Counterintuitive means contrary to what seems intuitively right or correct. A counterintuitive proposition is one that does not seem likely to be true when assessed using intuition or gut feelings.
Scientifically discovered, objective truths are often called counterintuitive when intuition, emotions, and other cognitive processes outside of deductive rationality interpret them to be wrong. However, the subjective nature of intuition limits the objectivity of what to call counterintuitive because what is counter-intuitive for one may be intuitive for another. This might occur in instances where intuition changes with knowledge. For instance, many aspects of quantum mechanics may sound counterintuitive to a layman, while they may be intuitive to a particle physicist.
Counterintuition in science 
Many scientific ideas that are generally accepted by people today were formerly considered to be contrary to intuition and common sense.
For example, most everyday experience suggests that the Earth is flat; actually, this view turns out to be a remarkably good approximation to the true state of affairs, which is that the Earth is a very big (relative to the day to day scale familiar to humans) oblate spheroid. Furthermore, prior to the Copernican revolution, heliocentrism, the belief that the Earth goes around the Sun, rather than vice versa, was considered to be contrary to common sense.
Another counterintuitive scientific idea concerns space travel: it was initially believed that highly streamlined shapes would be best for re-entering the earth's atmosphere. In fact, experiments proved that blunt-shaped re-entry bodies make the most efficient heat shields when returning to earth from space. Blunt-shaped re-entry vehicles have been used for all manned-spaceflights, including the Mercury, Gemini, Apollo and Space Shuttle missions.
The Michelson-Morley experiment sought to measure the velocity of the Earth through the aether as it revolved around the Sun. The result was that it has no aether velocity at all. Relativity theory later explained the results, replacing the conventional notions of aether and separate space, time, mass, and energy with a counterintuitive four-dimensional non-Euclidean universe.
Some further counterintuitive examples are:
- Gödel's incompleteness theorems -- for thousands of years, it was confidently assumed that arithmetic, and therefore similar systems of logic were completely solid in terms of being reliable for deductions. Gödel proved that such systems could not be both complete and consistent.
- Wave–particle duality / photoelectric effect - As demonstrated by the double slit experiment light and quantum particles behave as both waves and particles.
- Proof that 0.999... equals 1 - Some people find this difficult to accept.
- The violation of the monotonicity criterion in voting systems
- The Monty Hall problem poses a simple yes-or-no question from probability that even professionals can find difficult to reconcile with their intuition.
- Horseshoe orbits in orbital mechanics
- That light may pass through two perpendicularly oriented polar filters if a third filter, not oriented perpendicular to either of the other two, is placed between them.
- The Mpemba effect, in which, under certain circumstances, a warmer body of water will freeze faster than a cooler body in the same environment.
- That water vapor is lighter than air and is the reason clouds float and barometers work.
See also 
|Look up counterintuitive in Wiktionary, the free dictionary.|
||This article needs additional citations for verification. (January 2008)|
- http://dictionary.reference.com/browse/counter+intuitive "Counterintuitive: –adjective. Counter to what intuition would lead one to expect: The direction we had to follow was counterintuitive—we had to go north first before we went south." Retrieved: 09 NOV 2010.
- New Scientist, July 2005
- http://www.freshbrainz.com/2009/12/counterintuitive-science-fast-speed-fat.html Fresh Brainz. Counterintuitive Science: Fast Speed, Fat Shape. "It turns out that pointy-nosed spaceships perform well on their way out of the atmosphere, but not when they have to come BACK." Retrieved 09 NOV 2010.
- http://galileoandeinstein.physics.virginia.edu/lectures/michelson.html The Michelson-Morley Experiment. "As a result of Michelson’s efforts in 1879, the speed of light was known to be 186,350 miles per second with a likely error of around 30 miles per second. This measurement, made by timing a flash of light travelling between mirrors in Annapolis, agreed well with less direct measurements based on astronomical observations. Still, this did not really clarify the nature of light. Two hundred years earlier, Newton had suggested that light consists of tiny particles generated in a hot object, which spray out at very high speed, bounce off other objects, and are detected by our eyes. Newton’s arch-enemy Robert Hooke, on the other hand, thought that light must be a kind of wave motion, like sound. To appreciate his point of view, let us briefly review the nature of sound." Retrieved: 09 NOV 2010.
Further reading 
- Alvermann, S. A.; Hague (1989). "Comprehension of counterintuitive science text: Effects of prior knowledge and text structure". The Journal of Educational Research 82 (4): 197–202. JSTOR 27540341. More than one of
- Forrester, J. W. (1971). "Counterintuitive behavior of social systems". Technology Review (Alumni Association of the Massachusetts Institute of Technology). CiteSeerX: 10.1.1.35.4776. Based on testimony given to the Subcommittee on Urban Growth of the Committee on Banking and Currency, U.S. House of Representatives. Updated March, 1995.
- Havil, J. (2008). Impossible?: surprising solutions to counterintuitive conundrums. Princeton University Press. ISBN 978-0-691-13131-3.
- Norenzayan, A.; Atran, S.; Faulkner, J.; Schaller, M. (2006). "The cultural selection of minimally counterintuitive narratives". Cognitive Science 30: 531–553. CiteSeerX: 10.1.1.88.187.