Science Of...

The Odds In A Coin Toss Are Not Even

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A random coin toss really isn't as random and fair as you may think. Depending on the coin, each coin has a different bias. The center of gravity of the coin comes into play, and so both the edge-whether the coin has a beveled or serrated edge, for example. In fact, a coin flipped in the air is most likely to land with the same side facing up as before it was tossed. Preliminary data suggests this will happen about 51 percent of the time. However, it would take about 10,000 tosses before a casual observer would would notice this trend. According to Science News, a spinning penny will land tails side up about 80 percent of the time due to extra material on the head side that slightly shifts the center of mass.

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Key Facts In This Video

  1. Magicians often subtly shave down one side of a coin so it always lands on a certain side. 00:23

  2. Coins with unserrated edges tend to be more biased toward a certain side when falling after spinning on its side. 01:18

  3. Coins landing on the ground maybe be more biased toward landing on a certain side than coins caught in a hand. 02:39