Scientific Facts and Theories:
=================================
By: J. Lubek, PhD
Atom:
One of the minute indivisible particles of which according
to ancient materialism the universe is composed.
Molecule:
The smallest particle of a substance that retains all the
properties of the substance and is composed of one or more atoms.
-T he smallest particle of an element thaat can exist
either alone or in combination.
Proton:
an elementary particle that is identical with the nucleus of
the hydrogen atom, that along with neutrons is a constituent
of all other atomic nuclei, that carries a positive charge
numerically equal to the charge of an electron,
and that has a mass of 1.673 x 10¯24 gram.
Electron:
an elementary particle consisting of a charge of negative
electricity equal to about 1.602 x 10-19 coulomb and having
a mass when at rest of about 9.109534 x 10-28 gram or
about 1/1836 that of a proton.
Neutron:
An uncharged elementary particle that has a mass nearly
equal to that of the proton and is present in all
known atomic nuclei except the hydrogen nucleus.
Nuclei:
The small brighter and denser portion of a galaxy
or of the head of a comet.
or:
Nucleus:
A central point, group, or mass about which gathering, concentration,
or accretion takes place: as a : a cellular organelle of eukaryotes
that is essential to cell functions
(as reproduction and protein synthesis), is composed of nuclear
sap and a nucleoprotein-rich network from which chromosomes
and nucleoli arise, and is enclosed in a definite membrane.
b : A mass of gray matter or group of nerve cells in the central
nervous system.
c : A characteristic and stable complex of atoms or groups
in a molecule; especially : RING
d : The positively charged central portion of an atom that
comprises nearly all of the atomic mass and that consists
of protons and neutrons except in hydrogen which consists of one proton only.
Ion:
1 : an atom or group of atoms that carries a positive or
negative electric charge as a result
of having lost or gained one or more electrons.
2 : a charged subatomic particle (as a free electron).
Amphoterism:
in chemistry, the property of certain substances of acting either
as acids or as bases depending on the reaction in which
they are involved. Many hydroxide compounds are amphoteric.
For example, aluminum hydroxide, Al(OH) 3 , reacts as a base
with common acids to form salts, e.g., with sulfuric acid,
H 2 SO 4 , to form aluminum sulfate, Al 2 (SO 4 ) 3.
It reacts as an acid with strong bases to form aluminates,
e.g., with sodium hydroxide, NaOH, to form sodium aluminate,
Na[Al(OH) 4 (OH 2 ) 2 ]. Organic molecules that contain both
acidic (e.g., carboxyl) and basic (e.g., amino)
functional groups are usually amphoteric.
-Partly one and partly the other; specifiically:
capable of reacting chemically either as an acid or as a base.
Functional group:
In organic chemistry, group of atoms within a molecule that is
responsible for certain properties of the molecule and
reactions in which it takes part. Organic compounds are
frequently classified according to the functional group
or groups they contain. For example, methanol, ethanol,
and isopropanol are all classified as alcohols since
each contains a functional hydroxyl group.
The accompanying table shows important functional
groups and the classes of compounds in which they occur.
Osmosis:
Movement of a solvent through a semipermeable membrane
(as of a living cell) into a solution of higher
solute concentration that tends to equalize the concentrations
of solute on the two sides of the membrane.
Quantum Theory:
Modern physical theory concerned with the emission and absorption
of energy by matter and with the motion of material
particles; the quantum theory and the theory of relativity
together form the theoretical basis of modern physics.
Just as the theory of relativity assumes importance in
the special situation where very large speeds are involved,
so the quantum theory is necessary for the special situation
where very small quantities are involved, i.e., on the scale
of molecules, atoms, and elementary particles. A
spects of the quantum theory have provoked vigorous
philosophical debates concerning, for example,
the uncertainty principle and the statistical
nature of all the predictions of the theory.
Theory of Realitivity:
Physical theory, introduced by Albert Einstein,
that discards the concept of absolute motion and
instead treats only relative motion between two
systems or frames of reference. One consequence
of the theory is that space and time are no longer
viewed as separate, independent entities but rather
are seen to form a four-dimensional continuum called
space-time . Full comprehension of the mathematical
formulation of the theory can be attained only
through a study of certain branches of mathematics,
e.g., tensor calculus. Both the special and general
theories have been established and accepted into the
structure of physics. Einstein also sought
unsuccessfully for many years to incorporate
the theory into a unified field theory valid
also for subatomic and electromagnetic.
Space-Time:
Central concept in the theory of relativity that
replaces the earlier concepts of space and time
as separate absolute entities. In relativity one
cannot uniquely distinguish space and time as elements
in descriptions of events. Space and time are joined
together in an intimate combination in which time becomes
the fourth dimension. The mathematical formulation of the
theory by H. Lorentz preceded the interpretation
by A. Einstein that space and time are not absolute.
The abstract description of space-time was made by H. Minkowski.
In space-time, events in the universe are described in terms
of a four-dimensional continuum in which each observer
locates an event by three spacelike coordinates (position)
and one timelike coordinate.
The choice of the timelike coordinate in space-time is not unique;
hence, time is not absolute but is relative to the observer.
A striking consequence is that simultaneity is no longer an
intrinsic relation between two events; it exists only as a
relation between two events and a particular observer.
In general, events at different locations
that are simultaneous for one observer will not be simultaneous
for another observer. Other relativistic effects,
such as the Lorentz contraction and time dilation,
are due to the structure of space-time.
Physics:
Theoretical physicists use mathematics to describe certain
aspects of Nature. Sir Isaac Newton was the first theoretical
physicist, although in his own time his profession
was called "natural philosophy".
By Newton's era people had already used algebra and geometry to
build marvelous works of architecture, including the great
cathedrals of Europe, but algebra and geometry only describe
things that are sitting still. In order to describe things
that are moving or changing in some way, Newton invented calculus.
