BACKGROUND:
Are you really at rest, when
you sit down? When sometimes dies, do the atoms and molecules that make
up that organism stop moving? Can you ever stop the spinning of a
proton, neutron, or electron? Does our galaxy hang in the universe with
no motion? The answer to these questions are all "no". Motion
including spinning, velocity, acceleration, momentum and other terms,
reflect this movement that all substances, large and small, are
experiencing all the time. It is this motion that physicists must
understand in order to explain physical phenomena. Motion can be
accomplished by physical or electromagnetic waves. The study of motion
is traditionally thought of as "mechanics". It is from all
these motions that energy is emitted. Energy is created when matter
moves, and since all substances are moving, energy is always being made
even when an object is at rest. Terms like heat, solar, light, and sound
refer to different forms of energy.
Observing and then describing nature
is difficult. Precise definitions are needed. If the observations create
a pattern, scientists can develop a mathematical formulation, that would
help predict results. Other scientists, then attempt to observe and
verify the prediction, through experimentation. As each prediction is
verified, an understanding of the physical world slowly evolves.
Objects interact with each other.
Many books refer to fundamental forces in the Universe. However, the
word "force" is a very common term that means many things to
students. In our terminology we will refer to interactions. There are
four known interactions that seem to "rule" how all substances
react. These include:
- GRAVITY. An interaction
that is a mutual attraction between masses is called gravity. Any two
particles of matter attract one another with a force related to their
mass and distance between the masses. Drop a ball or pencil. Ask the
students what causes them to fall down? Gravity attracts objects to the
ground.
- ELECTROMAGNETIC. Use
examples of light, electricity, and magnetism to show electromagnetic
interactions. They will hopefully remember this from the 5th grade
curriculum. Many other forces we encounter in everyday life, like
friction or tension in a rope are physical waves and not
electromagnetic. Electromagnetic forces arise from interactions of
charged particles.
- WEAK NUCLEAR. The
interaction that holds atoms to other atoms including how compounds are
held together.
- STRONG NUCLEAR. The
interaction that holds atoms together. Fission and fusion of subatomic
particles are the processes by which these interaction can be released
as useable energy.
In the Integrating Science, Math, and
Technology program we use the commonly accepted four fundamental
interactions: gravitational, electromagnetic, strong nuclear, and weak
nuclear. Please recognize that these may change as scientists collect
more data on how matter interacts. These interactions try to explain how
matter lives in harmony with one another. Each of these interactions has
their own method of producing energy, motion, and heat. When looking at
the entire Universe, gravity is considered the weakest interaction,
electromagnetism, weak atomic, and strong atomic increasing in strength
respectively.
Gravitation is predictable in that we
can calculate how objects will react in a gravitational world.
Mathematical formulas model the consequences exquisitely. It is the
weakest of the interaction, yet it is the interaction that has created
the universe. Scientists do not know if gravitation moves in waves, or
in discrete units as the other 3 interactions occur. Is gravity matter
and how does it react? Does gravity bend space and time, and how did it
create such a chaotic Universe? Sir Isaac Newton’s mathematical
formulation of gravitational interaction is still used today. He stated
that gravity increases in proportion to the product of any two masses
and decreases in relation to the square of the distance between them.
Einstein reformulated the gravitational concept to show that space and
time become warped within a gravitational field (general theory of
relativity). All the consequences of relativity are still being
verified. For instance, inertia and gravity (if you look at the movement
within the universe) can be seen as equivalent. Gravity holds us to the
Earth, but if a person was in a box, and accelerated up, the person
would fall to the floor and remain there as long as the enclosed box
continued to accelerate. Most of the answers in understanding the nature
of gravity are experiments that will involve far reaches of the
Universe.
Many physicists feel that the three
interactions of electromagnetism, weak, and strong all have a common
mechanism. The structure of matter is affected by these interactions,
acting inside of the nucleus (neutrons and protons) and electrons.
Actually, the structure of matter includes other particles such as muon,
pion, kaon, sigma and several hundred more. Protons and neutrons emit
quarks and electrons emit leptons. There are four types of quarks. The
up, the down, strange, and charm quarks can be emitted during decay.
These quarks and leptons all decay into particles called gauge bosoms.
Electromagnetism emits photons from their quarks and leptons. Weak emits
"W" and "Z" bosoms from their quarks and leptons,
and strong emits particles called color gluon from their quarks and
leptons. All these gauge bosoms share a common mathematical description
and similar physical behavior. Confusing, yes! The concepts however
aren't confusing, electrons, protons, and neutrons are the basic
ingredients of matter, and the other particles are for
"flavoring."
The interaction termed
electromagnetism is the net electrical charge of particles which is
conserved throughout any reaction. All chemistry and hence all biology
is a direct consequence of electromagnetic interaction of atoms and
molecules.
The weak nuclear interaction was
recognized with the discovery of radioactive decay by Henri Becquerel in
1896. Particles easily "escape" from the atomic structure over
time. The energy of the original particles is conserved with new
particles called neutrino or sometimes antineutrinos.
Strong nuclear interactions act on
particles called hadrons which include protons, neutrons, pion, mesons,
and baryons. This interaction is one of the strongest per unit of space
known.
PROCEDURE:
- You may want to introduce each of
these interactions discussed above by demonstrating them. These
interactions have their own type of motion that may be particular to
that force. Within each of these major interactions make reference to
different forces.
- Give students the worksheet as a
classroom discussion or homework assignment. The worksheet for the
students should help them to begin classifying events that they see
everyday.
- ANSWERS:
1. gravity
2.
strong nuclear
3. electromagnetic
4. gravity
5. electromagnetic
6. gravity
7. gravity
8. weak nuclear
9. electromagnetic
10. gravity;
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11. gravity
12. gravity
13. electromagnetic
14. strong nuclear
15. gravity
16. electromagnetic
17. electromagnetic
18. electromagnetic
19. gravity
20. electromagnetic
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