Do shooting stars make noise? Yes, but the sounds result from two completely different physical processes. Most noise from these celestial objects is significantly delayed due to the vast distance they travel. A much rarer sound, however, can be heard instantly, an effect that puzzled scientists for centuries. Understanding the sound requires knowing what a shooting star actually is and how its high-speed atmospheric entry affects the air around it.
Defining Meteors and Atmospheric Entry
A “shooting star” is not a star at all, but the visual phenomenon created by a meteoroid entering Earth’s atmosphere. Meteoroids are small pieces of rocky or metallic debris traveling through space, ranging from dust grains to small boulders. As a meteoroid plunges into the atmosphere, it becomes a meteor, the bright streak of light observers see. This light is generated when the object’s incredible speed compresses the air in front of it, causing the air to superheat.
This intense compression and friction, known as ablation, vaporizes the meteoroid and the surrounding air molecules. The bright path is not the object burning, but the glow of the superheated gas in its wake. If a meteoroid is large enough to survive this fiery descent and land on Earth’s surface, it is then called a meteorite. Most meteors burn up completely at high altitudes, typically between 50 and 75 miles above the ground.
The Science of Delayed Meteor Sounds
The most common noise associated with a large, bright meteor (a bolide or fireball) is delayed, similar to the time lag between seeing lightning and hearing thunder. This delay occurs because light travels nearly instantaneously, while sound travels much slower, approximately 767 miles per hour at sea level. Since meteors typically appear around 50 miles high, the sound wave must travel that entire distance to the observer on the ground.
A meteor traveling faster than the speed of sound creates a continuous shockwave, known as a sonic boom. The extreme speed causes air molecules to pile up and compress into a single pressure wave. This shockwave, created high in the atmosphere, eventually reaches the observer as a delayed rumbling, or sometimes a loud boom if the meteor is large enough to penetrate the lower atmosphere. If a fireball appears 50 miles up, the resulting sound takes over four minutes to reach the ground, arriving long after the visual streak has disappeared.
Electrophonic Meteors: Sound Heard Instantly
In rare instances, observers report hearing a faint, instantaneous sound—often described as a hiss, sizzle, or crackling—at the exact moment they see the meteor. This phenomenon, known as an electrophonic sound, presents a paradox because a normal acoustic wave cannot travel 50 miles instantly. Scientists propose that the sound is transmitted not acoustically, but electromagnetically.
As a very bright bolide ablates, it generates extremely low frequency (ELF) and very low frequency (VLF) electromagnetic waves. These waves travel at the speed of light, reaching the observer instantly. The sound is not produced high in the atmosphere but locally, right next to the observer. The VLF waves excite nearby objects, such as dry hair, metallic materials, or eyeglass frames, which then produce the faint, audible sound.
This conversion of electromagnetic energy into an acoustic wave makes the sound seem simultaneous with the meteor’s appearance. These instantaneous sounds are only reported for the brightest fireballs, specifically those with an absolute visual magnitude brighter than about -9. This requires very specific atmospheric conditions to be heard. This local transduction mechanism explains why the sound is often faint and sometimes described as sounding “in the head,” as it is generated right at the observer’s location.