DOES NOT MATTER Both have p = 1 year

The Second and Third Laws The Second Law tells us what a particular planet does when it orbits a Star –The planet will move faster when it is close to the Sun and slower when it is farther from the Sun The Third Law how the orbital periods are related to the orbital distances for all the planets in the Solar System –planets that are in an orbit located near the Sun have short orbital periods –planets that are in an orbit located far from the Sun have long orbital periods

According to Kepler’s second law, a planet with an orbit like Earth’s would: 1. move faster when further from the Sun. 2. move slower when closer to the Sun. 3. experience a dramatic change in orbital speed from month to month. 4. experience very little change in orbital speed over the course of the year. 5. none of the above.

Which of the following best describes what would happen to a planet’s orbital speed if it’s mass were doubled but it stayed at the same orbital distance? 1. It would orbit half as fast. 2. It would orbit less that half as fast. 3. It would orbit twice as fast. 4. It would orbit more than twice as fast. 5. It would orbit with the same speed.

If a small weather satellite and the large International Space Station are orbiting Earth at the same altitude above Earth’s surface, which of the following is true? 1. The large space station has a longer orbital period. 2. The small weather satellite has a longer orbital period. 3. Each has the same orbital period

Heliocentric Model

The great scientist Galileo made discoveries that strongly supported a heliocentric cosmogony

Galileo was - 1.Polish 2.Danish 3.Italian 4.German 5.Greek

Galileo Probably died a virgin 2.Was a priest and Lawyer 3.Had artificial wooden and silver noses 4.Probably died of Mercury poisoning 5.Rumored to have died when his bladder burst 6.Was blind at the time of his death 7.Was labeled a heretic by the church

Galileo Probably died a virgin 2.Was a priest and Lawyer 3.Had artificial wooden and silver noses 4.Probably died of Mercury poisoning 5.Rumored to have died when his bladder burst 6.Was blind at the time of his death 7.Was labeled a heretic by the church

Galileo is known for - 1.First observations of the sun 2.First sun centered scientific model of the solar system or universe 3.Being the world’s best naked-eye astronomer 4.Creating first a theoretical model to explain planetary motions 5.Creating first a theoretical model for explaining gravity

Galileo is known for - 1.First observations of the sun 2.First sun centered scientific model of the solar system or universe 3.Being the world’s best naked-eye astronomer 4.Creating first a theoretical model to explain planetary motions 5.Creating first a theoretical model for explaining gravity

Milky Way There are thousands (billions) more stars in the Milky Way than are visible to the naked eye. Universe is bigger than imagined.

A Being with Ears

The Bulge of Saturn Saturn is not a sphere. Circles and spheres do not dominate the heavens.

The Moon The moon has craters. The moon is not a perfect heavenly body.

Sunspots The Sun is not a perfect heavenly body. The Sun rotates about its own axis.

Galileo’s discoveries of the phases of Venus with his telescope showed that Venus must orbit the Sun and strongly supported a heliocentric model Venus is clearly smallest when it in the full phase and largest when it is in the new phase. Then Venus must be very far from Earth when it is in the full phase and quite closes to Earth when in the new phase – which supports the argument that Venus is orbiting the Sun not Earth.

Galileo’s telescope revealed phases of Venus which could only occur IF Venus orbits the Sun.

Galileo’s telescope revealed that Jupiter had moons which orbited Jupiter instead of Earth.

Jupiter is much blamed by the poets on account of his irregular loves. Three maidens are especially mentioned as having been clandestinely courted by Jupiter with success. Io, daughter of the River, Inachus, Callisto of Lycaon, Europa of Agenor. Then there was Ganymede, the handsome son of King Tros, whom Jupiter, having taken the form of an eagle, transported to heaven on his back, as poets fabulously tell.... I think, therefore, that I shall not have done amiss if the First is called by me Io, the Second Europa, the Third, on account of its majesty of light, Ganymede, the Fourth Callisto.... This fancy, and the particular names given, were suggested to me by Kepler, Imperial Astronomer, when we met at Ratisbon fair in October So if, as a jest, and in memory of our friendship then begun, I hail him as joint father of these four stars, again I shall not be doing wrong. - Marius

IN MEMORY OF GALILEO

Isaac Newton (1642 – 1727) The Baddest Dead White Guy of Them All

Isaac Newton (1642 – 1727) was - 1.Polish 2.Danish 3.Italian 4.German 5.Greek 6.British

Isaac Newton (1642 – 1727) - 1.Probably died a virgin 2.Was a priest and Lawyer 3.Had artificial wooden and silver noses 4.Probably died of Mercury poisoning 5.Rumored to have died when his bladder burst 6.Was blind at the time of his death 7.Was labeled a heretic by the church

Isaac Newton (1642 – 1727) - 1.Probably died a virgin 2.Was a priest and Lawyer 3.Had artificial wooden and silver noses 4.Probably died of Mercury poisoning 5.Rumored to have died when his bladder burst 6.Was blind at the time of his death 7.Was labeled a heretic by the church

Isaac Newton (1642 – 1727) is known for - 1.First observations of the sun 2.First sun centered scientific model of the solar system or universe 3.Being the world’s best naked-eye astronomer 4.Creating first a theoretical model to explain planetary motions 5.Creating first theoretical model for explaining gravity and …..

Isaac Newton (1642 – 1727) is known for - 1.First observations of the sun 2.First sun centered scientific model of the solar system or universe 3.Being the world’s best naked-eye astronomer 4.Creating first a theoretical model to explain planetary motions 5.Creating first theoretical model for explaining gravity and …..

Isaac Newton formulated three laws of motion and the law of gravitation – these laws describe the motion of our physical world

Newton’s Three Laws of Motion First Law - A body remains at rest or moves in a straight line at a constant speed unless acted upon by an outside (net) force. Second Law - (net) Force = mass x acceleration Third Law - Whenever one body exerts a force on a second body, the second body exerts an equal and opposite force on the first body.

Newton’s First Law A body remains at rest or moves in a straight line at a constant speed unless acted upon by an outside (net) force. A rockets will coast in space along a straight line at constant speed. A hokey puck glides across the ice at constant speed until it hits something

Newton’s Second Law of Motion (net)Force = mass x acceleration or F net = m x a Acceleration is the rate of change in velocity – or how quickly your motion is changing. The accelerator in your car!!

Newton’s Third Law of Motion Whenever one body exerts a force on a second body, the second body exerts an equal and opposite force on the first body. Don’t need a rocket launch pad! The Bug and the Windshield – who is having the worse day?

Newton’s Law of Gravitation Newton’s law of gravitation states: Two bodies attract each other with a force that is directly proportional the product of their masses and is inversely proportional to the square of the distance between them. What the ….? I thought I understood gravity?

Newton’s Law of Gravitation To figure out the gravitational force just multiply the mass of the two things together then divide by the distance they are apart (squared). m1m1 m2m2 d

Newton’s Law of Gravitation Newton’s law of gravitation states: Two bodies attract each other with a force that is directly proportional the product of their masses and is inversely proportional to the square of the distance between them. g ~ 10 m/s 2 “the acceleration of gravity” And g x m is your weight!!

Newton’s Law and Gravitation All my favorite Projectiles behave like this!!! Force Velocity Acceleration

Newton’s Laws and Kepler's Laws Newton’s law of gravitation and his three laws of motion prove all of Kepler’s laws Gravity – From Newton to Einstein

Newton's friend Edmund Halley predicted the comet would return in 1758 and it did!