Chapter 2: History Astronomy Flashcards
1
Q
Geocentric theories
A
- believed that earth was the centre
- Aristotle and Ptolemy
2
Q
Aristotle
A
(400BC)
- before the invention of the telescope
- geocentric
- didn’t know about gravity thought crystal sphere
3
Q
Retrograde motion
A
- means going backwards
- when studying the motion of planets this backwards motion was a large problem for geocentric
4
Q
Ptolemy
A
(200 AD)
- decided a complicated system of epicycles
- while planets orbit around they have their own orbits
5
Q
Heliocentric models
A
Believed the sun was at the was the centre
-Aristarchus of Samus
6
Q
Aristarchus of Samus
A
(300 BC)
- first to suggest heliocentric
- was ignored for 2000 years
7
Q
Eratosthenes of Cyrene
A
(200 BC)
- first to measure earths size
- used the distance from 2 cites
8
Q
Parallax
A
Measuring distances within the solar system
- shift of views based on different eyes
- parallax happens to stars but can not be detected by the naked eye
- measured in angles
- the bigger the baseline the more it shifts
9
Q
Nicolas Copernicus
A
1500
- first to have heliocentric model widely accepted
- still had circular orbits though
10
Q
Galileo
A
1600
- did create the telescope but was the first to use it for the sky
- said Jupiter had 4 moons
- showed the moon has craters
- the Milky Way is a band of light that contains thousands of individual stars
- found that sun has dark spots and rotation of 28 days
- Venus showed phases and size changes
11
Q
Tycho Brahe and Jonhannes Kepler
A
1600
- Brahe’s observations were interpreted by Kepler
- knew orbits were elliptical
12
Q
Kepler’s laws
A
- Planets move in elliptical orbits with the sun as the focus
- Equal areas are swept out in equal times during an orbit
- The square of a planets period is proportional to the semi major axis
13
Q
Kepler’s third law
A
P^2 = a^3/M
Flaw is it doesn’t depend on mass orbity
It is only true when mass of orbit is less of mass orbiting
