# QuestionSpecial relativity considering sound waves

#### ajaipaulose

Can you explain the following thought experiment?
A train is travelling at the speed of sound. 2 speakers are installed on the track at equal distance from an observer in the train. For an observer outside the train, sound from both speakers reach simultaneously, but for the observer in the train there is infinite gap between the sounds. Does this mean time is relative?
What is the speciality of light vs sound in this experiment?

#### Helio

Is this a homework problem? Helping with homework isn't often done around here, I believe, but....

It often helps to exaggerate for effect. Imagine a speaker at the engine and one at the caboose of a stationary train where the observer was at an equal distance to both speakers. If both speakers produced a simultaneous Bang, would one speaker be heard sooner than the other? Now back the train up. Now have it move past the observer at a very fast speed, then initiate that Bang when both speakers are spaced equally apart from the observer. What timing will be heard by the outside observer?

#### ajaipaulose

I was not very clear on the question. Sound experiment seems to explain the relativity. But saying if we travelled at the speed of sound, time freezes is absurd.
1)What is the speciality of speed of light in this experiment?
2)Is biological aging and the time we are speaking is it same?

#### Helio

I was not very clear on the question. Sound experiment seems to explain the relativity. But saying if we travelled at the speed of sound, time freezes is absurd.
They seem to be trying to show how the same event is seen (heard) so differently by two observers due to their reference frames. But there’s nothing special happening that normal math won’t handle, unlike for light.
1)What is the speciality of speed of light in this experiment?
Unlike sound, light has only one observable speed, regardless of reference frames. Light speed is the same whether observed from coming from the from the front of the train or the rear. This is what Einstein discovered, bringing forth relativity.