7 Science myths debunked

I have collected a list of 7 widespread, alleged “scientific facts” and common misconceptions, with corresponding debunking.

This list is potentially much longer, but I decided to focus on those myths that I have encountered more often around me. It’s fascinating to see how common and persistent some of these cultural memes are: part of the reason must be their elegance and simplicity. The scientific truth is often more complicated — but by no means less elegant.

1. Menstrual synchrony

Myth: women who live/work together experience their menstrual cycle onsets becoming more synchronised together over time.

Truth: only one paper in 1971 measured such effect. All subsequent studies failed to replicate it, while others found methodological flaws in the first study. The scientific consensus is that menstrual synchrony likely does not exist.

2. Clockwise/counter-clockwise toilet flush rotation

Myth: water drains in different directions depending on the hemisphere you are in, because of the Coriolis effect.

Truth: while the Coriolis force does exist, it is not strong enough to affect the sense of rotation in flush toilets or bathtubs, where local factors are typically much more relevant (such as the geometry of the basin). Having said that, the Coriolis force has some real effects on larger scale phenomena like ocean currents and cyclones.

3. Humans evolved from chimpanzees

Myth: homo sapiens evolved from chimpanzees through natural selection over million of years.

Truth: humans and chimpanzees both evolved from a common ancestor who lived in Africa around 7 million years ago. While this primate was definitely very different from modern humans, there is no reason to believe it resembled today’s chimpanzees.

4. Evolution increases organisms’ complexity

Myth: biological evolution is a progression from simpler to more complex organisms.

Truth: evolution does not necessarily lead to an increase in complexity. Whatever works gets selected: sometimes what works is more complex than the starting point, sometimes it is simpler. After all, bacteria are among the most successful organisms on the planet.

5. The twin paradox and Einstein’s relativity

Myth: Einstein’s Special Relativity predicts that if one of two identical twins travels in space at high-speed and then returns home, the twin left on Earth should have aged more than the one who travelled. It’s called a paradox because it is at odds with our intuitive idea that time should pass at the same speed for everyone.

Truth: while the myth is correct in describing the Special Relativity’s prediction, it is wrong in interpreting its “paradoxical” aspect. It is not paradoxical because it is at odds with our intuition, but rather because it seems to contradict one of the principles of Relativity itself (specifically, the principle that all motions are relative, which would imply that time dilation should be the same for both twins). This paradox is only apparent though, and it disappears when you account for accelerations. It’s funny how the myth version of the paradox, which doesn’t even mention acceleration, is in effect an example of the naive interpretation of Relativity that prompts the paradox in the first place.

6. Galileo and flat Earth

This is more a historical rather than scientific misconception, but it’s so widespread that I felt I have to include it.

Myth: Galileo was a promoter of the idea that the Earth is round. He got persecuted because this idea was opposed by the Church. A somehow related myth wants Columbus challenging the idea of a flat Earth by sailing west.

Truth: the fact that the Earth is round has been known in the West since about the VI century BC. This fact wasn’t challenged by religious authorities even throughout the Middle Age, and it remained common knowledge among scholars and intellectuals. The controversy Galileo was involved in was about whether the Sun rotates around the (round) Earth or vice versa. For what concerns Columbus, he challenged the idea that the globe was too large to safely sail to the Far East from Europe (he was wrong, but he got lucky and found another continent on his way).

7. The supercontinent Pangea

Myth: when the ocean formed there was a single large continent, Pangea, which later split into our modern continents.

Truth: Our modern continents did split from Pangea, however this was far from being a first, primordial supercontinent: Pangea itself had formed from the “collision” of disjoint continents, which in turn formed from the division of an older supercontinent (called Rodinia)… and so on. Geologists believe that at least 6 supercontinents succeded since the formation of the Earth.