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Founded January 1970
Julian Date:  2459300.18
2020-2021: CI

THE DAILY ASTRONOMER
Friday, March 26, 2021
Exploratorium XXXIII: Entangled Strings

Contrary to student opinion, science does not frown. It merely scrutinizes
and its furrowed brow might be often mistaken for a frown. In science's
defense, it might be austere, but it's not hostile. The scientific method
merely demands that all conclusions be predicated on objective reasoning
that, itself, is based on data and observation. Though this requirement
might seem daunting, we can find simple examples all around us.

We theorize, for instance, that whenever we toss a rock off a cliff, it
will fall to the ground with a certain acceleration. That theory is all
very well, but science insists that we test it repeatedly. Such testing is
easy enough. We have a pile of rocks and we throw each one off a cliff and
observe the result. Each thrown rock falls to the ground and we measure its
descent time. From this measurement we can calculate the acceleration. Sure
enough, the acceleration is consistent for each rock. Unfortunately, we
haven't yet established a law. We have merely subjected the theory to a
series of trials that all confirmed it. Had one rock stopped in mid-air and
started ascending, or if one rock had accelerated much faster than the
others, we would have a contradiction to the theory. We'd have to search
for other causes to explain this anomaly. If we couldn't find any reasons
for the contradiction, we might have to modify our theory or abandon it all
together.
Science is rigorous and unsentimental. Even if your idea is elegantly
phrased and looks pretty when expressed as a triple integral, science will
make short work of it if it doesn't stand up to examination.

This discussion of the scientific method brings us clumsily to "String
Theory."
Admittedly, science does frown a bit at string theory. Dismissed by many
scientists as gussied-up metaphysics, string theory strives to both explain
the fundamental nature of matter as well as reconcile the disparate fields
of quantum mechanics and the General Theory of Relativity. If you're now
frowning too, please bear with us as we untangle these different threads.

We address the first aspect by finding a piece of chalk on the
planetarium's blackboard ledge. We can choose this little item simply
because the Universe includes chalkboard ledges as much as it includes
distant galaxies and Saturn's rings. Within this chalk piece we find
Calcium Carbonate, a compound of calcium, carbon and oxygen. Regard the
chalk as occupying the macro-level. The next level down is molecular: a
calcium carbonate molecule consists of one calcium atom, one carbon atom
and three oxygen atoms. Below the molecular level is the atomic and then
sub-atomic levels: a single calcium atom consists of twenty protons and
twenty neutrons in the nucleus that is surrounded by twenty electrons. Even
lower is the sub-sub-atomic level: each proton consists of a quark triplet.
These quarks are bound by the strong nuclear force.

Does another level lurk below this one?
A string theorist would suggest that the quark level is based on one lower
down: strings.




The simple idea is that fundamental matter consists of strings. Think
analogously of these strings producing different vibrations. Each
'frequency' generates a different type of particle, such as a quark or
electron,* in the same manner that certain string vibrations on instruments
produce specific notes. The beauty of this theory, according to its
defenders, is that it explains how matter can appear so different while
still being manifestations of the same phenomena. The problem with this
theory, according to its detractors, is that it doesn't lend itself to
testing. Scientists haven't devised any method by which to determine if
matter results from string interactions. Thus, some regard string theory as
a nifty idea, but not a true theory because rigorous trials are not
possible. At least not yet.
The second aspect pertains to quantum mechanics and the general theory of
relativity. Quantum mechanics is the physics of the infinitesimally small.
Quantum mechanics explains behaviors of minuscule entities that do not
conform to classical physical principles.  Look at an electron. Classical
physics would model electrons as being like small planets in orbit around
the nucleus: a solar system in miniature. The fact is that physics once
assumed atoms to be exactly like planet systems, only smaller. However,
inconsistencies in atomic models compelled physicists to develop a new
system of laws to explain how these sub-atomic particles behave. For
instance, if the negatively charged electrons were tiny balls revolving
around the positively charged nucleus, then the electrons would eventually
crash into the nucleus, thereby destroying the atom.
Obviously, this self-implosion doesn't happen because the cosmos is stuffed
with perfectly healthy atoms, thank you very much.
Quantum physics replaces the "flying ball" electrons with the "cloud
electrons," in which electrons are not solid objects occupying specific
space-time points. Instead, they are little cloud forms that can only
occupy shells at fixed distances from the nucleus.
General relativity is Albert Einstein's theory explaining gravity.
According to GR, gravity is not a force but is the result of macroscopic
objects bending local space-time geometries. Any highly massive object will
distort space-time enough to either deflect the paths of nearby objects or
trap them altogether. The classical analogy is a bowling ball on a taut
spandex sheet. The ball bends the sheet around it, producing an
indentation. If one tossed ball bearings across the sheet, the small little
ball bearings close to the large ball would fall into the indentation. They
would, in effect, be trapped by the bowling ball's gravity well. So, the
Sun isn't exerting a gravitational pull on the planets. The Sun is
distorting its local space-time geometry and the planets are moving within
the distortion.
Both quantum mechanics and general relativity are considered valid because
they both yield predictions about particle behaviors that scientists can
test.** A nagging issue pertains to how one can reconcile the macroscopic
model of relativity with the microscopic realm of quantum mechanics.
General relativity has given physicists deep insight into the nature of
stars, black holes, and even how time differs on Earth's surface as opposed
to high above it. However, general relativity assumes that all particles
have classical behaviors, such as those observed in rocks and planets. It
does not work well with quantum mechanics, hence the search for a unifying
theory of "quantum gravity."
String theory offers the needed reconciliation  by introducing the
"graviton," an elementary particle responsible for the space-time
distortions caused by massive, macroscopic particles. Nobody has found this
graviton and nobody is quite sure how one would be detected. Such string
theory reconciliations also come with a few conditions that are untestable
and, to some, seem bizarre, such as the proposition that the cosmos has
eleven dimensions. We think of the world as having four dimensions: three
spatial - length, breadth, width- and one temporal -duration. String
theorists believe that seven others are curled up somewhere. They have no
geometrical interpretation. Such extra-dimensions are necessary so the
complicated mathematics involved works out.
However, here again we encounter a great deal of theory with no possible
observation and consequently no testing. Perhaps someday a clever theorist
will devise a means to test these theories for confirmation, modification
or abandonment.
Until that time, of course, many will dismiss string theory as being a
great tangle of enjoyable mind play.





*If I had been lazy and allowed Uber Professor Xavier Trinket to pen this
article, he would have written exhaustively about the various types of
elementary particles, including leptons and quarks (both types of fermions)
and bosons, for instance. He would include all this extraneous material to
inform the reader that elementary particles are not confined to merely
quarks and electrons. This is why we're all grateful that he's a cranky
twerp who doesn't get along with anybody and prefers to remain in his
catacomb office where he doesn't have to write any articles or do any other
type of work.


**It might seem curious that scientists could test such a theory about such
an abstract concept as space-time bends. In 1919, Sir Arthur Eddington led
an expedition to South America to photograph the starfield around the Sun
during a total solar eclipse. When eclipsed by the moon, the Sun would be
dark and the stars beyond it would be briefly visible. According to
Einstein's General Theory of Relativity, the Sun's gravity field would bend
incoming starlight, causing the apparent star locations to shift slightly
from their usual positions. Eddington's team captured and then analyzed the
photographs to determine that, indeed, the Sun's gravity "well" deflected
the incoming starlight.



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