History of Astronomy

Evening Classes

Week Four

Presented by Oisín Creaner

The History of Astronomy 3200 BC to Present.

1.Prehistorical Astronomy

2.Greek and Arab Astronomy

1.Renaissance to Instruments

1.Modern Astrophysics

Newgrange

Passage Tomb, Co Meath

Built 3200BC

Light Box AlignedOn WinterSolstice

Newgrange Image Jimmy Harris

(1)Greeks were great theorists,but poor observers or experimenters.

(2)Greeks used Babylonian records & Greek geometry.

(3)Ionians (c 600 BC) - first Greekcosmology. Impersonal laws replacemythology.

GREEK ASTRONOMY (650 BC - 150 AD).

Pythagoras

Aristarchus (310 -230 BC) - How to measure therelative distances between the Earth, Sun and Moon

(4)Pythagoreans (c 600 BC) - saw numbers as the basis ofreality + wrote of a spherical earth.

GREEK ASTRONOMY (650 BC - 150 AD).

Aristotle & Plato

(5)Aristotle (fl 350 BC)-Round earth at thecentre of the cosmos.

Aristotle's cosmology isrooted in common sense& rationality.

Aristotle’s Cosmology

•Earth is at Rest

•Earth is Round

•Earth is the Centre of the cosmos

(6) Celestial Sphere's motions arepredictable, what about the 7 planets?

Plato (fl 400 BC) challengedgeometricians to describeplanetary motion in lawful terms.

This became Astronomy's project fornext 2000 years.

GREEK ASTRONOMY (650 BC - 150 AD).

(7) The most elaborateGreek astronomer.

The "Almagest“ (c 145 AD)gave mathematical modelof planet's motions thatcould be calculated for anydate, past or future.

Ptolemy ofAlexandria

Arab Medieval Astronomy

Early formal catalogues•Names of brigtest stars

Refined Greek Models•Doubts about Ptolemy

Advanced Mathematics•Calculated movement

Arab Medieval Astronomy

History of Astronomy

Evening Classes

Week Four

Presented by Oisín Creaner

Nicholas Copernicus

Tycho Brahe(14 December 1546 – 24 October 1601)

Johannes Kepler

Galileo Galilei

Isaac Newton(1642-1727)

When white light is passed through a prismit is split up into its component colours.

William Herschel

Otto Struve

Used parallaxmeasurements todetermine distanceto nearby stars.

Robert Bunsen (1811 - 1899)Gustav Kirchoff (1824 - 1887)

1859 - Elementsare identified insunlight

The Spectroscope

Frauenhofer Lines

Angelo Secchi’sStellar Spectra Classification

Sirius Type Stars

Sun-like stars

Red-Giant Variables

Red-dwarfs

Christian Doppler

Crab Nebula (M1) Original SN1054Lord Rosse Observed 1848

Messier Catalogue

Long observation

John Herschel(1792-1870)

Pioneer ofAstrophotography

Herman von Helmholtz

Suggested thatgravitational contraction

was the source of theSun’s energy.

Edwin Hubble

“The spiral nebulaeare receeding atspeeds proportionalto their distances”

Hans Bethe

Worked out thatsunlight comesfrom hydrogenfusion (1939).

Post WW 2

The observablespectrum is broadened

Thank You

www.astronomy.ie/handoutswww.stellarium.org

Useful websites