This series of posts is based on
Brian Greene's The Hidden Reality,
and I highly recommend buying it if you are interested in exploring the subject
further.
Quantum physics came about at a
time when people were wondering if they had reached the End of Science at the
end of the 1800s. Newton's concept of
gravity had ideally described motion for hundreds of years. Maxwell and others developed Maxwell's
Equations which seemed to completely explain the nature of light and
electromagnetism. All was good with the
world. Lord Kelvin's indicates the
general notion at the time:
"There is nothing new to be discovered in physics now. All that remains is more and more precise measurement" - Lord Kelvin, 1900
Little did they know that an
obscure worker at the Swiss patent office, Albert Einstein, was spending his
evenings developing his Special Theory of Relativity which would be published in 1905. That
would lead to a tectonic shift in the way all of us perceive the universe,
would meld space and time, and would climax with two giant mushroom clouds over
Japan in 1945. But we're here to talk
about another breakthrough round about the same time.
Quantum physics all came about
because someone wondered why things glowed red hot. Or more particularly why things glowed a
certain colour based on their temperature regardless of the material. Classical physics was having a hard time
explaining this until a fellow named Max Planck offered that you could get the
math to work if you made it so that electromagnetic could only be emitted in
multiples of a certain of a certain package size, called a
"quantum." Electromagnetism,
at small scales, was not continuous, but discrete, made up of bits, like a
digital computer.
Well, like any good physicist,
Planck and other physics luminaries kept going, and it was one of those
extremely satisfying moments like when you get your fingers under a corner of
wallpaper and a whole huge swath of it rips up in one piece. Several groundbreaking findings followed that
laid the basis for quantum physics.
Heisenberg's Uncertainty Principle
showed that you couldn't know both the position and the velocity of a particle
exactly. You could know exactly where it
was, but nothing about its velocity, or vice versa. But not both.
Not just because they didn't have machines sophisticated enough to
measure them, but because, at the tiny subatomic scale, reality itself became
smeared. At this scale, an electron or a
photon could not be thought of as a particle or a wave, but a particle and a wave.
Erwin Shrodinger developed an equation to predict the probable location of subatomic particles. Again, because of Heisenberg's Uncertainty Principle
and the mathematics involved, you never knew exactly where the little buggers
were hiding, but with Shrodinger's equation you could say "I'll lay two to
one odds the electron is over there" and come out a winner at the end of the
night.
So in twenty years they went
from the End of Science to black holes, the gravity-warped space-time continuum
and the idea that the stuff of nature, at the subatomic substrate doesn’t really exist per
se, but just kind of exists. This is what caused Reginald Bottomsley
III to remark, at the 1927 World Physics
Conference, "What f%@kery is this?"
OK, I made that last part up. But
they were all thinking it.
But was this "probability wave"
of Shrodinger's real or just a mathematically convenient description of what
was happening? The famous double-slit
experiments of the 1920s showed that the electrons behaved, in reality, like both
particles and probability waves. If
you're interested in the double-slit experiment, here's a good little youtube video on it.
Now if your head is spinning,
don't worry. That's pretty much
everyone's reaction upon exposure to the double-slit experiment. An electron exists as a probability wave,
harbouring within in it every possible future.
But when you point a machine to look, an electron jumps out at you
singing Here I am / The one that you love. It's only a probability wave when you're not
looking, but when you look at it, it
becomes a particle at a point in space.
Like little children, the electrons behave completely different when
people are watching. What the heck is
that all about?
 |
| View of electrons through microscope. Note the remarkable similarity to 80s cheezerock band Air Supply. |
This remains, probably, the most
popular interpretation, but it has some problems. Why, for example, should an electron care if
someone is watching it? What does
"observation" mean? Does a
sentient being need to be involved? Will
an electron show up singing the Greatest Hits of Air Supply if the measuring
machine is on but the grad student whose supposed to be watching it is playing
Second Life? Who or what chooses which probability actually happens? And then there's the niggling detail that
Shrodinger's Equation doesn't really allow for a sudden collapse like that.
So another interpretation of
quantum mechanics was proposed. In this one, the probabilities of the events
that didn't happen didn't collapse to zero.
All possible events happened, each in a co-existing universe. The universe splits for each outcome. A different parallel universe is created for
each possibility. To use a
not-completely-accurate "macro" analogy, when you roll a pair of
dice, eleven universes are created, one for each outcome. We are part of a vast, complex probability
wave function containing every possible future of every subatomic event within
it. Anything that ever could have
happened did happen—not necessarily in the universe we experience but in other,
parallel, universes that are being instantiated by the trillions every
microsecond from all the probability waves of the subatomic particles in our
universe.
This is the Many Worlds
Interpretation of quantum physics. It's
got it's issues too, but it's preferred by many of the great minds of quantum
physics, not the least of whom is Stephen Hawking. Many Worlds or the Copenhagen Interpretation? It's somewhat
of an academic question right now. Since
the various probability waves decohere, it doesn't seem that we can actually communicate
with any of these parallel universes. And
no one has thought of a way to feasibly test the Many Worlds Interpretation
(though there are some ideas).
But like the infinite universe
and the bubble universes of the last column, the Many Worlds Interpretation is
completely mathematically consistent.
So now we've got The Is containing, potentially, an infinite
number of infinite universes and a parallel universe for every
possibility of every subatomic event that ever happened or ever will happen in
all those universes. But we're not done
yet.
Next up: Simulated Universes.
