Re: all that was left was to find the 6th decimal place

The quote from Albert Michelson was from his address at the dedication ceremony for the Ryerson Physical Laboratory at the University of Chicago in 1894:

"The more important fundamental laws and facts of physical science have all been discovered, and these are now so firmly established that the possibility of their ever being supplanted in consequence of new discoveries is exceedingly remote.... Our future discoveries must be looked for in the sixth place of decimals."

Michelson's experiments generally involved incredible detailed measurements of the speed of light, to several decimal places - and his quote reflects his view that future developments in science would require measurements of this level of exactness or more. In fact, scientists these days often need very precise measurements of time and distance for their results and to distinguish between alternative models or theories to describe or explain the results.

Albert Michelson's most famous contribution to physics was in the Michelson-Morley experiment. It was actually famous as a "null result"; that is, the theories about light at the time was that light travelled as a wave through some invisible material in space, called "ether" or "aether", much like sound travels as a wave through invisible air.

Based on the presumed existence of ether, the Michelson-Morley experiment sought to detect the change in the amount of distance light would travel, based on the movement of the earth through the ether. The beam of light was split in two, and the paths of the two beams of light were directed into different angles. Since light travelling with the earth through the ether should be at a different speed than light travelling at a 90 degree angle to that, Michelson and Morley sought to find this change in the speed of light, by looking at interference patterns when the two beams of light were brought back together. However, they found no difference. This historic null result was proof that ether does not exist; this led to the development and acceptance of Einstein's special theory of relativity, which offers an alternative explanation for the propagation of light without this imaginary "ether".

Here are some links with more information:

(1) http://hum.amu.edu.pl/~zbzw/ph/sci/aam.htm

(2) http://nobelprizes.com/nobel/physics/1907a.html

(3) http://www.phys.virginia.edu/classes/109N/lectures/michelson.html

(4) http://www.phys.virginia.edu/classes/109N/lectures/spedlite.html