Before I say, I just want to mention that the Danish words for 15 and 18 are femten and atten Atten sounds a bit like the English word "eighteen". So that is where we get our metric prefixes femto- for 10-15 and atto- for 10-18. When you do cosmology the most common quantity, or one of the most, that you encounter is the present-day value of the Hubble parameter---something around 67.9 km/s per Mpc. If you type that into the google box and press return you get: 67.9 km/s per Mpc = 2.20...x 10-18 hertz. In other words, the google calculator thinks that Hubble growth rate is 2.20 attohertz. In other words, in one second of universe time, the distance between two objects at cosmic rest increases by a small fraction of itself, namely 2.20 billionths of a billionth or 2.20 x 10-18 Can we learn anything from the google calculator, in this case? Is there any point to taking that seriously for a moment, or do we just shrug it off as the calculator's quirky behavior? One thing we learn is that google thinks hertz is the metric term for "per second". It doesn't have to be anything in particular per second. It doesn't have to be wave-cycles per second, it can be other kinds of counting. Radians per second, fractional growth per second, rotations per second. OK, we can reject this and insist that hertz can only mean cycles per second. Or we can take a suggestion from the calculator and broaden our perspective a little---so we can take hertz as a metric term for seconds-1. A synonym for "per second" generally. Either way seems reasonable enough. I'll pick the latter. So I'm thinking of the Hubble parameter (at this point in universe standard time) as 2.20 attohertz. What happens if I want to convert back? Try it yourself. Type in [2.20 attohertz in (km/s per Mpc)] without the brackets. Google will convert back into the old units and give you 67.9 km/s per Mpc. The google calculator understands the word attohertz even though it may prefer to say "10-18 hertz." There's more that we can learn. I'll make another post of it so this one doesn't get too long.