Scientists Say: Paradox

Mind-bending, counterintuitive facts sometimes unlock deeper levels of understanding

Despite having more cells, most large animals — such as elephants — do not develop cancer at higher rates than smaller animals, such as mice. This fact puzzled biologists and was called Peto’s paradox. Studying this paradox eventually led scientists to a deeper understanding of cancer biology.

Vicki Jauron, Babylon and Beyond Photography/Getty Images

By Katie Grace Carpenter

1 hour ago

Paradox (noun, “PAR-uh-dox”)

A paradox is when a scenario seems — at first — impossible. It goes against what your gut feeling tells you is true. Once resolved, however, a paradox often reveals something crucial about how a system works. It may correct a common misconception. Or it may address incorrect assumptions.

Sometimes, a paradox consists of real facts that seem to defy expectation. Moravec’s paradox is one example. It notes that many abilities that come easily to humans are quite hard to program into a robot. Walking, for instance. On the flip side, many easy-to-program abilities, such as complex math, are hard for humans to learn. Exploring this paradox can help us better understand how the human mind works.

Peto’s paradox is another example. It points out that large, long-lived animals get cancer at about the same rate as small, short-lived ones. For a long time, that fact puzzled scientists. They expected large animals to get cancer more often. Cancer starts when something goes wrong with a single cell’s genetic material. Shouldn’t large animals — which contain many more cells — have this problem much more often than small ones? The data showed this was not the case.

Scientists studied this paradox. They learned that large animals have genes that help reduce cancer risks. Researchers did not know to look for such genes before noticing the paradox. This is one case of a paradox helping us learn things we didn’t know that we didn’t know.

Some paradoxes are thought experiments. That’s an imaginary scenario that allows us to explore an idea that we can’t test in real life. Imagine, for instance, you traveled to the distant past. But then, you accidentally killed a distant ancestor. (Oops!) This might mean that you would no longer be born. But wait. If you no longer exist, that means you wouldn’t be able to travel back in time to kill your ancestor in the first place, right?

On its own, this sci-fi paradox doesn’t answer questions. But it does help us think about the physics of time. And that can inspire new ideas in scientists who study the nature of our universe.