Superman can use his powers to ignore physics – but the speed of sound does not, and the Man of Steel’s super-hearing wouldn’t actually save anyone.
DC’s Superman is one of the most powerful superheroes of the genre, capable of sensing danger all over the planet – but the comics ignore a fundamental aspect of his super-hearing that would make it impossible for the Man of Steel to actually save anyone. Aside from his strength and flight capabilities, Superman has super eyesight and hearing, which allows him to respond to danger within seconds. Unfortunately, the laws of physics work against DC’s most popular superhero – namely, the speed of sound.
Superman initially had no super-senses of any kind in his first few appearances in the Golden Age of Comics; he was known for his strength, bulletproof skin, and ability to leap great distances (he wouldn’t be able to properly fly until much later). While he was often described as having enhanced senses, his first feat of super-hearing occurred in 1940, where he revealed he could hear communications from radio waves. It wasn’t until the Silver Age of Comics that Superman could hear every sound in Metropolis by flying overhead. Superman’s senses eventually became so powerful that he could hear individual voices anywhere on Earth – and even in space.
Unfortunately, Superman’s super-hearing is super-limited by the speed of sound. While traveling through air, the speed of sound is approximately 343 meters per second, or 761 miles per hour. This is relatively slow compared to fast-moving objects like planes, rockets, bullets, etc. and poses a major problem for Superman whenever responding to a far-off person in distress. For example, if Superman in Metropolis were to hear a cry of distress from Australia, it would already be too late; the distress would have occurred sixteen hours before the Man of Steel would ever hear a cry for help.
This problem is only exacerbated when Superman hears sounds while in space. Setting aside the fact that sound cannot travel through space at all, the problem with distance is only magnified. In the 2005 For Tomorrow storyline, Superman rescues Green Lantern after hearing a cry for help from across the solar system. Unless Green Lantern has a way of instantly teleporting sound waves, he would be out of luck, as the distance from Earth to Mars alone is over 130 million miles (and that’s not even taking into account the other planets).
Writers have previously scientifically explained how Superman can fly, and many have also attempted to explain Superman’s hearing as less of a physical sense and more of a psionic ability, but no canonical explanation exists for why he can hear sounds faster than sound itself. A superhero breaking the laws of physics is no rare feat. But Superman’s hearing abilities simply cannot work – unless he were to live in a universe where sound travels faster than light.
