Download Quantum Physics and Human Affairs

MODERN TIMES
Art Hobson
[email protected]
NWA Times 6 Jan 2007
Quantum Physics and Human Affairs
You've probably at least heard of “quantum mechanics." Quantum
physics (a better name, as we'll soon see), invented after 1900 to account for
certain microscopic phenomena, is important for you to understand because of its
insights into reality as scientists perceive it.
Quantum physics replaced "Newtonian physics," which reigned supreme
during 1600 to 1900. Although most people still think of the universe in
Newtonian terms, the scientifically accepted quantum description is radically
different.
According to Newtonian physics, the universe behaves like a perfect
mechanical device such as a precise clock. The universe, according to this view, is
made of many tiny independent parts (atoms) interacting with each other in
accordance with natural laws. Although this worked well scientifically until 1900,
Newtonian physics is philosophically difficult because it is uncompromisingly
mechanistic. It predicts that the universe behaves deterministically, like a clock. It
is difficult to find a place for free will, or human feelings, or even simple sense
impressions, in this theory, and in fact many philosophers considered such human
experiences to be “secondary qualities,” mere reflections of the primary physical
reality of atoms moving mechanically in empty space.
Quantum physics is radically non-mechanical. It's not based on individual
objects behaving deterministically. In fact, it says that the universe is not made of
particles at all, but rather of "fields"—more precisely, "quantized fields." Here's
what this means.
You've probably played with a magnet, picking up hairpins and other
objects from a short distance away. To describe this, we say that a "magnetic
field" surrounds the magnet. Similarly, a "gravitational field," surrounds Earth,
holding us down and causing dropped objects to fall downward.
As another example of a field, think of a flashlight beam shining on a
movie screen. Scientists learned around 1800 that every light-beam is a wave
traveling through an unseen "electromagnetic field" that fills the space between the
source (the flashlight bulb) and the illuminated object (the screen), sort of like a
water wave moving through water.
These and all other physical fields contain energy—the ability to bring
about change in the physical world.
A different view of light emerged beginning around 1905. Experiments
showed that, if you shine an extremely dim light on a movie screen, it makes tiny
flashes at separated points on the screen, as though tiny particles of light were
hitting the screen. At first glance, this particle-like behavior seems inconsistent
with the smooth, spread-out electromagnetic wave description given above.
But by 1950, physicists had found a theory that could reconcile these
apparent particles of light, called "photons," with the electromagnetic wave theory
of light. This "quantum field theory" states that the energy of the electromagnetic
field is "quantized," meaning simply that the field can contain only certain specific
amounts of energy and never any intermediate amount. Here's an analogy: A
quantized field is like water in a bucket that, for unknown reasons, must contain
either exactly 1 gallon, or 2 gallons, or 3 gallons, etc. of water and never any
intermediate amount such as 1.7 gallons. Such a "quantized bucket of water" could
gain or lose water only in sudden 1-gallon increments or "bundles." Similarly, a
quantized field must, for unknown reasons, gain or lose energy only in definite
"bundles." Each bundle is called a "quantum" (an abbreviation for "quantity of
energy").
A quantum of light is utterly non-mechanical. Once emitted by a bulb,
each quantum quickly fills the space around the bulb. If the light is shining on a
movie screen, each quantum of light fills the space between bulb and screen. Yet
when it interacts with the screen, it instantly "collapses" and is absorbed by a
single atom in the screen. Furthermore, the interaction is entirely unpredictable—
the quantum is just as likely to interact with one atom in the screen as
another. "Nature doesn't know" which atom will absorb the photon. Furthermore,
the interaction causes the quantum to instantly vanish everywhere between bulb
and screen, a phenomenon known as "non-locality" because it happens
simultaneously, everywhere within a spread-out region of space.
Furthermore, non-locality extends to groups of photons: Two (or more)
photons emitted from a single microscopic source behave in many ways as a single
object even though they are separated in space. If one photon happens to interact
with an atom while passing the sun, for example, the other photon will
simultaneously alter its behavior accordingly even though it might be passing Mars
at the time. The two photons are said to be "entangled." They are really a single
object, a "two-photon," in two different places.
It was known by 1950 that not only light, but all other "particles" of nature
behave this way. Atoms and molecules are not really particles at all. Like
photons, they are quanta of various kinds of fields. Quantized fields, uncertainty,
and non-locality extend to everything, including the atoms of your body. This is
nothing like a machine. In most ways, it's the opposite of a machine.
Many people reject scientific views such as evolution or the big bang
because such views seem to imply that natural processes are automatic,
mechanistic, and hence "godless." But seen in the light of quantum physics, such
processes are not mechanistic at all, and not necessarily threatening to religious
views. Although humankind is just beginning to figure out what quantum physics
means, one thing's certain: Compared with Newtonian physics, quantum physics
leaves far more room for human qualities.