THE UNIVERSE IS FULL OF MAGICAL THINGS PATIENTLY WATING FOR OUR WITS TO GROW SHARPER. - Eden Phillpotts-

HUMAN UNDERSTANDING OF THE UNIVERSE HAS CHANGED OVER TIME. OUR ANCESTORS WERE WATCHING THE SKY IN ORDER TO PREDICT THE SEASONS FOR THE GROWING AND HARVESTING OF CROPS – PROBABLY AS EARLY AS 10,000 YEARS AGO. SOME ANCIENT MONUMENTS REMAIN THAT WERE SET UP TO MARK IMPORTANT SOLAR EVENTS SUCH AS THE SOLSTICES. STONEHENGE IS ONE EXAMPLE. THIS EARLY, THERE WAS NO WRITTEN LANGUAGE.

THE CHINESE KEPT ASTRONOMICAL RECORDS AND WERE REPORTING EVENTS SUCH AS COMETS AS EARLY AS 1000 BC. THE EARLIEST WRITTEN RECORDS IN WESTERN ASTRONOMY WERE FROM THE BABYLONIANS IN ~1600 BC. THE GREEKS BUILT ON THESE. ANAXIMANDER, AND LATER PYTHAGORAS (600 BC), HAD THE IDEA OF A GEOCENTRIC (EARTH CENTERED) UNIVERSE.

IN THE PYTHAGOREAN VIEW, THE EARTH WAS AT THE CENTER, AND THE PLANETS, THE SUN, AND OTHER VISIBLE OBJECTS OCCUPIED POSITIONS ON CRYSTAL SPHERES AND THEIR MOTIONS WERE PERFECT CIRCLES. THIS VIEW WAS LATER ADOPTED BY ARISTOTLE (384 – 322 BC). A DRAWING OF THE UNIVERSE FOR A BOOK PUBLISHED IN 1539 IS SHOWN ON THE NEXT SLIDE.

ARISTARCHUS (310 – 230 BC) PROPOSED THAT THE UNIVERSE MUST BE HELIOCENTRIC (SUN CENTERED). HE EVEN ESTIMATED THE RELATIVE SIZES AND DISTANCES OF THE SUN, MOON, AND EARTH. ARISTOTLE HAD SUCH A GREAT REPUTATION AS A PHILOSOPHER THAT THE IDEAS OF ARISTARCHUS WERE LARGELY OVERLOOKED. THE GEOCENTRIC VIEW OF THE UNIVERSE HAD SOME MAJOR PROBLEMS – ESPECIALLY RETROGRADE MOTION OF THE PLANETS.

PTOLEMY (85 – 165 AD) CAME UP WITH A COMPLEX MATHEMATICAL MODEL THE COULD EXPLAIN THE RETROGRADE MOTION BY HAVING THE PLANETS MOVE IN CIRCLES WITHIN CIRCLES.

COPERNICUS ( ) CAME UP WITH A MATHEMATICAL MODEL OF A HELIOCENTRIC MODEL OF THE SOLAR SYSTEM THAT DID A MUCH BETTER JOB OF PREDICTING THE POSITIONS OF THE PLANETS. TYCHO BRAHE (1546–1601) USING ONLY A SEXTANT MADE SOME OF THE MOST ACCURATE OBSERVATIONS OF THE MOTIONS OF PLANETS AND STARS THAT HAD BEEN MADE TO THAT TIME.

TYCHO BRAHE WANTED HELP WITH THE MATHEMATICAL INTERPRETATION OF HIS OBSERVATIONS, SO HE HIRED JOHANES KEPLER AS AN ASSISTANT. KEPLER INHERITED BRAHE’S DATA AFTER BRAHE’S DEATH, AND HE REALIZED THAT THE DATA DID NOT MATCH PERFECT CIRCLES. AFTER MUCH WORK, THE CAME UP WITH HIS THREE LAWS.

The orbits of the planets are ellipses with the Sun at one focus. The planets sweep out equal areas during equal times of the orbit. The square of the orbital period is proportional to the cube of the planet's distance from the Sun. (If you measure the period in Earth years and the distance in Astronomical Units (1 A.U.= the average distance of the Earth from the Sun), then Period 2 = Distance 3.)

KEPLER’S THREE LAWS ACCORDING TO NASA KEPLER’S WORK LEAD SIR ISAAC NEWTON ( ) TO HIS LAWS OF MOTION AND THEORY OF GRAVITY. F = G (mM)/d 2 Where F = force of attraction due to gravity G = gravitational constant m = mass of body 1 M = mass of body 2 d = distance of separation

AT THE SAME TIME BRAHE AND KEPLER WERE DOING THEIR WORK, GALILEO GALELEI ( ) WAS CONDUCTING HIS OWN RESEARCH IN ASTRONOMY. HE TOOK THE IDEA OF THE TELESCOPE THAT HAD JUST BEEN DEVELOPED IN THE NETHERLANDS AND USED IT TO SCAN THE SKIES. HE DISCOVERED THE MOONS OF JUPITER AND THE RINGS OF SATURN AND HELPED PROVE THAT THE EARTH WAS NOT THE CENTER OF THE SOLAR SYSTEM.

KNOWLEDGE OF THE UNIVERSE HAS GREATLY EXPANDED DURING THE LAST 100 YEARS DUE TO IMPROVEMENTS IN TELESCOPES. THESE HAVE INCLUDED: 1.OPTICS 2.PHOTOMETRY (IMAGING AND MEASUREMENT OF LIGHT INTENSITY AND WAVELENGTH) 3.SOLVING THE PROBLEM OF ATMOSPHERE 4.HIGH SPEED COMPUTERS 5.USE OF SATELLITES SOME OF THESE WILL BE DISCUSSED IN LATER TALKS.