i GUESS what he means is something like inverse of covariance matrix gives correlation matrix, something like this question: https://stats.stackexchange.com/q/140080

No more electronic road pricing gantries, every car's position will be tracked via gps in real time

No more electronic road pricing gantries, every car's position will be tracked via gps

I am just curious that is the speed of gravity wave travel at different speed in different medium?

I knew this is a bit irrelevant, just want to show a pure js ripple effect which I borrowed before: http://jsfiddle.net/esteewhy/5Ht3b/6/