Left to right

Left to Right is a short story by science fiction writer Isaac Asimov, featured in the short story collection Gold. Robert L. Forward has created a doughnut that is spinning at such a speed that something will interchange. Another character (who is unnamed) suggests sending protons through it, but he says that he has done that and that he will send himself through. The other character argues that he will not be able to digest but he argues that he can just pass through it a second time. He travels through, checks his heartbeat and appendectomy scar (which are on the same side as before). He says that everything is the same as before, being "as sure as my name's Robert L. Backward."