In the Student Text, “Tracing
the Origins of Quarks," we have chosen to trace the origins
of quarks by running the movie of the beginning of the universe
“in reverse.” During this time the universe is getting
smaller and smaller. If you continue this process back in time,
you come to a point where the mass of the universe is “crammed”
into an infinitely dense point. At this time, matter is thought
to have been a mixture of quarks, leptons (particles,
including electrons, that are not influenced by the strong nuclear
force), and theoretical particles, which may have been the
source of quarks (and antiquarks).
Where did the particles in the “primal stew” come from?
If we had an answer to this question, we would have insight into
the beginning of the universe. They may have been produced from
energy during the second, very brief epoch or during the Mysterious
Epoch immediately preceding it, when the universe was very compact
and temperatures were very high. This is in agreement with a premise
of the standard cosmological model that the early universe was in
a state of high density and high energy.
If this is the case, then matter is frozen energy. The universe,
which began in a high-energy state, has been cooling off ever since
and hot energy congealed into cold matter. We continue to study
quarks in this activity because they appear to be one the first
forms of matter in the universe and they are still present today.
Not only are they fundamental particles of matter, but they also
played a vital role in the formation of atoms and molecules that
form the vast structures of today’s universe.
As your students work with this model, emphasize that it is consistent
with observations of chemical constituents in the universe. These
observations include studies of young and old stars; planetary nebulae;
shells of gas ejected by unstable stars; glowing gas clouds; lunar
soil samples that Apollo astronauts brought to Earth; and particles
of solar wind gathered by sheets of aluminum foil deployed on the
surface of the moon. The observed abundances of hydrogen and helium
in space match the abundances of those elements predicted from this
model.
This model is also consistent with known physical laws and properties
of fundamental forces. Examples include the fact that the temperature
of matter decreases as it expands (so the reverse would be true
as matter condenses) and that the fundamental attractive forces
have different strengths and operate through different distances.
As you guide your students through this activity, continue to use
the background material in “The Universe is Expanding”
and “Remnants of the Big Bang” sections of Appendix
A from the original Cosmic Chemistry: Cosmogony module.
For additional background reading, see Appendix A and Appendix
C, Student Texts, “The Invisible Fire” and “ Models
in Science” from Cosmic Chemistry: Sun and Solar Wind. |
Distribute
copies of the nine 
their
tactile card sets available and arranged in order on their desks
as they answer the classroom discussion questions. You may also
wish them to use their student texts for reference during this
time.
basis of the descriptions of the different epochs of the universe?
[Epochs are based on models that incorporate observations of
the universe today, descriptive mathematics, and fundamental
laws of physics.]
During
what epochs were quarks found as free particles? [from Epoch
2 to Epoch 4]
a set of “Density Balls” that have the same mass in
different volumes.
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accountability report