history

Question 1

What is the significance of Nicolaus Copernicus (1473-1543)?

Answer 1

• study of planetary motions- doubted validity of accepted system.
• from philosophical view
• sun centred universe

Question 2

What was Nicolaus Copernicus’ model?

Answer 2

• perfect circles for orbits

- introduced small epicy-cles to improve accuracy.

Question 3

what were the impacts of the model?

Answer 3

1- Rotation of Earth rather than heavens
2- natural order of planets
3- relative distance of planets- found grew systematically within increasing distance from sun
4-further out planet is- slower moves
5-simple explanation for retrograde motion
6-explanation of seasons
7-explanation of changes in planetary brightness

Question 4

What was the intent of Tycho Brahe (1546-1601) and what did he do?

Answer 4

• observatory on island of Hveen.
• variety of instruments; 31 1/2 foot radius quadrant- improved angular scales and sighting design
• accurate observations of positions of planets (1 minute of arc, 10 x better)

Question 5

what did Tycho Brahe observe in 1577?

Answer 5

observed a bright comet, showed that comet was very distant

accumulated large body of data on planetary motion

Question 6

Why could Tycho Brahe not accept the heliocentric view?

Answer 6

no evidence for Earth moving- protestant

developed model with earth fixed, sun orbiting it, all other planets orbit sun.

Question 7

What was Johannes Kepler (1571-1630) interested in?

Answer 7

• copernican system- mathematical simplicity
• celestial harmony (spacing between planets determined by the spacing of geometric solids)
• inherited all Tychos data

Question 8

What did Kepler do?

Answer 8

• mapped path Mars followed around sun
• realised sun played central role in making planets move
• but sun was not central to planets orbit
• orbit of mars is oval, found it was simple ellipse with sun at focus.
• found mars moves fastest when near sun

Question 9

What are Keplers laws of planetary motion?

Answer 9

1st: orbits of planets are ellipses- sun at one focus
2nd: for each planet, area swept out in space by a line connecting that planet to sun equal in equal intervals of time
3rd: square of period of a planet is proportional to cube of the semimajor axis.
P^2 ∝ a^3
.

Question 10

what did Galileo Galilei (1564-1642) do?

Answer 10

• simple experiment and deduction in advancing the perception of universe
• invented own telescope and discovered:
  1: moon not smooth sphere-craters and mountains
  2: milky way not cloud- stars
  3: Jupiter attended by four satellited
  4: Varying aspect of Venus, like phases of moon- showed venus shines by reflected sunlight- must orbit sun not Earth.
  5: studied dark spots sometimes appeared on face of sun- some thought planets but actually on surface

Question 11

What did Galileo’s observations violate?

Answer 11

ancient philosophies of idealised universe with Earth Centre of all motion. Criticism from the church

Question 12

What book did Isaac Newton (1642-1726) in 1687?

Answer 12

Philosophi, Naturalis Principia Mathematica

Question 13

What are Newtons three laws?

Answer 13

1st: object at rest or in uniform motion will maintain that state unless compelled to do so otherwise with external force
2nd: rate of change of momentum (mass x velocity) of a object is equal to force applied. F= M X A
3rd: for every action, equal and opposite reaction.

Question 14

How is Newton’s Universal law of gravity wrote?

Answer 14

Fgrav= G x (m1 x m2/r^2)

Fgrav= force of gravity 
G= gravitational constant (6.67 x 10^-11)

Question 15

what does the combination of universal law and newtons 2nd law?

Answer 15

why the gravitational acceleration at the Earth’s surface is 9.8 m/s^2 (different on other bodies)

Question 16

Newtonian gravity is a basis for explaining what?

Answer 16

Keplers empirical formula laws .

-an attractive force acting between sun and bodies in the solar system explains why they orbit in the way that they dp