Thursday, October 14, 2010

Steph’s Science Corner: Schrödinger's Cat, The Quantum Mechanical Celebrity of Culture, Theology, and Philosophy.

pictures of adorable kittens make quantum physicists look like jerksLast spring I was in the process of choosing a graduate school, and one of my visitation weekends was hosted by the University of Oregon Physics department.  I remember standing in a circle of PhD candidates, listening to one student’s entertaining rant about the nutty antics of a retired professor. Apparently, this crazy old coot had run wild with the mind-bending implications of Quantum Mechanics – the alternate realities, the eastern mysticism, and the ontology. He was now spending his retirement writing books about the existence of god, the mind-body connection, and something he called “quantum consciousness.” I was told I might recognize him from his interview in What the Bleep Do We Know!? I was treated to a hilariously detailed impression of a short, aging Indian professor who would insist that he could “collapse the wave function” of something and thus impose his will on it during lectures. It sounded a lot like new-age, alternative medicine voodoo that I, like most young science majors who are drawn to the field by observable evidence and logical proof, am naturally skeptical of. This guy sounded like a goofy, burnt-out nut-job to me.

His name sounded vaguely familiar at the time, as I enjoyed a laugh with a crowd of not-yet-disenchanted young researchers, but it wasn’t until months later when I finally made the connection. Dr. Amit Goswami is the author of the Quantum Mechanics text book that I used in college. The text book that I faithfully turned to just this week when I needed a reliable reference on the Quantum paradox of Schrödinger’s cat.

It’s funny how these things come full-circle.

The Schrödinger Cat paradox is a “thought-experiment” that was proposed by Erwin Schrödinger, one of the mega-pioneers of physics in the 20th century. It’s an idea that prompted many late-night discussions between the great minds of the era like Niels Bohr and Albert Einstein. It’s a reference that pops up frequently in popular culture from T-shirts to TV shows. In fact, “Schrödinger’s cat in popular culture” even has its own wikipedia page. But what most people get wrong is the existence of a universally agreed upon answer. Schrödinger’s cat is all about the questions.

The background in three paragraphs or less

As the 20th century dawned, scientists started asking themselves about the nature of light. It had no mass, and yet it packed a punch of energy, and it could interact with solid matter. One important discovery, led by Max Planck and Albert Einstein, was that light behaved as both a beam of particles and as a propagating wave, like the ripples in a pond. Seeing it as a particle helped us understand how it interacted with matter. Seeing it as a wave helped us understand how it interacted with itself.

In 1924, a French physicist named Louis de Broglie looked at this dual wave-particle nature and wondered if solid matter might also have a wave side to it. It turns out that it does.

But that’s crazy. When we think of atoms, we think of little balls of solid matter that move in a straight line when we nudge them. So how can a bunch of atoms flying through space interact as if two waves crossed paths, rather than just bouncing off of each other like billiard balls? It was this observation that lead to the revolutionary science that was Quantum Mechanics.

Clouds of probabilities

What we call a wave, we can for now understand as a way to visualize probability. The wave describes the places that we can expect to find an object at any given time. It’s not related to anything we directly observe, so what does it represent? Do we understand it as a group of objects like 100 coin flips, where probability tells us that 50 will be heads and 50 will be tails? Does it make sense to talk about this for a single object, since, once a coin is flipped, it has to be 100% heads or 100% tails?

Quantum mechanics explains this by saying that until we observe a system, it exists as all possible outcomes at once. Until I point out the exact location of an electron, it’s a sort of smeared-out cloud, existing everywhere with different degrees of likelihood. This is where Dr. Goswami got the term “collapsing the wave function” that his students loved to joke about. When you actually find where the electron is, that wave of probability just instantly reduces to a a single value. It can no longer be anywhere else.

This implies something very deeply disturbing – that simply our observation can change the nature of something. What constitutes looking? How does it just this magical reduction just happen? It’s these questions that Schrödinger’s cat fantasy asks.

