What Michelson and Morley did, without actually intending to, was undermine a longstanding belief in something called the luminiferous ether,
a stable, invisible, weightless, frictionless, and unfortunately wholly imaginary medium that was thought to permeate the universe.
Conceived by Descartes, embraced by Newton, and venerated by nearly everyone ever since,
the ether held a position of absolute centrality in nineteenth-century physics as a way of explaining how light traveled across the emptiness of space.
It was especially needed in the 1800s because light and electromagnetism were now seen as waves, which is to say types of vibrations.
Vibrations must occur in something; hence the need for, and lasting devotion to, an ether.
As late as 1909, the great British physicist J. J. Thomson was insisting:
“The ether is not a fantastic creation of the speculative philosopher; it is as essential to us as the air we breathe.”
This more than four years after it was pretty incontestably established that it didn’t exist.
People, in short, were really attached to the ether.