From JOHN GRIBBIN
John Gribbin writes: The correct name for the number in question is
the Hubble ‘parameter’, which is a measure of how fast the Universe is expanding
(and therefore of how much time has elapsed since the expansion began).
As the Universe ages, the expansion slows down, and the parameter gets smaller.
The term Hubble ‘constant’ is cosmologists’ shorthand for the present day
value of the Hubble parameter.
