Space, a boundless universe shrouded in mysteries and riddles. We humans are always eager to explore and learn all its mysteries. And one of the most interesting mysteries is sound in space. We used to think that there is no sound in space, that there is complete silence. But in fact, it’s not that simple.
What is sound and how does it spread?
Sound is a vibration that travels through a medium as a wave. It cannot propagate in a perfect vacuum, where there is nothing to move through. Space is a vacuum, but it is not perfect. The sun constantly emits particles that create a flux known as the solar wind. This flux has a very low density, but enough to allow sound to propagate.
Sound in interplanetary space
Although the density in interplanetary space is low, sound can still propagate. The Voyager space missions have measured the waves propagating through the plasma emitted by the Sun in the form of the solar wind. When the solar wind is emitted by the Sun, it is very hot and travels at high speed. As it expands outward, it cools and has less density. Thus, sound waves can propagate through the interplanetary plasma.
Plasma and the speed of sound
Plasma is a special medium where sound waves propagate in a very different way. In classical physics, we know that sound propagates faster in liquids than in gases, and faster in solids than in liquids. But compared to plasma, these speeds seem tiny.
The reason for the difference is that sound waves can be interpreted as pressure disturbances propagating in a medium. The speed of sound depends on pressure and is inversely proportional to density. In plasma, where there is something big (hot) divided by something small (density), the speed of sound through the plasma becomes much greater.
The mind-blowing sounds of the cosmos
Because sound can propagate through interplanetary plasma, some mind-blowing sounds can be heard in space. Here are some of them:
1. Solar wind: This is a stream of particles emitted by the Sun. It creates low-frequency sounds that can be heard with special instruments.
2. Pulsars: are neutron stars which emit regular pulses of radio waves. If these pulses are converted into sound waves, you can hear strange and unusual sounds.
3. Gravitational waves: these are oscillations of space-time caused by massive objects such as black holes or neutron stars. Although we cannot hear them directly, they can be converted into sound waves to hear their effects.
Thus, sound in space is not a myth, but a reality. Although it may not be what we are used to hearing on Earth, it still exists and can be studied.