apocalyptic
adj. the end of the world or universal disaster, often related to a prophecy. In the Judeochristian beliefs, the apocalypse is the end of times, when good ultimately triumphs over evil – after much destruction. Also see eschatological.

apocryphal
adj. of dubious authorship and origin, usually not true. The Apocrypha are the Christian texts that didn't make it into the bible – they were considered useful, but not divinely inspired.

b’ak’tun
n. a length of time in the Mayan calendar, equating to 5,125 years. The current b'ak'tun will end in December 2012.

butterfly effect
n. a metaphor for sensitive dependence on initial conditions in chaos theory – ie. if you change even the smallest thing at the beginning, the rest of the system will change too. It was coined by Edward Lorenz, a meteorologist, in the 1960s, and is also used in quantum physics and popular culture.

collective consciousness
n. the shared beliefs and world view of a society – not just the beliefs we're aware of, but also the ones we take for granted. Often used with spiritual undertones and sometimes confused with Jung's collective unconscious.

endorphin
n. a compound released by the brain which raises one's pain threshold and give a feeling of well-being. Endorphins can be released through exercise, orgasm, spicy food, pain, and excitement – hence "endorphin rush".

eschatological
adj. theology or doctrines about the end of the world. Similar to apocalyptic, it has a narrower, theological meaning.

falsifiable
adj. something which it's possible to prove or disprove. The logic runs that if you can think of a way to prove that something isn't true, you can test it. (It's easier to disprove things than prove them. For example, "all stars are balls of burning gas" can be disproved if we find one star that isn't. To prove it, however, we will need to test every star in the universe.) If something isn't falsifiable, there is no way to test whether it's true or not.

hypothesis
n. in general terms, a conjecture, a guess, often used as a synonym for a theory. In scientific terms, a hypothesis can't be proven but is falsifiable; a theory is a more established hypothesis, generally accepted as true.

light’s duality
n. the way light behaves as both a particle and a wave. This doesn't mean it is a particle and a wave (or particles moving in waves). Rather, we don't know what it is, but depending on what experiments we do, we see its different behaviors. Instead of referring to light waves or light particles, the term "wavicle" has been suggested.

meme
n. a cultural "gene" – a belief, idea, symbol, or practice, that is passed down through society much like our genes are passed down from our parents. A catch-phrase can be a meme; so can a religious rite. A group of memes is a memeplex. The word was coined by Richard Dwarkin in his 1976 book, The Selfish Gene.

observer effect
n. the theory in quantum mechanics that observing a system will change the state of that system. If we measure an electron's position, we change its momentum, and vice versa. Interpretations of quantum theory disagree about what this means.

operative fiction
n. something which is not neccessarily true, but which works if we believe it is true – for example, taking a placebo. In science, something which hasn't been proven or can't be proven, but which works anyway, is called a working hypothesis.

paradigm shift
n. in general use, a paradigm is a society's set of assumptions and beliefs about the world, similar to zeitgeist (also see meme). When these basic, underlying assumptions change, it is a paradigm shift. Originally coined by Thomas Kuhn in The Structure of Scientific Revolutions (1962), it was first used only for the hard sciences before broadening its usage.

punctuated equilibrium
n. the theory that evolution moves forward in jolts, with long gaps of stasis in between, rather than a smooth and constant progression. First proposed by Niles Eldredge and Stephen Jay Gould in 1972, it became popular with the media and has been criticized by fellow scientists, but also has its supporters.

quantum leap
n. in general use, a sudden or dramatic change. In quantum physics, it describes how an electron "jumps" from one orbital (orbit) in an atom to another, apparently without moving between them.

quantum uncertainty
n. the theory that it's impossible to know an electron's precise speed and position at the same time – the more accurate one measurement is, the less measurement the other is. This is Heisenberg's uncertainty principle and is also related to the observer effect.

reductive materialism
n. the philosophy that everything can be reduced to its material components – that everything has a scientific origin and explanation, even if we don't have that yet. For example, explaining faith-healing according to neurological and chemical states in the mind. Also known as "identity theory".

scientific method
n. a means of acquiring knowledge based on observable, empirical, measurable evidence. The four stages are as follows: check whether something is explained already; if not, form your own explanation (conjecture); make a prediction based upon that explanation; test for whether the opposite happens to what you predict, to see if you can disprove it. (Also see falsifiable).

scientific model
n. an scientific explanation or mental picture of how something works, when it's impractical or impossible to test it in real life – for example, a climate change model (because it's impractical to experiment on our climate) or a model of the Big Bang (because it's currently impossible to replicate that). A model is not the truth about how something really is, but it must make accurate predictions that match with data we actually get. For example, climate change models are compared against previous climate change data to see if they predict what really happened.

sociocultural evolution
n. a general term for how our cultures and societies change over time. (Also see meme.)

thought-experiment
n. an idea about an experiment that would test a principle or theory, but which is impractical or impossible to carry out – for example, Schrödinger's Cat. Even if we were willing to risk sacrificing the cat, we still wouldn't know what state the cat was in before we opened the box.