A Century of Cosmic Surprises Jim Lochner (USRA/GSFC) Barb Mattson (Adnet/GSFC)

I.Who’s Your Neighbor? II.The “State” of the Universe III.Trouble with the Big Bang IV.Determining the Fate of the Universe V.Dark Energy and Beyond Materials Drawn from Cosmic Times (More on that later …)

The year is 1919… What’s going on? What’s going on in science? What is your view of the Universe?  Unchanging/static  Infinite  Ageless

Understanding the Nature of the Universe Our understanding of the nature of the Universe has changed as our questions and technology have changed. What are some questions we might ask ?

Understanding the Nature of the Universe Our understanding of the nature of the Universe has changed as our questions and technology have changed. What are some questions we might ask ? What are the tools we might use?

Section I Who’s your neighbor?

How Far Away are “Spiral Nebulae”? In 1920, astronomers pondered the distance to the “spiral nebulae.”  Harlow Shapley and Heber Curtis debated whether they were within our own Galaxy or outside our Galaxy.  The question was settled when Edwin Hubble determined the distance to Andromeda Galaxy.

Tools for answering “How Far Away are Spiral Nebulae?” How do astronomers use them to determine distances? What are Cepheid variables?

Tools for answering “How Far Away are Spiral Nebulae?” Cepheid Variables These stars vary in brightness due to pulsations.

Tools for answering “How Far Away are Spiral Nebulae?” Cepheid Variables The period of brightness variation is related to star’s intrinsic luminosity. By measuring the observed luminosity, and knowing intrinsic luminosity we can determine distance L o µ L i / r 2

Tools for answering “How Far Away are Spiral Nebulae?” 100” Telescope at Mt Wilson, CA (1917)  provided the added aperture and resolution to resolve the stars. Hubble determined distance to Andromeda to be 800,000 LY (actual distance is 2.8 million LY)

Vesto Slipher showed the “nebulae” were red-shifted.  i.e. moving very fast away from us. Hubble put together the redshifts with their distances. Universe is expanding! Consequence of asking “How Far Away are Spiral Nebulae?”

Lets Pause for Questions

Scientists Game

Unsung Heroes: Lesser Known Astronomers Objectives: The students identify and describe unfamiliar scientist “heroes” that contributed to the field of astronomy.

How would you use this in your classroom?

Section II The ‘State’ of the Universe

Is Universe a “Steady State” or Did it originate from a “Big Bang?” Steady State Theory: As universe expands, matter is created  Creation rate – a few hundred atoms per year per galaxy Big Bang: running expansion backwards leads us to a point of high density and high temperature from which universe originated  Create everything all at once

Reading Strategies Use one of the reading strategies to understand the CT article “Origin of Everything”

Reading Strategy: Reciprocal Teaching Pair up Both partners read the same paragraph (aloud or to yourselves) One partner summarizes the paragraph for the other The other partner “checks and perfects” – state what you agree with, question parts you don’t understand, add more information, connect ideas Read the next paragraph and switch roles Continue with each paragraph until you’ve read and understood the article 20 Do Paragraphs 2, 4, 5, 6, 7

Summarize Articles What do you know about the steady state theory from the readings? What do you know about the evolutionary theory of the universe from the readings?

Steady State Universe Fred Hoyle, Hermann Bondi and Thomas Gold see the movie The Dead of Night, in which the end of the story circles back to its beginning.  Unchanging situations need not be static  New matter can be created spontaneously as the universe expands (a few hundred atoms per year per galaxy)  Expansion of universe and creation of new matter balanced via a negative energy.  The universe is constant in its overall density

Evolutionary Universe Starting from earlier work, George Gamow & Ralph Alpher worked out the conditions in the early universe  Universe is expanding from a state of high density and pressure.  Hydrogen & Helium were formed as universe cooled.  There should be left over a background radiation with a temperature of ~ 5 Kelvin  Hoyle scoffed at this theory and coined the term “Big Bang”

Inference vs. Observation How would you define an observation? How would you define an inference?

