Chapter 1:
Why Learn
Astronomy?
We Have Studied Astronomy
Since Ancient Times
Astronomy is the
oldest science.
Every ancient
culture studied
motions in the sky
Compared to the universe, the
Earth is less than a grain of
sand on a beach
Watch YouTube Size Comparison and
Journey to the Big Bang WMAP videos
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
Astronomers study the
“patterns among the stars”
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°