Nah - sorry Bob, you're wrong! We can blame Mr. Bell for the silly sound behavior, Mr. Newton for the Laws of Gravity and Mr. Einstein for not letting us go faster than the speed of light!
Anyway, it seems an odd and illogical thing to say that a 5 watt amp is only half the volume of a 50 watt. People who buy 100 watt amps think they are getting one which is twice as loud as a 50 watt! They would be very disappointed to know that it isn't so. Again, this is with all things being more or less equal; speaker sensitivities etc. I think you might find that the majority of musicians, guitarists etc. are ignorant of the physics of power and volume - apart from the well-informed members of this site of course!
Thanks for the info Didier - I knew you would have it!
Cheers, Lionel