PHYS 1403 Introduction to Astronomy
Learning stops when someone tells
you the answer
Think about this Phrase
Introductory Concepts: What is Science??
What is the very first step of the scientific
method?
a) Generate a conclusion.
b) Analyze results.
c) Perform an experiment.
d) Form a hypothesis.
e) Make a model
Introductory Concepts: What is Science??
Which one of these statements applies to
Technology and not Science?
a) Discover the laws of Nature
b) Is independent of social, political and
economic conditions
c) Find products that benefit human
civilization
d) Predict human fate and future
http://hea-www.harvard.edu/~pgreen/educ/concep/measures.txt
What is an Argument?
Measurements and Units
Argument = Premises/fact(s) + Conclusions
One can say that a Scientific hypothesis is an
argument
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System International (SI) Units
Dimensions
Fundamental Units of Measure can be
represented with symbols
Mass -> M
Length -> L
Time -> T
http://sciencewithme.com/learn-about-si-units/
Conversion from MKS to FPS
Scientific Notation
Astronomical numbers are
very large
or
very small
so Astronomers use Scientific
Notation
http://www.tpub.com/doephysics/classicalphysics6.htm
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Astronomy Education at the University of Nebraska-Lincoln Web Site (http://astro.unl.edu)
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Astronomy Education at the University of Nebraska-Lincoln Web Site (http://astro.unl.edu)
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Significant Numbers
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Astronomy Education at the University of Nebraska-Lincoln Web Site (http://astro.unl.edu)
Getstartedinsicence.weebly.com
Significant Numbers
Significant Numbers
slideplayer.com
Uncertainty
Introductory Concepts: Units?
You are analyzing driveway lengths within your
neighborhood and surrounding neighborhoods, and
your data is to be presented to the city council.
Which would be the most appropriate unit of
measurement?
a) millimeter's
b) inches
c) miles
d) kilometers
e) feet
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Introductory Concepts: Scientific Notation?
Multiplying together two numbers N*10x and
M*10y in scientific notation yields the
following, again in scientific notation
a) (N*x) * 10 (M*y)
b) (N+M) * 10 (x+y)
c) (N*M) * 10 (x*y)
d) (N*M) * 10 (x+y)
Introductory Concepts: Significant
Numbers?
Introductory Concepts: Significant
Numbers?
Say you need to multiply together
measurements of differing precision, some
with more significant figures than others. For
example, the product of 7.00 * 6.1 is
properly written as
a) 42.70
b) 42.7
c) 43
d) 43.0
Introductory Concepts: Precision?
Say you want to add measurements of
differing precision, some with larger
uncertainties than others, such as the sum
4.371 (+/- 0.001) cm + 302.5cm (+/- 0.1).
This sum is correctly written as
a) 306.001 cm
b) 306.872 cm
c) 306.9 cm
d) 307 cm
Attendance
Scales of Size and Time
Astronomy deals with objects on a vast
range of size scales and time scales.
Most of these size and time scales are way
beyond our every-day experience.
Humans, the Earth, and even the solar
system are tiny and unimportant on cosmic
scales.
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A Campus Scene
A City View
1 mile x 1 mile
16 x 16 m
The Landscape of Pennsylvania
100 miles x 100 miles
Earth and Moon
Distance Earth – Moon: 384,000 km
The Earth
Diameter of the Earth: 12,756 km
Earth Orbiting Around the Sun
Distance Sun – Earth = 150,000,000 km
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Earth Orbiting Around the Sun (2)
The Solar System
In order to avoid large numbers beyond our
imagination, we introduce new units:
1 Astronomical Unit (AU)
= Distance Sun – Earth =
150 million km
Approx. 100 AU
(Almost) Empty Space Around Our
Solar System
Approx. 10,000 AU
The Solar Neighborhood (2)
The Solar Neighborhood
Approx. 17 light years
The Extended Solar Neighborhood
New distance scale:
1 light year (ly) =
Distance traveled by light
in 1 year
= 63,000 AU = 1013 km
= 10,000,000,000,000 km
(= 1 + 13 zeros)
= 10 trillion km
Approx. 17 light years
Nearest star to the Sun:
Proxima Centauri, at a
distance of 4.2 light years
Approx. 1,700 light years
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The Milky Way Galaxy
Diameter of the Milky Way: ~ 75,000 ly
The Universe on Very Large Scales
The Local Group of Galaxies
Distance to the nearest large galaxies:
several million light years
Scale of Universe
The distance to a nearby star might be…
a) 100 miles
b) 100 km
c) 10 ly
d) 10 AU
Clusters of galaxies are grouped into superclusters.
Superclusters form filaments and walls around voids.
ClassAction: Astronomy Education at the University of Nebraska-Lincoln Web Site (http://astro.unl.edu)
Scale of Universe
ClassAction: Astronomy Education at the University of Nebraska-Lincoln Web Site (http://astro.unl.edu)
Scale of Universe
ClassAction: Astronomy Education at the University of Nebraska-Lincoln Web Site (http://astro.unl.edu)
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Scale of Universe
How long does it take light to cross the
diameter of our Milky Way Galaxy?
a) 75000 yrs.
b) 75000 ly
c) 75000 AU
d) 75000 seconds
Scale of Universe
Venus orbits 0.7 AU from the Sun. What is
this distance in kilometer?
a) 0.105 x 108 km
b) 105.0 x 108 km
c) 1.05 x 108 km
d) 10.5 x 108 km
Acknowledgment
• The slides in this lecture is for Tarleton:
PHYS1411/PHYS1403 class use only
• Images and text material have been
borrowed from various sources with
appropriate citations in the slides,
including PowerPoint slides from
Seeds/Backman text that has been
adopted for class.
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