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A100 Solar
System
Today’s APOD
Read Preview in text – “Cosmic Landscape” Quiz Monday (essential facts and scientific
notation) Rooftop Session Sept. 10, 9 PM 1st Homework due Sept. 12 (get it on
Oncourse)The Sun Today
Wednesday, Sept. 5
The Sun Today
SolarOrbiting
Heliospheric Observatory
(SOHO)Orbits between the Sun and Earth, about a million miles
away – a constant view of the Sun
No sunspots – the Sunis in a phase of low
activity
Write and work with very large or small numbers without so many digits.
Only one digit should be in front of the decimal.
The exponent positive when the number is greater than one, negative when the number is less than one.
Review Scientific Notation
43,000,000. = 4.3 x 107
0.000043 = 4.3 x 10-5
Use the worksheet with the syllabus for practice
Powers of 10Power of 10 Notation Prefix Abbr.
billion 109 “giga” G
million 106 “mega” M
thousand 103 “kilo” k
hundredth 10-2 “centi” c
thousandth 10-3 “milli” m
millionth 10-6 “micro” billionth 10-9 “nano” n
Basic DefinitionsDistances Solar Radius (700,000 km)Astronomical Unit (AU)Light year
MassEarth massesSolar masses
SpeedSpeed of light(300,000 km per second)
Use approximate numbers
Using those essential facts! Which of the following diagrams most
closely depicts the relative sizes and distance between Earth and the Moon?
How do Astronomers Know?
Create a CONCEPT MAP Start with concepts (words we have for ideas) Form concepts into a hierarchical organization
lower levels that are more specific and less general than the higher levels
Add examples (illustrative nouns or names of specific people, events, places, or objects, at the lowest level of the hierarchy)
Add linking words or phrases (describe how one concept relates to another)
Add cross-links (show the relationship between one branch and another)
Hints: Concepts appear only once
Are all links and concepts relevant? Are examples relevant, appropriate, and representative?
About Learning Astronomy1. Pay attention to the diagrams
– What is shown in the diagram?– What basic concept is illustrated?– Why is the diagram included in
the text or lecture?
Looking at Scale
What information is shown in these two diagrams of the local bubble?
What is the relationship between them?
About Learning AstronomyUse physical models
Physical models can help you visualize the relationships among bodies in the Solar System
Understanding Science
Purpose – to understand the universe well enough to figure out the basic relationships that govern it
A process for understanding and predictingwill it rain tomorrow?what will be on the quiz?what will happen if…?
What about facts?new discoveriesbetter datanew theoriesfacts change!
The Science
of Astronomy
Learn what is known
and what is NOT known…
Develop a model to explain or describe what is knownUse the model to predict what is not known
TEST the predictions
Refine the model
But science rarely proceeds in this idealized way… For example: • Sometimes we start by “just looking”
then coming up with possible explanations.
• Sometimes we follow our intuition rather than a particular line of evidence.
Testing the PredictionsExperiments and Observations
repeatablequantitative well definedfair
Statistics evaluate the reliability of observations
Examples What time is it? Heads or tails?
Laws and Theories (and models)
A law is a set of hypotheses that explains WHAT is happening – usually mathematicalKepler’s laws of planetary motion
A theory is a well-developed set of hypotheses that explains why many related natural phenomena happenEinstein’s Theory of General Relativity
Laws and theories are both based on detailed and repeatable observations and measurements
Laws and theories both yield testable predictions
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, rather:
• A scientific theory must:—Explain a wide variety of observations with a few
simple principles, AND—Must be supported by a large, compelling body
of evidence.—Must NOT have failed any crucial test of its
validity.
Is a Theory Right? Can’t ever “prove” a theory rightDoes the theory make correct
predictions?If it doesn’t, then it’s wrong
If it’s not tested or testable, it’s NOT a scientific theory
Burden of proof is on the person making the claim“Extraordinary claims require
extraordinary proof” (Sagan)
An Ongoing Process
The process of science has been so successful becauseresults are widely shared and
evaluatedexperiments are reproduced and
checkedvalue of ideas based on observation
and usefulness, not authority
Criteria of ScienceConsistent: The results of repeated observations or experiment are more or less the same.
Observable: The event under study can be observed or natural evidence must be available.
Natural: A natural caused must be used to explain why or how the event happens
Predictable: The natural cause can be used to make specific predictions.
Testable: Predictions must be testable through observations or experiments.
Tentative: Science is subject to revision and correction based on new observations
• Consistent • Observable • Natural • Predictable • Testable • Tentative
Debating Scientific IssuesHow do we tell who is correct?
Majority vs. minority opinionsMajority isn’t always right Debate is a poor technique for deciding
EVIDENCE and DATAHow was the experiment done?Was it repeated by others
Is a new theory TESTABLE?
How can we distinguish
science from non-science?
• Defining science can be surprisingly difficult
• Science from the Latin scientia, meaning
“knowledge”
• But not all knowledge comes from science…
Warning Signs of Bad ScienceHow is it announced? Is the source reliable?
How good is the evidence?is it anecdotal? does it appeal to authority?does it fit what you already know?does it violate widely-accepted laws or theories?is contrary evidence ignored?
What kind of reasoning is used?Can the claim be tested?
The Baloney Detection Collection
Phil Plait's Bad Astronomy: Home Page
PLANET-DISSOLVING DUST CLOUD IS HEADED TOWARD EARTH!
September 12, 2005, by Yahoo! News
• By MIKE FOSTER
CAMBRIDGE, Mass. -- Scared-stiff astronomers have detected a mysterious mass they've dubbed a "chaos cloud" that dissolves everything in its path, including comets, asteroids, planets and entire stars -- and it's headed directly toward Earth!
Discovered April 6 by NASA's Chandra X-ray Observatory, the swirling, 10 million-mile- wide cosmic dust cloud has been likened to an "acid nebula" and is hurtling toward us at close to the speed of light -- making its estimated time of arrival 9:15 a.m. EDT on June 1, 2014. The bad news is that the total annihilation of our solar system is imminent.
To avoid widespread panic, NASA has declined to make the alarming discovery public. But Dr. Sherwinski's contacts at the agency's Chandra X-ray Observatory leaked to him striking images of the newly discovered chaos cloud obliterating a large asteroid.
“If it continues unchecked, the chaos cloud will eventually reduce our galaxy to the state of absolute chaos that existed before the birth of the universe,” the astrophysicist warned.