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Transcript of © Sierra College Astronomy Department1 Objectives u General Celestial Concepts/Astron. History u...
© Sierra College Astronomy Depa© Sierra College Astronomy Departmentrtment
11
Objectives
General Celestial Concepts/Astron. History Basic Principles of Physics
– Nature of Light, Atoms, Spectra, and Telescopes Earth, Moon, and the Rest of the Solar System The Sun Stars (Properties and Evolution) Galaxies The Universe and Cosmology
Mars – Spirit 2004 - 2007
Dust Devils
Mars – Opportunity: 2004-2007
Saturn from the Hubble Space Telescope
CassiniCassini: Mission to Saturn: Mission to Saturn
Titan
Saturn
Huygens probe
lands on Titan
UV
X-ray
magnetogram
optical
Different Faces of the Sun
NGC 1232What the Milky Way looks like?
The Andromeda Galaxy (M31)
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Use of the CPS keypads Coming up next week
1010© Sierra College Astronomy Depa© Sierra College Astronomy Departmentrtment
Why do we use special units in astronomy?
See, I told you this room is exactly 0.0023 miles wide!
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Lecture 1: Overview, Dimensions, and the Scientific Method
Dimensions and the Language of Math
Units determined by the scale of the object(s) under study (e.g., nm, AU, ly, and Mpc)
Fundamental constants and particles symbolically represented (e.g., c, G, e-, and )
Even with large assortment of units, the vast extremes inin time and space scales require exponents
Astro 10 minimum math: “simple” algebra– Kepler’s Third Law, Newton’s Second Law,
Universal Gravitation
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Numbers in Astronomy
We express very big or very small numbers in terms of scientific notation– See Appendix C– Large and small numbers:– Distance from Earth to Sun:
149,600,000,000 m– Mass of hydrogen atom:
0.00000000000000000000000000167 kg
Powers of Ten
Numbers greater than one Numbers less than one
10 = 101 0.1 = 10-1
100 = 10×10 = 102 0.01 = 10-2
1000 = 10×10×10 = 103 0.001 = 10-3
1,000,000 = 106 0.000001 = 10-6
1,000,000,000 = 109 0.000000001 = 10-9
Move the decimal to the left Move the decimal to the right
Scientific Notation
We often express large or small numbers in terms of a number between 1 and 10 multiplied by a power of ten
149,600,000,000 m = 1.496 × 1011 m
0.00000000000000000000000000167 kg= 1.67 × 10-27 kg
Units See Appendix C3, C4 Most quantities have units
–Most common exception: ratios We will be using the MKS system (meter-kilogram-
second) Other units are hybrids of these e.g. :
–Newton (N): kg·m/s2 (Force)–Joule (J): N·m (Energy)–Watt (W): J/s (Power)
For any problem you solve treat units separately and cancel/combine appropriately
Prefixes (see Appendix C4)
symbol
prefix meaning
n nano- One billionth = 10-9
micro- One millionth = 10-6
m milli- One thousandth = 10-3
c centi- One hundredth = 10-2
k kilo- One thousand = 103
M Mega- One million = 106
G Giga- One billion = 109
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Scales of the Cosmos
Earth to Universe Scale of the Solar System Moving Around
UniverseScale
SolarSystemScale
Motion 1 Motion 2 Motion 3
Lecture 1: Overview, Dimensions, and the Scientific Method
What is science?
Name some important elements in the scientific method:
Lecture 1: Overview, Dimensions, and the Scientific Method
What is science? “The true scientific method is to test
hypotheses. A good hypothesis must predict some things about nature, and if the predictions are wrong, the hypothesis must be rejected or modified. Though a hypothesis can never be proven ultimately true, if experiments keep turning up consistent results, it is considered more and more reliable and comes to be an accepted theory or law.” Hartmann (from another astronomy text)
Lecture 1: Overview, Dimensions, and the Scientific Method
What is science? Error analysis
– How well do you know what you know? Contradictory results
– Which result do you ignore? Framing questions
– Creativity Aesthetics
– How do you define simplicity, beauty?
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Lecture 1b: Overview, Dimensions, and the Scientific Method
Astronomy and the Scientific Method
How far is it? What are its physical characteristics? How fast does it move and why? What allows it to be detected? How are any of the above features
related? What created it?
Lecture 1: Overview, Dimensions, and the Scientific Method
The Laws of Nature
The rules of the game played by nature– universal
Laws cannot be suspended– Good science fiction
Laws may be modified with better understanding– e.g. Kepler’s Laws Newton’s Laws
Einstein’s Special Relativity
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Lecture 1: Overview, Dimensions, and the Scientific Method
Scientific Models - A Geocentric Model
A scientific model is a theory that accounts for a set of observations in nature.– Ex: Stars residing on a giant celestial
sphere is a model. A scientific model is not necessarily a
physical model. The Sun’s motion along the ecliptic can
be explained by a geocentric model.
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Lecture 1: Overview, Dimensions, and the Scientific Method
Criteria for Scientific Models
Three modern criteria of scientific models:
– Model must fit the data
– Model must make predictions that can be tested and be of such a nature that it would be possible to disprove it
– Model should be aesthetically pleasing - simple, neat, and elegant (Occam’s razor)
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Lecture 1: Overview, Dimensions, and the Scientific Method
Model, Theory, and Hypothesis
Theory is a hypothesis or set of hypotheses that have been well tested and verified.– The geocentric model could just as well
have been labeled a theory. Hypothesis is a tentative explanation
awaiting further development and testing.
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The End
Significant figures
Bottom line: final answer cannot be more accurate than any quantity that was used to get answer
Examples:– 3.56 3 sig figs– 0.034 2 sig figs (zeroes are placeholders)
– 3.560 4 sig figs (zero is significant)
– 3.556 106 4 sig figs
NEXT
Example 1 distance = velocity time [D = vt] v = 32 m/s t = 10.2 s D = (32 m/s)(10.2 s) = 326.4 m proper number of sig figs: 330 mNEXT
Example 2
Same formula solved for t : t = D/v v = 1.02 m/s D = 3.4 m t = (3.4 m)/ (1.02 m/s) t = 3.4mm/s) t = 3.3 s (proper number of sig. figs.)
NEXT
Lecture 1: Overview, Dimensions, and the Scientific Method
What is astronomy?
How far is it? How big is it? How does it move? What powers it? How hot is it?
NEXT