We know science cannot
tell us anything about the world beyond our perception. What then can it tell
us about the reality that surrounds us? Is it able to give us a sturdy
foundation on which to build our lives? Can it answer our daily questions? We
will explore a bit of modern physics to see just how stable, or unstable,
science really is. The information in this section is based on generally
accepted theories at the time of writing, please note that
by the time you read this book these theories may have been replaced by equally
exotic scientific descriptions of reality. No matter what millennium you live
in, you will be able to discover and recognize the absolute limits of science.
If we are to accept
our observations of falling apples as proof of the law of gravity we must first
assume several things, for instance, that our eyes accurately perceive the
motion of the apple, that our ruler accurately measures the distance the apple
travels, and that our watch correctly records the time it takes for it to drop.
If confronted with the question "does the ruler you are using shrink and
grow if you look at it while moving at different speeds?",
most of us would laugh and say to ourselves of course it doesn't, a fixed
length is what makes a ruler a ruler. We would think the person asking the
question would have us questioning whether the apple is real.
Indeed I would have
you question all "scientific facts", for a scientist named Einstein
shook the assumptions about distance, time, and space that scientists had
relied on for thousands of years. In his theory of relativity he
"proved" the length measured on a "perfect" ruler and the
time measured on a "perfect" clock vary according to the relative
motion of one object to another.
Because the change in
length and time is unbelievably small where relative speeds are slow, as in the
case of a falling apple observed by an earthbound viewer, we can ignore the
affect of relativity on everyday life. None-the-less the effects are real and
sensitive instruments have confirmed them. Because our eyes cannot measure any
difference does not alter the effect. The affect on a ruler becomes so great
when relative speeds approach the speed of light that what was measured to be a
foot would actually become a millionth of a millionth of a millionth of an
inch.
Time is also affected
by relative motion. If an identical twin could travel to another planet and
back in a spaceship that flies at speeds approaching the speed of light, on
return to Earth the space traveler would find that he or she had aged much less
than his or her sibling. Perhaps the astronaut who left at age fifteen would be
only twenty years old when he or she returned, while the earthbound twin would
be ninety! This is not science fiction, the radical
results predicted by relativity have been confirmed by countless experiments,
including experiments where atomic clocks placed in jet planes ran slower than
their earthbound counterparts!
Here is another example
of an everyday "fact" taken for granted as being absolutely true.
What is the shortest distance between two points? Without hesitation the answer
for many, many years was "a straight line". The theory of relativity
tells us the universe may be shaped like a piecrust with bumps and valleys.
Thus the shortest distance between any two points in the universe, whether it
is between towns on earth or stars in space, must be drawn on the surface of
the lumpy crust (the area outside the crust is outside the universe and does
not exist) and, therefore, must be slightly curved! The curvature is so
infinitesimally small it cannot be easily observed, none-the-less the shortest
distance between two points may be a slightly curved line!
Over the last few
decades, some of the things which have been discovered are that energy and
matter are different forms of the same thing (energy = mass times the speed of
light squared); the speed of light is constant and nothing can go faster than
that speed; as matter approaches the speed of light it becomes infinitely
massive and shrinks in its direction of motion to become infinitely small; and
at the sub-atomic level matter is neither a particle nor a wave but is
incomprehensibly both. There are several excellent books written for
non-scientists that explain relativity and other topics in modern physics (also
please see these on-line resources The Light
Cone - An Illuminating Introduction to Relativity :
UseNet Physics FAQ : Reflections of Relativity).
Another foundation of
modern science, quantum physics, appears to offer a description of reality that
is radically different from the one relativity gives us. Laws that operate at
the subatomic "quantum" level provide probabilities of observing one
of many possible results instead of giving a single observable solution to a
problem. Quantum mechanics is a relatively new branch of science developed to
explain why subatomic particles do not behave according to the Newtonian and
relativistic laws that describe the behavior of "normal" size objects
(please see Quantum Mechanics
FAQ).
