> **The Evidence is "Clear"!**

Suggested Grade Level(s): 9-12

Estimated class time: 1 class period plus time for a lesson summary

# Summary

Students consider observations and inferences about the Steady State and
Big Bang theories.

# Objectives

-   Distinguish between data collected from empirical observations and
    inference, which may or may not arise from data.

-   Compare and contrast the Steady State and Big Bang theories for the
    origin of our universe.

# National Science Standards

-   NS.9-12.1 SCIENCE AS INQUIRY

> As a result of activities in grades 9-12, all students should develop

-   Abilities necessary to do scientific inquiry

-   Understandings about scientific inquiry

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-   NS.9-12.4 EARTH AND SPACE SCIENCE

> As a result of their activities in grades 9-12, all students should
> develop an understanding of

-   Origin and evolution of the universe

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-   NS.9-12.7 HISTORY AND NATURE OF SCIENCE

> As a result of activities in grades 9-12, all students should develop
> understanding of

-   Nature of scientific knowledge

-   Historical perspectives

# Knowledge Prerequisite

Students should have read the Cosmic Times 1955 article *Origin of
Everything: Hot Bang or Ageless Universe* and be familiar with the
general ideas presented in both the Steady State and Big Bang Theories.
Spectral Red Shift due to expansion and cosmic microwave background
(CMB) are important terms in the study of cosmology. Use the Internet to
find out more about them.

Important terms:

-   Light year -- the distance light travels in one year. The light we
    are viewing now from a distance of 500 light years took 500 years to
    get here. We are "seeing" the past!

-   Interstellar reddening -- Light traveling through space from very
    distant objects is scattered by clouds of dust in space. More blue
    light is scattered than red so objects will appear more reddish than
    they actually are. Many of the blue spectral lines disappear

-   Red shift -- Objects moving away from the viewer appear to be more
    reddish because all of the wavelengths of light coming from them are
    stretched. All of the spectral lines are shifted toward the red end,
    but none disappear. See
    http://www.classzone.com/books/earth_science/terc/content/visualizations/es2802/es2802page01.cfm

# Teacher Background

Consult the sites listed here as well as k-12 student and college
astronomy texts about cosmology.

<http://map.gsfc.nasa.gov/m_uni/uni_101bb1.html>

<http://cosmology.berkeley.edu/Education/IUP/Big_Bang_Primer.html>, 
<http://www.damtp.cam.ac.uk/user/gr/public/bb_home.html>, 
<http://www.newtonphysics.on.ca/BIGBANG/Bigbang.html>, 
<http://curious.astro.cornell.edu/cosmology.php>
<http://www.answers.com/topic/cosmic-microwave-background-radiation?cat=technology>
<http://www.answers.com/topic/steady-state-theory>

# Materials

-   One set of 34 Evidence cards per pair of students (included at the
    end of this lesson plan). Note: a shorter version of the activity
    may be done using 16 cards. See the Teacher Notes on page 5)

-   Two large (about 40×80 cm) sheets of butcher paper for each pair of
    students

# Procedure:

### I. Engagement 

Set up the following scenario for your students:

> You arrive at school one morning and observe a group of your friends
> clustered in the hall. They are laughing and seem to be passing
> something around among the group. Each person looks at it for a few
> seconds, then bursts out with new peals of mirth and releases it to
> someone else who eagerly grabs it away. Is it a picture; are they
> reading something; is it some object or toy? Then you remember that
> note of passionate love you were writing to your sweetheart and
> somehow lost yesterday. When they see you, the group falls silent,
> still grinning, and quickly disperse in different directions at the
> sound of the morning bell.
>
> What has happened? Did the group read your note? Perhaps their actions
> had nothing to do with you at all. What did you actually observe? What
> might you infer from those observations? How do you find out what was
> really happening? Believe it or not, this is exactly what science is
> all about!

### II. Exploration

Explain to your students that science is the process of trying to find
out what is happening. Scientists make careful quantitative observations
of the world around them. Then they try to explain the meaning of those
observations by making inferences that lead to the design of experiments
that lead to new observations and new inferences. In the best scientific
procedure, inferences are based on direct observation. As continued
observations lead to similar inferences, scientists begin to construct a
"model" which is an idea that we think represents how the real world
works. As we collect more bits of information through observations, we
decide whether they support or refute the model we have built. Sometimes
our minds "jump to conclusions" and make inferences or even models
before we have collected enough observations.

