Topic 4 Motions of the Planets, Stars, Sun, Earth, & Moon

History Of Astronomy

70,000 years old History of Astronomy Page 1 Astronomy is the oldest science known to man It’s approximately _____________________________ 70,000 years old Scientists know the age of Astronomy by finding & studying artifacts left behind by ancient man

History of Astronomy Page 1 Some of the oldest artifacts & monuments dedicated to studying astronomy found worldwide

History of Astronomy Life was tough 70,000 years ago Page 1 Life was tough 70,000 years ago Astronomy must have been important to Ancient Man Why did Ancient man study the sky thousands of years ago??

Why Did Ancient Man Study The Sky? Survival Time of Day Time of Year (Seasons) Direction (celestial compass) Recreation Page 1

Why Develop Models? Page 1 Models help man study & understand the world around Models can be mental, mathematical, or physical Can you name the type of models below:

What Were the Earliest Models of the Universe?? Page 1 The earliest models regarding the structure of the universe were: ______________________________________ Geocentric Model or Earth Centered Model

Aristotle born in 384 BC and died 322 BC Who is the Father of the Geocentric Model? Aristotle born in 384 BC and died 322 BC He said “All celestial objects revolve around Earth including the Sun” The Earth is stationary or non moving This model was used to explained structure of the “heavens” and the observed motions of the known celestial objects Page 2

The Geocentric Model Was Good It could explain the motion of most celestial objects That why it lasted for over 2,200 years But the geocentric model was known to be flawed Page 2

Geocentric Model Page 2 According to the Greeks Designed using only NAKED-EYED observations No instruments were used to aid them Model was accurate when explaining some motions but could not explain others Why?? Because it was fundamentally flawed

What motions could the Geocentric Model explain & not account for?? YES Moon?_______________ YES Sun? ________________ YES Stars? _______________ NO Planets?______________ Specifically the retrograde motions of Planets Page 2

So Why did the Geocentric Model Last for so long even though it was wrong? The Church Comfortable Lack of Technology to disprove Geocentric model No other good theories being developed. Why? Bubonic plague

Retrograde Motion Page 2 The apparent backward movement of a planet over a period of time NOT real motion, only observed motion What accounts for retrograde motion? Why did they see backward movements of planets? Why to you think planet Mars was studied the most? Retrograde motion Video

Retrograde Motion Lets see what it looks like Show video clip from the Universe series & then tell story

What causes Retrograde Motion?? This occurs because Earth moves faster in its orbit than the outer planets Page 2 Retrograde Animation in folder Retrograde motion 1:49 Retrograde Video: Good for website 6:25

Ptolemy (85 A.D.- 165 A.D.) Ptolemy modified the geocentric model to account for the retrograde motion of planets (add to bottom of page 2) The "solution" to retrograde motion came in the form of a mad, but clever idea Add to bottom of page 2

Ptolemaic Geocentric Model "Epicycles", and the concentric spheres to which they were attached were termed the "Deferents” Analogy Tea Cup Ride Add to bottom of page 2

Ptolemaic Model Add to bottom of page 2

Claudius Ptolemaeus (Ptolemy) At first, not widely accepted because scientists thought the model to be too complicated Although the geocentric model with epicycles did explain the motions of the planets better. Important in terms of predicting astrology and fate.

Introduced to explain retrograde (westward) motion of planets Epicycles Introduced to explain retrograde (westward) motion of planets The Ptolemaic system was considered the “standard model” of the Universe until the Copernican Revolution.

Epicycles Insert Seeds Disk (SLIDESHOW MODE ONLY)

Epicycles Add to bottom of page 2 Animation Use seeds disk to play animation (SLIDESHOW MODE ONLY)

Epicycles Add to bottom of page 2 Animation Use seeds disk to play animation (SLIDESHOW MODE ONLY)

Who is the Father of Heliocentric Model Page 2 Nicolaus Copernicus (1473 – 1543) Father of the Heliocentric Universe (Sun in the Center) Tell the story & news reference the newspaper article

Nicolas Copernicus (1473-1543) Polish cleric first proposed the heliocentric model Wrote the book De Revolutionibus and stashed it under his mattress Proposed all planets including Earth revolve around the Sun Circular orbits at constant velocities Copernicus’ model was the best to date but still had problems accurately pinpointing the position of the planets

Was the Copernican Model completely correct? Why?? Heliocentric Model In this model, the is at the center and all the planets, including Earth, revolved around it in CIRCULAR orbits Page 2 Sun Was the Copernican Model completely correct? Why??

Heliocentric Model Was the Copernican Model completely correct? Why?? Page 2 Heliocentric Model Was the Copernican Model completely correct? Why?? No the planet’s orbits are slightly elliptical

Copernicus’ new (and correct) explanation for retrograde motion of the planets Explanation of Retrograde Motion Retrograde (westward) motion of a planet occurs when the Earth passes the planet. This made Ptolemy’s epicycles unnecessary.

Explain the difference between the geo- and helio-centric models of the solar system. Helio-centric Geo-centric Earth- centered Sun- centered Page 2

The Copernican model was better but it was still slightly wrong b/c it stated the planets revolved around the sun in circular orbits Until… Helio-centric Geo-centric Earth- centered Sun- centered Page 2

Galileo Galilei (1564 – 1642) Invented the modern view of science: Transition from a faith-based “science” to an observation-based science. Greatly improved on the newly invented telescope technology. (But Galileo did NOT invent the telescope!) Was the first to meticulously report telescope observations of the sky to support the Copernican Model of the Universe.

Major Discoveries of Galileo (2) Surface structures on the moon; first estimates of the height of mountains on the moon

Major Discoveries of Galileo Moons of Jupiter (4 Galilean moons) (What he really saw) Rings of Saturn (What he really saw)

Major Discoveries of Galileo (3) Sun spots (proving that the sun is not perfect!)

Major Discoveries of Galileo (4) Phases of Venus (including “full Venus”), proving that Venus orbits the sun, not the Earth!

Galileo Galilei (1564 – 1642) His discovers led to propelled forward the ideas of Copernicus and heliocentric model

Historical Overview