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Exploratories

Creation of the Universe

You May Tape!

Texas Instruments has made it possible for you to videotape THE CREATION OF THE

UNIVERSE and use it in class as a teaching tool. The program should not be edited, and

statutory underwriter credit should be preserved. It is our hope that these liberal off-air tape

rights, combined with the free materials in this package, will increase the usefulness of THE

CREATION OF THE UNIVERSE in the secondary school science classroom.

Questions, Discussion Topics And Projects For Use Before Viewing

1. Scientists develop theories or models as a result of observations and experiments to describe the nature of objects and events. These theories and models tend to be replaced by new theories and models as new knowledge is gained. Describe how atomic theory has changed, and ask students to identify others theories that have changed as we gained new knowledge. (For example, spontaneous generation, place tectonics, DNA, etc.)

2. Especially in recent times, advancements in science and technology have often resulted from the cooperative efforts of a number of people rather than from the efforts of one person working alone. Have students identify and compare the development of the atomic theories proposed by individuals and the theories proposed by teams of scientists working in laboratories such as Fermilab and CERN.

3. What four "elements" did some early Greek scientists believe to be the basis of all matter? (Earth, water, fire, air.) What alternative theory did Democritus advance? (That all matter is made up of indivisible atoms, at motion in a void.) Democritus' suggestion was an early example of a unified field theory. From this example, what do your students think this phrase means? (A theory that attempts to unify and simply apparently disparate phenomena.)

4. What two forces were demonstrated to be "unified" by Maxwell? (Electricity and magnetism.) What two qualities of the universe are "unified" by Einstein's equation E=mc 2 ? (Energy and matter.) If a unified theory reduces complication and provides a simpler model of the system under consideration, what other theories might qualify? (For example, Copernicus, heliocentric model of the solar system, plate ectonics, relativity.)

5. Put up the Poster and invite students to examine it. Assign each student to prepare a brief report on one of the scientists on the Poster. The report should focus on the scientist's contribution to the development of a unified field theory.

6. What is the basic definition of a force put forth in today's physics? (A force is a charge carried by interacting virtual particles that are exchanged between objects or between other particles.) What are the four forces scientist recognize in the universe today? (Electromagnetism, gravity, the strong nuclear force and the weak nuclear force.) Which is the strongest of these? (The strong nuclear force.) The weakest? (Gravity.) Ask students to identify the particle that is thought to carry each of these forces, and to pay special attention to the chart of the four forces on the Handout.

7. Which of the four forces have, at least in theory, already been shown to be unified? (The electromagnetic, the weak and the strong.) If , in fact, the four forces ultimately can be demonstrated to be unified, what prevents science from demonstrating that unification now? (The inability to generate, even in the most powerful particle accelerators, levels of energy that equal those at the very beginning of the universe.)

8. Scientists at CERN and Fermilab aim particle beams at targets, then try to determine the makeup of the target by the scattering of particles that leave the target. Draw on the board the three "hidden targets" as well as the particle accelerator "shooting galleries" in which sub-atomic particles are fired at them. Ask students to identify by the scattering patterns which of the hidden targets is in gallery A, B, and C.

9. Many students have difficulty comprehending the reality of large numbers. To provide a vivid example of how large the number 1 million is, hold up page 5 of this manual, "1/200th of 1,000,000 X Particles," which contains 5,000 images of the letter X. Ask the class how many copies of the page would contain 1 million X particles (200.) Photocopy the page 200 times, and have the class tape the copies together vertically into a single long ribbon, rolling it up as they go. Then take the ribbon outside and unroll it to show the class 1 million X particles. Now ask them to consider the real meaning of some numbers they have already discussed. For example: How far does light travel in a minute? In an hour? In a year?

10. Ask students which bodies, astronomically speaking, are closest to Earth? (Our moon and the other planets.) Which are next farthest away? (The stars in our own galaxies.) Farther still? (Other galaxies.) Farthest of all? (More distant galaxies and quasars.)

11. Discuss the evidence for the proposal that the universe is expanding. Ask students to report on the experiment Christian Doppler set up to demonstrate the Doppler effect, or actually to demonstrate the effect by swinging a whistle on the end of a long string. Why does the tone of the whistle rise in pitch when the whistle approaches us and drop as the whistle recedes? (The waves that reach our ears are shortened when emitted by an approaching object and lengthened when emitted by a receding one.) Why would light also demonstrate the Doppler effect? (Light also reaches us in wave patterns.)