Tell students that in this activity they will be examining statements
about two theories that try to explain our understanding of the nature
of our universe and how it began.

Have students work in partners. Hand out a set of Evidence cards to each
pair, and tell students to take turns drawing an Evidence card and
deciding if the statement describes direct evidence as an
observation/experiment or if it describes an inference or
interpretation. Have them make two piles, one for observations, and one
for inferences. If they disagree with their partner, tell them to set
the card aside until later. There are two cards labeled "Model" in each
set, have students set them aside until after they've made their two
piles.

Next ask students to reread the *Origin of Everything* article in the
1955 Cosmic Times.

While they are rereading the article, hand out the butcher paper, two
sheets to each pair of students. When they are finished reading, have
the groups label one of the large sheets "Steady State Theory" and the
other "Big Bang Theory". Ask them to chose the appropriate "Model" card
for each theory, and place it under the theory it describes.

Next, have them make two columns down each sheet with one labeled
OBSERVATION/experiment and the other labeled INFERENCE/interpretation.

Students should now go back through their stack of cards, beginning with
the stack of "observation" Evidence cards, decide with their partner
which theory the observation supports. Place the card on the appropriate
Theory sheet. Then they should do the same with their stack of
"inference" Evidence cards.

When everyone is finished, have teams of students exchange places to
examine the other team's placement of cards. If they disagree on any of
the cards, they should discuss the matter among the four of them and try
to come to a consensus. They should also try to resolve any cards they
had set aside previously. Blank cards are available if students feel
that any piece of evidence belongs in more than one place.

### III. Explanation

Remind the students that the most reliable scientific explanations are
based on observation and experiment. Inferences and interpretations must
ultimately be based on actual data. Ask students as they examine their
Theory sheets, which one contains more examples of observations and
experimental data? Which theory is supported mostly by conjecture and
"guessing"? Do they have enough information to prove either of these
Theories?

### IV. Evaluation

You may want to display the class results on the board and discuss any
which caused disagreement. Have students return to their seats and write
a summary of the theory they feel has the most reliable evidence
supporting it and why.

You may want to conclude by returning to the scenario at the beginning
of class, telling students:

> Later in the day one of your friends shows you a photograph of his
> little brother trying to paint their cat with whipped cream. The
> expression on the cat's face indicates disapproval while the child's
> shows deep concentration. You laugh.... could this be what the group
> was looking at earlier? Are you sure?

**Teacher notes:**

Some of the information on the Evidence cards may be very strange to the
students and they may not totally understand the statements. However you
can guide them to make a list of words that are more likely to represent
inference and those words that indicate actual observations. For
instance could, might, suggest, should, predicts, ought to be,
theoretical are all terms which would be appropriate for inferences.
Specific dates, records of data from specific experiments and numerical
records indicate observations. The term empirical refers to actual data
from an observation. The most important lesson to be learned from this
activity is that good science is experimentally based. Inferences are
valuable evidence only if they are theoretical explanations of actual
data. The Steady State theory lost most of its support with the
prediction and discovery of the cosmic microwave background radiation in
1965. Those who supported it based most of their belief on inferences
that had little data to support them. Although the hot Big Bang model
has been successful in describing most of the observations we have
recorded so far, there are unanswered questions. Refer to
<http://www.damtp.cam.ac.uk/user/gr/public/bb_problems.html>

The final explanation of the origin of the universe is yet to come.

Results may vary:

-   (For a shorter version, use cards
    3,9,5,6,7,10,11,12,8,24,26,16,27,17,20,25)

-   Steady State observations: 2, 3, 9

-   Steady State Inferences: 1,4,5,6,7,10,11,12,13,14,15

-   The observations do not lead to any of the inferences, but the
    information that Hoyle wrote more science fiction that science might
    suggest a pattern of thinking which was comfortable with "poetic
    license"

-   Big Bang observations 2, 18, 19 lead to inference 21 that the
    universe does show difference through time.

-   Big Bang observations 8, 23, 24 lead to inference 26 that some of
    the low mass elements could only be produced during such a violent
    event.

-   Big Bang observations 22 and 30 lead to inference 29 that the Big
    Bang would create a perfect Black Body radiation.

-   Big Bang observation 16 and 27 lead to inference 17 that the Cosmic
    Microwave Background indicates a Black Body.

