I've been trying to get my head around the rate at which the universe is currently expanding and have been trying to put a number on it in order to try and visualise how fast this is happening.

OK so the rate that is now quoted is around 70megaparsecs/sec/sec.

If a parsec is (roughly) 31million,million kms then a megaparsec is 31million.million.million kms or 31000000000000000000kms

So x 70 = 21700000000000000000000kms

How far is this in light years???

So if I were able to conduct an experiment in the complete abscence of any gravitational forces and hold two tennis balls, one in each hand, and let one go, then in 1second they the space between them will have expanded 21700000000000000000000kms. Thus placing the free tennis ball roughly..where??

In 2 seconds, double that and in 3 seconds, quadruple it etc.

Can somebody please check me on this..it sounds way off the mark but I can't think of another way to try and visualise it.

Thanks in advance.