Just prior to the time
subatomic particles and events were first measured, physicists had declared
that, with very minor exceptions, all the fundamental forces and laws of the
universe had been discovered and described. When scientists started to apply
the traditional laws of physics to nuclear reactions they were literally amazed
to find that the laws did not work! The search was on for a way to modify
Light is made up of
energy in the form of "photons" which have mass (in motion) and which
behave like particles, SOME OF THE TIME. The rest of the time photons behave
like waves of energy, similar to ocean waves. If you will think about an ocean
wave you will realize water making up the wave simply moves up and down, not
forward. Only the wave itself moves forward. Thus if a boat is sitting a mile
from shore, each wave will cause it to rise and fall, but will do little to
move it toward shore. The boat will move a bit as each successive wave exerts a
slight pushing force in the direction of the shore, but the boat won't be
carried to shore by any one wave as the wave itself sweeps toward land. The
vast majority of the water is simply moving up and down, while only the wave
moves forward.
The problem occurs
when you try to measure photons using different tests. Some tests detect
"particles" of light hitting targets while other tests detect
"wave" interference when light passes through narrow slits. Back to
the ocean example, when two ocean waves meet they either cancel each other if
the trough of one overlaps the crest of the other, OR they reinforce each other
when the crest of one joins the crest of the other, forming a single doubly big
wave (or any combination in-between can occur). When two waves interact they
are said to be interfering with each other.
The problem is a
particle CANNOT act like a wave and a wave CANNOT act like a particle, yet
photons act like both! The solution of modern physics to this apparently
unsolvable problem is to say that photons are neither waves nor particles until
they are measured, and that the measurement itself determines the nature of the
photon. In other words, it is the measurement of the event that determines the
nature of the event.
To some degree this
phenomena can be said to express hidden problems with what reality really is.
In a sense physics is not able to describe the "reality" of an
individual photon since it appears to have two inconsistent, coexistent, yet
separate, natures. To the extent the point at which a photon is measured (known
as the collapse of the wavefunction) can be
considered an "event", an unsolved dilemma occurs in determining when
the event "actualizes". If light is both a wave and a particle until
measured, is it "truly" a wave (when measured as a wave by an
interference experiment) at the point it interferes with itself, or at the point
it strikes a photographic plate, or at the time the film is developed, or at
the point a human observes the final picture, etc.? The answer is simply not
known.
One of the greatest
philosophical shocks of this century came in the form of the Heisenberg
uncertainty principal. As far as many philosophers were concerned the last
straw was when, to help explain the observed phenomena, Heisenberg noted that
if you measure the momentum of one of the particles ("momentum" is
velocity, which is speed in a given direction, times mass) that make up an atom
you must in some way affect its position. For example, if you measure the
momentum (or velocity, the uncertainty principal is equally true for both
momentum and velocity) of a subatomic particle by "observing" it move
over a given distance, the observation alters its position in some
unpredictable manner. Similarly, if you measure position you must alter
momentum, thus at any given moment you CAN NEVER measure both the exact
momentum and exact position of a subatomic particle. The more precise you are
in measuring momentum, the less precise you will be about position, and vice
versa. The problem is actually more than a problem of measurement, to be more
accurate, the wave function of a subatomic particle (which describes the
particle at the quantum level) that has not been "observed" is
precisely determined (without using probabilities) by a formula known as Schrodinger's wave equation. However, the very moment you
attempt to measure the momentum or position of the particle, the wave function
collapses, introducing probabilities into the equation, and the exact momentum
and position of the particle CANNOT be determined.
Heisenberg's theory
can be interpreted as supporting the proposition that at the quantum level the very
concepts of momentum and position have no real meaning. At the level of
measured observation, modern physics can tell you how many particles in a group
of particles have certain momentums and positions, and how many have other
momentums and positions, but physicists CANNOT tell you what the momentum and
position of any one particle is. This failure is far more than just some
inability to measure momentum and position, it is due to the fact that it is
fundamentally uncertain what the momentum and position of any single observed
particle is! A single particle when measured simply does not have position and
momentum in any normal sense of the words, but members of a group do, and the
probability of x number having x momentum and x,y,z position can be precisely computed!
One interpretation
(there are others) of this finding is that nature appears to determine the
behavior of its "particles" by a flip of a coin. Einstein spent the
latter part of his life attempting to disprove this disturbing idea, it flew against his concept of the universe and
prompted him to say, "My God does not throw dice". Yet he was unable
to disprove quantum theory in general, and the uncertainty principal in
particular, both of which have correctly predicted every subatomic event that
they have been tested against!
To emphasize the
significance of the uncertainty principal remember it says that the uncertainty
about momentum and position is not due to limitations on humankind's ability to
make measurements, but rather is based on the apparent fact that when observed
the momentum and position of an individual particle is fundamentally uncertain.
