originally published April 7, 2012
Any physicists reading today’s article (and I’ve been told that my site is tremendously popular among physicists, especially when I write about stacking chairs or old Andrew Dice Clay movies) should stop now. I’m about to make an ass of myself, trying to understand a handful of ‘thought experiments’ that were designed by and for brains sharper than mine.
A thought experiment is when people sit around a table (though I’m not certain the table is necessary) and postulate on some grand experiment that could usually never actually be performed. They discuss possible outcomes the way we common-folk would discuss what might have happened if Jay Cutler had stayed healthy last year, or whether or not Greedo shot first.
The first thought experiment that Ms. Wiki crammed into my consciousness this morning is the Cosmic Catastrophe. What would happen if the sun suddenly disappeared? Isaac Newton’s theory of gravity states that the planets would immediately stop moving in a circle, and because of their inertia they’d just keep truckin’ in a straight line, off into the unknown.
Einstein wasn’t sold on that idea. He felt that the disappearance of the sun would cause gravitational waves in spacetime that would reach us only at the speed of light. Only when we got hit by that wave would we start heading in a straight line. I’m pretty sure we’d all be dead anyway, so it wouldn’t really matter. This is probably why I don’t get invited into a lot of thought experiments – my “we’ll all be dead anyway” refrain gets a little old.
There are a lot of these thought experiments listed, ranging from the field of physics to philosophy, economics to biology. Then you have the buttered cat paradox.
If cats always land on their feet, and toast always lands butter-side down, if you strapped (or stapled, but that’s mean) a slice of toast to a cat’s back, then threw it in the air, would it hover, spinning, a few inches off the ground and never land? The correct answer is, “Yes.”
I thought I was being clever, but in 2003 Kimberly Miner won a Student Academy Award (which is actually a junior Oscar) for a short film about how this act of perpetual motion through science could power a monorail.
We’ve all heard of the Infinite Monkey thought experiment. If a monkey (or a room full of them) was placed in front of a typewriter, eventually he’d happen across the keystrokes that could reproduce the complete works of Shakespeare. The general consensus is that, with a single monkey, it would probably take longer than 100,000 times the age of the universe for this to happen, but it can’t be said that it would never happen.
While we’ve all heard of this little gem of mental self-floggery, some people have put actual math into this. Math that looks like this:
I think the moral here is that, next time you’re bemoaning the meaninglessness of your job, be it paper-shuffling office drone, retail peddler of cheap, plastic trinkets, or print-shop worker who prints government books that nobody really reads, remember that there are people with actual college degrees who spend their days contemplating a magical and eternal monkey.
The Ship of Theseus thought experiment dates back to Socrates and Plato, but is officially credited to Plutarch in the 1st century. The question is this: if you take a ship and restore it by replacing all of its parts, is it the same ship? Philosophers have hung their feathery hats on this one for centuries. The “George Washington’s Axe” question is similar – if his axe had its handle replaced three times and its head replaced twice, is it still the same axe? And why George Washington’s axe? Was he known for having a really bitchin’ axe?
Okay, my mind is frothing now. Let’s move on to a thought experiment that actually has some practical value, the Monkey & the Hunter. This demonstrates the effect of gravity on projectile motion, and once again incorporates a monkey into abstract theoretical concepts. Deep thinkers love monkeys.
The thought experiment here imagines a hunter out for a day of shooting monkeys.
If he comes across a monkey hanging from a branch at eye level, where should he aim? This experiment assumes that the monkey will let go from the branch the very instant the trigger is pulled, so the hunter has to compensate, not only for the monkey’s rate of descent, but also for the rate of descent of his bullet as it travels forward. Once again math is involved, so once again we’ll move on.
Here’s one that relies purely on one’s personal ethics. Imagine you wake up in a hospital, somehow acting as the life support for a famous violinist. If you disconnect yourself, the violinist dies. If you stick it out for nine months, you can both walk out with no problem. What do you do?
More importantly, why a famous violinist? How does that affect anything? This was conceived in 1971, when I suppose being a famous violinist may have carried some societal impact. I guess an updated version of this thought experiment would have you connected to a reality show host or something.
This argument was used to support the right-to-life argument in abortion – substitute the violinist for a fetus. Wow. I didn’t mean to get tangled up in that debate. Let’s try one more.
Possibly the most famous thought experiment is Schrödinger’s Cat, involving a cat locked inside a box (thought experimenters love to torture cats almost as much as monkeys). The cat is stuck with a tiny piece of radioactive matter and a Geiger counter. A single atom may or may not decay over a period of time; if it does, the Geiger counter detects it and releases a dose of poison to kill the cat. If not, the cat’s fine. One can argue that, after that period of time, before opening to box to check, the cat is simultaneously alive and dead.
Fascinating stuff. Also fascinating is how many of these theoretical scientists enjoy ruminating on dead or dying animals. And they have the audacity to kick me out for my “we’re all dead anyway” stance.