Everyone Should kNow that "know" starts with a 'k'.

• Le Chatlier's Principle: if I heat a solution, it undergoes reactions that will tend to cool it down. If I increase pressure, it does things to decrease it. I'm not sure whether I can phrase it well (which is why I started with examples), but the rule is that an external change to the system will be met by internal changes that partially mitigate it. For another example, if the government raises the gas tax, (after-tax) prices will increase, but not by as much as the tax went up; also, when more workers join the work force, jobs tend to be created (so that the concept of illegal immigrants "displacing" American workers is at least somewhat flawed).
• There Ain't No Such Thing As A Free Lunch. Things can sometimes be arranged so that different people will bear the costs in different ways; perhaps the producer will give his time and any other resources voluntarily or by force, but eliminating the cost to the consumer does not evade the use of resources, which can not then be used for something else.
• On a related note, prices have meaning. Price is how the consumers communicate to the producers of a good how much they want it, and how the producers communicate how hard it is and how many resources are required to produce it. If consumers change their behavior and prices decrease, the producers know that they should divert resources to production of other things; if producers change behavior and prices decrease, the consumers know that the commodity is less resource-intensive and should be preferred to something more resource-intensive so that those resources can be saved for something else.
  Notes:
  • Interest is a price (expressed in somewhat odd terms); it is the price of money today in terms of money tomorrow. Some people want money now instead of later, often because they can use the money to produce something worth more money, or to avoid costs they might otherwise have to pay (e.g. buying instead of renting); the interest rates indicate to lenders how valuable that money is to the different borrowers, and helps them to divert it towards the people who can do the most with it. Just like anything else, there is a tradeoff between having the money now and having it later, and they aren't equally valuable in equal dollar quantities.
  • Taxes on specific items will tend to screw with the prices, changing the message that is sent; price controls eliminate the messages altogether, which is far worse. Even when we tax something that may be bad for the consumer, we are artificially making it appear even worse for that consumer, instead of allowing them simply to weigh their own costs and benefits against those of society, which would be contained in the natural price. Taxes on environmental pollutants, on the other hand, arguably impose on the consumer a cost to society that is not naturally factored into the price (economists call such costs "externalities"), though costs of environmental regulations on the producers will be reflected in the "natural" price. If both are used, it should be remembered that they are cumulative.
• Everyone should have a rudimentary sense that economic and legal incidences of a tax — or, for that matter, of anything else regarded as an external disturbance — can be different. As the price of jet fuel rises, both airlines and customers feel it, regardless of who directly buys jet fuel; similarly, both a landlord and a tenant will feel the impact of a change in property tax, and often it's the tenant who will feel it more strongly, even though the landlord actually sends the money to the government.
• An object at rest tends to stay at rest, and an object in motion tends to continue in the same direction at the same speed. Objects on earth tend to come to a stop; this is due to a frictional force. In the absence of such a force, the object will keep going, and inertia is how hard it is to stop it. If a ball is rolling along a circular track, and the track ends, the ball will continue in a straight line from where the track ended; it will not continue to go in a circle. (It was going in a circle before because the track provided the force to keep it changing directions.) "Inertia" is how difficult it is, how much force is required, to change the motion of the object.
• Everyone Should Know how to use percentages at at least a fifth grade level. If something costs a dollar, but is then discounted by 50%, it will cost 50 cents; if it is discounted 50% again, it will now cost 25 cents, so that the cumulative effect is a 75% discount, not a 100% discount. This is because the second 50% is 50% of the lower cost, not the original cost; 50% of the lower cost is 25% of the initial cost, and 50+25=75. Similarly, a 50% increase followed by a 50% decrease yields a 25% decrease. A 50% decrease followed by a 50% increase also gives a 25% decrease; the former is multiplication by 0.5, the latter by 1.5, and multiplication, like addition, is commutative, i.e. can be done in any order to get the same result. Thus, while sequential increases of 10%, 20%, 30%, and 40% will not result in a 100% increase (it will be about 140%), they will result in exactly the same increase as sequential increases of 20%, 40%, 30%, and 10%. (Beyond the scope of this is a discussion of natural logarithms and how they can be used to make percentages behave more the way many people believe they do; Everyone Should Know about natural logarithms, but I'm not optimistic on that happening any time soon.)
• Hot air rises; heat does not. Almost all heat that we deal with on earth consists of the internal (molecular-scale) energy of matter, and the most efficient way of transferring heat from place to place is to move the matter; since most things, air included, become less dense when they heat up, they will tend to rise above the denser, colder air, on which gravity is pulling more strongly. Water is actually at its most dense at 40 degrees Fahrenheit; below that it begins to expand, so that a fish in a 36 degree pond might well believe that heat sinks. (Incidentally, if this weren't the case, ponds would probably freeze solid in the winter, killing the fish that lived there; instead, the top freezes over, insulating the water below, which stays around 40 degrees near the bottom of a sizeable lake pretty much year-round.)
• Evolution
  • Natural Selection and Evolution favor complexity to the extent that complexity is favorable for survival in the environment, and they favor intelligence to the extent that that is favorable for survival, but it is perfectly possible for a less complex or less intelligent species to evolve from one that is more complex or intelligent. It does not make sense to speak of one species as "more evolved" than another species that exists at the same time. A single organism may mutate, but can not evolve; mutations will occur at random, some beneficial but most not, while evolution is the process of mutating lots of organisms at the same time and throwing away the mistakes.
  • We did not evolve from modern apes; we evolved from the same ancestors as they did. (The term "ape" seems to be used in exclusion of humans, but the chimpanzee, generally included, is more closely related to us that it is to the gorilla. Insofar as we, chimpanzees, and gorillas are "apes", it is reasonable to call our last common ancestor an ape.)
• If I oppose a law requiring people to eat chocolate ice cream, that does not mean that I don't like chocolate ice cream.
• Everyone Should kNow the difference between aggregate quantities and rates:
  • The national debt is how much money the government owes to bondholders etc.; the budget deficit is how much that increases in a given year. The deficit is how much more is spent than is taken in; the debt is the total of all deficits from the past up to this point.
  • Power is energy per unit time; a kilowatt is a unit of power, and a kilowatt-hour is the amount of energy that is used in one hour if it is being used at the rate of one kilowatt. If a power plant is being slowly brought on line, it may increase its capacity at a certain number of kilowatts per day, but a power plant running continuously under normal conditions will produce a certain number of kilowatts -- or, if you like, kilowatt-hours per hour.