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Why Space Is Silent
Age 13 · Physics
Sound is a vibration that has to be passed from particle to particle, so it needs a material such as air, water or metal to travel. Light needs no material at all, which is why it can cross the empty vacuum of space while sound cannot.
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Age 13: open this week
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In the picture
- Ringing clock in air: its vibrating bell shakes the air particles around it
- Sound waves: the vibration passes from air particle to air particle until it reaches the ear
- Vacuum pump: it pulls the air out of the jar, leaving almost nothing to carry sound
- Glowing clock face in the vacuum: its light still crosses the empty space to the eyes
Examples
- During a thunderstorm you see the lightning before you hear the thunder, because light travels much faster than sound.
- Astronauts on a spacewalk talk by radio, because their voices cannot travel through the vacuum between them.
Key takeaways
- Sound needs a medium (solid, liquid or gas) and cannot travel through a vacuum.
- Light can travel through a vacuum, which is how sunlight reaches Earth.
Quiz: Why Space Is Silent (Age 13)
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Why can’t sound travel through the vacuum of space?
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Which statement about sound is true?
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Why does sunlight reach Earth even though space is almost empty?
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