Download presentation

Presentation is loading. Please wait.

Published byAubrey McCoy Modified over 2 years ago

1
1 Ako ďaleko sú hviezdy Peter Ballo

2
2 Very Early (Pythagoras: 550 BC) Cosmology

3
3 Aristotle’s reasoning for why the earth is round 1.Different stars can be seen, depending on location 2.[below] Perfection demands that objects fall toward the Earth center, which is only “down” everywhere if Earth is sphere 3. [right] Eclipses would look strange (lunar depicted)

4
4 The Eudoxus model Two inner ones turn slowly in opposite directions, to account for retrograde, speedup, slowdown and ecliptic crossings Third one gives Mars year, with axis tipped a few degrees, slipping backward on the ecliptic Fourth one gives usual diurnal motion

5
5 Note the order in which the celestial objects are lined up and that Moon and Sun need no epicycles The Complete Ptolemaic Model

7
7 How Far To Moon? Aristarchus’s (270 BC) clever idea if you know the size of the Earth… (not very well, actually) during a lunar eclipse, measure how many moon diameters fit into earth’s (slightly) cone-shaped shadow: call that n diameters now you know the size of the moon too!!! so D M = D E /n (it’s a bit trickier due to “coniness” of shadow…) now you know the size of the moon too!!! knowing angular size of moon … simple proportion, then: d M = D M

8
8 How Far To Sun? Another of Aristarchus’s clever ideas at quarter moon, angle at M to E and S is 90º precisely measure angle between M and S he measured 87º; correct answer is 89.83º in modern trigonometry, we’d say d S = d M sec A [sec A = 1/cos A] he got d S = 19 d M correct: d S = 390 d M

9
The Alexandrian School Aristarchus of SamosAristarchus of Samos –Relative Sizes of Earth, Moon and Sun Earth Found that Sun is 6-7x larger than the Earth, compared to 109x Found that Sun is 6-7x larger than the Earth, compared to 109x The Sun is larger than the Earth! The Sun is larger than the Earth! Led him to suggest a Sun-centered (“heliocentric”) universe Led him to suggest a Sun-centered (“heliocentric”) universe

11
1.71400 1.51200 1.41000 1.3800 1.1600 Diameter of hole /mmLength of tube / mm

12
From Sun 7 o Alexandria 7 o Syene Distance around Earth = 360 o /7 o x Distance Syene to Alexandria = 50 x 5000 stades ! From Sun

13
Evolution of Greek Cosmologies Hipparchus150 BC (Island of Rhodes)Hipparchus150 BC (Island of Rhodes) –Cataloged Positions and Brightnesses of 850 Stars –Length of Month and Year, With Errors Year Accurate to 6 minutes, Month accurate to secondsYear Accurate to 6 minutes, Month accurate to seconds –Precession – Non-Uniform Motion of Sun and Moon Solar motion is faster in (northern) winter Solar motion is faster in (northern) winter – The “Eccentric Circle” Primacy of observation over dogma Primacy of observation over dogma Inter-relation of observation and theory Inter-relation of observation and theory The role of the aesthetic in understanding the universe The role of the aesthetic in understanding the universe

17
E S V M 46 o 28 o

18
E M V S M J S 46 o 28 o Daily

19
M S J S M E Not to scale! V

24
R d d = R/Tan() R/

26
Cover page from S. Majewski Key Project proposal

Similar presentations

OK

C/2002 T7 (LINEAR). Bit of Administration …. HomeworksHomeworks –Due in lecture or by 3:45 on Friday at 6515 Sterling –Error in Question 5: replace ‘3’

C/2002 T7 (LINEAR). Bit of Administration …. HomeworksHomeworks –Due in lecture or by 3:45 on Friday at 6515 Sterling –Error in Question 5: replace ‘3’

© 2018 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on pi in maths Ppt on video teleconferencing jobs Ppt on nelson mandela and mahatma gandhi Free ppt on companies act 1956 Brainstem anatomy and physiology ppt on cells Ppt on global pharmaceutical industry Ppt on unity in diversity quotes Ppt on social networks Download ppt on coordinate geometry for class 9th 2015 Ppt on taj lands end