Quantum Theory in a Coffee Break

Ever thought "hey, I want to learn quantum theory", but then realized that you just don’t have the time needed to go get a degree in theoretical physics? Maybe you’d like to learn quantum theory in the time it takes to drink a nice cup of coffee?

Instead of introducing this topic, I’m going to get right in to it. A while back, physicists got bored. They’d just realized that light was both a particle and a wave, which was no small discovery, and they wanted to confuse the real world even more. The first thing they noticed was that all ‘waves’ diffract when they go through small slits, and that when there are two slits that are really close together they make a very distinctive diffraction pattern. So they thought ‘hey, we shot a bunch of photons at these slits and they diffracted, let’s try it with electrons!’ And thus, Quantum theory was born!

When they tried electrons, which are particles with mass (unlike those pesky massless photons) they diffracted too! So, this must be a mistake, only waves diffract, we know electrons are particles. So they toned it down, let’s shoot one electron at a time… at two separate slits! Well, turns out the single electron diffracted, and that after a few million electrons, they were getting the double slit pattern. So this is weird. The scientists decided they’d go put a detector near the slits to figure out where the electron would go, but then something even weirder happened… when they were watching; the electron just chose a slit and went through. No diffraction.

Now, this got scientists thinking, and they decided that the only reasonable response is that the universe didn’t know where the electron was until it got a wake-up call by the scientists’ detection instruments (either before or after the slits), and that if we thought of the electron as a field of probability, that field could diffract as long as we didn’t force the universe to decide on where the electron was by taking a peek.

After that, it was obvious that there was a universal and irrefutable uncertainty with everything at every point in time. This even meant that you can’t know both the place and velocity of a particle, so particles have uncertain place, mass, energy, speed… you name it! Now, we know that when particles have too much energy, they release other particles, and that the uncertainties associated with most particles are big enough to make particles out of energy… imaginary energy. The problem is that when the imaginary particles get too far away without hitting anything, the fact that they’re imaginary stops them from existing. Now, why do we care about imaginary particles made of imaginary energy? Because when two particles are really close, and the probabilities line up just right… an imaginary particle can slam in to another particle. We say an ‘interaction’ took place, which means energy was transferred. We now believe that these interactions are responsible for literally every physical event in the universe.

Now, you must be wondering why we can predict physical events when they’re based off random collisions of imaginary particles. The answer is simple. In any given radius, every single possibility for an interaction is considered, and since uncertainty is larger the closer you are to something, more interactions occur when objects are close together. This explains electromagnetism and gravity, which are forces at a distance. The force between the actual ‘collision’ of two particles is much more powerful, but the probability of events at long-distances is so low it only happens when things get really close together.

Now, the last question you might be having, is why gravity pulls things together, when they’re actually shooting particles at each other. Well, physicists ran the numbers, and it turns out that gravitons (that’s what they call those interaction particles) are probably made of negative energy, and travel backwards in time at least the speed of light so that they hit the interacting particle ‘from behind’, and move it closer to the massive object. The subsequent discharge of directional negative energy also applies a force to the particle emitting a graviton.

So there you have it! That’s quantum theory, and if you’re wondering what that giant European particle accelerator is for… well, they’re trying to get concrete proof for some of this stuff. That’s all for now, folks.



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Alma Galvez
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Posted on Mar 17, 2010
Suba Lakshminarasimhan
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Posted on Mar 16, 2010