I wanted to write a post about something scary for Hallowe'en, and I think I just found it. I came across this Answers.com question and answer. The asker wants to know if he can use the Archimedes principle to weigh an airplane without a scale. And he knows that Archimedes developed this principle to determine whether a crown purported to be solid gold was indeed solid gold.
Several people tried to answer this question. Two suggested that the way to do this would be to completely submerge the airplane, evacuating all air. One concluded that this would work, assuming one knew the density and composition of the materials from which the airplane was made ("measure the volume of water displaced and multiply it by the mean average density of the plane to get the weight") and the other, citing "I'm a vampire blur" as sources concluded that such calculations were not possible, "so neh." Three suggested floating the aircraft and one didn't read the question properly, so suggested weighing the airplane on scales, using more or less the methodology cited by the asker in the original question.
The Archimedes principle is this:
"When a body is wholly or partially immersed in water, the upthrust, or loss of weight is equal to the weight of the water displaced."
One of the people who gave me my start in science and mathematics had come from an educational tradition where students learned things by rote memorization and demonstrated their knowledge by standing next to their desks and reciting them. A generation or so earlier they probably had to say it in the original Greek. That was never demanded of me, in any language, but when learned snippets of natural philosophy are recited by someone you respect, they stick anyway. I never have to look that up. Rote memorization is obviously not sufficient for understanding and application, but it's an anchor for the knowledge.
An airplane could be weighed by the water displacement method if you put it on a floating platform in a tank of water, and noted the water level in the tank. Then you hoist the airplane off the platform and measure how much water you must pump in to fill the tank back to the identical water level. That is the amount of water the weight of the airplane displaced, and by multiplying its volume (which you measured while pumping) by its density at that temperature, you have the weight of the airplane. That's easier than filling the tank to the brim without the airplane then collecting and weighing the water that spills over the top when you add the airplane, but it's functionally identical.
But because this is the way the world works now, on Answers.com people voted on which was the correct answer. The vampire blur who wanted to sink the airplane "won." I know this is by no means the nadir of stupidity in online question and answer polls. You might tell me not to get too upset about this because he only received two votes and one of the floaters received one, but it's a second risk of the democratization of knowledge: not only has popularity become the definition of truth, but low voter turnout makes it easy to influence "truth."
Once upon a time in some parts of human history, when people didn't know things and they couldn't easily test them for themselves, they went to people who were wise, or powerful or lucky and asked them for the truth. What they said was accepted as the truth, even in the face of meticulous contradictory observations. Then came the scientific revolution. It wasn't about new knowledge. It was about how we know knowledge. We test it in a way that anyone can reproduce, and experience as truth instead of being told. That's the purpose of laboratory science training in schools, to show students that what they are learning is real and discoverable, not rote and on faith. Scientists worked in Latin and Greek not to be obscure and elitist, but to communicate. The Greeks and the Romans had the first literate engineers in the western world, and theirs became the tradition for communication. Newton reported on some of his discoveries in English, and despite a few centuries of language change, it's some of the most clear readable reporting of primary scientific results you'll ever read. It's not laden with jargon, just uses and defines existing terminology for the phenomena.
Since then knowledge has become more esoteric, experiments more expensive, scientific language more obscure, and people have to rely not only on others to do their experiments for them, but on others to read the results and filter them. We've gone back to individuals choosing which wise man they will turn to, and we've lost the distinction between philosophy and experimental knowledge. There's nothing wrong with turning to someone whose experience, subject knowledge and capacity for thought is greater than yours and asking for help understanding the world. There's nothing wrong with taking ones own knowledge of the world and trying to share it with others (at least there had better not be, because I do it all the time). But it results in a breakdown in the distinction between what is empirical fact and what is opinion. There is very little real historical fact. Some bones, some photographs, some rusted swords, are all. We assume that when numerous sources close in time and space to the occurrence agree with each other and with the physical evidence that we have historical fact, but we have to be open to the possibility of collusion by the only people who knew the truth. Wikipedia has rapidly become a major source of information for individuals and for the media we depend on to give us a broader view. Wikipedia is kind of a shoutocracy. When the only version of events that anyone looks at is the one laid down by he who shouts loudest, then did anything else really happen. Ethics have no empirical truth, and all we can do to determine which are right is to consult our wise people, our consciences, and the norms of our society. But some things are either real or not, and when there is a conflict among voices on determinable facts, but the "winner" is determined by volume1, popularity, tenacity, intimidation, tradition or apathy, that is very scary. Happy Hallowe'en.1. Not by immersion in water, but that might be nice, in certain cases, incidentally settling the matter of who is a witch, just in time for Hallowe'en.