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The Living Force
http://www.physorg.com/news88249076.html
'Mach c'? Scientists observe sound traveling faster than the speed of light
Superluminal sound set-up
In this schematic of the acoustical test system, the scientists could create superluminal group velocity of sound waves, as well as negative group velocity. In the latter case, the peak of the output pulse traveling through the loop filter exited the filter before the peak of the input pulse had reached the beginning of the filter. Image credit: Bill Robertson, et al.
For the first time, scientists have experimentally demonstrated that sound pulses can travel at velocities faster than the speed of light, c. William Robertson’s team from Middle Tennessee State University also showed that the group velocity of sound waves can become infinite, and even negative.
Past experiments have demonstrated that the group velocities of other materials’ components—such as optical, microwave, and electrical pulses—can exceed the speed of light. But while the individual spectral components of these pulses have velocities very close to c, the components of sound waves are almost six orders of magnitude slower than light (compare 340 m/s to 300,000,000 m/s).
“All of the interest in fast (and slow) wave velocity for all types of waves (optical, electrical, and acoustic) was initially to gain a fundamental understanding of the characteristics of wave propagation,
'Mach c'? Scientists observe sound traveling faster than the speed of light
Superluminal sound set-up
In this schematic of the acoustical test system, the scientists could create superluminal group velocity of sound waves, as well as negative group velocity. In the latter case, the peak of the output pulse traveling through the loop filter exited the filter before the peak of the input pulse had reached the beginning of the filter. Image credit: Bill Robertson, et al.
For the first time, scientists have experimentally demonstrated that sound pulses can travel at velocities faster than the speed of light, c. William Robertson’s team from Middle Tennessee State University also showed that the group velocity of sound waves can become infinite, and even negative.
Past experiments have demonstrated that the group velocities of other materials’ components—such as optical, microwave, and electrical pulses—can exceed the speed of light. But while the individual spectral components of these pulses have velocities very close to c, the components of sound waves are almost six orders of magnitude slower than light (compare 340 m/s to 300,000,000 m/s).
“All of the interest in fast (and slow) wave velocity for all types of waves (optical, electrical, and acoustic) was initially to gain a fundamental understanding of the characteristics of wave propagation,
