Humans and Scientific Thinking

Humans and Scientific Thinking 

Notes from September 12th, 2012

Where it Began. 

Scientific thinking begins at a young age, based on everyday observations and trial-and-error experiments. Astronomical observations benefit ancient societies, and can be used for agriculture, religious and ceremonial purposes, as well as for navigational purposes. Scientific thinking began long ago when people learned to predict the weather with reasonable accuracy in Central Africa. Ancient civilizations were able to observe the Suns path through the sky, use sundials to follow shadows and predict time, and at night, people could estimate the time of day using the position of the moon. Ancient people were also able to predict the seasons by building structures to mark them, for example, the Stonehedge in Southern England. 

Lunar Calendars. 

Ancient civilizations used lunar phases to develop months, lasting about 355 days. The Metonic cycle was a cycle of lunar phases which repeat on the same dates about every 19 years. 

Ancient Greek Science. 

Ancient science led to modern science through repeated observations. Alexander the Great, tutored by Aristotle, founded Alexandria in Egypt. The Greek developed three major innovations. First, they developed traditions of trying to understand nature without relying on supernatural explanations. Secondly, Greeks used math to guide precision to their ideas. And third, Greeks saw the power of reasoning from observations, explanation could not be right unless it agreed with observed facts. 

Planetary Motion

Greeks explained planetary motion by adding separate spheres for the Sun and Moon. Planets also moved relative to the stars, so Greeks added additional spheres for each planet. Aristarchus proposed a Sun centered model to help explain this. The Ptolemaic model was used to show that each planet moved on a small circle whose center moved around the Earth. 

Other Scientists 

Copernicus: Discovered simple geometric relationships that allowed him to discover each planets orbital period around the Sun and its relative distance to the Earth and Sun. Still believed everything rotated in a perfect circle- caused him to add numerous complexities to his system.

Tycho: Compiled careful observations of stellar and planetary positions in the sky. Observed a supernova. Could not detect stellar parallax,caused him to believe Sun orbits Earth while all other planets are stationary. 

Kepler: Worked under Tycho, found set of circular orbits that matched most of Tycho's observations. Kepler's key discovery was that planetary orbits are not circles but instead are a special type of oval called an eclipse. Three laws of planetary motion: 

1) The orbit of each planet about the Sun is an eclipse with the Sun at one focus- planet's distance from the Sun varies during its orbit 

2) As a planet moves around its orbit, it sweeps out equal areas in equal time. 

3) More distant planets orbit the Sun at lower average speeds.