-   Both inferences 29 and 17 lead to inference 32

-   Big Bang observation 20 leads to inference 25 that the universe is
    expanding.

-   Big Bang inference 28 is suggested by inferences 17 and 29

+-----------------------------------+-----------------------------------+
| > 1\. MODEL: We think that the    | > 2\. In 2002 the Hubble Deep     |
| > universe is ever expanding,     | > Field photograph showed the     |
| > without beginning or end. The   | > most distant, therefore oldest, |
| > universe is the same at all     | > view of the universe. It shows  |
| > points, in all directions and   | > unusual galaxies shaped like    |
| > at all times. Galaxies of all   | > tooth picks and links on a      |
| > ages are intermingled.          | > bracelet that are not similar   |
|                                   | > to galaxies that have formed    |
|                                   | > more recently.                  |
+-----------------------------------+-----------------------------------+
| > 3\. In 1946 Hoyle, Bondi, and   | > 4\. Hermann Bondi thought that  |
| > Gold saw a movie, *The Dead of  | > if the universe was expanding,  |
| > Night*, in which the ending of  | > new matter would need to be     |
| > the movie had circled back to   | > created continually in order to |
| > the beginning. Hoyle noted that | > keep density constant.          |
| > unchanging situations need not  |                                   |
| > be static.                      |                                   |
+-----------------------------------+-----------------------------------+
| > 5\. Bondi suggested that new    | > 6\. In order to both expand in  |
| > matter could be created         | > size and create new matter, a   |
| > spontaneously due to the        | > reservoir of energy is needed.  |
| > interchangeability of matter    | > To prevent the energy from      |
| > and energy.                     | > being used up, Hoyle proposed   |
|                                   | > that the energy is negative so  |
|                                   | > that expansion and creation     |
|                                   | > work against each other and     |
|                                   | > equilibrium is maintained.      |
+-----------------------------------+-----------------------------------+
| > 7\. Hoyle wrote that matter     | > 8\. Experimental chemistry has  |
| > could arise from a field        | > shown that all of the naturally |
| > generated by matter that        | > occurring elements **except**   |
| > already existed, "chasing its   | > Hydrogen can be produced inside |
| > own tail", in the same manner   | > of stars. Spectroscopy of       |
| > as the ghost film.              | > starlight has confirmed the     |
|                                   | > presence of most of them.       |
+-----------------------------------+-----------------------------------+
| > 9\. Fred Hoyle wrote, and had   | > 10\. Hoyle proposed a C-field   |
| > published, 15 science fiction   | > area in space which could have  |
| > novels and 14 non-fiction       | > a negative pressure in order to |
| > works.                          | > be consistent with conservation |
|                                   | > of energy and drive the         |
|                                   | > expansion of the universe       |
+-----------------------------------+-----------------------------------+
| > 11\. It would be necessary to   | > 12\. Cosmic background          |
| > spontaneously produce Hydrogen  | > radiation was possibly caused   |
| > at a rate of 1 atom per cubic   | > by light from very distant,     |
| > meter per billion years. Also   | > therefore ancient, galaxies     |
| > it would be necessary to        | > which has been scattered by     |
| > produce small amounts of        | > galactic dust                   |
| > Deuterium, Helium, and Lithium, |                                   |
| > but the amounts would be so     |                                   |
| > small that they would not be    |                                   |
| > directly detectable.            |                                   |
+-----------------------------------+-----------------------------------+
| > 13\. Theoretical studies        | > 14\. If the red shift of        |
| > suggest that collisions between | > distant galaxies is caused      |
| > light energy photons and atoms  | > because the light coming from   |
| > of matter result in loss of     | > them is losing energy as it     |
| > energy of the photons. As they  | > collides with intergalactic     |
| > approach us they would appear   | > matter, the universe might not  |
| > to be red shifted.              | > really be expanding. It could   |
|                                   | > just be very, very large and    |
|                                   | > there is a lot of matter out    |
|                                   | > there scattering light.         |
+-----------------------------------+-----------------------------------+
| > 15\. If the universe had been   | > 16\. The cosmic microwave       |
| > the size of an electron when it | > background was discovered in    |
| > was only a fraction of a second | > 1965 by Wilson and Penzias. It  |
| > old, it must have been a black  | > is very uniform and comes from  |
| > hole. Therefore its gravity     | > every direction.                |
| > would have been so intense that |                                   |
| > it could not have expanded to   |                                   |
