**NEED TO STUDY SCIENCE** • Science “to know” • Relevance to almost every profession • Involves method of inquiry requiring reason • Requires understanding; not memorization • Provides insight into the scientific method

**Origin of Science** • Cyclic nature of seasons and navigational needs - Astronomy • Farming - Geometry to measure fields • Taxes and Business - Arithmetic, weights and measures • Beginning of mathematics - Replace multiple words for numbers with system (Babylonian sexigesimal number system ~3000 BC)

**The Babylonian symbols from 1 to 13 as transcribed from a** clay tablet of about 1700 BC

**Egyptian Astronomy** • Measured 365 day year - 4000 BC • Relation between Astronomy and Astrology • Star charts, 365 1/4 day calendar; 3:4:5 triangle; water clock - 2000 BC • How would you accomplish these tasks today? Describe a method to determine the length of day and year?

**Greek Science** • Naturalistic not mystic interpretation of the universe • Believed earth was a sphere - 400 BC • Ionian Philosophers - 2500 BC to 300 BC • Hippocrates ( 500 BC); Pythagoras (530 BC); Aristarchus (270 BC) • Eratosthenes (276-195 BC- measured the diameter of the earth)

**Eratosthenes (276-195 B.C.) measured the circumference of** the earth to be 24,650 miles (real value (24,900 miles )

**Other Important Greek Philosophers** • Aristotle (384-322 B.C.) Organized Lyceum; believed stars were distant; observed phases of the moon; observed stellar parallax • Ptolemy (127-151 A.D.) member of the Museum at Alexandria (Ptolemy,Euclid, Eratosthenes, Archimedes,); wrote the “Almagest” which describes geocentric universe

**DARK AGES** • Fall of Rome in 410 A.D. • Most information from previous civilizations lost • Knowledge saved in Middle East • Greek and Latin manuscripts translated into Arabic • Eventually returned to western Europe

**Epicycle as used by Ptolemy (geocyntric model) go to**

**Copernicus (1473-1543)** • The sun is at rest (heliocyntric model) • The earth is spherical • Planets revolve about sun • Periods of revolution decrease with orbit radii • The motion of planets about the sun involve epicycles (34 circles)

**Tycho Brahe (1546-1601)** • Danish Astronomer • Developed accurate astronomical instruments (quadrant ) • Built elaborate observatory • Plotted motions of planets • Improved measurements of Greeks by a factor of 6 ( 5’ of arc )

**Johannes Kepler (1571-1630)** • http://es.rice.edu/ES/humsoc/Galileo/People/kepler.html • Used Tycho’s Data and developed three laws of Planetary motion • Firmly established heliocentric theory • Published his results in 1609, 1618

**Kepler’s Laws** • Orbits are elliptical • Orbits sweep out equal areas in equal times • Period2 = Distance3 (If Period in in years and Distance is in AU) (AU - astronomical unit - distance between earth and sun)

**Galileo Galilei( 1564-1692 )** • http://es.rice.edu/ES/humsoc/Galileo/ • Constructed 30x telescope • Phases of Venus • Structure on moon

**Moons of Jupiter** • Sunspots • Many new stars • Structure of Saturn

**Galileo** • Studied the motion of falling bodies • Refuted the teachings of Aristotle • Reinstituted the scientific method • Suffered under the reformation • Published the Dialog Concerning the Two New Sciences in 1638 at age 70 • Began the modern sciences of astronomy and mechanics

**Newton (1642 - 1727)** • Developed Mechanics • (study of motion) • To do this had to invent Calculus

**Newton’s Laws of Motion** • A body in motion will remain in motion unless a force acts upon it. • Force = mass times acceleration (F = m a) • Every action has an equal and opposite reaction

**Newton’s Law of Universal Gravitation** • Note that it depends upon 1/r2

**Motion of moon (see p. 19 of text)**

**Lunar eclipse**

**Solar Eclipse** • Total Solar Eclipses occur when the umbra of the Moon's shadow touches a region on the surface of the Earth. • Partial Solar Eclipses occur when the penumbra of the Moon's shadow passes over a region on the Earth's surface. • Annular Solar Eclipses occur when a region on the Earth's surface is in line with the umbra, but the distances are such that the tip of the umbra does not reach the Earth's surface.

**Homework ** • p. 40 review and discussion: 2, 4, 5, 7, 8, 10, 14 answer in complete sentences