Chapter 1:
Why Learn Astronomy?
Astronomers study the
“patterns among the stars”
The origins of Astronomy lie
in keeping track of the
changes in the patterns
Compared to the universe, the
Earth is less than a grain of
sand on a beach
Watch YouTube Size Comparison video
and Zoom Out To CMB WMAP video
Our Cosmic
Address
We believe that superclusters are
the largest structures to have
formed thus far in the universe.
Will something larger form in the
far future? Probably not but we
can’t say for sure.
Light travels at a finite speed:
about 300,000 kilometers/second
Watch One Small Step HD video
Because of the finite speed of
light, we can see back in time
WMAP image of the Cosmic
Background Radiation. Light
from the edge of the visible
universe.
Play with Look Back Simulator
in ClassAction Introductory
Concepts module
Astronomers use the
Scientific Method to gain an
understanding of the
Universe
In order to make sense of what
we see we need a
Cosmological Principal
Mathematics is the language
of Astronomy and Physics
Pythagoras
569 – 475BC
“The underlying
Structure of the
Universe is
Mathematical”
Isaac Newton 1642 – 1727
Newton invented
calculus to
explain his
mechanical
universe. The
orbits of the
planets were like
the hands on a
giant clock
Albert Einstein 1879 – 1955
According to
Einstein, the
Universe is a much
stranger place than
Newton thought.
Newton could never
have imagined black
holes but Einstein’s
theories predict
them.
Dealing with numbers large
and small
Scientific Notation
4,500,000,000,000,000 = 4.5x1015
0.000000000000000028 = 2.8x10-17
Common Prefixes
centi = 0.01 = 10-2 (c)
milli = 0.001 = 10-3 (m)
nano = 0.000000001 = 10-9 (n)
kilo = 1,000 = 103 (k)
mega = 1,000,000 = 106 (M)
giga = 1,000,000,000 = 109 (G)
Range of numbers we deal
with in astronomy
Distances
Around the Earth…meters (m) or kilometer (km)
1 m ≈ 39.37 inches
1 km = 1000 m = 0.621 miles
Around the Solar System…AU
1 AU = Average Earth – Sun distance
1 AU = 1.496x1011 m = 149.6 million km
Beyond the Solar System
Lightyear (ly)
1 ly = distance light travels in 1 year
1 ly = 9.46x1015 m = 9.46 trillion km
Parsec (pc): distance at which an object shows a
parallax of 1 arcsecond: 1pc = 3.26 ly
= 30.84 trillion km
Other Units
Mass…kilograms (kg)
1 kg = 1000 grams
1 kg = 2.205 lbs*
*(a pound is not really a mass, it is a force. In the US, we tend to use it like a mass, though)
Time…Years, Days, Hours, Minutes
and Seconds
Temperature…°C
°C = (°F - 32°) x 5/9
also use Kelvin scale
°K = °C + 273°