Space is a hollow surface, an emptiness in which no sound can propagate. So you might think that space is in absolute silence. Suppose you turn your ears into receivers of radio waves. In that case, the space around the Earth suddenly becomes a symphonic constant of strange and incredible sounds.
Let's listen to the music of space! You don't have to climb too high above the Earth to already be in space. Only 160 km high, the sound is no longer audible because there are not enough particles to spread sound waves.
Even here in space, you can find many other types of waves.
In fact, right now, you are enjoying electromagnetic radiation through the light when you watch this video.
- Radiation ranges from gamma rays with extremely high frequencies to radio waves that can be miles long.
- There are also radio observatories and radio telescopes, some of which are currently orbiting the Earth.
We will enjoy what they have captured in the way radio waves are most frequently experienced: in sound frequencies that are converted into sound.
When we reach the Van Allen Belt, some fascinating sounds can already be heard in the large radiation band surrounding the Earth.
These sounds are produced by high-energy particles in the Earth's plasmasphere, which are hurled back and forth by the rotation of the Earth's magnetic field.
Around the Earth, there is a plasmasphere containing clusters of ions and electrons.
As the Earth and its magnetosphere rotate, magnetic fields penetrate these particles and accelerate them with a wave called plasma, similar to how disturbances in the oceans can cause waves to form.
You can hear these disturbances in the form of radio waves as they pass through one of NASA's Van Allen Probes:
- They are called chorus waves and are often heard during sunrise, so it seems to be the Earth's singing.
A fantastic type of chorus wave closest to Earth is the hissing plasma wave, which sounds like space battles and lasers. These are generated in the colder and denser part of the plasmasphere and are caused by electromagnetic radiation emitted by lightning in the atmosphere.
The waves generated by these rays can bounce off the Earth's magnetic field.
Since higher frequencies propagate faster than lower frequencies, they sound with a characteristic descending tone, similar to a whistle.
It is believed to be caused by electrons that, due to reconnection in the Earth's magnetic tail, move to the night side of the Earth and transfer their energy to the plasma when they collide with it.
In another area of the plasmasphere, we can find something called hiss waves:
- These are believed to be chorus waves that have emerged from the inner plasmasphere.
- They sound much more threatening and colder than the others we have heard so far.