The History and Philosophy of Astronomy Lecture 11: Galileo. Presentation

Astronomy 350L (Fall 2006)

The History and Philosophy of Astronomy (Lecture 11: Galileo I)

Instructor: Volker Bromm TA: Jarrett Johnson The University of Texas at Austin

Galileo Galilei: The First Scientist

• 1564 (Pisa)  – 16 1642 42 (Ar (Arc cet etri ri)) • fo foun under der of mod modern ern ph phys ysic ics s - la law w of of ine inert rtia ia - la law w of of fr free ee fa fallll

• fi firs rstt ast astro rono nomer mer to us use e telescope • Th The e “Tr “Trial ial of Ga Galil lileo eo”” (conflict with Catholic Church)

Galileo: Timeline and Context

• be betwe tween en Coper Copernic nicus us and and Newton Newton • co cont ntem empo pora rary ry of Ke Kepl pler er an and d Ty Tych cho o

Born in Pisa (1564)

• Pi Pisa sa:: part part of of Gra Grand ndduc duchy hy of Tuscany • Un Univ iver ersi sity ty to town wn

Professor in Pisa (1589-92)

• Prof Profess essor or of math mathema ematic tics s (badly (badly paid paid)) • New laws laws of of motion motion (ine (inertia rtia,, free free fall) fall)

Philosophy of Science: Two Traditions 1) Aristotle

2) Archimedes

(287-212 BC)

Archim Arc himedes edes of Syr Syracu acuse se (287 (287 – 212 BC) BC)

“Give me a place to stand, and I will move the Earth”

• emi eminent nent engine engineer, er, mathemat mathematici ician, an, and scient scientist ist!!

Philosophy of Science: Two Traditions 1) Aristotle

• ph philo iloso soph phy y mo most st important • ma math thema ematic tics s seco seconda ndary ry • “laws” of nature based on common sense and intuition • un unlilimi mite ted d sc scop ope e • tr trut uth h by ar argu guin ing g its its plausibility • se sear arch ch fo forr cau cause ses s

2) Archimedes

• ph phys ysic ics s mo most st important • ma mathe themat matics ics es essen sentia tiall • la laws ws of na natu ture re based on simple mathematical principles • lilimi mite ted d sco scope pe • tr trut uth h by exp exper erie ienc nce e (carry out experiments)

• Galil Galileo eo strongly strongly follow follows s Archimed Archimedean ean traditi tradition! on!

Professor in Pisa: Laws of Free Fall

1

2

• Gal Galile ileo: o: If fric frictio tion n from from air can can be ignored ignored,, all objects reach ground at same instant, with the same speed constant acceleration (“one g”)

Professor in Pisa: Laws of Free Fall

• Ga Galilile leo’ o’ s tri trick ck:: Slo Slow w dow down n gra gravi vity ty!! • Exp Experi eriment ment wit with h incli inclined ned pla planes! nes!

Professor in Pisa: Laws of Free Fall

• Gal Galile ileo o didn’t didn’t have pre precise cise clo clock ck • Id Idea ea:: Use Use lit littl tle e bell bells! s!

Professor in Pisa: Laws of Free Fall

Galileo’s Law of Free-fall

Earth’s Gravity (1 g)

Professor in Pisa: Law of Inertia Geda Ge dank nken en Ex Expe perim rimen entt (thought experiment)

• Law of of inertia inertia:: Bodies Bodies remain remain at rest rest or or in a state state of linear uniform motion, unless acted upon by force!

Law of Inertia: Implication for Astronomy

moving ship:

moving Earth:

• Mot Motion ion of Earth Earth is is entirel entirely y plausi plausible! ble! • Ari Aristo stotel telian ian theor theory y of moti motion on is wron wrong! g!

Great Gre at Summa Summary: ry: Disco Discorsi rsi (Tw (Two o New Scien Sciences) ces) • Discorsi  (The Two New Sciences, 1638)

• fir first st mode modern rn scie scientif ntific ic text textboo book k • la laws ws of mo moti tion on (inertia, free fall) • se sets ts out out sci scien enti tific fic met method hod

Galileo’s role in the Scientific Revolution Newton (1642-1727) - dynamics - la law w of of gra grav vit ity y

Kepler (1571-1630) - ce cele lest stia iall mo moti tion on - 3rd Law

“Standing on the shoulders of giants”

Galileo (1564-1642) - la laws ws of fr free ee-f -fal alll - pr prin inci cipl ple e of ine inert rtia ia

Professor in Padua (1592-1610)

• Prof Profess essor or of mathem mathemati atics cs (much (much better better paid) paid) • Pad Padua: ua: one one of most most pres prestigi tigious ous and and oldes oldestt universities in Europe

Padua and Venice (1592-1610)

• Pa Padua dua:: par partt of of grea greatt fre free e Rebu Re bubl blic ic of Ve Veni nice ce • Ga Galilile leo’s o’s Go Gold lden en Ti Time me