The Evidence is “Clear”! Bowl of Evidence Scientists sort through theories by examining evidence and making inferences

How would you use this in your classroom?

Is Universe a “Steady State” or Did it originate from a “Big Bang?” Resolution of Steady State vs Big Bang won’t come until the mid-to-late 1960s. But as a competing theory, the Steady State provides the impetus to make observations to test the theories.

Lets Pause for Questions

Tool for Determining “Steady State” vs. “Big Bang” Penzias and Wilson were using a 20-foot horn detector to make radio observations of the Milky Way. Effort to reduce noise in the detector left them with a 3 K residual. But they didn’t know its origin.

Tool for Determining “Steady State” vs. “Big Bang” Peebles and Dicke (Princeton) had just calculated an estimate for the temperature of the residual background temperature, and found it was detectable in the microwave region. P & D were convinced P & W had found it. This solved the Steady State vs Big Bang question. Isn’t it time for a break?!

Explore the CMB – balloon model #1 Take balloon and draw a line connecting two dots and a wavy line, as pictured The “dots” represent galaxies. The “wave” represents the wavelength of light emitted in the Big Bang.

Cosmic Times Posters, Newsletters, Teacher Guide, Lessons

Themes in Cosmic Times Our understanding of the Expansion of the Universe Nature of Supernovae The size and scale of the Universe A number of other themes also appear.  Lesser known astronomers  Impact of improved technology

Online Resources Recently introduced online editions of each of the Cosmic Times issues Expanded teacher resources  Teacher’s Guide to the articles  Master downloads page  “Keyword clouds” to find materials tied to different keywords (such as “redshift” or “big bang”)  Sort-able table of the lesson plans

Detour Misbehaving Galaxies

Why are Galaxies Misbehaving? In the ‘60s, researchers start to “weigh” galaxies They begin to find that there must be “unseen” matter to account for their observations Not the first glimpse at unseen matter - Zwicky ran into trouble when he measured mass in clusters in the ‘30s

Tools for determining misbehavior in Galaxies Cosmological Motion Rotational Motion Use redshift to map the rotation of a galaxy. Here we are interested in the rotational redshift.

Tools for determining misbehavior in Galaxies Use redshift to map the rotation of a galaxy. Here we are interested in the rotational redshift. Create a map by determining the redshift of several slices of the galaxy.

Tools for determining misbehavior in Galaxies Use redshift to map the rotation of a galaxy. Here we are interested in the rotational redshift. Create a map by determining the redshift of several slices of the galaxy. Compare the resulting rotation curve to that expected if all of the mass were visible as luminous matter

Tornados & Galaxies Tornado image from Florencia Guedes on Flickr

Doppler shift

Doppler mapping

Section III Trouble with the Big Bang

Why do different parts of the Universe all have the same temperature? Horizon problem  Parts of the Universe that should not have had time to “talk” to each other since the Big Bang all have the same temperature Problem with Big Bang theory! Early Universe Causally disconnected regions Now Observable Universe

Tool for understanding why different parts of the Universe have the same temperature Inflation Theory solves this  The Universe we see all started in a small, “causally-connected” region  This region underwent an exponential expansion  The detailed mechanism expansion is not currently understood  However, inflationary theory makes predictions that have been shown to be correct Early Universe Causally disconnected regions Now Observable Universe Without Inflation With Inflation

What are characteristics of the Cosmic Microwave Background? The CMB represents the radiation nearest to the time of the Big Bang that we can see Astronomers need to study the CMB to understand the nature of our Universe

Tool for exploring the characteristics of the CMB The Cosmic Background Explorer is launched in 1989 to examine the CMB in finer detail

Tool for exploring the characteristics of the CMB The first result was the spectrum of the CMB Which was a perfect black body (the error bars are contained in the line thickness!) Almost too perfect!

Consequence of exploring the characteristics of the CMB Astronomers hold their breath for two years…  Some “lumps” are needed in the CMB to act as seeds of the structure we see in the Universe today - galaxy clusters, galaxies, stars, everything  If the lumps were not detected by the limit of COBE’s abilities, the Big Bang and Inflationary theories would be in trouble

Consequence of exploring the characteristics of the CMB In 1993, NASA’s COBE mission finds “lumps” in the CMB! These “lumps” are tiny, consisting of changes on the order of 1 part in But they are enough to produce the structure we see.

