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The mathematicians of ancient Greece attributed characters to numbers and awarded some of the status of perfection. For Euclid, one of the finding fathers of modern mathematics, a perfect number was one that equaled the sum of its own divisors – that is numbers that will divide into it without leaving a remainder. The first perfect number is 6: its divisors are 1, 2, and 3, 14 which add up to 6. The second is 28 (1 + two + four + seven + 14). The Greeks knew only two other perfect: 496 and 8,128.

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The sight of a dam – one of the largest and most complex structures that humanity has ever created – can be quite breath-taking. Take a look at some of the most spectacular of these structures.

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Initially scientists investigate the causes of population explosion of a jellyfish this small recently. Turritopsis Nutricula originally came from the warm Caribbean sea, but now has spread to the whole world, until the United States, Italy, and Japan. Until scientists finally find the reason. Jellyfish this, the biological, can not die.