Of course, future physicists may find an underlying set of rules that can be
used to predict the behavior of individual particles, or may discover a
fundamental unified law which is consistent with the observed behavior.
Einstein's discomfort may well have been the result of human limitations on his
understanding of God. Even though many questions remain unanswered, repudiation
of the uncertainty principal, however comforting it would be to philosophers,
seems uncertain at best.
One current theory,
which we mentioned earlier, that is popular among cosmologists and that would
eliminate the uncertainty, shows just how confusing and exotic the universe may
be. The truly wild (and from some scientists' points of view, virtually
unbelievable) "many-worlds theory", suggests that every time an event
occurs which has a possible required alternative, the universe splits into two
identical parts, except that in one universe one alternative occurs, while in
the other the other alternative occurs. According to this theory (or at least
to the most popular interpretations of it), there are potentially an infinite
number of identical, except for the required alternatives, versions of each of
us living simultaneously in different worlds. Uncertainty is eliminated because
every alternative is guaranteed to occur. Rather than being a model of reality,
this idea may be a product of human limitations.
If you want some more
disturbing news I can give it to you. There is a controversial extension of
quantum physics that deals with the problem of "locality". Components
of atoms have a property called "spin". Spin is one of the
fundamental quantities in the universe that must, and we do mean must, be
conserved. For each particle that possesses positive spin, there MUST exist a particle with negative spin. When two such particles
fly off in different directions from an atom, they always have opposite spin.
So
far, no problems. We can "entangle" the particles
and change the spin of one of them. The very instant we do so the other
particle's spin changes, no matter what the distance is that separates them!
Physicists, who accept that a problem exists, are at a loss to explain how a
particle in a different location without any means of communication knows what
another particle's spin is. It is a mystery how one particle knows to change
spin at the very instant the spin of the other particle is altered (experiments
seem to confirm the phenomena, however there may be a
hidden variable that would explain the observations by extending current
theory).
Einstein believed that
any "rational", in the sense of "objective", description of
nature is incomplete unless it is both a local and realistic theory. A theory
is "realistic" if a particle has "intrinsic" properties
that exist even before they are measured. A theory is "local" if
measuring the properties of one particle cannot affect the properties of
another, physically separated particle, in a length of time that would require
"communication" between the particles that is faster than the speed
of light. Yet quantum "entanglement" of spatially separated particles
may require that realism, or locality, or both, be violated!
One highly speculative
explanation of entanglement eliminates the normal assumption of
"locality", the assumption that events occur at one specific location
in the space-time continuum. If it is possible to have a rational description
of the universe without a local theory, then you can have events that appear to
be occurring in different locations actually occurring in the same place. Thus,
no matter how far apart they may seem to be, two particles could know each
other's spin because they are, in some as yet unexplained manner, in the same
"location". Perhaps the two particles occupy the same position in
some unknown dimension where there is no such thing as separation. Speculation
about the significance of lack of locality is really unproductive, except to
note that lack of locality could help explain premonitions and extrasensory
events.
Other complex examples
of conflicts with accepted concepts of reality, truth, and classical philosophy
and logic, are found within the fascinating, unsettling, discoveries of modern
physics. We are left with fundamental paradoxes, the solutions to which are
totally unknown. Indeed, despite what we are told by many scientists, it is not
at all clear to those working at the leading edge of scientific inquiry that an
objective physical description of the universe actually exists. The destruction
of traditional concepts of time, space, matter, energy, of life itself, is both
frightening, and hopeful. Given the dramatic efforts of modern physics to
unravel the mysteries of the physical world, coupled with the possibility of
the discovery of theories that better explain space-time (or atemporal space), perhaps even the discovery and/or
existence of other "dimensions", all manner of extraordinary event
may eventually be explained. Yet it is also possible that, despite appearances
to the contrary, the universe does not have an objective and/or observable
fundamental physical nature, and that no explanation is possible.
Again we need to
remember that all theories owe their credibility to repeated statistical
successes. Even in the case of generally accepted physical laws, like the ones
we have just discussed, one observed deviation would result in the probability
of the theorem being correct going to zero. When a theory is for the first time
shown to be false it is not merely more likely to be false, IT IS FALSE. On the
other hand, the more observations reported which confirm the predictions of a
"law", the higher the probability is that the law is true. No matter
how many observations are made, the possibility will always exist that the law
is in fact false.