WEEK 2
Planetary Motion
(SU ch. 3 or OM. ch 1)
The Great Comet of 1577 Woodcut by Jiri Daschitzsky, 1577, Public Domain PD-1923. Johannes Kepler wrote of his mother taking him to see this comet when he was six.[i]
DAY 1: Kepler's First Law
READING
From "beginning of chapter" to "...movements became much simpler."
NARRATION PROMPTS
1. Tell what you know about Kepler's first law.
TIMELINE AND BOOK OF CENTURIES
Johannes Kepler (1571 -1630 AD, Germany)
NOTES
We did the ellipse-drawing demo.
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DAY 2: Kepler's Second Law
READING
From "Because their orbits..." to "...it moves in its orbit.")
NARRATION PROMPTS
1. Tell what you know about Kepler's second law.
NOTES
None yet.
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DAY 3: Kepler's Third Law
READING
From "Planets farther/further..." to "end of chapter."
NARRATION PROMPTS
1. Tell what you know about Kepler's third law.
NOTES
I really like the inclusion of planetary motion. As I flipped through my high school physics books, Kepler was only mentioned in one of the four. Even then, it was only a cursory mention, and there was no mention of the three laws. It was only in college level textbooks the three laws first came up.
Grasping the full meaning of the third law will be tough if a child has not yet made it there in Algebra, and I would just ignore the equation. In the most simple form, there is a relationship between the distance a planet is from the sun and the time it takes to complete a revolution around the sun, and this relationship is the same for every planet (that is the amazing part--but don't force this connection for the child if he is not bringing with him the background to see this). As distance increases, the time increases or vice versa. Good enough. However, it is not a linear relationship, but again, if a child has not yet gotten there in math, this could be confusing. For the students who do take interest in the equation, if the child would care, I would point out Fleisher is not using standard symbols. The time it takes to make one full revolution around the sun is a Period and the standard symbol for that is almost always T. Almost everywhere else in Physics, R or r will be reserved for a radius or distance. Using D or d as a distance is fine, but a student is more likely to see an r or an R in the future when dealing with the planets because we are usually dealing with an average radius. This is why it is so important to be able to put the relationship or equation into words and not tie too strong of a meaning to the symbols. I'm actually tempted to glue a piece of paper over the equation and write: T*T/r*r*r. Why does this bother me? I guess it gets back to the whole spelling thing. I would hate to put a mental image in my child's mind with which he might then need to struggle for the rest of his life. |