1. The Beginnings of Classical Astronomy
The Early Period
The Beginnings of Classical Astronomy

2. Early Ideas
The Ancient Greeks were the first to try and explain the workings of the heavens in a ________________ manner
They used ____________ and _______________ made only with the naked eye
They also used what they knew about logic and mathematics, especially ______________

3. The Shape of the Earth
Ancient Greeks knew the Earth was _________________
Pythagoras taught that the Earth was spherical because the believed that a sphere was the perfect shape and this would have been how gods would have created the Earth with the perfect form

4. The Shape of the Earth
Aristotle argued for a spherical Earth based on his observations
He noticed that the shadow cast during a lunar eclipse was ___________________
He also noticed that if one traveled south they would see stars that were previously hidden below the southern horizon

5. The Size of the Earth
Eratosthenes, head of the library at Alexandria made the first measurements as to the size of the Earth
He devised an experiment to determine the circumference of the Earth

7. The Size of the Earth
After determining the angles Eratosthenes knew that the distance from Alexandria to Syene was ___________________ stadia (1 stadia = .1 miles)
The angle was __° and therefore 7/360 of the Earth’s circumference (about 1/50)
50 x 5000 stadia = 250,000 stadia or 25,000 miles (Actual = 24, miles) (24, miles at the poles)

8. Distance and Size of the Sun and Moon
75 years before Eratosthenes Aristarchus of Samos had estimated the relative sizes of the Earth, Moon, and Sun and the relative distances from Earth to the Moon and Sun

9. Aristarchus of Samos
Calculated Moon’s diameter to be about ____ that of Earth based on eclipse data
Sun was _______ X further away from the Earth than the Moon was
Sun’s diameter was _____ X that of Earth
He also gave thought to the idea that the sun was the ______________ of the heavens, an idea that wasn’t accepted for another 2000 years

10. Aristarchus of Samos
Others argued that if the Earth moved around the sun the positions of the stars should change during the course of the year something called ___________________
The did not observe any parallax (it wasn’t successfully measured until 1838)

11. The Motion of the Planets
Geocentric Theory: Earth as the ________________ of the universe
Those bodies that move the fastest are closest to the Earth
Model didn’t explain ____________________
Retrograde motion was explained by the planets have ________ motions

13. Ptolemy
Planets moved on one small circle called the _________________ and one large circle
Helped explain retrograde motion
Still were problems
Models became more and more _________________
Theory survived until the _____________

14. Occam’s Razor A British philosopher
___________________________________________________
Astronomical models had become unbelievable complicated

15. Contributions from Islam
Used celestial observations to set their _____________________________
Many Arabic words in use today: __________, the names of the bright stars
They revolutionized mathematical techniques through innovations like algebra
Gave us the Arabic numerals, and the concept of ___________________

16. Contributions from the Asians
Kept detailed ___________________ of unusual celestial events like eclipses, comets, and exploding stars
Were the first to note _____________ on the sun which we now know were sun spots
They became proficient at predicting ____________________

17. Measuring the diameter of Astronomical Objects
Angular size changes inversely with distance
L= 2πDA
360
L= Diameter of the body
D= Distance to the body
A= Angular Size

18. Astronomy in the Middle Ages to the Modern Era
From Copernicus to Galileo to man on the moon

19. Copernicus
Began the process of disproving the _________________ theory
A _______________ model of the universe offers a much simpler explanation of the universe (remember Occam’s Razor)

20. Heliocentric Model Explains __________________________
Planets will appear to change direction every time Earth _____________________ their orbit
Could now determine the distance a planet is from the sun using ____________________
There were still problems with his model because he said the orbits of the planets were ___________________________
His views were _____________ to be accepted

22. Tycho and Kepler Copernicus opened the door to new ideas
A cultural renaissance was taking place in Europe
The Protestant Reformation had begun
The new world was being settled
It was an environment ripe for intellectual stimulation

23. Tycho Brahe
Believed that God placed the planets in the heavens as a ________ to humankind of events on Earth
Made precise measurements with______________ he constructed

24. Tycho Brahe
First to show the existence of heavenly bodies ____________ of our solar system
Suggested that the heavens were more ________________ than we first believed
He had Earth still as the ____________ of the universe with the Sun orbiting around it and the other planets orbiting the Sun

25. Johannes Kepler
Explained Brahe’s precise observations in _______________ terms
Developed_________ laws that explained most aspects of planetary motion

26. Kepler’s Laws
Law of ________________

27. Law of Ellipses
Each planet orbits the sun in an _____________________ path
Each ellipse has two _________ – one of which is the sun
This means the planet is not always the ___________________ from the sun
Have students draw an ellipse
If you draw a line from any point on the ellipse to teach of the two foci the total length of these lines will always be the same.

28. Law of Ellipses
________________ – the point where the planet’s orbit is closest to the sun
________________ – the point where the planet’s orbit is furthest from the sun
The distance given is usually the ________________ of the perihelion and the aphelion

29. Law of Equal Areas
Describes the ______________ at which planets travel at different points in their orbits
Earth’s orbit is _____________ a perfect circle with the sun off center
Earth moved ____________ when it was ____________ to the sun

30. Line from center for the sun to the center of the planet sweeps through equal areas in equal periods of time.
Both shaded areas have the same area. Shorter area moving faster, longer area moving slower.

31. Law of Periods
Describes the relationship between the ___________________ of a planet from the sun and the orbital period of the planet
___________________ – the time it takes to make one revolution around the sun
The cube of the average distance of a planet from the sun (a) is always proportional to the square of the period (p)

32. The Mathematics K X a3 = p2 K is a mathematic constant
If we measure distance in AU and use earth-years, K = 1 and therefore a3 = p2
a = average distance of the object from the Sun
p = period
Examples: Earth is 1 AU and its period is 1 so 1 x 1 cubed = 1 squared and 1 = 1
Any errors are accounted for by the rounding off of distances or periods
Jupiter 5.2 AU’s and period is years – do the calculations

33. Kepler’s Three Laws
Describe the essential features of planetary motion around our Sun
Were the first laws to describe the heavens correctly
Kepler also gave us the word ___________

34. Galileo Galilei
Used the newly invented telescope to study the motions of the planets (Note: Galileo ___________ invent the telescope)
Proved that the _______________ model was the correct one

35. Galileo Galilei
Was the first to use the telescope to study the heavens
Observed that the moon was a ____________
Observed _______________ and that they changed from day to day and deduced that the sun _______________
Discovered that Jupiter had _______________
Examined the _________________ and saw that it was made up of millions of stars
Observed that Venus went through _______________ just like the Moon

36. Galileo Galilei
That fact that Venus had phases left no doubt that it orbited the Sun and put an end to the Geocentric model of the universe
The originator of the ______________________ still in use today
Was brought up on charges of _____________ against the church (1992 the church admitted it made a mistake)

37. Newton’s Application of Kepler’s Laws
Newton wanted to know why the planets moved liked this
Newton said that a moving body will only change its motion if an ________________ causes it to do so
An outside force must cause it to _______
This force he determined was _________
The gravitational pull of the __________ is what keeps the planets in orbit around it.
Inertia – straight line or at rest

38. Isaac Newton and the Birth of Astrophysics
Some consider him to be the greatest scientist of all time
Studying the moon he came up with the laws of gravity
Invented __________________
His laws of gravity and motion were totally accepted for ___________ years

39. The Growth of Astrophysics
New Planets were discovered
Stars had companions that orbit with them
Irregularities in the orbit of Uranus led to the discovery of _________________
Bigger telescopes – Telescopes in space
Applying photography
Space Exploration