| > what we see today.              |                                   |
+-----------------------------------+-----------------------------------+
| > 17\. A hot big bang would have  | > 18\. Maarten Schmidt produced a |
| > produced very high energy,      | > survey of quasars, small but    |
| > short wavelength radiation. The | > very brilliant extragalactic    |
| > red shift caused by the         | > systems discovered in 1966.     |
| > expansion of the universe over  | > They are found only at several  |
| > billions of years would produce | > billion light years, but none   |
| > a smooth, uniform long          | > are found nearby.               |
| > wavelength (microwaves) which   |                                   |
| > would come from every           |                                   |
| > direction.                      |                                   |
+-----------------------------------+-----------------------------------+
| > 19\. Radio galaxies have been   | > 20\. In 1929 Hubble observed    |
| > observed most frequently at     | > that every galaxy he saw        |
| > billions of light years from    | > exhibited a spectral red shift  |
| > earth, but much less frequently | > which was proportional to its   |
| > at closer distances.            | > distance from us.               |
+-----------------------------------+-----------------------------------+
| > 21\. Very distant objects such  | > 22\. The cosmic microwave       |
| > as quasars and radio galaxies   | > background (CMB) produces a     |
| > that appear very far away, but  | > spectrum which fits the curve   |
| > not nearby, could mean that the | > for an ideal Black Body         |
| > universe was different long ago | > radiation which was originally  |
| > than it is today and therefore  | > 3000K degrees but is today only |
| > is not constant in time.        | > 2.73K                           |
+-----------------------------------+-----------------------------------+
| > 23\. Although the synthesis of  | > 24\. The observed amount of     |
| > most elements can be explained  | > Helium4 today is more than can  |
| > by the fusions within stars, no | > be accounted for by the fusion  |
| > theoretical method can account  | > of Hydrogen in stars. Almost    |
| > for the Deuterium or Helium 3   | > one quarter of the known matter |
| > (atomic masses of 2 and 3) that | > in the universe today is        |
| > has been observed.              | > Helium4.                        |
+-----------------------------------+-----------------------------------+
| > 25\. Hubble concluded that all  | > 26\. Atoms with masses of one   |
| > of the galaxies he observed     | > to four amu could have been     |
| > were moving away from us at a   | > produced in the extremely high  |
| > speed proportional to their     | > energy in the very early period |
| > distance from us.               | > shortly after the Big Bang.     |
|                                   | > That could account for the      |
|                                   | > Hydrogen, Deuterium, Helium3,   |
|                                   | > and some Lithium found in the   |
|                                   | > universe today.                 |
+-----------------------------------+-----------------------------------+
| > 27\. The cosmic microwave       | > 28\. The uniformity of the CMB  |
| > background is uniform in        | > would be difficult to explain   |
| > temperature to better than one  | > if there were many different    |
| > part in one thousand.           | > sources and ages of radiation.  |
+-----------------------------------+-----------------------------------+
| > 29\. In the early universe      | > 30\. The FIRAS experiment       |
| > there were no atoms, only free  | > between 1989-90 on NASA's COBE  |
| > electrons and nuclei. The       | > satellite shows the CMB closely |
| > photons of energy could scatter | > follows the Black Body spectrum |
| > off electrons and the tiny      | > at 34 equally spaced points on  |
| > universe would have been a      | > the curve.                      |
| > dense collection of photon      |                                   |
| > energy called a Black Body      |                                   |
+-----------------------------------+-----------------------------------+
| > 31.MODEL: We think that the     | > 32\. The Big Bang Theory        |
| > universe did begin from nothing | > predicts a perfect Black Body   |
| > as a singularity about 15       | > temperature curve and a         |
| > billion years ago and has been  | > background radiation with very  |
| > expanding ever since.           | > slight differences in density   |
|                                   | > throughout.                     |
+-----------------------------------+-----------------------------------+
| > 33\.                            | > 34\.                            |
+-----------------------------------+-----------------------------------+
| > 35\.                            | > 36\.                            |
+-----------------------------------+-----------------------------------+
| > 37\.                            | > 38\.                            |
+-----------------------------------+-----------------------------------+
| > 39\.                            | > 40\.                            |
+-----------------------------------+-----------------------------------+
|                                   |                                   |
+-----------------------------------+-----------------------------------+