A meteor, often called a shooting star, is the streak of light produced when a small piece of space debris enters Earth’s atmosphere at high speed and vaporizes due to friction. A meteor shower occurs when Earth passes through a stream of cosmic debris left behind by a comet or asteroid. These events can produce dozens or even hundreds of visible meteors per hour, raising the question of whether this rapid atmospheric passage generates any audible sound. The answer involves the physics of high altitude, the speed of light versus the speed of sound, and the size of the space rock.
Altitude, Speed, and the Silent Passage
The vast majority of meteors visible during a shower are silent because they disintegrate at extremely high altitudes. Most debris is tiny, often no larger than a grain of sand, and begins to burn up at altitudes between 80 and 100 kilometers (about 50 to 62 miles) above the ground. At this height, the atmosphere is incredibly thin, meaning the air density is too low for the shockwave created by the meteor’s supersonic speed to efficiently transmit acoustic energy.
Any sound generated at this altitude must travel a long distance to reach an observer on the surface. Sound travels slowly, roughly 343 meters per second at sea level, meaning the journey takes many minutes. By the time a shockwave from a high-altitude meteor reaches the ground, the energy has dissipated significantly and the resulting sound is too faint to be heard. Furthermore, the sound waves must pass through atmospheric layers with varying temperatures and wind patterns, which scatter and refract the acoustic energy.
The Electrophonic Paradox (Simultaneous Sounds)
Despite the physical limitations on sound transmission, many observers report hearing sounds like a hiss, crackle, or sizzle exactly when they see a bright meteor streak across the sky. This phenomenon, called the Electrophonic Effect, presents a paradox because it defies the difference between the speed of light and the speed of sound. The sound is not an acoustic wave traveling from the meteor, but rather a sound generated locally near the observer.
The mechanism involves the superheated plasma trail created by the vaporizing meteor, which generates very low frequency (VLF) electromagnetic waves. These VLF waves travel at the speed of light, reaching the observer instantly alongside the visual sighting. The sound is produced when these instantaneous electromagnetic waves interact with certain materials on the ground.
These materials, such as sharp metallic objects, dry vegetation, wire-rimmed glasses, or an observer’s hair, act as a transducer. They convert the electromagnetic energy from the meteor’s trail directly into mechanical vibrations audible to the human ear. This localized conversion explains the simultaneous sound and visual event. The Electrophonic Effect requires an exceptionally bright meteor, known as a fireball or bolide, to generate enough VLF energy to be detectable.
Actual Acoustic Events (Delayed Sounds)
The loudest true acoustic sounds from meteors are produced by exceptionally large objects that penetrate deep into the lower, denser layers of the atmosphere. These large meteoroids, or bolides, generate a powerful shockwave when traveling faster than the speed of sound during atmospheric entry.
This shockwave causes a sonic boom, similar to those created by supersonic aircraft. Unlike the instantaneous electrophonic sound, this boom is always heard a significant time after the meteor has disappeared from sight. For example, if a meteor penetrates to an altitude of 30 kilometers (about 18 miles) before breaking up, the sound waves will take nearly a full minute to reach the ground. This delay is calculated based on the distance, as sound takes roughly five seconds to travel a single mile.
Many of the loudest reports, such as the 2013 Chelyabinsk event, result from a terminal burst or explosive fragmentation, not just a continuous sonic boom. When a large meteoroid encounters intense atmospheric pressure, it can shatter violently. This releases a massive burst of energy that creates a much stronger, delayed pressure wave. These delayed acoustic events, perceived as rumbles, thunder, or sharp booms, are the only sounds directly propagated from the physical interaction of the meteoroid with the atmosphere.