Preview Chapter

The Cosmic Landscape

Warm Up • Come in and start

• In your notebook define the following

words to the best of your abilities

– Satellite

– Planet

– Star

– Solar-System

– Galaxy

– Universe

A Few Definitions

• moon or satellite: a body orbiting a planet.

A Few Definitions

• planet: a celestial body that:

1. is in orbit around the sun

2. has sufficient mass that it assumes a nearly round shape

3. 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.

A Few Definitions

• Universe: Consists of everything around us

Includes

Everything!

Concept Question

Which one of the following is listed in the

correct order from smallest to largest in size?

A) star, planet, solar-system, galaxy, Universe

B) planet, star, solar-system, Universe, galaxy

C) star, planet, galaxy, solar-system, Universe

D) planet, star, solar-system, galaxy, Universe

Science and PseudoScience

Science and PseudoScience

Science and PseudoScience

Science and PseudoScience

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

Timeline of the Universe

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 Notation

Examples:

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 orbitting

a 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

Astronomical

Distance

Scales are

Astronomical!