This question came up at work today. I argued that despite Superman’s superhearing, the shock wave generated at supersonic speeds would destroy any identifiable sound waves before they could reach his ears. He would just hear a loud roar, if he could even hear anything at all. What say you Dopers?
There is a book called “The Physics of Superheroes” where the author talks about this problem (using the Flash as an example). If I recall correctly, Superman could hear sounds that originated in front of him (though changed in pitch due to “crowding” of the wave), but, of course, not that originated behind him because they couldn’t catch up to him.
As for the shock, the “sonic boom” would follow in his wake as the air collapsed back into the partial vacuum created by moving through the atmosphere at that speed. That would occur behind him, so it would not “destroy” the sound waves coming at him from ahead.
The sonic boom created by Superman as he is traveling at or greater than the speed of sound cannot catch up to him, because the sonic boom propagates at the speed of sound. Any other sounds created behind him also can’t catch up (because they are also moving at the speed of sound), so the net effect is that Supes won’t hear anything from behind him.
He will hear plenty from sounds originating from in front of him. Their frequency will be higher though, just like that of a train horn moving toward you.
Because the sonic boom is behind him, it will have no effect on sounds originating in front of him.
No replies for 7 hours, then someone slips one in right before me. :smack:
Anyway, here’s more info on sonic booms:
Well, if Superman Returns is accepted as canon, he should be able to hear fine. I mean, if he can hear people from orbit (i.e., in a vacuum), he should certainly be able to her people astern if he’s going supersonic.
If he was going at Mach 5 down say 3rd street in New York, would he have a bunch of debris
(cars, people, buses, etc.) flopping around in his wake a la Neo in Matrix II?
Yes, because the partial vacuum would pull in surrounding debris.
I’m not sure I agree with the analysis that Superman would be able to hear sounds ahead of him. the problem would lie, not in the familiar shockwave, but cumulative nascent shockwaves, internal reflections, etc. of the various forward surfaces of his body striking the subsonic air at supersonic velocities. I mean surfaces as small as the tragus (the small cartilage-cored flap just “in front of” the ear canal, or other parts of the external ear (in a head-down position) Only at a distance do these pressure effects (or deflection of molecules onto supersonic mean free path trajectories) superpose to form the familar shockwave
Maybe he could hear in front of him if his ears were on his fingertips, and he flew hands-forward, but I doubt any apreciable information would survive the multiple nascent shockwaves coming off every surface much less their echoes in his ear canal. Each would represent an information destroying catastrophic regime change converting energy between heat, pressure, etc. just as in the familiar shockwave.
Of course I suppose he has a super auditory cortext that can decode the sound of even one atom beating out of step or some such, but I’m not sure that any “sound” would actually survive those transition regimes.
In that case, Superman doesn’t merely have superhearing but some form of telepathy, which would probably not be bound by atmospheric conditions. Let’s presume that Superman does not have telepathy and is bound by the normal physics of sound.
You just mentioned Superman and bound by physics in the same sentence. I don’t think you can do that.
He has supernatural abilities. It may not be telepathy but he does have the ability to hear beyond the realm of normal physics. Just like he can see beyond the realm of normal physics.
It’s been pretty well established in the comics that Superman can hear WAY beyond anything human. He can pick out a single heartbeat in a crowd from 100 miles away. He can “hear the clouds scrape together”, etc. I wouldn’t say it is too much of a stretch to say that he does, in fact, have a “super auditory cortext”.
There was a story in the 70s–probably during the Maggin/Swan era–where Superman heard a gun being cocked in California, from Metropolis, and flew out there in time to save Johnny Carson (well, “Johnny Nevada”) from being shot. Clearly, he hears on some advanced wavelength beyond “sound.”