Copyright © 2012 Pearson Education, Inc. Planetary Motions II and Student Projects

Copyright © 2012 Pearson Education, Inc.

Planetary Motions IIand Student Projects


Student Projects

• Everyone is required to hand in a project.• Submission at start of class Wed 10th August.• Absolutely no late submissions.• Worth 20% of your grade.• It is a substantial piece of work so start ASAP.• The project is an opportunity to express your

own creative in the context of Astro110.• Project 2 … ‘Misconceptions’ may be difficult

in the time available.


Student Project - Format

• You must reference (i.e. give credit to) the original author of articles\images\websites that you use.– Examples of citations

• Put citations in your text in brackets like this (Dixon 1999).

– Bibliography• This is a list of all your referenced articles.• Examples of bibliography

– Journal article, ‘Author(s), title, Journal, date of Article’.– Image, ‘‘Author(s), title, Book\website, date of Article’.– Website article, ‘Author, title, url’.– Give enough information so that a reader can find the original material.

• Include a full list of all references in the bibliography.• Put the bibliography at the end of your article.

• Follow the rules the write-up format.– Font size, margin size etc. (otherwise you will lose marks).


Student Project - Grading

• Projects will receive an average (C) grade if the basic requirements of the project are met and the project displays some originality and creativity.

• Higher grades will need to display substantial effort, significant creativity and/or evidence that you have learned some astronomy that is beyond what we have learned in class.

• Suggestions for extra effort are given for each project, but there are plenty of other ways to illustrate extra creativity and effort.

• It will probably take you 20-30 hours of work to do the project. • If you are doing 10 hours or less of work you are heading for at best a C-

grade.• If you simply regurgitate something form the lectures you are also heading

for at best a C-grade.• You may work with others on the same project but your write-up must

show your own work\opinions\learning. Students that hand in similar work will get at most a C-grade.

• Your work should be presented so that it is understandable by other astronomy 110 students.


The Scientific Method


• Based on proposing and testing hypotheses

• Hypothesis = educated guess

• Test hypothesis against observations.

• Make new predictions that can be tested.

The idealized scientific Method.


Hallmarks of Science: #1

Modern science seeks explanations for observed phenomena that rely solely on natural causes.

(A scientific model cannot include divine intervention.)



Science progresses through the creation and testing of models of nature that explain the observations as simply as possible.

(Simplicity = “Occam’s razor”)



A scientific model must make testable predictions about natural phenomena that would force us to revise or abandon the model if the predictions do not agree with observations.


What is a scientific theory?

• The word theory has a different meaning in science than in everyday life.

• In science, a theory is NOT the same as a hypothesis.• A scientific theory must:

—Explain a wide variety of observations with a few simple principles

—Be supported by a large, compelling body of evidence—NOT have failed any crucial test of its validity


Thought Question

A. Scientific opinion is about evenly split as to whether evolution really happened.

B. Scientific opinion runs about 90% in favor of the theory of evolution and about 10% opposed.

C. After more than 100 years of testing, Darwin’s theory stands stronger than ever, having successfully met every scientific challenge to its validity.

D. There is no longer any doubt that the theory of evolution is absolutely true.

Darwin’s theory of evolution meets all the criteria of a scientific theory. This means:


Planetary Motions II


More distant planets orbit the Sun at slower average speeds, obeying the relationship

p2 = a3

p = orbital period in years a = average distance from Sun in AU

Kepler’s Third Law


Kepler’s Third Law

Kepler's Third Law


Graphical version of Kepler’s third law


Thought Question

A. 4 years

B. 8 years

C. 16 years

D. 64 years

(Hint: Remember that p2 = a3.)

An asteroid orbits the Sun at an average distance a = 4 AU. How long does it take to orbit the Sun?


The Copernican Model


How did Galileo solidify the Copernican revolution?

Galileo (1564–1642) overcame three major objections to the Copernican view.

1. Earth could not be moving because objects in air would be left behind.

2. Noncircular orbits are not “perfect” as heavens should be.

3. If Earth were really orbiting Sun,we’d detect stellar parallax.


Galileo’s experiments showed that objects in air would stay with a moving Earth.

Overcoming the first objection (nature of motion):

• Aristotle thought that all objects naturally come to rest.

• Galileo showed that objects will stay in motion unless a force acts to slow them down (Newton’s first law of motion).


Overcoming the second objection (heavenly perfection):

• Observations of comet and supernova already challenged this idea.

• Using his telescope, Galileo saw:

— Sunspots on the Sun (“imperfections”)

— Mountains and valleys on the Moon (proving it is not a perfect sphere)


• A lack of parallax seems to rule out an orbiting Earth.

• Galileo showed stars must be much farther than thought—in part by using his telescope to see that the Milky Way is countless individual stars.

• If stars were much farther away, then lack of detectable parallax was no longer so troubling.

Overcoming the third objection (parallax):


Galileo also saw four moons orbiting Jupiter, proving that not all objects orbit Earth.

Galileo also measured the phases of Venus, which proved that it went around the sun (not the Earth).


Galileo’s observations of phases of Venus proved that it orbits the Sun and not Earth.

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Galileo Galilei

In 1633 the Catholic Church ordered Galileo to recant his claim that Earth orbits the Sun.

His book on the subject was removed from the Church’s index of banned books in 1824.

Galileo was formally vindicated by the Church in 1992.


• Kepler’s Third Law - Tutorial Book page 25-27.

Documents

Copyright © 2012 Pearson Education, Inc. Planetary Motions II and Student Projects