Don't throw eggs at me! Just want to throw my 2 cents into the debate...![Smile [:)]](/emoticons/emotion-1.gif)
Figuratively speaking, no living being can run at 186,000 per hour,or the speed of light. “Stronger than the locomotive and faster than the speeding bullet” is the opening intro. In the 60’s Superman show which was a metaphor used to dramatize the fictional hero. There is nothing grammatically wrong but conceptually I think there is a problem with saying “one runs at the speed of light”. If I said “His mind can process numbers like the speed of light”, I am merely using a simile to dramatize my point. However, if I said “His mind can process numbers at the speed of light”, the impression to me is that of exaggeration. There is definitely a big difference between exaggeration and dramatization.
Learners need to clearly distinguish the difference.