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The Scale of the Cosmos “The Universe is a big place.” Really big. Really, really big! You might be wondering… How big is it?!

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Page 1: The Scale of the Cosmos “ The Universe is a big place. ” “ The Universe is a big place. ” Really big. Really big. Really, really big! Really, really big!

The Scale of the Cosmos

“The Universe is a big place.”

Really big. Really, really big! You might be

wondering… How big is it?!

Page 2: The Scale of the Cosmos “ The Universe is a big place. ” “ The Universe is a big place. ” Really big. Really big. Really, really big! Really, really big!

We’ll get to that…

But first, let’s list some essential questions for

Chapter 1.

Page 3: The Scale of the Cosmos “ The Universe is a big place. ” “ The Universe is a big place. ” Really big. Really big. Really, really big! Really, really big!

Essential Questions

Where and when are you in the universe?

How do astronomers express distance?

Which objects are big and which are small?

How do scientists know about nature?

Page 4: The Scale of the Cosmos “ The Universe is a big place. ” “ The Universe is a big place. ” Really big. Really big. Really, really big! Really, really big!

Starting at home The Earth The planet Earth is

about 12,800 km across. (That’s about 8,000 miles for you non-metric folks.)

How do you convert from km to miles?

Page 5: The Scale of the Cosmos “ The Universe is a big place. ” “ The Universe is a big place. ” Really big. Really big. Really, really big! Really, really big!

The Solar System

The solar system contains:

The Sun The 8 Planets Dwarf Planets,

Asteroids, Comets, dust and gas.

Page 6: The Scale of the Cosmos “ The Universe is a big place. ” “ The Universe is a big place. ” Really big. Really big. Really, really big! Really, really big!

3rd Rock from the Sun The Earth is the

3rd rocky (terrestrial) planet from the Sun.

The average distance from the Earth to the Sun is 150,000,000 km.

This is called an Astronomical Unit (AU for short).

Page 7: The Scale of the Cosmos “ The Universe is a big place. ” “ The Universe is a big place. ” Really big. Really big. Really, really big! Really, really big!

Table of Solar System ObjectsObject Distance in

kmDistance in AU

Mercury

Venus

Earth 150,000,000 1 AU

Mars

Asteroid Belt

Jupiter

Saturn

Uranus

Neptune

Pluto

Page 8: The Scale of the Cosmos “ The Universe is a big place. ” “ The Universe is a big place. ” Really big. Really big. Really, really big! Really, really big!

Scientific Notation

Did you notice anything about the large numbers you used to fill in the table on the last slide?

A shorthand notation that astronomers and all scientists use for writing large numbers is scientific notation.

Why don’t you practice with this now…

Page 9: The Scale of the Cosmos “ The Universe is a big place. ” “ The Universe is a big place. ” Really big. Really big. Really, really big! Really, really big!

Light Years

A light year is an even larger unit of distance than an astronomical unit.

A light year is the distance light travels in one year. It is about 10 trillion km.

That’s 10,000,000,000,000 kilometers. Convert that to scientific notation and to miles please…

Page 10: The Scale of the Cosmos “ The Universe is a big place. ” “ The Universe is a big place. ” Really big. Really big. Really, really big! Really, really big!

Hey, how fast does light travel anyway?

Light travels at 300,000 km/s! That’s how fast in miles per sec?

In one second light can travel around the Earth 7.5 times! It’s fast!

That being said, the universe is a big place…and light takes about 8 minutes to get from the Sun to the Earth.

Page 11: The Scale of the Cosmos “ The Universe is a big place. ” “ The Universe is a big place. ” Really big. Really big. Really, really big! Really, really big!

How long does it take for sunlight to reach each planet

in our solar system? Dig out your solar system chart

and work with a partner and/or teacher to add a column entitled: “Time for Sunlight.”

Check you answers when you are done.

Page 12: The Scale of the Cosmos “ The Universe is a big place. ” “ The Universe is a big place. ” Really big. Really big. Really, really big! Really, really big!

The nearest star…

How far is the nearest star? 1 AU of course, but seriously, the next

nearest? About 4.2 lightyears (ly). The triple

star system Alpha Centauri.

Page 13: The Scale of the Cosmos “ The Universe is a big place. ” “ The Universe is a big place. ” Really big. Really big. Really, really big! Really, really big!

Definitions:

Planet—a small non-luminous body that shines by reflected light (non-technical definition)

Star—a self luminous sphere of hot gas with a core undergoing nuclear fusion

Galaxy–a great cloud of stars, gas, and dust bound together by gravity (they can contain >100 billion stars)

Page 14: The Scale of the Cosmos “ The Universe is a big place. ” “ The Universe is a big place. ” Really big. Really big. Really, really big! Really, really big!

The Milky Way

Page 15: The Scale of the Cosmos “ The Universe is a big place. ” “ The Universe is a big place. ” Really big. Really big. Really, really big! Really, really big!

The Milky Way

We live in a spiral shaped galaxy called the Milky Way (if you’ve ever seen it you know why).

It’s about 80,000 ly across and contains about 100 billion stars!

Our solar system is about 2/3 of the way out in one of the spiral arms.

Page 16: The Scale of the Cosmos “ The Universe is a big place. ” “ The Universe is a big place. ” Really big. Really big. Really, really big! Really, really big!

The “Pinwheel” Galaxy M31

Page 17: The Scale of the Cosmos “ The Universe is a big place. ” “ The Universe is a big place. ” Really big. Really big. Really, really big! Really, really big!

Structures larger than Galaxies:

Only 100 years ago, astronomers thought the Milky Way was the entire universe. Now we know there are many more galaxies.

The nearest galaxy to our own is called the Andromeda Galaxy and is the only one visible to the unaided eye.

Page 18: The Scale of the Cosmos “ The Universe is a big place. ” “ The Universe is a big place. ” Really big. Really big. Really, really big! Really, really big!

The Andromeda Galaxy

Page 19: The Scale of the Cosmos “ The Universe is a big place. ” “ The Universe is a big place. ” Really big. Really big. Really, really big! Really, really big!

The Local Group Andromeda is

about 2.5 million ly away and is (along with the Milky Way) a member of about few dozen galaxies called “The Local Group.”

Ingenious name, don’t you think?!

Page 20: The Scale of the Cosmos “ The Universe is a big place. ” “ The Universe is a big place. ” Really big. Really big. Really, really big! Really, really big!

Galaxy SuperClusters The Local Group is a member of a much

larger group called a cluster or supercluster. The Virgo Supercluster to be exact!

Page 21: The Scale of the Cosmos “ The Universe is a big place. ” “ The Universe is a big place. ” Really big. Really big. Really, really big! Really, really big!

One more note on units of distance…

There is another unit of distance astronomers sometimes use based on the Earth’s orbital diameter and an angle measurement of 1 second (3600 hundred seconds in a degree).

This measurement is called a parsec (pc) and is about 3.26 lightyears.

Page 22: The Scale of the Cosmos “ The Universe is a big place. ” “ The Universe is a big place. ” Really big. Really big. Really, really big! Really, really big!