ASTRO 101 Principles of Astronomy

Instructor: Jerome A. Orosz (rhymes with “boris”) Contact : Telephone: WWW: Office: Physics 241, hours T TH 2:00-3:20

Text: “Investigating Astronomy, A Conceptual View of the Universe, Second Edition” by Timothy F. Slater & Roger A. Freedman

Course WWW Page Note the underline: … ast101_fall2014.html … Also check out Nick Strobel’s Astronomy Notes:

Syllabus: Prerequisites Course Materials Homework, Exams, Grades Conduct in class Safety

Why Take this Class?

We want to understand and appreciate everything in the Universe!

Since the earliest recorded times, people have looked up at the sky and wondered about the things they saw. Most early cultures had extensive mythologies relating to the workings of the Earth and things in the sky.

We live in interesting times. We are in a position to investigate and answer many basic and profound questions about our world and beyond...

Here are a few representative object categories we can observe

We live in interesting times. We are in a position to investigate and answer many basic and profound questions about our world and beyond. In this course we will survey such topics as…

The Earth Why are there seasons on Earth? What causes the day/night cycle? How old is the Earth?

The Sun What is it? How does it shine? How old is it? Will it go on forever, or will it “die”?

The Moon What is it? Where did it come from? Is there life on it?

The Solar System Planets What are they? What are they like? Where did they come from? Do they have life?

The Stars What are they? Why are some stars red and other ones blue? Why do they twinkle? How old are they? Will they last forever, or will they “die”?

Galaxies What are galaxies? How big are they? What is the Milky Way? Is it a typical galaxy?

Strange Objects What is a White Dwarf? What is a Neutron Star? What is a Black Hole? What is a Quasar, and how do they work? What is a Nova explosion? What is a Supernova explosion?

Deep Questions How big is the Universe?

Deep Questions How big is the Universe? Does the Universe have a beginning and an end? If so, how old is it?

Deep Questions How big is the Universe? Does the Universe have a beginning and an end? If so, how old is it? The meaning of infinity…

The Meaning of Infinity Suppose the universe is infinite in size and in age:

The Meaning of Infinity Suppose the universe is infinite in size and in age: –Then everything that is possible to happen has already happened, an infinite number of times.

The Meaning of Infinity Suppose the universe is infinite in size and in age: –Then everything that is possible to happen has already happened, an infinite number of times. –Therefore there are exact copies of you, me this classroom, this earth, etc. somewhere out there.

The Meaning of Infinity Suppose the universe is infinite in size and in age: –Then everything that is possible to happen has already happened, an infinite number of times. –Therefore there are exact copies of you, me this classroom, this earth, etc. somewhere out there. –There are also an infinite number of near copies of you out there, e.g. someone like you but with different hair, more money, etc.

Deep Questions How big is the Universe? Does the Universe have a beginning and an end? If so, how old is it? The meaning of infinity…

Deep Questions How big is the Universe? Does the Universe have a beginning and an end? If so, how old is it? The meaning of infinity… Is there other life out there?

Deep Questions How big is the Universe? Does the Universe have a beginning and an end? If so, how old is it? The meaning of infinity… Is there other life out there? While your friends are thinking about what socks to wear, we will ponder these and other questions!

Course Philosophy We will emphasize understanding concepts, not just memorizing jargon. We will spend a great deal of time discussing how we know what we know, e.g. the use of the Scientific Method. A good understanding of the Scientific Method will benefit you in situations beyond this class, so the effort is worthwhile.

Next: Math Review Introduction to the Sky

Math Review Powers of 10 and a sense of scale: – –

Math Review Powers of 10 and a sense of scale:

Math Review What is a googol?

A googol is 10,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000 (i.e. a 1 followed by 100 zeros)googol

Scientific Notation In Astronomy, and elsewhere, large numbers are often needed. A more compact notation is needed, usually called Scientific Notation. It is based on powers of 10.

Powers of = 10 x 10 = = 10 x 10 x 10 = = 10 x 10 x 10 x 10 = 10,000 etc…

Powers of = 10 x 10 = = 10 x 10 x 10 = = 10 x 10 x 10 x 10 = 10,000 etc… 100 = = ,000 = 10 4

10,000,000,000,000,000,000,000, 000,000,000,000,000,000,000, 000,000,000,000,000,000,000, 000,000,000,000,000,000,000, 000,000,000,000,000 = a googol = googol

To write out a number given as a power of 10, the number of zeros is the given by the exponent. Example: 10 4 = 10,000

To write out a long number (consisting of a 1 followed by zeros) as a power of 10, the exponent is the number of zeros. Example 100,000 = 10 5

Some Rules for Powers of 10 To multiply two different powers of 10, add the exponents:  10 2 x 10 3 = = 10 5  10 3 x 10 3 = 10 6 To divide two different powers of 10, subtract the exponents:  10 4  10 2 = = 10 2  10 5  10 3 = = 10 2

10 5 = 100, = 10, = = = = ?

