Universal GravitationUniversal Gravitation

Nature and Nature's laws Nature and Nature's laws lay hid in night; lay hid in night;

God said, Let Newton be! God said, Let Newton be! and all was light.and all was light.

- Alexander Pope- Alexander Pope

Ancient TimesAncient Times

The oldest recorded The oldest recorded astronomical astronomical observations were observations were from around 4,000 BC from around 4,000 BC (Egypt, Central (Egypt, Central America).America).

Aristarchus of Samos 310-230 BCEAristarchus of Samos 310-230 BCE

Aristarchus Aristarchus proposed a proposed a heliocentric heliocentric model.model.

Calculated ratio Calculated ratio of distances of distances between Earth, between Earth, Moon, and Sun.Moon, and Sun.

EratosthenesEratosthenes276 BCE – 194 BCE276 BCE – 194 BCE

Determined Determined Earth's Earth's circumference to circumference to within 5 percent within 5 percent of the accepted of the accepted value.value.

Claudius Ptolemy d. 180 CEClaudius Ptolemy d. 180 CE

Earth-centric system. Earth-centric system. Could accurately Could accurately

predict astronomical predict astronomical events with his model.events with his model.

Explained retrograde Explained retrograde motion.motion.

Claudius PtolemyClaudius Ptolemy

Ptolemy’s theories last Ptolemy’s theories last for 1,400 years!for 1,400 years!

Nicolaus Copernicus Nicolaus Copernicus (1473 to 1543)(1473 to 1543)

There is no one center in the universe.There is no one center in the universe.

The Earth's center is not the center of the The Earth's center is not the center of the universe.universe.

The center of the universe is near the sun.The center of the universe is near the sun.

The distance from the Earth to the sun is The distance from the Earth to the sun is imperceptible compared with the distance to imperceptible compared with the distance to the stars.the stars.

The rotation of the Earth accounts for the The rotation of the Earth accounts for the apparent daily rotation of the stars.apparent daily rotation of the stars.

The apparent annual cycle of movements of The apparent annual cycle of movements of the sun is caused by the Earth revolving round the sun is caused by the Earth revolving round it.it.

The apparent retrograde motion of the planets The apparent retrograde motion of the planets is caused by the motion of the Earth from is caused by the motion of the Earth from which one observes.which one observes.

Galileo GalileiGalileo Galilei(1564-1641)(1564-1641)

Using a telescope he Using a telescope he made, Galileo made, Galileo observed:observed: Moons of Jupiter.Moons of Jupiter. Phases of Venus.Phases of Venus.

His findings His findings supported a supported a Copernican model.Copernican model.

He spent the end of He spent the end of his life under “house his life under “house arrest” for his beliefs.arrest” for his beliefs.

Johannes KeplerJohannes Kepler(1571-1630)(1571-1630)

Deeply religious, Deeply religious, Kepler thought God Kepler thought God made the Universe made the Universe according to a according to a mathematical plan.mathematical plan.

Attempted to relate Attempted to relate structure to nested structure to nested geometric solids. geometric solids.

Kepler’s Three LawsKepler’s Three Laws

11stst Law: Path of Law: Path of planets are elliptical.planets are elliptical.

Planet sweeps out Planet sweeps out equal area in a given equal area in a given time.time.

rr33/T/T22 = k for objects = k for objects orbiting a common orbiting a common center.center.

Sir Isaac NewtonSir Isaac Newton(1642-1727)(1642-1727)

If I have been able to If I have been able to see further, it was see further, it was only because I stood only because I stood on the shoulders of on the shoulders of giants.giants. - - Letter to Robert HookeLetter to Robert Hooke

Sir Isaac NewtonSir Isaac Newton(1642-1727)(1642-1727)

The fact orbits are constant must be due to a force keeping planets in orbit.

The same force that makes an apple fall to the ground, could be acting on planets!

BibliographyBibliography http://www.astromax.org/astrocourse/history.htmhttp://www.astromax.org/astrocourse/history.htm http://wps.prenhall.com/esm_chaisson_astronomytoday_5/0,9185,1383966-http://wps.prenhall.com/esm_chaisson_astronomytoday_5/0,9185,1383966-

content,00.htmlcontent,00.html www.nos.noaa.gov/.../ geodesy/geo02_histr.html www.nos.noaa.gov/.../ geodesy/geo02_histr.html http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/http://www-groups.dcs.st-and.ac.uk/~history/Mathematicians/

Copernicus.htmlCopernicus.html