Introduction to the UniverseChapter 1

Traxoline

• Did we discuss the montillation of traxoline already?

Related Goals

• Appreciating science in general, and astronomy in specific.

• Understanding how knowledge is gained and be critical of what you see and hear. You will begin to ask “How can we test that?” when forming hypotheses or “How do we know that?” when reading new information.

• Developing a working knowledge of the scientific method and how to apply it to real world situations.

• Critically analyzing and evaluating information, scientific or otherwise

Related Outcomes

• Learn some simple astronomical nomenclature/terminology

• Learn about some problems astronomers and astrophysicists are trying to solve, and understand the methods scientists are using to try to solve these problems.

• Develop a sense of what scientists know about the overall universe, its constituents, and our location

Topics in this presentation

• Astronomical numbers• Light travel time• Composition of universe• Why the composition changes

– What causes the change?• Sizes, distances, and ages• Motions• Expanding universe, how we measure age

Learning Objectives

• Know some ages & distances– Distinguish different types of large quantities

• Understand the consequences of light traveling over large distances

Astronomical numbers

• 1 million = 1,000,000 = 106. 1 million sec = 11.6 days• 1 billion = 1,000,000,000 = 109 (aka. Giga or G). 1 giga-sec =

– 31.8 years. • 1 light sec = distance light travels in …• = 300,000 km = 186,000 miles. Almost to the Moon.• 1 light year = distance light travels in one year• TRIVIA: 1 light year = 6 trillion miles.• Nearest star to Sun = 4.3 light-years away.• The Sun, all 8 planets are about 4.6 Gyr old.

– How many years is that?– Distance to Sun? 3 answers. __ Light __, ____ miles, __AU

• Universe & everything in it is 13.7 Gyr old (some things weren’t born at the beginning, so are younger)

Calif. School Science Standards for Earth’s age & life development

• From California Science Standards, grade 6– Students know that evidence from geologic layers and

radioactive dating indicates Earth is approximately 4.6 billion years old and that life on this planet has existed for more than 3 billion years.

– Newest evidence: life probably started 3.5 billion years ago, maybe even earlier (4 Gyr?).

• And from the high school standards:– Students know the evidence from Earth and moon

rocks indicates that the solar system was formed from a nebular cloud of dust and gas approximately 4.6 billion years ago.

• The standards should include evidence from meteorites (space rocks that landed on Earth)

Astronomers can detect a galaxy that is 10 billion light-years away right now.

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Can astronomers detect something 20 billion light years away, right now?

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Will it ever be possible to see something 20 billion LY away?

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Finding baby & senior citizen galaxies

Talk to your neighbor for 1 minute and answer these:• Where would astronomers need to look to take a picture

of galaxies in their earliest stages of life (babies)?– Hint given after 30 seconds. DV: the hint is Unogen.

• Where would we look to take pictures of galaxies in their later stages (senior citizens)?

Where would astronomers need to look to take a picture of galaxies in their earliest

stages of life (babies)?

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0 1. Nearby2. Far away

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Light years and observations• Like letter through post office:

– Letters from far away take longer to arrive• We receive “ancient” letters

– Letters from Los Angeles arrive quickly• We receive “today’s” letters

• FOR MORE HELP:

• See figure 1.5 on p. 9

• Lecture Tutorial workbook “Looking at Distant Objects,” page 131.

Furthest things seen• As of 4/29/2009, the furthest object ever seen

by astronomers is a Gamma Ray Burst (giant star explosion, “hypernova”) 13.035 billion light years away. Dist measured by redshift = 8.2– Occurred only 630 million years after the Big Bang.

Probably a 1st generation HUGE star that died.• Gigantic early generation stars make a GRB, which are

probably a hypernova = big supernova with powerful jets at poles

• “Merely” large or newer stars “only” make a supernova

• We see LIGHT leftover from the Big Bang, only 380,000 yrs after the Big Bang.

California Elementary School Science Standards for atoms

• From California Science Standards, grade 5

– Students know that each element is made of one kind of atom and that the elements are organized in the periodic table by their chemical properties.

Seating Chart

• I still only know 5 (or less) student names. I need more help, in addition to the name placards that I still need you to use.

• Please fill out the seating chart being passed around.