It does not answer them.

The story of the cat

Here is the experiment: Let’s say you have a cat in a box with a single radioactive atom, a Geiger 800px-Schrodingers_cat.svgcounter (something that measures radioactive decay), a hammer, and a bottle of poison. This atom has a half-life of one hour, which means that there is a 50% chance it will decay within that time period. If the atom decays, the counter will tick. Suppose we have wired this counter to trigger the falling of the hammer, which is rigged to break the bottle of poison, which will kill the cat. If the atom doesn’t decay, none of the above occurs, and the cat will live. What is the state of the cat after the hour?

Since we live in a classical world of coin flips and lottery tickets, we’re comfortable with simply leaving it as a 50-50 chance and calling it good. But quantum mechanics forces us to think differently. Quite literally, during that hour, the cat exists as a superposition of both outcomes, half dead and half alive. You cannot see this dichotomy, because as soon as you check on the cat, you find it as one or the other. What that means is that, in the instant that you look, you change the state of the cat. That’s a lot of power you’re wielding just by looking.

But does this even make sense? How can the cat be both alive and dead? And who or what determines when an observation is made? Is it you? Is it the Geiger counter? Is it the cat? Einstein, bitter about the implications of this hot new field, was paraphrased as saying “God does not play dice with the universe.” But that’s exactly how quantum mechanics manages to explain the world of the very small. Without this superposition of possible states being very much real, we cannot explain things like quantum tunneling, which we know happens because we use it to make high-resolution Tunneling Microscopes.

An effort was made to simply treat quantum mechanics as an abstraction -- a mere mathematical tool. But others saw this as a way to recognize, scientifically, the inseparability of the of the event and the measurement – the subject and the object -- which is how scientists started dipping their feet into philosophy and, consequently, spirituality.

The crazy sister that science has always been ashamed of

The debate between the modern minds of science quickly resolved itself into something much larger than equations, measurements, and derivations. Quantum mechanics started shifting the focus towards the nature of reality, which, to be fair, is what scientists have been seeking all along, but it put it rather in-step with the now undeniably related beast that is philosophy. Is reality independent of our consciousness of it? Or does reality only exist because we are aware of it, and making measurements on it? When we look, we see a localized quantum object. This so-called wave nature never seems to manifest itself. If we’re stuck debating reality, how can we ever hope to prove that quantum mechanics is real if we can’t even see it?

And yet, because we act under the assumption that it is real, we can make things like atomic-scale microprocessors and nano-machines. This concept is at the heart of all your modern technologies – your smart phones, your computers, your high-definition TVs. As we make and resolve things at smaller and smaller sizes, we must face the consequences that very small things do what quantum mechanics predicts they will do. What does the development of technologies based off a fundamental principle of science that we still don’t fully understand imply about the world we are moving towards, and how we observe it?

The collapse of clear understanding

There is no one easy answer to this challenging set of ideas. This is why Niels Bohr famously said (loosely translated) “Those who are not shocked when they first come across quantum theory cannot possibly have understood it.”

...That’s the quote featured on the back of my textbook, written by Dr. Goswami. I looked up his website the other day and read a bit about what he’s been up to lately. He has a new movie about something he calls “Quantum Activism.” One critic calls it “Quantum Quackery,” and I’ll admit, he seems a little bizarre. Here is a brilliant man who spent his entire life studying the tenets of this sub-field, and he came out toting proof of the existence of god and the universal importance of consciousness like an eastern mystic. Quantum mechanics has become his religion, quite literally.

It’s funny how a set of mathematical equations, a few late night philosophical questions posed, and a physicist’s obsession with obscure ways to kill cats can lead us here, finding me opening up this book again after nearly three years of it sitting on my shelf again. It makes me think about probabilities. It makes me want to go out and collapse some wave functions with the power of my mind.

If you have any feedback, questions, or topic suggestions that you would like to see featured, feel free to sound off in the comments section or email me at science@charge-shot.com. Until next time!