Galileo and the telescope
A modern telescope...
Hubble space telescope.
Galileo's "Starry Messenger" 1610
Opticians in the Netherlands hit on a way of arranging lenses to make a 'spyglass' of obvious use for sailors. Galileo Galilei heard about this, and set about building one in order to look up at the night sky and started making observations in 1608. His first telescope had 3x magnification, and he eventually achieved 30x telescopes. The observations published in Sidereus Nuncius in 1610 were made with a ~20x device.
One of his first observations was the multiplicity of stars not seen by the naked eye. (Above, his sketch of Orion). Milky areas of the sky turned out to be thick with dim stars which could not be seen with the naked eye.
The face of the moon
Galileo sketched the Moon as seen through his telescope. It appeared to have mountains and craters--very much like the earth itself.
He looked closely at the moon and found irregularities at the edge of the terminator. These changed in time in a way that could be interpreted as light illuminating higher elevations before lower elevations were illuminated. The moon appeared to have mountains and craters, and was indeed just as 'imperfect' as the earth. Plato and other Greeks had argued that the heavenly spheres were perfect orbs, devoid of the kind of imperfections of earth.
Detail from a painting by Ludovico...
The changing picture of the universe was rapidly picked up by some artists, if not by church authorities.
Jupiter
Galileo pointed his 'scope at Jupiter. He saw
- Jupiter appeared bigger than other stars
- 3 or 4 'little stars' that moved fast (changing position over the course of several nights), always close to Jupiter, and always in the same plane.
- ???
He received permission from papal authorities to publish Sidereus Nuncius ("Starry Messenger"). But between the time of receiving permission, and publication in March of 2010 he decided to insert (sneak) his latest observations of Jupiter into the manuscript.
The Greeks viewed the Earth as a special place, quite different from the far-away perfection glimpsed in the heavens. This picture was breaking down.
Phases of Venus
With the naked eye, Venus appears as a 'dot' of light. It's not possible to
make out the shape of that dot.
Shine an overhead projector lamp on a ball to see "phases" even in a well light room.
Spend more time on phases using Moon as example. Then do writing exercise with Venus. Show picture of earth, moon, with a "V" on it depicting field of view. Why do you *ever* see a full moon? (means orbit of moon is tilted....).
Galileo's telescope revealed that the shape was at times "horned" like the crescent moon. That is, it appears to be reflecting light (from the sun) rather than being a source of light.
[Writing - Phases of Venus]Galileo was able to observe the phases of Venus with his telescope. His observation of a complete set of phases for Venus convinced many that, at least the inner planets rotated around the sun rather than the moving on epicycles around the earth.
Roots of a scientific worldview
- Pythagoreans believed in natural harmonies--that the Universe is organized by patterns or principles which can be uncovered by observation.
- European civilization picked this up, but certain discoveries of the Greeks hardened into a worldview: A belief in a dichotomy between earth and the heavens.
- Copernicus, Galileo, and other contemporaries showed that the Earth is a planet similar to other planets--that the natural world would appear to be the same everywhere.
The story of Galileo pointedly illustrates how new observations, or higher precision measurements might overturn theories. In what sense might our current theories be said to be true or false?
The nature of science
Science is a human attempt, frequently collective, to organize experience using rational thought. It is a process, not a set of facts.
Direct experience includes observation, measurement, and experimentation.
A theory is a well-confirmed set of ideas that explains what is observed.
A scientific theory must be falsifiable.
Image Credits
Wikimedia - Hubble, Matthew Spinelli, NASA / JPL,Galileo Galilei, Sidereus Nuncius, Transl Albert Van Helden, Copernicus' Conversation with God painted by Jan Matejko (1872), Tycho Brahe's Wall Quadrant
