© sierra college astronomy department1 objectives u general celestial concepts/astron. history u...

© Sierra College Astronomy Depa© Sierra College Astronomy Departmentrtment

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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


What is science?

Name some important elements in 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)


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?


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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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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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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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.)

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What is astronomy?

How far is it? How big is it? How does it move? What powers it? How hot is it?

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