• Notebooks: We had a very BASIC notebook check. For our next notebook check you need to have your cover completed, table of contents filled out, titles on pages, and unit table of contents completed! You can use consecutive pages just save a left side on notes and vocabulary. Don’t forget title page for Astronomy!

• Get out homework-vocabulary

• Bell Ringer:

• List what you know about astronomy?

• What is the universe? What is it made of?

• What is a galaxy? What galaxy is Earth located in?

Astronomy Chap. 22

EARTH IN THE UNIVERSE

HISTORY OF ASTRONOMY

• Astronomy is the science that studies the universe. It includes the observation and interpretation of celestial bodies and phenomena.

• The Greeks are credited with many astrological discoveries because they developed the basics of geometry and trigonometry.

• Aristotle-Earth is round because the moon casts a curved shadow.

ERATOSTHENES

• Eratosthenes first calculated the size of the Earth.

IT IS ALL GREEK TO ME

• 7/360=1/50

• 5000 stadia apart x 50=250,000stadia

• If 1 stadia = 157.6 m then,

250,000 stadia x 157.6m/1m = 39,400,000m=

39,400 km.

• 39,400km-40,075 (accepted circumference)/40,075 X 100 = 1.7 %

MODEL’S OF UNIVERSE

• The ancient Greeks believed in the geocentric view of the universe.

• The moon, sun, and all known planets orbited the Earth.

• In the heliocentric model, the Earth and all known planets revolve around the sun.

PTOLEMAIC SYSTEM AND RETROGRADE MOTION

• Ptolemy created a model of the universe that accounted for the movement of the planets.

• Retrograde motion is the apparent westward motion of the planets with respect to the stars.

• http://www.keplersdiscovery.com/Hypotheses.html

• http://www.youtube.com/watch?v=72FrZz_zJFU

BIRTH OF MODERN ASTRONOMY

• Nicolaus Copernicus

• Copernicus concluded that Earth is a planet. He proposed a model of the solar system with the sun at the center.

• Tycho Brahe

• Tycho Brahe designed and built instruments to measure the locations of the heavenly bodies. Brahe’s observations, especially of Mars, were far more precise than any made previously.

JOHANNES KEPLER

• Kepler discovered three laws of planetary motion:

1. The path of each planet around the sun is an ellipse.

2. Planets revolve around the sun at varying speed.

3. There is a proportional relationship between a planet’s orbital period and its distance to the sun.

1. An ellipse is an oval-shaped path.

2. Also know as the law of equal area.

3. Harmonic Law

• T2 = d 3

http://www.youtube.com/watch?v=GcKiG-CuvtA

SO…HE MAPPED THE SOLAR SYSTEM!

• An astronomical unit (AU) is the average distance between Earth and the sun; it is about 150 million kilometers.

• So if you know orbital period you can calculate the solar distance of the planet.

• Mars=1.88 years (T) squared = 3.54. the cube root of 3.54=1.52 and that is the distance to Mars in AU.

GALILEO GALILEI

• He was the first to use a telescope to make astrological observations.

• He made discoveries that supported Copernicus’s heliocentric model

GALILEO’S MAJOR DISCOVERIES

1. The discovery of four satellites, or moons, orbiting Jupiter.

• There was another center of motion other than Earth.

2. Planets are circular disks not just points of light. Therefore planets must be Earth-like.

3. Venus has phases like the moon. Also supports heliocentric model.

4. The moon’s surface was not smooth.

5. Discovered that the sun had sunspots, or dark spots that allowed him to track the rotational period of the sun at just under a month.

• http://www.teachersdomain.org/resource/ess05.sci.ess.eiu.galileomoon/

• http://www.teachersdomain.org/resource/ess05.sci.ess.eiu.galileosys/

BIRTH OF MODERN ASTRONOMY

• Sir Isaac Newton

• What kept the planets in orbit? Why don’t we just spin off into space?

• Although others had theorized the existence of gravitational force, Newton was the first to formulate and test the law of universal gravitation.

UNIVERSAL GRAVITATION

• Every body in the universe attracts other bodies with a force that is directly proportional to their mass and inversely proportional to the square of the distance between their centers of mass.

• Huh?

• Every object in the universe attracts every other object in the universe. The amount (force) of the attraction depends on the mass of the object.

• We don’t feel all of the pull’s of other objects gravity because the pull of Earth’s gravity is much greater.

• On Earth the pull of gravity is towards the center of Earth. In space it is towards the center of the sun. This is why the planets orbit the sun.

• The greater the mass the greater the pull of gravity. Ex. Moon causes tides.

• The distance between two objects, the less the objects will attract each other. In other words, the farther away an object is from the Earth (or any large body), the less it will weigh.

• The planets have a tendency to follow a straight line path but the force of gravity pulls it towards the sun.

• This proved Kepler’s elliptical orbit.