Topic: medical

Cracking your knuckles does not cause arthritis. Multiple studies have found no link between habitual knuckle cracking and the development of arthritis, despite the long-standing belief to the contrary.

Deoxygenated human blood is not blue. It is always red—ranging from bright red to dark maroon—regardless of oxygen content. The idea that it is blue comes from a misunderstanding of how veins and skin interact with light.

The claim that hormone replacement therapy (HRT) broadly “causes cancer” is an oversimplification. Certain forms of HRT can increase the risk of specific cancers (notably breast cancer with combined estrogen-progestin therapy), but risk varies significantly depending on formulation, duration, patient history, and whether estrogen-only therapy is used.

The idea that humans only use 10% of their brains has been widely circulated, but neuroscience shows that almost every part of the brain has a function and is active over a normal day.