The Infinitely Large Universe

It was only in the 1920's that astronomers discovered nebulae were in fact other galaxies outside our own. In the late 1990's, using  the Hubble Space Telescope, it was estimated there were 125 billion galaxies. Current thought puts it at about 200-500 billion. This is just the "observable" universe! Victorian era mathematician Augustus De Morgan added some lines to Swift's verse:

"And the great fleas themselves,
In turn, have greater fleas to go on,
While these again have greater still,
And greater still, and so on."