1000 ml of vacuum will weight in on the as ,lets say 100000000000000 ml, they fill volume but when released they will dissappear. they have no mass (ok there are a lot of energy jumping in and out of existence), it is nothing. what about a tube 300.000 km long with vacuum inside, if we release in one end, how long before we see pressurefall in the other end of tube. I think maybe no time elapsed because vacuum has no direction and it is nothing so pressurefall will be all over at the same time. in air or gasses the pressure will have to move in a similar as sound does and thatb is rather slow.