Monday, February 02, 2009

Know Your (Planck) Limitations

Know Your (Planck) Limitations: Many, many years ago, when I was a college freshman, I got into a moronic metaphysical conversation with a few other people in my dorm hall. The topic was not moronic, the people discussing it were (which is redundant to point out since I already said we were college freshman). Naturally the topic of discussion was nothing less than the nature of the universe, which we were going to determine, and being a lifelong, knee-jerk contrarian I argued that the universe was discrete, that space-time was not infinitely divisible. This was met with sarcastic missives about all of us walking around like images on film, moving in chunks at a time, or living as drawings on a deck of cards being flipped through. Patently absurd, right? (Actually I think this conversation started as a discussion about Zeno's paradox of Achilles and the Tortoise.)

In all honesty I had no actual reason for making the argument other than it was not disprovable, and because then as now, I love to be the outlier, and because then and hopefully not as now, I was something an ass. (Did I mention I was college freshman?) But current research indicates I may have been right.

We all know about the universal speed limit, right? Nothing can go faster than the speed of light (~186,000 miles per second). Not even relatively. If you were in a car going 50 MPH and another car was going the opposite direction at 50 MPH and you hit it with a radar gun, the gun would tell you the other car's speed in 100 MPH. Makes sense. If both cars were going 186,000 miles per second, the radar gun would not measure the other car at 372,000 miles per second, but 186,000 miles per second. Makes no sense whatsoever.

The reason it doesn't make sense to us is because of evolution. The human animal has never seen, heard, smelled, tasted or touched a world with conceptual limitations. However fast anything was, there was always something that could go faster. However far away something was, there was always something a bit farther. You can divide things into smaller and smaller pieces, but you can always divide it again. Our minds accommodate infinity. That our brains evolved with the understanding of a limitless existence was probably a tremendous gift. It is almost certainly the basis of the species continued struggle to see beyond current boundaries and thus make constant improvements throughout the millennia.

It took a particularly highly evolved brain (Einstein) to discover that we were wrong; that when you reach magnitudes well beyond our current purview, there is a limit. No matter what you do, or how hard you strive, you will never exceed the speed of light. Perhaps one day, our brains will evolve such that that is as intuitive as limitlessness is now.

But how weird is that? Here we have this time-space continuum that is essentially limitless except for velocity. Other than velocity, there are no limits that we know of, right? Why just the one? Well, there is not just the one after all; the speed of light is just the most famous one. The other limits grow out the work of another highly evolved brain named Max Planck, who was one of the founders of quantum theory. Quantum theory states that energy is not infinitely divisible. In other words, a particle might have energy equivalent to 1 unit, and it might have energy equivalent to 2 units, but it cannot have energy equivalent to 1.5 units. Again, this is entirely illogical to our evolutionary ingrained sense of limitlessness.

From this understanding of energy only taking discrete values (quanta) Planck came up with something called Planck Length -- the shortest possible distance there can be; Planck Time -- the shortest possible time interval (which intuitively corresponds to how long it would take something at the speed of light to cover Planck Length); and a slew of others. I'll be damned if the universe is not discrete after all. The structure of the universe, to the best of our knowledge, is a thing we can calculate and imagine but not naturally comprehend.

Actually, that only goes as far as our current knowledge level. There is a phenomenon called Quantum Entanglement that makes even less sense that a limited universe. Two particles can be linked in such a way that no matter the distance between them, one reacts simultaneously to a change in the other. Think of it this way: two spinning tops both rotating clockwise are sent off in opposite directions. Eventually one suddenly begins spinning counterclockwise. The other does also, at the exact same instant. How does the other one know the first one changed? It couldn't be from having seen it or received any signal from it because we know the speed of light is finite, there would have to be a time lag before the second one changed, however small. But there isn't. No matter how far separate the two tops, they are perfectly in sync at all times. This is so bizarre that physicists have referred to it as "spooky action". It may indeed open the door to limitlessness again at some point in the future once we better understand it. Or it may be something even weirder.

I have no reason to delve into all this other than stumbling across an article in New Scientist about the world being a giant hologram that took me back to that conversation from freshman year. I guess the lesson is that no matter how obnoxious some little twerp can be he still might have a good idea. Doesn't mean he shouldn't be smacked-down on principle, though, just for being an ass.