5 Science Myths That Refuse to Die: What the Evidence Actually Says

First published: October 16, 2026

Science myths are stubborn. They repeat themselves in classrooms, comment sections and dinner conversations because they are simple, quotable and feel useful. Here are five that refuse to die, and what the evidence actually says.

Myth 1: We only use 10 percent of our brains

The claim: 90 percent of the brain sits silent, waiting for some future breakthrough to unlock it.

The reality: brain imaging tells a completely different story. Scans using fMRI and PET show that over a normal day nearly every region of the brain becomes active – moving your hand, listening to music, even sleeping. There is no giant idle zone. The number is usually traced to misquotes of psychologist William James, who wrote that people meet only part of their potential – a motivational idea, not a brain scan. Damage to almost any brain area causes measurable deficits, which is the final nail in this myth’s coffin.

Myth 2: Lightning never strikes the same place twice

The claim: a second strike at the same spot is impossible.

The reality: lightning repeatedly finds the easiest path to the ground, and tall pointed objects are the easiest path. The Empire State Building in New York is hit roughly twenty times every year, and its lightning rod does its job on every single one of those strikes. If lightning refused to repeat, engineers would not install protection systems in the first place.

Myth 3: The Great Wall is the only man-made object visible from space

Both halves of this sentence are wrong. Astronauts in low Earth orbit report that the wall is very hard to see with the naked eye – it is built from materials the same color as the surrounding ground, so it blends in. Chinese astronaut Yang Liwei, asked after his 2003 flight whether he had seen it, said he had not. Meanwhile, plenty of other human structures are clearly visible: city lights at night, large airports, greenhouse grids and open-pit mines. The Great Wall is neither special in visibility nor alone in being man-made.

Myth 4: Goldfish have a three-second memory

Researchers have trained goldfish to press a lever for food, to associate colors with feeding times, and even to tell different people apart. Those memories last weeks or months, not seconds. A goldfish in a tiny bowl that stops growing or keeps circling is not showing a short memory – it is showing stress and boredom. The three-second myth is really a story about how little attention we pay to fish.

Myth 5: Shaving makes hair grow back thicker and darker

Uncut hair tapers to a fine soft tip. A razor slices it off straight at the skin surface, so the regrowth feels coarse and stubbly – it is the same hair, now with a blunt edge. Shaving does not change the number of follicles, the growth rate or the color. Studies from the 1920s through modern dermatology all reach the same conclusion. The stubble is an illusion you can feel but not measure.

Why these myths survive

Myths spread because they are simple, they sound clever, and correcting them takes longer than repeating them. The 10 percent brain idea sells books. The Great Wall story carries national pride. The goldfish excuse makes a small bowl feel acceptable. Once a myth gives comfort or identity, evidence alone rarely kills it.

The takeaway

Treat confident-sounding claims as hypotheses, not facts. Ask who measured it and how. A thirty-second search turns most stubborn myths into teaching moments – and teaching moments make better content, better dinner talk and better science readers. If a claim sounds like a movie line, it probably came from one.