Early reading of the speed of C (light) were 'surprisingly variable but by 1927 speed of light was thought to be 299,796 kilometres per second which was considered a very accurate reading. But from 1928 until through till 1945, the speed of light dropped all around the world by 20 kilometres per second. Suggesting perhaps cyclical rhythms in light speed. In late 1940's, the speed of light increased again by 20 m/s. t keeps varying.
The speed of light keeps varying but to solve this problem a bunch of scientists fixed the speed of light by definition i.e,299 792 458 m / s.
A Brief History of the Speed of Light - http://www.pbs.org/wgbh/nova/blogs/physics/2015/02/brief-history-speed-light/
The speed of light keeps varying but to solve this problem a bunch of scientists fixed the speed of light by definition i.e,299 792 458 m / s.
Scientists slow the speed of light -http://www.bbc.com/news/uk-scotland-glasgow-west-30944584
Rupert Sheldrake speaks, argues that speed of light is dropping - https://whyevolutionistrue.wordpress.com/2013/03/06/tedx-talks-completely-discredited-rupert-sheldrake-speaks-argues-that-speed-of-light-is-dropping/