Transcript Ch.3
Astronomy and Cosmologies Mon.11.April, week 3, Spring 2005, Zita • Solar motion wrap-up, old questions • New questions: moon and eclipses • Moon & Eclipse workshop • • • • Discuss workshop Research planning Logistics Seminar at 5:00 – Greek myths Solar motion You found that Sun’s position in the sky depends on • latitude • season • time of day Let’s induce a general rule, based on our observations. What is the Sun’s greatest altitude a at a given latitude q, on a given day? Sun at its highest point latitude q location max alt. a relation equator tropics N pole Olympia Fill in what you know, from solar motion wkshp. Can you generalize a rule to find the maximum altitude a at a given latitude q? Find a relation between latitude q and max. altitude amax latitude q location amax 0 23.5 equator tropics 90 + 23.5 =90 – 0 + 23.5 90 = 90 – 23.5 + 23.5 90 47 N pole 23.5 = 90 – 90 + 23.5 Olympia ___ = 90 – 47 + 23.5 Does this rule work? amax = 90 – q + 23.5 Sun at its lowest point latitude q location 0 equator amin relation 90 - 23.5 = 90 – 0 - 23.5 23.5 tropics 90 –2*23.5= 90–23.5 - 23.5 90 -23.5 = 90 – 90 - 23.5 N pole 47 Olympia ___ = 90 – 47 - 23.5 Does this rule work? amin = 90 – q + 23.5 Altitude varies through the year Altitude(q,t) = a0 + A sin(wt) where t = day number (time), A= amax - a0, and average altitude a0=(amax + amin)/2 period of oscillations T = 365 days angular frequency w = 2p/T Your new questions for today… Investigate questions about Moon and eclipses as you do the workshop. Break until 2:10, do your predictions by 2:25. Measuring Earth, Moon, Sun Simon Singh, Big Bang, Ch.1 Measure Moon’s size Measuring Moon’s distance Measuring Sun’s distance Measuring Sun’s size Research planning What topic are you interested in? What can you observe? What QUESTION might you investigate? What can you DO to investigate your question? Hypotheses? Guess some possible answers to your question, and plan how to TEST your hypotheses. Form a team and post on WebX this Friday. Logistics Good job on essays and PIQs! Credit all teammates. A few people still need to get their * photos on WebX * introductions on WebX Come to class on time. Do not leave early. (If you have special circumstances, talk to Zita privately, but please do not disrupt class or seminar with a public exit.)