Okay, so recently i realized that there is actually physics applied to the way a string orchestra is organized. (minus the woodwinds in there its exactly what im used to) The larger instuments such as cellos and double bass take longer to speak because of the distance between the back of the instrument where thr sound peg produces resonence and the front of the instrument to where it speaks is greater. Therefore they need to be closer to the audience and more on top of the beat than the smaller instruments such as violins and violas.
First violins are always in the front because they are almost always the melody of the Piece, thus their sound needs to be mroe forceful and by decreasing the distance between instrument and audience, the sound will be more audible and better balanced between harmony, melody, and background beats.
Also, the further back you are, the more on top of the beat you need to be, because in the time it takes for the instrument to speak, then reach the front of the stage could be off by a few thenths of a second. This would end up for a jumbled and badly timed piece.
~sorry, in the orchestra room and definately felt like posting that.