The most puzzling and intriguing moving things visible
to humans have always been been the sun, the moon,
the planets and the stars we can see in the night sky.
Newton's new calculus, combined with his "Laws of Motion",
made a mathematical model for the force of gravity that not
only described the observed motions of planets and stars
in the night sky, but also of swinging weights and flying
cannonballs in England.
Today's theoretical physicists are often working
on the boundaries of known mathematics,
sometimes inventing new mathematics as they need it,
like Newton did with calculus.
Newton was both a theorist and an experimentalist.
He spent many many long hours, to the point of
neglecting his health, observing the way Nature
behaved so that he might describe it better.
The so-called "Newton's Laws of Motion" are not abstract
laws that Nature is somehow forced to obey,
but the observed behavior of Nature that is
described in the language of mathematics.
In Newton's time, theory and experiment went together.
Today the functions of theory and observation
are divided into two distinct communities in physics.
Both experiments and theories are much more complex
than back in Newton's time. Theorists are exploring
areas of Nature in mathematics that technology so far
does not allow us to observe in experiments.
Many of the theoretical physicists who are alive today
may not live to see how the real Nature compares with
her mathematical description in their work.
Today's theorists have to learn to live with
ambiguity and uncertainty in their
mission to describe Nature using math.
String Theory:
Think of a guitar string that has been tuned by stretching
the string under tension across the guitar.
Depending on how the string is plucked and how much tension
is in the string, different musical notes will be created
by the string. These musical notes could be said to be
excitation modes of that guitar string under tension.
In a similar manner, in string theory, the elementary
particles we observe in particle accelerators could be
thought of as the "musical notes" or excitation modes
of elementary strings.
In string theory, as in guitar playing,
the string must be stretched under tension in order
to become excited. However, the strings in string theory
are floating in spacetime, they aren't tied down to a guitar.
Nonetheless, they have tension. The string tension in
string theory is denoted by the quantity 1/(2 p a'),
where a' is pronounced "alpha prime"and is equal to the
square of the string length scale.
If string theory is to be a theory of quantum gravity,
then the average size of a string should be somewhere
near the length scale of quantum gravity,
called the Planck length, which is about 10-33 centimeters,
or about a millionth of a billionth of a billionth of a
billionth of a centimeter. Unfortunately,
this means that strings are way too small to see by current
or expected particle physics technology (or financing!!)
and so string theorists must devise more clever methods
to test the theory than just looking
for little strings in particle experiments.
String theories are classified according
to whether or not the strings are required
to be closed loops, and whether or not the
particle spectrum includes fermions. In order
to include fermions in string theory,
there must be a special kind of symmetry called
supersymmetry, which means for every boson
(particle that transmits a force) there is a corresponding
fermion (particle that makes up matter).
So supersymmetry relates the particles that
transmit forces to the particles that make up matter.
Supersymmetric partners to to currently known particles
have not been observed in particle experiments,
but theorists believe this is because supersymmetric
particles are too massive to be detected at current accelerators.
Particle accelerators could be on the verge of finding
evidence for high energy supersymmetry in the next decade.
Evidence for supersymmetry at high energy would be compelling
evidence that string theory was a good mathematical model for
Nature at the smallest distance scales.
Why did strings enter the story?
Relativistic quantum field theory has worked very well to describe
the observed behaviors and properties of elementary particles.
But the theory itself only works well when gravity is so
weak that it can be neglected. Particle theory only works
when we pretend gravity doesn't exist.
General relativity has yielded a wealth of insight into the Universe,
the orbits of planets, the evolution of stars and galaxies,
the Big Bang and recently observed black holes and
gravitational lenses. However, the theory itself only
works when we pretend that the Universe is purely classical
and that quantum mechanics is not needed in our description of Nature.
String theory is believed to close this gap.
Originally, string theory was proposed as an explanation for the
observed relationship between mass and spin for certain particles
called hadrons, which include the proton and neutron.
Things didn't work out, though, and Quantum Chromodynamics
eventually proved a better theory for hadrons.
But particles in string theory arise as excitations of the string,
and included in the excitations of a string in string theory is a
particle with zero mass and two units of spin.
If there were a good quantum theory of gravity,
then the particle that would carry the gravitational force would
have zero mass and two units of spin. This has been known by
theoretical physicists for a long time. This theorized particle is
called the graviton.
This led early string theorists to propose that string theory be applied
not as a theory of hadronic particles, but as a theory of quantum gravity,
the unfulfilled fantasy of theoretical physics in the particle and gravity
communities for decades.
But it wasn't enough that there be a graviton predicted by string theory.
One can add a graviton to quantum field theory by hand, but the calculations
that are supposed to describe Nature become useless. This is because,
as illustrated in the diagram above, particle interactions occur at a single
point of spacetime, at zero distance between the interacting particles.
For gravitons, the mathematics behaves so badly at zero distance that
the answers just don't make sense. In string theory, the strings collide
over a small but finite distance, and the answers do make sense.
This doesn't mean that string theory is not without its deficiencies.
But the zero distance behavior is such that we can combine quantum
mechanics and gravity, and we can talk sensibly about a string excitation
that carries the gravitational force.
This was a very great hurdle that was overcome for late 20th century physics,
which is why so many young people are willing to learn the grueling
complex and abstract mathematics that is necessary to study a quantum
theory of interacting strings.
I doubt there is only one string theory, a unifying theory
that will combine all the theories of string and the universe together
both on atomic and subatomic level, however theories could be combined
into few similar or dissimilar theories, but one theory, it can not be,
it would make no sense, be too long to comprehend and it would be wrong.
Few good theories and equations work together well, with each other.