Introduction to the Universe
Chapter 1
Some review material that you’ve probably seen before…
The Montillation of Traxoline
It is very important that you learn about
traxoline. Traxoline is a new form of zionter. It
is montilled in Ceristanna. The Ceristannians
gristerlate large amounts of fevon and then
brachter it to quasel traxoline. Traxoline may
well be one of our most lukized snezlaus in the
future because of our zionter lescelidge.
Traxoline Comprehension
It is very important that you learn about traxoline. Traxoline is
a new form of zionter. It is montilled in Ceristanna. The
Ceristannians gristerlate large amounts of fevon and then
brachter it to quasel traxoline. Traxoline may well be one of
our most lukized snezlaus in the future because of our zionter
lescelidge.
Directions: Answer the following questions.
If you don’t remember this AND
1. What is traxoline?
you’re having trouble with these
2. Where is traxoline montilled? very simple questions, you
probably won’t succeed in this
3. How is traxoline quaselled?
class…
4. Why is it important to know
about traxoline?
KIDDING!
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 vocabulary
• 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:
– our location in the universe,
– The things in the universe, and
– the the overall universe.
Topics in this presentation
•
•
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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. (aka. Mega or M) 1 million sec = 11.6 days
• 1 billion = 1,000,000,000 (aka. Giga or G). 1 giga-sec =
– 31.8 years.
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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
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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)
Today, astronomers can detect a galaxy that
is 10 billion light-years away.
1. True
2. False
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Can astronomers detect something 20
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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)?
1. Nearby
2. 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 11/5/2009, the furthest object ever seen by
astronomers* is a Gamma Ray Burst (giant star
explosion, “hypernova”) 13.035 billion light years
away. The light arrived on Earth on April 23, 2009.
– Dist measured by its Doppler redshift = 8.2 (see chapter 5)
– GRB occurred only 630 million years after the Big
Bang. Probably a 1st generation HUGE star death.
• Gigantic early generation stars make a GRB, which are
probably a hypernova (big supernova with powerful jets at
the north and poles)
• “Merely” large or newer stars “only” make a supernova
• We also see LIGHT leftover from the Big Bang,
emitted only 380,000 yrs after the Big Bang.
*One of my former roommates, Edo Berger, is one of the astronomers who made this discovery!
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.
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. But 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!
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H, He, etc (elements) are only 10% of stuff
Dark matter is 90% of stuff
We know dark matter is 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 massenergy. Matter/stuff (including “dark”) only is 27%.
Summary:
Universe’s mass-energy composition
Composition of the Universe
0.6%
4.4%
22%
Dark Energy
Dark Matter
"Normal Stuff" (baryons)
Neutrinos
73%
What grade do astronomers get for
understanding the universe?
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Normal (NOT dark) matter
• Everything you know about is normal matter,
(baryonic) 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?
1. Increasing
2. Decreasing
3. Staying the Same
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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?
1. Yes
2. No
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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 make one
circle around the Earth’s axis?
1. Yes
2. No
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Galaxies outside the Local Group
are moving:
1. Towards us
2. Away from us
3. Randomly towards & away
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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 _________”?
1. Further apart
2. Bigger
3. Both further apart and bigger
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Have you read chapter 1 yet?
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2. No
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Expanding universe
• Expansion refers to empty space between galaxies
– Objects don’t grow because …
• Gravity and other forces hold THINGS together.
– Examples: Stars, galaxies, planets, people.
• We see galaxies moving away
• Draw a picture on chalkboard – space expands
• 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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Composition
Speed
Distance
Brightness
Luminosity
Number of stars
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Is the composition of the universe
changing?
1. Yes
2. No
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(Question asked by a student) Stars that were
made of the MOST Hydrogen and Helium are:
1. Born recently
2. Born long ago
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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