10 5 = 100, = 10, = = = = 1

10 5 = 100, = 10, = = = = = ?

10 5 = 100, = 10, = = = = = 1/10 = 0.1

10 5 = 100, = 10, = = = = = 1/10 = = ?

10 5 = 100, = 10, = = = = = 1/10 = = 1/100 = 0.01

What about other numbers, like 6,000,000?

6,000,000 = 6 x 1,000,000

6,000,000 = 6 x 1,000,000 = 6 x 10 6

6,000,000 = 6 x 1,000,000 = 6 x ,200,000 = 1.2 x 1,000,000 = 1.2 x 10 6

How do we say it?

10 3 = 1,000 = one thousand

How do we say it? 10 3 = 1,000 = one thousand 10 6 = 1,000,000 = one million

How do we say it? 10 3 = 1,000 = one thousand 10 6 = 1,000,000 = one million 10 9 = 1,000,000,000 = one billion

How do we say it? 10 3 = 1,000 = one thousand 10 6 = 1,000,000 = one million 10 9 = 1,000,000,000 = one billion = 1,000,000,000,000 = one trillion

How do we say it? 10 3 = 1,000 = one thousand 10 6 = 1,000,000 = one million 10 9 = 1,000,000,000 = one billion = 1,000,000,000,000 = one trillion = 1,000,000,000,000,000 = one quadrillion

How do we say it? 10 3 = 1,000 = one thousand 10 6 = 1,000,000 = one million 10 9 = 1,000,000,000 = one billion = 1,000,000,000,000 = one trillion = 1,000,000,000,000,000 = one quadrillion Many numbers in Astronomy have no common names, and are written in scientific notation.

How do we imagine it?

Example: what is my age, in seconds?

How do we imagine it? Example: what is my age, in seconds? (a) about 1 million seconds

How do we imagine it? Example: what is my age, in seconds? (a)about 1 million seconds (b)about 1 billion seconds

How do we imagine it? Example: what is my age, in seconds? (a)about 1 million seconds (b)about 1 billion seconds (c)about 1 trillion seconds

How do we imagine it? Example: what is my age, in seconds? (a)about 1 million seconds (b)about 1 billion seconds (c)about 1 trillion seconds (d)about 1 quadrillion seconds

How do we imagine it? Example: what is my age, in seconds? (a)about 1 million seconds (b)about 1 billion seconds (c)about 1 trillion seconds (d)about 1 quadrillion seconds Hint: I am 47 years old.

Well, there are 60 seconds in one minute, 60 minutes in one hour, 24 hours in one day, and days in one year.

Well, there are 60 seconds in one minute, 60 minutes in one hour, 24 hours in one day, and days in one year. So, age = 47 x 60 x 60 x 24 x = x 10 9 seconds

Example: what is my age, in seconds? (a)about 1 million seconds (b)about 1 billion seconds (c)about 1 trillion seconds (d)about 1 quadrillion seconds Hint: I am 47 years old.

Example: what is my age, in seconds? (a)about 1 million seconds (b)about 1 billion seconds (c)about 1 trillion seconds (d)about 1 quadrillion seconds Hint: I am 47 years old. 1 billion sec = 31 yr d + 7 hr + 46 min

Which makes more sense?

Which makes more sense? “I am 1.48 billion seconds old.”

Which makes more sense? “I am 1.48 billion seconds old.” “I am 47 years old.”

Which makes more sense? “I am 1.48 billion seconds old.” “I am 47 years old.” “My neighbor Francis was 3.13x10 9 seconds old.”

Which makes more sense? “I am 1.48 billion seconds old.” “I am 47 years old.” “My neighbor Francis was 3.13x10 9 seconds old.” “Francis was 99 years old.”

Where possible, scale things to sensible units:

Where possible, scale things to sensible units: Example: “This black hole has a mass 7 times larger than the Sun’s mass.”

Where possible, scale things to sensible units: Example: “This black hole has a mass 7 times larger than the Sun’s mass.” “This black hole has a mass of 1.39x10 34 grams.”

Next: The Scientific Method