Because your eyes are placed horizontally on your body not vertically ..... The monty hall one is good ... but i cant see any other answer than no difference to your chances at all It is 50 - 50 all the way.... fact not fiction .... how about the old classic .... place a living cat into a steel chamber, along with a device containing a vial of hydrocyanic acid. There is, in the chamber, a very small amount of a radioactive substance. If even a single atom of the substance decays during the test period, a relay mechanism will trip a hammer, which will, in turn, break the vial and kill the cat. Come back after an hour - is the cat dead or alive ?