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Path of the Sun project: Capri, Amy, Courtney?. Where someone says, or you read, that “the sun is overhead at midday” is this strictly correct?. Review : Eclipses. What type of eclipse would be seen by observers on the night side of the earth in this diagram?. Total solar eclipse - PowerPoint PPT Presentation
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Path of the Sun project: Capri, Amy, Courtney?
Where someone says, or you read, that “the sun is overhead at midday” is this strictly correct?
Review: Eclipses
What type of eclipse would be seen by observers on the night side of the earth in this diagram?
A) Total solar eclipseB) Total lunar eclipseC) No eclipseD) Partial lunar eclipse
And what is wrong with the way this picture is drawn?
Moon Phases: putting it all together
Another demo, with everyone out of your seat! Time for “moon balls” demonstration
If tonight the moon is full when it rises in the east, what phase will it be when it sets in the west?
A) FullB) last quarterC) New moonD) First quarter
Lecture tutorial, p.81, Cause of moon phase
Now, back to motions of the Planets: Copernicus and Circles
Copernican theory: planets revolve around the sun, not around the earth
Let’s watch what you might observe for Venus, Mars
http://astro.unl.edu/naap/ssm/animations/configurationsSimulator.html
This was before the telescope, so no ideas about what planets actually looked like – just points, like stars
Lecture-tutorial, p. 99, Observing Retrograde motion
Digress: what is a theory?
The word "theory" means something very different in everyday language than it does in science: to the average person, a theory is just an idea…
A scientific theory is an explanation of something that has been demonstrated through repeated experiments or testing.
A scientific theory can also make predictions that can be tested
What can we predict about the appearance of Venus when seen through a telescope?
Galileo was the first to look at planets through a telescope. These are views of Venus at different points in its orbit:
And again…
Kepler: planets move in almost circular orbits
Kepler lived at the same time as Galileo, both born shortly after Copernicus published his book. He used the careful observations made by Tycho Brahe to modify Copernicus’ idea of circular motion.
He realized, from the orbit of Mars, that the planets move not on circular, but in elliptical orbits.
You will also have a chance to explore these in a computer lab. The web page looks like this:
http://astro.unl.edu/naap/pos/animations/kepler.html
Simulator, Worksheet for Kepler’s Laws
Review…
1. Planets orbit sun in ellipse
2. Line connecting sun and planet sweeps out equal areas in equal
3. Period (“Year”) squared = semi-major axis cubed
Kepler : provided understanding of motions of planets, and thus, every other body in the universe in his three laws
Wdefine the astronomical unit (a.u.), as the distance from the sun to the earth
Next : Isaac Newton, explained Kepler’s
laws
Breakthroughs in mechanics, optics, gravity, mathematics (invented calculus)