The Science of Astronomy. Ancient Civilizations Ancient Greek European Renaissance Modern Science. Ancient Astronomical Knowledge.
Many of the surviving ancient structures have obvious astronomical purpose. These ancient structures clearly demonstrated that all ancient civilizations developed extensive knowledge of the celestial objects…most likely because of the need to predict the seasons due to the development of agriculture. Astronomical knowledge are also very useful tool for navigation. Usually knowledge of mathematics and geometry were usually developed at the same time.
A Polynesian navigational instrument
The astronomy of the Pythagoreans marked an important advance in ancient scientific thought, for they were the first to consider the earth as a globe revolving with the other planets around a central fire.
Although the majority of ancient Greek philosophers arrived at the wrong conclusion about the model of the universe, they did so based on sound logical reasoning processes, good (albeit crude in today’s standard) observational data, (no stellar parallax, apparent retrograde motion of planets), and good modeling efforts (Ptolemaic geocentric model and Aristarchus’s heliocentric model). They followed a very rigorous scientific method, and their failure was not the failure of the scientific method. It was due to the limited technology. They couldn’t have done better!
The ancient Greeks were the first to rely on logical thinking to explain the natural phenomena. This is the same principle that was followed by the scientist of the 15th and 16th century to proof the validity of the heliocentric model of the solar system, and is the foundation of modern science.
In attempting to explain Tycho’s observation of the planetary motion, Kepler concluded that planets do not orbit in perfect circles. Instead, the planets travel around the Sun in elliptical orbit.
The ellipse The distance from one focus to a point on the ellipse to another focus is a constant
The orbit of each planet about the Sun is an ellipse with the Sun at one focus.
As a planet moves around its orbit, it sweeps out equal areas in equal time.
Kepler’s second law states that as a planet moves around its orbit, it sweeps out equal areas in equal time.
Click image to start animation
3. If Earth is orbiting the Sun, then why couldn’t we observe any stellar parallax? Stars are too far away. We do measure it today!
In Hawaii, the linear speed of Earth’s rotation is about 1,566 km/hr = 0.435 km/sec, or 435 m/sec. If I drop a stone from a height of 1.25 meter above the ground, it is going to take approximately 0.5 second to reach the ground. The ground moves 217 m during the time it takes the stone to fall to the ground. How comes the stone does not get left behind?
It is interesting to note that up to this point, there were still no discussions on why the planets should move in elliptical orbits, or on what is keeping the planets from running away from the Sun?