Learning Objectives

• What is the universe composed of?• How do we know?• Is the composition changing? Why or why

not?

What the universe is made of & how we know. Part 1.

• Things in the universe:– Stars– Star leftovers such as _______________– Gas clouds (and other stuff) between stars– Galaxies (HUGE collections of stars)

• Analyzing their light (chapter 5), we discover, all of these* are made of:– Hydrogen (often gas) ~73%– Helium (often inert gas) ~25%– Everything else ~2%

• Oxygen, Carbon, Iron, Sulfur, Neon, Potassium, etc.• Gold, silver, platinum are VERY rare.

– *except not inner 4 planets. Outer planets are.

What the universe is made of & how we know. Part 2a.

• Astronomers studied motions of stars, star clusters, and gas clouds inside galaxies– Move too fast must be extra gravity inside

galaxies– Don’t see anything causing gravity– Extra gravity from invisible stuff– “Dark matter”

• Existence hypothesized in 1933, Fritz Zwicky @ CIT• Vera Rubin gathered first STRONG evidence described

above in 1970s. She’s still doing astronomy today!

What the universe is made of & how we know. Part 2b.

• Then, studying gravity, found “dark matter” in MANY other places:– Halos of galaxies– Inside & around galaxy clusters

• especially in center of clusters

• Based on gravity: there is 10 times more dark matter than regular matter!– H, He, etc (elements) are only 10% of stuff– Dark matter is 90% of stuff– We know it’s not elements– We know some properties of dark matter based on

gravity (how it clumps with elements, called “bias”)

What the universe is made of & how we know. Part 3.

• Measure how quickly universe expands.– (more on this soon)

• In 1998-99, multiple researchers discovered far away galaxies are moving faster than predicted– Discovered by seeing supernovas in distant galaxies– Confirmed by studying Cosmic Background Radiation

• Universe expands faster today than in the past• Don’t know why, “Dark energy”• Dark energy accounts for 73% of the universe’s mass-

energy. Matter/stuff (including “dark”) only is 27%.

Summary:Universe’s mass-energy composition

Composition of the Universe

73%

22%

4.4%

0.6%

Dark EnergyDark Matter"Normal Stuff" (baryons)Neutrinos

What grade do astronomers get for understanding the universe?

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Normal (not dark) matter• Everything you know about is made of a few

elements– Hydrogen, Helium, Carbon, Nitrogen, Oxygen, Gold– Periodic Table, page A-13 @ end of textbook.

• Most things are molecules: 2+ atoms– Water (H2O), Carbon dioxide (CO2)

• Science tells us right after the Big Bang, the universe only had 2 elements:– Hydrogen (75%), Helium (25%)– TINY bit of 1-2 more.

• Where did everything else come from?• Book calls it “recycling”. See pages 6-7.• Only makes up 2% of matter today. But that’s

enough to form planets like Earth, luckily.

How is the amount of elements OTHER THAN hydrogen & helium in the universe changing?

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Calif. Elementary School Science Standards for atoms & compounds

• From California Science Standards, grade 8– Students know the structure of the atom and

know it is composed of protons, neutrons, and electrons.

– Students know that compounds are formed by combining two or more different elements and that compounds have properties that are different from their constituent elements.

• And from the high school standards:– Students know the evidence indicating that all

elements with an atomic number greater than that of lithium have been formed by nuclear fusion in stars.

Learning Objectives

• Know some ages & distances– Put the ages and distances into perspective

with other, more familiar things• Understand motions on Earth, of Earth

and of the Solar System

Ages of a few things

• When things formed:– The Big Bang = 13.7 billion years ago– The Sun & Earth = 4.6 billion years ago– The Milky Way galaxy = 12-13 billion years ago

• See the calendar & discussion on page 14.

Sizes & Distances – See pages 9-14• Planet order & sizes with hands…• In the “Voyage” scale model, 10 billion:1

– Sun is the size of a large grapefruit– Earth is the size of 1mm, located 50 ft from

Sun. Real radius is ______________.– Moon is ¼ Earth’s size, located 1.5 inches

from Earth– Jupiter is …– Pluto is …– Nearest star is named …, size & dist …– Size of Milky Way is …

• Light travel times to these objects…

California Elementary School Science Standards for solar system

• From California Science Standards, grade 5– Students know the Sun, an average star, is

the central and largest body in the solar system and is composed primarily of hydrogen and helium.