Padua and Venice: Personal Life • Longte term rm re rellatio ion nshi hip p with wi th Mari Marina na Gamb Gamba a (V (Veni enice ce)) • 3 dau daugh ghte ters rs,, 1 so son n • “G “Gal alilileo eo’s ’s Da Daugh ughthe ther”: r”: Sister Maria Celeste

The Invention of the Telescope (1609)

Hans Lippershey

• Tel Telesc escope ope was was inven invented ted in the Nethe Netherlan rlands ds

Invention of the Telescope: Basic Idea

Galilean Design (convex + concave)

Kepler Kep lerian ian Des Design ign (conv (convex ex + convex convex))

• Com Combine bine two two curved curved lenses lenses (conve (convex x or concave concave)! )!

Galileo’s Discoveries with the Telescope

• Gal Galile ileo o constr construct ucts s his own teles telescope cope!!

Galileo’s Discoveries with the Telescope

• Gal Galile ileo o the the Gre Great at Propa Propagand gandist ist!!

Galileo and the Telescope: The Moon

• Mountain Mountains s and valley valleys! s! Not a perfect perfect,, smooth surface surface!! • Ar Aris isto totl tle e is wr wron ong! g!

Galileo and the Telescope: Sunspots

• Blemi Blemishes shes on the Sun! Not a perfect perfect,, smooth surface surface!! • Ar Aris isto totl tle e is wr wron ong! g!

Galileo and the Telescope: Moons of Jupiter

4 Galilean (Medicean) moons

• Fou Fours rs satell satellite ites s (moons) (moons) around around another another planet planet!! • Ear Earth’s th’s Moo Moon n not an anoma anomaly ly anymo anymore! re!

Galileo and the Telescope: Moons of Jupiter

• Min Miniat iature ure model model of the the Solar Solar Sys System! tem! • Cruc Crucial ial suppo support rt for for Copern Copernican ican mode model: l: - new sat satell ellite ites s def defini initiv tively ely don’t  orbit Earth! - remo remove ve anom anomaly aly of Ear Earth’s th’s Moon

Galileo and the Telescope: Phases of Venus

• Gal Galile ileo o sees sees full full cycl cycle e of pha phases! ses! • One of the the most most important important disco discoveries veries of astronomy! astronomy! • Why???

Galileo and the Telescope: Phases of Venus

• Defini Definitive tive proof for Copernic Copernican an model model of of Solar Solar System! System! • Bu Butt (to (to be ho hones nest): t): Ty Tych cho’s o’s mo model del ca can n expla explain in it it,, too! too!

Galileo and the Telescope: Phases of Venus

A riddle for Kepler: “C “Cyn ynth e fi figu gura aemu mula turrfr mate amor “Ha “H aethia ciae imm mma aturas ras aae m me e ja jlatu am frma ustter rar lam egu eg uorum num” tur ” (Venus O y” emulates the phases of the Moon)

• Galil Galileo eo the the Great Great Salesma Salesman n (he create creates s suspense suspense)! )! • Delayed releas release e of his discov discoveries: eries: Attemp Attemptt to secure his priority!

Galileo and the Telescope: Nature of Milky W

• With telesc telescope: ope: Many more stars stars become visibl • St Star ars s appe appear ar as po point ints s

Sid ider ereu eus s Nu Nunc nciu ius s (T (The he Sta Starr rry y Mes Messe seng nger er)) • Sidereus Nuncius  (Starry Messenger, 1610)

• de desc scri ribes bes new new astr astrono onomi mical cal discoveries made with telescope • Ga Galilileo leo mak makes es sur sure e that that his his fame would spread • Ea Earns rns him lo longng-des desir ired ed appointment in Florence

Galileo and the Medici • Cosimo II, Grand Du Duke of Tuscany • Ga Galilile leo o app appoi oint nted ed Court Mathematician • No mo more re te teac achi hing ng,, generous salary

Galileo’s Return to Florence (1610-42)

• Aft After er leavin leaving g Padua/Ven Padua/Venice ice,, he slowly slowly gets gets into into crosshairs of Roman Inquisition trial of 1633

Galileo (part 1) • Ga Galilile leo o Gal Galililei ei:: - fou founde nderr of mode modern rn physi physics cs - law laws s of free free fal falll and ine inerti rtia a - est establis ablished hed scientif scientific ic method method based based on exeriments exeriments

• Sta Starry rry Messen Messenger ger (Telesc (Telescopic opic Discov Discoveri eries) es) - Phas Phases es of Venus Venus:: Proves Proves Coperni Copernican can model model - Suns Sunspots pots and moun mountain tains s on the the Moon: Moon: celestial objects are not perfect and immutable - Mo Moon ons s of of Jup Jupit iter er

• Re Retu turn rn to Fl Flor oren ence ce - conf confront rontatio ation n with Catholic Catholic Church Church begins begins to gather gather