I wrote:
> Scientific instruments and techniques hundreds of years old can measure > temperature, the speed of an object, the speed of light and many other > important values with as much confidence as the best technology can today; > albeit with far less precision. > > Note that the speed of light was measured by Roemer in 1676 by observing > the eclipses of the moons of Jupiter. He measured 2.14 * 10E8 m/s. The > modern value is 3.00 * 10E8 m/s. I have confused the issue here. Let me explain what I mean by "confidence" in this case. I don't mean the mathematical version, which is what I meant elsewhere. In the 1600s there was a debate over whether light goes instantaneously everywhere, or whether it propagates at some speed. Roemer established that the latter is correct. He established with 100% confidence that light does move at a certain speed. Proof of that cannot be made more certain with the best modern methods. The actual number he came up with was remarkably accurate given the tools and knowledge of the time, but that's not the "confidence" I had in mind. I mean confidence in the conclusion that light moves. As far as I know, everyone at the time accepted his result. Here is an interesting footnote to history. I believe the speed of sound was not established with this much precision until later. This was done by assuming for simplicity that the speed of light is close to infinite over short distances, and firing a cannon. The time delay from the flash to the sound of the explosion gave the speed of sound. This was done in 1826 at Lake Geneva to establish a value to within 1% of the modern figure. I don't know how they recorded it. I guess by pressing buttons to start and stop a timer. You would think this would mainly record human reaction time but I suppose it depends on how far away the cannon was. - Jed
