From the ancient times myths has been passed by generation to generation through "grandmothers and old wives". Though myths doesn't really have any serious impact in our day to day life, it was told by elders just not to let their young ones to do some particular thing, which they don't want from them to happen.
5 Scientific Myths
Only 10% of our brain we can use
It is very much true that there are still many things to know about brain and its function due to its complicated structure, but doesn't mean we cannot use entire brain. The figure 10% is totally wrong, there are no evidences that human brain's capacity is just 10%, at times we might not use entire brain all times but we do use our whole in the period of whole day.
The full moon causes erratic behavior in humans
All this while this myth has led us astray, it is believed by some specially working elderly or abnormal people that full moon influences behavior of a person. It is supposed that water in the brain is affected by the tidal force in the moon and causes erratic behavior. Lots of studies occurred on this topic but no evidences found, in simple words there is no relation between full moon and erratic behavior of an individual.
Cracking your knuckles led to arthritis
Well it makes a sense when your joints are stretched repeatedly from the surface that can affect your joints and this is called as osteoarthritis. There is fluid present "synovial fluid" which acts as a cushion at the joints and during sitting as well as standing the joint capsule separates and forms a bubble, when the bubble bursts it make a popping sound.
Hair and fingernails grow after death also
There are some who believe that nails and hair continue growing after death, but this statement or myth completely invalid, because nails and hair are cells which are dead as there is formation of new cells, for this process to happen one must eat to provide nourishment to our body and it is obvious that being dead no one can eat.
Lightening never strikes the place twice
People believe lightening never strikes the same place twice, but it does, which means something bad going to happen but actually there is nothing to do with lightening, because it is merely a electrostatic force which finds a way to come down and can strike anywhere as many times as it want. Usually it strikes tall buildings and trees many times as there is distance for it covers.