Sure there are. https://en.wikipedia.org/wiki/Alcubierre_drive#Damaging_effect_o...

pdonis · on Feb 11, 2017

> Sure there are.

If you include "believed to be impossible" in the definition, I guess.

pmoriarty · on Feb 12, 2017

"When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong." -- Arthur C. Clarke

pdonis · on Feb 12, 2017

Thanks for the implicit compliment, but I'm not a distinguished but elderly scientist. :-)