Modern myths

Two myths that are untrue:

"You only use ten percent of your brain."
If that were true, the remaining 90% would be vestigial remnants and eventually degrade away due to evolution, much like our appendices and the eyes of cave-dwelling animals.

The saying more closely corresponds to saying "You're only using ten percent of your muscles at one time." Over the course of the day, you'll use parts of your brain for various activities and by the end of the day end up using most, if not all, of the brain.

More detail here.

"Science has proven that bumblebees cannot fly. Bumblebees do not know this, however, and therefore are able to fly."

In the 1950s science tried to apply rigid-wing aerodynamic equations to insects and were unable to determine from said equations how the insects could fly. However, insects wings are flexible and rotate in ways that the equations couldn't accommodate for. So it is not that bumblebees cannot fly, but it's that they fly in a manner unlike our airplanes.