– Students know the solar system includes the planet Earth, the Moon, the Sun, eight other planets and their satellites, and smaller objects, such as asteroids and comets.• Satellites = moons

California Elementary School Science Standards for solar system

• And from the high school standards:– Students know the evidence indicating that the planets

are much closer to Earth than the stars are.– Students know the Sun is a typical star and is

powered by nuclear reactions, primarily the fusion of hydrogen to form helium.

– Students know the solar system is located in an outer edge of the disc-shaped Milky Way galaxy, which spans 100,000 light years.

– Students know galaxies are made of billions of stars and comprise most of the visible mass of the universe.

• Not true anymore. Most visible mass seems to be located in the center of galaxy clusters.

Are you moving right now?

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Motions• Daily motion – Earth’s rotation once per __

– Speed varies: ___ for Santa, 1000 mph for Ecuador• Yearly motion – Earth’s revolution once per __

– Distance: 1AU = ____– Speed: average ~66,000 mph– Direction “tilted” 23.5˚ relative to rotation.

• Sun orbits Milky Way center once per 200-230 Myr

– 28,000 ly radius, speed ~500,000 mph– Studying this motion dark matter discovered

• Galaxies moving relative to each other.– Nearest galaxies get closer to us. Most move away.

Do all continents take 24 hours to spin?

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Galaxies outside the Local Group are moving:

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Learning Objectives

• Understand the nature of the “expanding universe” and how we know it’s expanding– Hubble’s Law

• Interpret expansion of universe to determine a fundamental property– “Car universe”

• Understand what we need to measure about the universe to determine its age

Expanding universe means “objects are getting _________”?

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Have you read chapter 1 yet?

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Expanding universe• Expansion refers to space between galaxies

– Objects don’t grow because …• Gravity and other forces hold THINGS together.

– Examples: Stars, galaxies, planets, people.• We see things moving away• Speed away from us depends on distance

– Objects twice as far are moving twice as fast– Objects 100x further are moving 100x faster

• This rule is now called “Hubble’s Law”• Let’s see how Hubble’s law works with cars

Car “expanding universe”• Make a chart like the one I put on the board• Car 1 is 60 miles away and travels 30 mph• Car 2 is 120 miles away. How fast is it moving if

it follows Hubble’s Law?• Car 3 is 240 miles away. How fast?• How long since Car 1 left you?• Car 2?• Car 3?• How old is the “car universe?”• This is exactly what we see with galaxies,

except the time is _________ years.

Which of the properties below do astronomers need to measure about galaxies to determine the age of the

universe? Select all that apply. DON’T VOTE UNTIL YOU’VE MADE YOUR FINAL DECISION.

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Is the composition of the universe changing?

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(Question asked by a student) Stars that were made of the MOST Hydrogen and Helium are:

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And the stars that have the LEAST?

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California Elementary School Science Standards for astronomy

• From California Science Standards, grade 8– Students know galaxies are clusters of billions of stars and may

have different shapes. – Students know that the Sun is one of many stars in the Milky

Way galaxy and that stars may differ in size, temperature, and color.

– Students know how to use astronomical units and light years as measures of distances between the Sun, stars, and Earth.

– Students know that stars are the source of light for all bright objects in outer space and that the Moon and planets shine by reflected sunlight, not by their own light.

• (technically, Moon & planets shine by scattered light)– Students know the appearance, general composition, relative position

and size, and motion of objects in the solar system, including planets, planetary satellites, comets, and asteroids.

Learning Objectives

• Know some ages & distances– Distinguish different types of large quantities– Put the ages and distances into perspective with other, more familiar things

• Understand the consequences of light traveling over large distances• What is the universe composed of?

– How do we know?– Is the composition changing? Why or why not?

• Understand motions on Earth, of Earth and of the Solar System• Understand the nature of the “expanding universe” and how we know it’s

expanding– Hubble’s Law

• Interpret expansion of universe to determine a fundamental property– “Car universe”

• Understand what we need to measure about the universe to determine its age

Summary – chapter 1

• Astronomical numbers• Light travel time• Composition of universe• Why the composition changes

– What causes the change?• Sizes, distances, and ages• Motions• Expanding universe, how we measure age