Quiz 1 Flashcards
What did Karl Popper say a statement had to be if it could be considered scientific?
Falsifiable
e.g. the sun rising because Apollo pulls it across the sky is not falsifiable so it is not scientific
Occam’s Razor
The simplest answer is generally correct
What did some ancient groups think that the stars were? (3)
- distant campfires
- we are inside a large animal
- fire of heaven shining through the black velvet
How did the Greeks know that the world was round? (3)
- Ships don’t shrink into the distance, they sink into the horizon
- The shadow of the Earth on the Moon is round
- Views of constellations change as you go north and south
Why did Greeks think that the Earth was stationary? (3)
- We would feel it if we were travelling 1000mph
- If you drop something, it just goes straight down
- Birds do not fall backwards when they land
What did the Greeks think about theory v. observation?
Theory was more important than observation. You could not always trust human experience but you can always trust maths
What were the Earthly elements for Aristotle? (4)
- Earth
- Water
- Fire
- Air
What was the heavens made out of for Aristotle?
Quintessence
What shape did Aristotle think the planets moved in and why?
Assumed they moved in circles because this shape was considered the most perfect of them all (Plato) and the heavens were perfect and unchanging
What were the original 7 planets that Aristotle saw? (7)
Earth Moon Sun Mars Venus Jupiter Saturn
What is Retrograde Motion?
The planets move either in an ‘S’ shape or in a loop against a backdrop of unchanging stars
How did Ptolemy explain Retrograde Motion?
He had the idea of epicycles
What were Ptolemy’s Epicycles?
The planets would orbit the earth on a deferent whilst orbiting the deferent on their own epicycle
What was Ptolemy’s main contribution to astronomy?
He was able to give accurate predictions of the positions of the planets at different days
Why were epicycles problematic?
They were clunky. You need epicycle upon epicycle, of varying sizes and shapes to properly account for their position
What was Copernicus’ revolutionary idea?
That the sun was at the centre of the universe
What did Copernicus say about the speed of the orbits?
The planets closest to the Sun would move the fastest
What did the RCC think of Copernicus’ theory? (2)
They were very open to it because they wanted to learn more about the heavens to better understand God.
They also wanted to better predict Easter, which comes on the first full moon after the first day of spring
What was Copernicus’ book called
‘On the Revolution of the Celestial Orbit’
What did Copernicus think about the Moon?
That it still orbited the Earth
Copernicus’ Retrograde
Earth moves faster around the sun and its orbit is smaller. RM happens when Earth passes the orbit of a slower planet
What is Parallax?
The apparent motion of an object caused by looking at it from 2 different points of view
When will we see Parallax in Astronomy?
When Earth is at 2 different parts of its orbit around the Sun
What is problematic about the Stars and parallax?
They do not move
Why did Copernicus think stars didn’t move from parallax?
They were so far away that it is undetectable
What was Tycho Brahe’s ‘new star’?
A supernova explosion
What was Tycho Brahe’s observatory called?
Uraniborg
What was Tycho’s aim?
To avoid the mathematical absurdity of Ptolemy and the physical absurdity of Copernicus
What was Tych’s model of the universe?
The sun and the moon orbited the earth but the rest of the planets orbited the sun on its way around the earth
What did Kepler discover about the ratios of Saturn and Jupiter using geometry?
That the ratios of their orbit were 2:1 because he saw them in the circle, surrounded by a triangle, surrounded by a circle shape
What are the Platonic solids?
dodecahedron Tetrahedron octahedron icosahedron cube
What 2 key principles did Kepler have to abandon in order to explain Mars’ orbit?
- The idea that planets moved in circles
- The idea that planets moved at a constant speed
How close did Kepler get to explaining the orbit or Mars without abandoning these shapes?
8 arc minutes
What is an arc minute?
1/160 of a degree
What is eccentricity?
how squished the ellipses is
What is the eccentricity of Mars’ orbit?
0.09
When do planets move faster?
When they are closer to the sun
Who invented the telescope (officially)?
Hans Lippershay
What did Galileo discover about the Sun?
It had sunspots. This allowed him to show that the heavens were not perfect, and allowed him to calculate the orbit of the Sun
How did Galileo discover that the moon was 3D?
It had mountains and craters and stuff
what did Galileo discover about planets?
They were disks, not points of light like the stars
What constellation did Galileo discover?
The Pleiades (7 sisters)
What did Galileo discover about Jupiter?
It had moons that orbited it, which he called the ‘Medician Stars’
What did Galileo discover about Venus?
It had phases, just like the moon
What did Ptolemy think about Venus?
It was always close to the sun because of the nature of the epicycle around the Earth
Predicted that it would have phases
What did Copernicus think about Venus
Predicted that it would have phases
It was always close to the sun because its orbit was between that of the Earth around the Sun and the Sun itself
According to the inverse law of gravity, what happens when the distance between two objects is doubled?
The gravitational force between them gets 4x weaker
