I also found the paper hard to read, but check page 6 of the pdf at http://www.brophy.net/Downloads/AIL%20Class%20on%20Reality%20&%20Unreality/READING%20MATERIA

I also found the paper hard to read, but check page 6 of the pdf at http://www.brophy.net/Downloads/AIL%20Class%20on%20Reality%20&%20Unreality/READING%20MATERIAL%20IN%20PDF%20FORMAT/87%20SWIMMING%20in%20curved%20spacetime.pdf http://www.brophy.net/Downloads/AIL%20Class%20on%20Reality%2... (Adventures in Curved Spacetime, Eduardo Guéron, Scientific American Vol.301)