當溫度極高時,音速有無可能快過光速?

Unlike electromagnetic wave (light is electromagnetic wave in nature) which doesn't require a mdeium to propagate, sound wave is mechanical wave and thus must travel in a medium.

Sound wave propagates in air by transmission of molecular vibration. The speed of sound is thus limited by the speed of transmission of these vibrations. Since air itself has a thermal random motion, the transmission of vibration could not be faster than the root-mean-square (rms) speed of air molecules at that temperature.

Although the rms speed does increase with temperature, the speed would not be definitely increased. Since air molecules are matter and have mass, their rms speed could not reach the speed of light. The speed of sound, which is lower than the rms speed of air molecules, thus could not reach the speed of light as well.

In reality, at very high temperature, neutral air molecules become ionized because of vigorous collisions between molecues. As a result, plasma state is reached. There will then be electrostatic effect between ions and electrons. Sound wave might not be able to travel in the same way as in neutral air.

Therefore, it is not practical for sound speed to exceed light speed in the way you described.

聲音必須透過物質來傳遞,聲波是由粒子以波的方法傳遞
所以聲音的速度是取決於有質量的粒子的移動速度,有質量的野無可能超越光速,所以聲音無可能超越光速,接近唔系唔可以,不過個溫度唔可以用你以上的方法計出
因為當物質接近光速時,個質量會出現明顯變化,從而令到要用更多的能量先可以再加速

只要把靜止時的質量除以[1-(v/c)^2]^0.5
就可以計到移動時的質量
v系度速(要以ms^-1為單位)
c系光速(即300000000ms^-1)

2010-02-23 17:45:08 補充：
上面果句"有質量的野無可能超越光速"有少少修改,應該系物質無可能超越光速

無可能，因為速度接近光速時你要把相對論效應也計算在內