Transcript ppt
Looking out at the Night Sky What questions do you have? Motions in the Sky: How does the sun move during the day? How do stars move during the night? Does the motion of the sun change with the seasons? Does the sun set at the same point along the horizon (from the same location)? Do the stars change with the season? How about the motion of the moon? How does the shape change? What else…? Activity 1. Let’s explore these questions with a globe. (what are we assuming about the earth when we do this?) How long does the earth take to rotate once? Which direction does it rotate? (east? west? ) When do we see the stars? How long does it take the earth to revolve around the sun? Ok: the north star, or Polaris, or “the star that does not walk”; why does it have this name? Use your planisphere (star wheel) for this. The Earth as a top: let’s experiment with tops… Next Activity: Becoming the earth (aka kinesthetic astronomy) let’s form a circle around our sun, with your head representing the earth. I will tell each of you what month it is on your “earth” Using your star wheel, decide what constellation is overhead at midnight! Next, we introduce the “tilt” of the earth Terms we will use: horizon, zenith, ecliptic, angles Motions in the Sky: More Questions Are there stars we never see in Arizona? Are there stars that never go below the horizon in Arizona? How do stars move if we are at the north pole? Do they rise and set? The Large Magellanic Cloud Where is the north star if we are at the equator? When the sun is high in the sky in Arizona where is it in the sky in Rio de Janiero? When it is low in our sky, where is it in Rio? Lecture Tutorial, p. 3 Part 1: Looking North Work with someone else, and ask me if you are confused! Use the props I brought! Use your star wheel from class 1! For those people with more background, continue to part II: Looking East The Moon: How much does the moon change from day to day? Why does it change? “It’s not science if we can’t measure it!” We will be measuring the position of the moon, of sunset, and of Venus for much of the semester. How could we do this? How was it done in the past? Angles and units for measuring them: degrees (How many degrees in a circle?) Terms: Azimuth: angle around the horizon measured from north through east Altitude: angular distance from horizon to object. We can use our fist as a pretty good estimate of angles. For greater accuracy, we can use a compass to measure azimuth: free download on your ipad Or a magnetic compass is just fine: I have a few Measuring angles, or altitude : Let’s build a protractor for measuring angles, or angular diameter, in degrees Next, let’s go measure the moon! Angular size? Altitude? Homework: Concepts covered this class: Daily motion, stars, sun Height of north star, path of stars in sky Seasonal change of constellations Intro to motion of moon Measuring angles, protractor Terms: horizon, zenith, angles (angular diameter), azimuth& altitude The sun, image taken through a solar filter. How big would the moon be if taken with the same camera?