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1. Our Place in the Universe. 1.1 A Modern View of the Universe. Our goals for learning:. What is our physical place in the Universe? Describe our cosmic origins and why we say that we are “star stuff.” Why does looking into space mean looking back in time?. Star.

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1. Our Place in the Universe

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1 our place in the universe l.jpg

1. Our Place in the Universe

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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1.1 A Modern View of the Universe

Our goals for learning:

  • What is our physical place in the Universe?

  • Describe our cosmic origins and why we say that we are “star stuff.”

  • Why does looking into space mean looking back in time?

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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Star

A large, glowing ball of gas that generates heat and light through nuclear fusion

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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Planet

A moderately large object which orbits a star; it shines by reflected light. Planets may be rocky, icy, or gaseous in composition.

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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Moon

An object which orbits a planet.

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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Asteroid

A relatively small and rocky object which orbits a star.

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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Comet

A relatively small and icy object which orbits a star.

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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Solar (Star) System

A star and all the material which orbits it, including its planets and moons

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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Nebula

An interstellar cloud

of gas and/or dust

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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Galaxy

A great island of stars in space, all held together by gravity and orbiting a common center

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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Universe

The sum total of all matter and energy; that is, everything within and between all galaxies

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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Where do we come from?

  • The first (and simplest) atoms were created during the Big Bang.

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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Where do we come from?

  • The first (and simplest) atoms were created during the Big Bang.

  • More complex atoms were created in stars.

  • When the star dies, they are expelled into space…. to form new stars and planets!

Most of the atoms in our bodies were created in the core of a star!

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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Looking back in time

  • Light, although fast, travels at a finite speed.

  • It takes:

    • 8 minutes to reach us from the Sun

    • 8 years to reach us from Sirius (8 light-years away)

    • 1,500 years to reach us from the Orion Nebula

  • The farther out we look into the Universe, the farther back in time we see!

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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Announcement

  • Telescope class will be Mar 12 and Mar 15

    (a Mon and a Thurs) in the evening, for (typically) 1.5 hrs

    Replaces lectures of Mon Mar 12 and Fri Mar 16

  • You only need go to one!!!

  • Surnames A-M Mon Mar 12

  • Surnames N-Z Thurs Mar 15

  • OK, if you need to swap for the other night -don’t need to clear a swap with me

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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Announcement

  • First Homework Assignment

  • Introduction to MasteringAstronomy

  • Due date 02/09/07 11:00 pm

  • Assigned reading, chapters 1&2 by Feb 7 2pm

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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More on getting things in Perspective before we start…..

Our goals for learning:

  • What does our solar system look like when viewed to scale?

  • How far away are the stars?

  • How do human time scales compare to the age of the Universe?

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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How would the Universal post office find us?

Address: Earth

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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How large is the Solar System?

  • Let’s view it to scale

    • say the Sun is the size of a large grapefruit (13.9 cm)

    • then:

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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How large is our Galaxy?

The Sun ~ 26,000 light-years from the center of the Milky Way Galaxy, which is about 80,000 to 120,000 light-years across (and less than 7,000 light-years thick).

We are located on on one of its spiral arms, out towards the edge.

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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How far away is the nearest galaxy?

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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How large is the Universe?

  • Now let’s view the Universe in terms of meters

    • Powers of 10 or 10?

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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Timeout

  • Scientific Notation

  • Compact/convenient way of expressing very large and very small numbers using powers of 10. You've all probably encountered scientific notation before. Examples below are reminders for those who haven't used it in a while.

  • The Mass of the Sun:

    1,989,000,000,000,000,000,000,000,000,000 kilograms = 1.989x1030 kg

  • The Size of a Hydrogen Atom:

    0.0000000000106 meters = 1.06x10-11 m

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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Timeout

A quick word on powers of 10

  • FactorPrefixExamples

  • 103kilo-kilogram, kilometer, kilobyte

  • 106mega- megawatt, megayear, megabyte, megaton

  • 109giga- gigayear, gigaton, gigabyte

  • 1012tera- terawatt, terabyte

  • 10-2centi- centimeter

  • 10-3milli- millimeter, millisecond, milliliter

  • 10-6micro- microsecond, micron

  • 10-9nano-nanosecond, nanometer

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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A quick word on powers of 10

  • Common Examples

  • Length:

  • 1 kilometer = 103 meters (1000 meters)

  • 1 centimeter = 10-2 meters (1/100th of a meter)

  • 1 millimeter = 10-3 meters (1/1000th of a meter)

  • 1 micron = 10-6 meters (short for "micrometer")

  • Time:

  • 1 nanosecond = 10-9 s (1 billionth of a second)

  • 1 Gigayear = 109 years (1 Billion years)

  • 1 Megayear = 106 years (1 Million years)

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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  • Astronomical Units of Length

  • Meters and kilograms are fine for most terrestrial applications, but when we start talking about the enormous distances between the planets, stars,galaxies, we need to define special units to keep the numbers from getting too big. The most important of these for this course are:

  • The Astronomical Unit (AU):

    1 AU is the Mean Distance from the Earth to the Sun:

    1 AU = 1.496x108 kilometers

    The AU is used for expressing the distances between planets.

  • In round numbers, you can use "1 AU = 150 Million km" for the purposes of this class.

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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  • Astronomical Units of Length

  • Meters and kilograms are fine for most terrestrial applications, but when we start talking about the enormous distances between the planets, stars,galaxies, we need to define special units to keep the numbers from getting too big. The most important of these for this course are:

  • The Light Year (ly):

  • 1 Light Year (ly) is the Distance Traveled by Light in 1 Year:

  • 1 ly = 9.46x1012 kilometers

  • The light year is used for expressing the distances between stars.

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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Timeout

  • Space is BIG

  • For example, what is the distance between the Earth and:

  • *The Moon: 384,000 kilometers

  • *The Sun: 1 AU (149,600,000 km)

  • *Alpha Centauri (nearest star): 4.2 light years (266,000 AU)

  • *Center of the Milky Way Galaxy: 26,000 light years (1.65x109 AU)

  • As you can see, if you only use kilometers or meters, the numbers would get out of hand very fast.

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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How old is the Universe?

  • The Cosmic Calendar

    • if the entire age of the Universe were one calendar year

    • one month would be approximately 1 billion real years

Big Bang Jan

Milkyway forms Feb

Earth forms Sept 3

Rise of the dinosaurs Dec 26!!

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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How old is the Universe?

Dec 31 11:58pm Modern humans evolve

11s ago, pyramids built

1s ago:- Kepler /Galileo

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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Spaceship Earth or “lets get some perspective on motion….”

Our goals for learning:

  • Describe the basic motions of “spaceship Earth.”

  • How do we know that the Universe is expanding?

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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A Universe in motion

  • Contrary to our perception, we are not “sitting still.”

  • We are moving with the Earth.

    • and not just in one direction

The Earth rotates around it’s axis once every day!

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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The Earth orbits around the Sun once every year!

The Earth’s axis is tilted by 23.5º!

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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Our Sun moves relative to the other stars in the local Solar neighborhood!

Our Sun and the stars of the local Solar neighborhood orbit around the center of the Milky Way Galaxy every 230 million years!

Equates to 800,000 km/hour

© 2004 Pearson Education Inc., publishing as Addison-Wesley


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