• Question: Why does light travel faster than sound??

    Asked by caoimheneary to Aggelos, Andrew, Eileen, Naomi, Shane on 13 Nov 2012. This question was also asked by hannahnlovescheese.
    • Photo: Shane Bergin

      Shane Bergin answered on 13 Nov 2012:

      Great question. Both light and sound are waves – that means there’s a periodic disturbance from rest (just like a mexican wave going around a stadium – where you go up and down (disturbance from rest) and the wave goes around and around.

      Sound waves are due to periodic vibrations of things like a tuning fork, a stretched string (guitar) or a column of air (pipe organ). they cause the air around them to vibrate too. the air causes the air next to it to vibrate aswell, spreading out from the source of the sound until it reaches your ear which also starts to vibrate . your brain turns that vibration into a signal and you ‘interpret’ the sound. Because sound waves need air to travel through, they are slow.. like swimming through honey

      Light waves are really fast (3,000,000,00 meters every second). the do not need to travel through a medium like air. Light waves arise from the energy given out by electrons (that orbit atoms) when their energies change.. what does that mean? try throwing salt in the fire (with an adult there!). it burns yellow.. because you are giving the electrons in the sodium (NaCl is salt) more energy and when they relax and lose the energy they give out a bit of light (called a photon) that is yellow. Other elements give different colours.. barium is ref. copper is green. this is how light is made. And because it doesn’t need a medium to travel through (like sound) light rays travel at the fastest speed possible – the speed of light

    • Photo: Andrew Jackson

      Andrew Jackson answered on 13 Nov 2012:

      whats cool about Shane’s answer aswell is that as he says, sound needs air in which to move, so in a perfect vacuum you cant hear anything… hence, “in space, noone can hear you scream” (which is from the amazing movie Alien)

    • Photo: Eileen Diskin

      Eileen Diskin answered on 14 Nov 2012:

      Shane’s answer is brilliant, and helps explain why we see a lightning bolt before we hear the thunder that it produces.

      A lightning bolt heats the air around it, causing it to expand really quickly. This is what makes the ‘thunder’ noise! It just takes a little bit longer for that noise to reach us than it takes for the light to reach us…because light travels faster than sound.