Chapter 3: The Science of Astronomy Flashcards
What did Anaximander do and when?
610-546 B.C.
Suggested the idea of the celestial sphere.
What did Pythagoras do and when?
560-480 B.C.
That that earth itself is a sphere.
What did Eratosthenes do and when?
276-196 B.C.
Accurately estimated the circumfrence of the earth.
What did Ptolemy do and when?
100-170 A.D.
Developed an earth centered model that remained in use for over 1500 years.
How did the Ptolemaic model describe apparent retrograde motion?
It used a complex system of circles within circles.
What was the Copernican Revolution
The origin of modern science.
What did Copernicus do?
He proposed a sun centered model of the universe, but contiued to make the assumption that orbits must occur in perfect circles.
What did Tycho do?
Proposed a model in chich the sun orbits earth and all other planets orbit the sun.
What did Kepler do?
Found that orbits occur in ellipses and not perfect circles. He also proposed three laws of planetary motion.
What is Keplers First law?
The orbit of each planet about the sun is an ellipse with the sun at one focus.
What is Keplers Second law?
A planet moves faster in the part of the orbit near the sun and slower when farther from the sun, sweeping our equal areas in equal times.
What is Keplers Third law?
More distant planets orbit the planets at slower average speeds, obeying the mathimatical relationship:
p^2 = a^3
Where p is the orbital period in years and a is the averge distance from the sun in astronomical units.
What is a major axis of an ellipse?
The long axis of an ellipse
What is eccentricity?
A quantity that describes how much an ellipse is stretched
What is the perihelion?
The closest part of a planets orbit to the sun.