12. When we look back in space, why do we also look back in time? (Because it takes time for light to reach us from distant objects; the farther away the object is, the more time it takes.) When we look at a galaxy 3 million light years away, how far back in time are we looking? (3 million years.) How far away, in miles, would that galaxy be? (3 million years x the number of seconds in a year x 186,000 miles.) Is that galaxy actually where we perceive it? (No.) Why not? (It has continued to move away from us during the 3 million years since it emitted the light we see.)

13. Ask student to create a space-time diagram that shows the orbits of the Earth and Jupiter around the sun over the course of 12 Earth years, the length of time it takes Jupiter to complete a single orbit. The motions of the planets should be to accurate scale on the vertical (space) axis.

14. Ask students to create their own light cone, letting onto it the positions of galaxies 5 million and 7 billion light years apart, and of a quasar 9 billion light years distant.

Questions, Discussion Topics And Projects For Use After Viewing

1. Now that your students have viewed the program, who would they most like to meet among the scientist who were featured and whose achievements were highlighted? Why? Whose ideas most appealed to them? Whose ideas, if anyone's, baffled them?

2. Ask students to discuss the increasing simplicity of the universe as viewed through each of the "windows"

3. Ask students to use parts from a molecular model kit to construct quark models of a proton or a neutron, and to remember the colors of the quarks, since most of these kits do contain colored parts.

4. Ask students to choose a quotation and discuss it. With reference to the quotation from Through the Looking Glass, ask students to speculate on why some of the concepts of recent physics seem to be "impossible things" when put into words.

5. Here are two quotes from The Creation Of The Universe: "Every single atom in your body was once inside a star." Allan Sandage "Every scrap of matter and every in our blood and bones, and in the synapses of our thoughts, can trace its lineage back to the origin of the universe." Timothy Ferris

Have your students discuss the meaning of Sandage's and Ferris' quotes. Are Ferris and Sandage expressing a philosophical idea or describing a fact? How does Ferris change or expand on Sandage's idea?

 

Background Information For Teachers and Selected Students

Fundamental Particles

All matter is made up of two types of particles, leptons and quarks. There are six leptons and six quarks (see Table I). Quarks are controlled by the strong force, and the way quarks combine account for all matter that is not a lepton. All particles made up of quarks are called hadrons. The proton is a hadron. It consists of three quarks: u, u, d. Because quarks have a fractional charge ± 1 /3 and ± 2 /3, the sum of charges on a quark must equal the charge of the particle they make up. The up quark has a charge of 2 /3 and the down quark has a charge of - 1 /3, thus, a proton has a charge of 2 /3 + 2 /3 - 1 /3 = 1. In addition to spin and charge, quarks have a property called color: red, green and blue. The names up, down, etc., and the colors red, green, and blue have nothing to do with the conventional meanings of those words. These names are merely identifiers.

In the quark model of a proton (see Fig. I), the proton consists of three quarks held together by gluons. The gluon is a carrier of the strong force that confines the quarks. When quarks form triples, they must be of three different colors. The proton contains one red, one green and one blue quark. The gluons that confine the quarks also come in colors and transmit color between the quarks. Quarks change color with the continual exchange of gluons. Theory states that quark groupings must be "colorless." Since quarks occur only in twos or threes, all groups of three quarks would contain each color, red, green and blue. Twos would contain one quark of color and one antiquark with anticolor. These combinations of the three colors or color-anticolor are equivalent to being "colorless"

For every type of particle, there is postulated an antiparticle. The theory of antiparticles was first proposed by Paul Dirac in 1928. The theory has since been confirmed with the discover, by Don Anderson in 1932, of a positively charged electron (positron), or antielectron. The proton (p) has the antiproton (p) as its antiparticle. Both the proton and the antiproton have the same mass but opposite charge. The antiproton consists of antiquarks: u, u, and d of charge -2 /3 - 2 /3 + 1 /3 = -1. Each quark of the antiproton has a different anticolor: antired, antigreen and antiblue.

Electromagnetism

A basic principle of electricity is that like charges repel and unlike charges attract. Similarly, in magnetism, like poles repel and unlike poles attract. In the 1860s, James Maxwell showed that electricity and magnetism are one and the same. By demonstrating the unity of these two ideas in four concise equations, Maxwell may be credited with the first unified field theory. But the question remained as to how this repulsion and attraction takes place.

