Getting taller, getting smaller

Much time has passed by since Dad and I had a visit.
On that day, he looked puzzled, and I asked, "What is it?"
"You've grown taller," he said, "Since I saw you last."
"That's untrue," I replied, "My growth days have now passed."

"People gain their full height by late teens, that I know;
I'm well past that time," I said, with some woe.
He shook his head sagely, "It can happen," he said.
"Reptiles keep on growing up until they are dead."

I let it go; if I agreed, he would hurry
To cite some statistics and facts in a flurry.
My father delighted in telling tall stories
Of dining with princes, and other past glories.

If I gave him his head, he'd elaborate tales
Of genial genies making friends with blue whales.
My Dad was well-versed in a magical series
Of antic events and marvelous theories.

The truth of the matter? I think you'll agree;
As we age we get shorter, it's just gravity.