Right, dogmatic as politicians are who are using science as their well for dominating human beings. That ‘the gravity constant’ varies on earth is quite well known but it is put as a constant to make calculations easier but not more understandable. That speed of light is constant if it is wave, is understandable for putting on a torch in moving train does not effect the speed of light, hence it has to be a ‘wave’ and don’t ask what a wave is. If light would be a particle then it would get the speed of the train too added to the speed of light. Due to matter speed of light varies. Don’t ask what matter is.