Galileo’s Contribution to Galileo’s Contribution to Astronomy:Astronomy:

The TelescopeThe Telescope

Galileo’s TelescopeGalileo’s Telescope

Galileo didn’t actually invent the telescopeGalileo didn’t actually invent the telescope– Terrestrial version was invented in the Netherlands by Terrestrial version was invented in the Netherlands by

spectacle makers (Hans Lippershey, Zacharias Janssen, and spectacle makers (Hans Lippershey, Zacharias Janssen, and Jacob Metius)Jacob Metius)

He did, however, improve upon the design in 1609He did, however, improve upon the design in 1609 Also first to point toward the night sky (only his Also first to point toward the night sky (only his

improvements made this possible)improvements made this possible) ““Telescope” (Greek for “far seeing”) was first coined Telescope” (Greek for “far seeing”) was first coined

by Greek mathematician to refer to Galileo’s deviceby Greek mathematician to refer to Galileo’s device

Support for Heliocentric ModelSupport for Heliocentric Model Phases of Venus:Phases of Venus:

– Because Galileo observed Because Galileo observed all phases all phases of Venus, it of Venus, it must orbit the sunmust orbit the sun

– Such an observation was Such an observation was impossibleimpossible in the in the geocentric model of Aristotle or Ptolemygeocentric model of Aristotle or Ptolemy

Venus photo credit: Doug Anderson, Shoestring Astronomy

Moons of Jupiter:Moons of Jupiter:– Galileo observed the 4 largest moons of Jupiter Galileo observed the 4 largest moons of Jupiter

and traced their orbits around this gas giantand traced their orbits around this gas giant– This provided proofThis provided proof

that bodies orbitedthat bodies orbited

objects other thanobjects other than

the Earththe Earth

Jupiter photo credit: Doug Anderson, Shoestring Astronomy

Support for Heliocentric ModelSupport for Heliocentric Model

Other Contributions: The MoonOther Contributions: The Moon Galileo first to Galileo first to

report craters and report craters and mountains on the mountains on the moonmoon– Moon not perfect Moon not perfect

sphere like sphere like Aristotle claimedAristotle claimed

First to observe rings First to observe rings of Saturn but was of Saturn but was confused by their confused by their appearance and appearance and couldn’t explain themcouldn’t explain them

Other Contributions: SaturnOther Contributions: Saturn

Even small telescope allowsEven small telescope allows

one to distinguish individualone to distinguish individual

stars out of ‘milky’ cloudstars out of ‘milky’ cloud

Other Contributions: The Milky WayOther Contributions: The Milky Way

Galileo was one of first in Europe to observe Galileo was one of first in Europe to observe sunspotssunspots

Made detailed drawingsMade detailed drawings Argued sunspots were actually on sun and not Argued sunspots were actually on sun and not

satellites of the sunsatellites of the sun Further evidence against Aristotle’s view that Further evidence against Aristotle’s view that

everything in the heavens was perfecteverything in the heavens was perfect

Other Contributions: SunspotsOther Contributions: Sunspots