All particles that have charge exchange "virtual" photons. They are called "virtual" because they do not exist independent of the charges that emit or absorb them, unlike real photons such as radio waves or light. It is the exchange of virtual photons that accounts for the Coulomb repulsion between two like charges.

In THE CREATION OF THE UNIVERSE, a pitcher gives up a home run to Reggie Jackson. The sequence that follows immediately simulates the exchange of photons between the bat and ball representing the electromagnetic force. When the bat and ball are apart, few photons are exchanged, signaling a repelling force. That force gets stronger as the bat and ball -nearing collision - exchange increasing numbers of photons. Ultimately the photon exchange stops the ball and reverses its direction. This exchange of virtual photons takes place between all charged particles, and the photons convey attraction as well as repulsion.

Weak Force

Radioactivity is a property of many natural elements. The form of radioactivity known as beta decay involves the conversion of neutrons into protons (or up quarks into down quarks) and electrons and neutrinos. Interactions in an atomic nucleus can occur in 10 -23 seconds (the radius of the nucleus over the speed of light), but beta decays take much longer - up to 10 -17 seconds. Because the probability of a beta decay during the nuclear time scale of 10 -23 is so low, the interaction that causes the decay is very small, and is called the weak interaction. The weak interaction between particles may be shown by sketches called Feynman diagrams after their inventor, Richard Feynman. In a simplification of these diagrams, we may let a solid line represent the path of a real particle, a broken line the path of a virtual particle, and a sinusoidal line the path of a photon. Figure 2a shows the disintegration of a neutron with the emission of an electron. This is as it would appear under laboratory conditions. Figure 2b shows the mechanism, weak interaction for this decay by the exchange of a W boson. Compare this decay to Figure 2c where electromagnetic repulsion takes lace by the exchange of virtual photons.

Gravity

All matter attracts all other matter, and this attraction is called gravity. Gravity is the weakest force in nature. However, given a large enough amount of matter, the forces of attraction become great enough to override the other forces of nature and cause thermonuclear reactions such as those found in our sun and in distant stars. The carrier particle for gravity is called the graviton. No gravitons have ever been observed. Scientists all over the world are trying to measure gravitational waves that would provide some information about the graviton. Because gravity is the weakest force in nature, an event that generated detectable waves would have to be very large, and such events happen only in deep space. An event in space would be so far away that, by the time the event reached the Earth, it would be extremely weak. It would require very sensitive equipment to detect such an event, and such equipment has not yet been developed.

Communication

Communication is the exchange of information. This is exactly what happens with the four forces of nature. With gravity, any two masses attract each other. How does one mass "know" the other is there? The graviton carries the information, and it carries the information in such a way that the two masses will attract.

Consider the weak interaction. A W particle spans the gap, carrying with it the necessary charge, energy and momentum, so that whatever mass and charge a particle had when it entered the disintegration, the particles that exit will carry away the same total charge, energy and momentum.

Likewise, the photon is the carrier of information signaling electromagnetic interactions.

The strongest force, the nuclear force, is conveyed by the gluon.

Unified Field Theories

In the last decade, much progress has been made toward finding a unified theory of the forces of nature. The electroweak theory of Steven Weinberg and Abdus Salam states that the electromagnetic and weak forces are really manifestations of one unified force. At high enough energies, this unified force can be observed in accelerators. Models for Grand Unified Theories (GUTs) suppose that at much higher energies the strong force and the electroweak force will be one common force. For this theory to work, there must be new types of intermediate bosons, known as X and Y bosons. These bosons are also called leptoquarks because they can turn leptons into quarks. Thus a positron can emit an X particle and turn into a d quark, or a d quark can absorb an X particle and turn into a positron. This kind of transmutation between quarks and leptons suggests the possibility of proton decay. If quarks cannot turn into lighter leptons, then the proton, which is the lightest combination of three quarks, could never decay. But if the X particles exist, then protons can decay. Proton decay would be a new form of radioactivity: A very long half-life but very high decay energy process that would occur in all materials, not just in a few isotopes. thus proton decay experiments, such as the one your students will see the THE CREATION OF THE UNIVERSE, use water, because it is cheap in large quantities and can be purified to remove known radioactive isotopes. If high energy decay would be discovered. So far the decay has not been observed, so the half-life of protons is more than 10 32 years.

Suggested Student Handouts