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Solve a puzzle about mixed dog breeds, sexual reproduction and the COVID-19 pandemic.

Readers poked holes in our paradoxical April Fools’ Day claims about perpetual energy and whether this puzzle solution would ever be published.

This April, find the fatal flaws in two paradoxical claims — one about a perpetual source of energy and the other about whether you will ever see the solution to these puzzles.

While the age-old chicken-and-egg paradox is easily answered, the question of infinite regress in physics is far from resolved.

The apparent paradox of the chicken and the egg smells like “turtles all the way down.” This puzzle shows how biology and physics can overcome infinite regress.

While mathematics gives us elegant explanations for many physical phenomena, real-world situations often require us to scramble through dense numerical thickets.

Many of us are drawn to beauty in mathematics. But is that the way nature really works?

Readers’ modifications of a bean machine showed how deterministic laws are capable of producing random-seeming behavior.

Mathematicians have figured out exactly how many moves it takes to randomize a 15 puzzle.

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