Why Bother???
• Exciting subject filled with new discoveries!
• Affects our every day lives!
• Mind blowing ideas that challenge our way of
thinking!
• The wave of the future!
A Few Definitions
• planet: a celestial body that is in orbit around the sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a ... nearly round shape, and has cleared the neighborhood around its orbit.
A Few Definitions
• star: a massive gaseous body held together by
gravity and generally emitting light by nuclear
reactions.
A Few Definitions
• solar-system: A collection of celestial objects (e.g. planets, comets, asteroids) orbiting around a common star.
A Few Definitions• galaxy: A collection of stars, gas, dust, and
dark matter held together by their mutual gravity.
Concept Question
Which one of the following is listed in thecorrect order from smallest to largest in size?
A) star, planet, solar-system, galaxy, UniverseB) planet, star, solar-system, Universe, galaxyC) star, planet, galaxy, solar-system, Universe D) planet, star, solar-system, galaxy, Universe
Astrology or Astronomy?• Uses the positions of planets to predict human behavior• Is a branch of Physics• Uses the scientific method to interpret observations• Is considered a pseudoscience• A detailed study of all the celestial bodies in the
Universe, including planets, moons, stars, galaxies, etc.• Associates the signs of the zodiac with personality traits
Scientific Notation
• express very small or very large numbers in powers of ten• Format: . X 10
1.0= 1.0 X 100 (100)100.0= 1.0 X 102 (102)
1,000.0= 1.0 X 103 (103)10,000.0= 1.0 X 104 (104)
100,000.00= 1.0 X 105 (1005)
0.1= 1.0 X 10-1 (10-1)0.01= 1.0 X 10-2 (10-2)
0.001= 1.0 X 10-3 (10-3)0.0001= 1.0 X 10-4 (10-4)
0.00001= 1.0 X 10-5 (10-5)
Scientific NotationExamples:
Average Distance from the Earth to the Sun:
149,600,000.0 km 1.496 X 108 km
Mass of ant:
0.004 g 4 X10-3 g
Concept Question
Write -0.00000315 in scientific notation
A) 3.15 X 10-6
B) 3.15 X 106
C) -3.15 X106
D) -3.15 X 10-6
Concept Question
Write 7.89 X 10-6 in regular format
A) 000007.89 B) 0.00000789
C) 7890000 D) 0.0000789
Astronomical Units
1 A.U. = 1.5 X 108 km
Average Distance from the Earth to the Sun Astronomical Unit
Distance that light travels in a year Light Year
speed of light in a vacuum: c = 3 x105 km/s (186,000 mi/s)so one light second: 3x105 km
and one light year: 9.46x1012 km more practical to use
Looking Backwards in Time
on a planet orbittinga distant star
70 years old
here on Earth
70 years old
55 light years away
15 years old
68 light years away
2 years old
Because of the finite speed of light, we are able to look backwards in time!!!
Astronomical Distance Scales are Astronomical!
Alpha Centauri: 4.2 light years away
Andromeda Galaxy: 2.4 million light years away
Galaxies in the Hubble Deep Field: as far as billions of light years away
The Sun: 8.3 light minutes away
The finite speed of light gives us a fossil record of the history of the Universe!!!!
The Moon: 1.3 light seconds away
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