The reason why only one object can break the sound barrier at a given time has to do with the physics of supersonic motion and the formation of shockwaves.
When an object moves through a medium, such as air, it creates pressure waves that propagate outward from the object. These pressure waves are what we perceive as sound. When an object reaches or exceeds the speed of sound (which is approximately 343 meters per second or 1,235 kilometers per hour in dry air at 20 degrees Celsius), it is said to be traveling at supersonic speed.
At supersonic speeds, the object is moving faster than the pressure waves it creates, causing those pressure waves to accumulate and form a shockwave. A shockwave is a sudden change in pressure and temperature that travels with the object. It is a cone-shaped region of compressed air that extends outward from the object's leading edge.
When two or more objects are traveling at supersonic speeds in close proximity, their shockwaves interfere with each other. This interference can lead to an effect called "wave cancellation" or "destructive interference," where the pressure waves from one object partially or completely cancel out the pressure waves from another object. As a result, the shockwaves cannot form simultaneously, and only one object's shockwave becomes dominant.
In other words, the shockwaves produced by multiple objects traveling at supersonic speeds interfere with each other and prevent them from breaking the sound barrier simultaneously. This phenomenon is related to the physics of wave propagation and is consistent with the principles of fluid dynamics and wave behavior.
It's worth mentioning that there are certain circumstances, such as in military aviation or supersonic air shows, where multiple aircraft may attempt to break the sound barrier in quick succession. In such cases, proper coordination and timing are required to ensure that the shockwaves do not interfere with each other, but they still do not break the sound barrier simultaneously.