Why does the CMB need anisotropies? We’ve seen that the CMB is  isotropic – observed in all directions  smooth – similar in all directions What does our Universe look like today?  Lumpy/structured, not smooth!  Problem!! We need *some* lumpiness – some “anisotropies”

Let’s Pause for Questions

CMB anisotropy

Explore CMB anisotropy – balloon model #2 Go back to your balloon, turn it to the other side and draw two regions. Imagine that gray (or marker color) is one temperature, pink (or balloon color) another temperature. Region 1 Region 2

How would you use this in your classroom?

Section IV Determining the Fate of the Universe

What is the fate of our Universe? By the mid-90s, cosmologists thought that they had only to “fill in the details” Remaining questions:  Will the expansion continue forever, or will Universe eventually collapse back on itself?  What is the mass-density of the Universe (which would answer the above)?

Cosmology’s End? Things may not be what they seem. When we see odd behavior, we look more carefully at what’s going on.

How Fast is the Expansion Slowing Down? Saul Perlmutter (UC Berkeley) wanted to determine the deceleration rate of the expansion. Amount of deceleration depends on average mass density.  So we’d be “weighing the universe” This would lead to determining the fate of the universe – expand forever, or contract.

Tools for Determining “How Fast is the Expansion Slowing Down?” Compare a galaxy’s measured distance with its redshift. Get distance by comparing observed and intrinsic luminosity of an object in the galaxy. Enter Supernovae! (But we need a special kind of supernova)

A dying star becomes a white dwarf. 1. Create a White Dwarf

The white dwarf strips gas from its stellar companion…. 2. Dump more mass onto it

….and uses it to become a hydrogen bomb. Bang! 3. Until it explodes

The explosion is as bright as an entire galaxy of stars…. …..and can be seen in galaxies across the universe. 4. Observe it in a distant galaxy 12

5. Compare its distance to its velocity Distance via Redshift Distance (via SN Ia) Place the next three points (with increasing distance) on the graph, if the expansion is slowing down. A B C 11

5. Compare its distance to its velocity These supernovae are more distant than expected. Space-time has expanded more than expected. Distance (via SN Ia) More distant galaxies recede from us more rapidly. 10 Distance via Redshift

Let’s Pause for Questions 9

History of the Universe’s Expansion 8

Section V Dark Energy and Beyond Whew! Last section!

Dark Energy Comprises 73% of Universe Dark Energy 73% Dark Matter 23% “Normal Matter” 4% 6

Dark Energy is an Unfinished Story WE DON’T KNOW WHAT IT IS! But this story of our understanding of the nature of the universe illustrates the process of science.  Science is alive and on-going.  Our ideas change as the data changes.  Scientific debate differs from social/political debate.  Progress in science results from both individual and group efforts. 5

The year is 2010… What’s going on? What’s going on in science? What is your view of the Universe?  Changing  Finite  13.7 Billion Years Old 4

Century Timeline Compare the Cosmic Times timeline with events in: Other Science Arts/Entertainment/Culture World History/Politics Opportunities for cross-disciplinary collaboration 3

Cosmic Times Timeline Henrietta Leavitt determines Cepheid Period-Luminosity relationship Einstein’s Theory of Gravity Hubble’s Law “Super-nova” identified by Baade & Zwicky Alpher & Gamow discuss nucleosynthesis Baade recalibrates Cepheid P-L relationship Penzias & Wilson discover CMB Vera Rubin makes case for Dark Matter Guth proposes Cosmic Inflation COBE measures anisotropies in CMB Dark Energy discovered WMAP refines anisotropies in CMB 2

Cosmic Times Posters, Newsletters, Teacher’s Resources, Lessons & Online-Edition all on our website: Also on Twitter & Facebook (Cosmic Times group) Yipee! We’re done!