The cosmos is roaring with activity produced by the fourth state of matter – and now we can listen to it.

Contrary to popular belief, space isn’t a total vacuum – it’s actually full of activity, with 99.999% of the universe’s matter found in the form of the mysterious fourth state of matter: plasma. Plasma is made up of charged particles released from sources such as the Sun, and the movement of these particles through space creates waves that are similar to sound waves. But those waves are imperceivable to human ears, falling far below our range of hearing at around 1 Hz and even lower.

These waves are known as ultra-low frequency waves. The Earth's surrounding magnetic shield, which protects us against harmful solar rays, is full of these waves as plasma interacts with it. Their activity plays a role in space weather, which can impact things from GPS and power grids, causing communication issues with things like flights and cell phones. 

Identifying the different types of ultra-low frequency waves in satellite data has, until recently, been incredibly difficult and tedious because space is a cacophonous and noisy place. Dr Martin Archer, who works in the Department of Physics at Imperial – and who is working with NASA on the Heliophysics Audified Resonances in Plasmas (HARP) project – wanted to find a better way to study them. 

Watch the video below to find out more about the project:

Listening to outer space

The activity of these waves is completely analogous to the tension in a guitar string or harp string. Dr Martin Archer Department of Physics

Noting that the waves produced by plasma moving through space are similar to sound waves produced by a vibrating guitar or harp string, Dr Archer came up with the ingenious idea to translate that activity into audio that we can actually hear. This process is known as audification, and it uses software to speed up data captured by space satellites to a much higher frequency that falls within humans’ range of hearing.  

“I think this is really exciting because what everyone in my field does is completely invisible,” Dr Archer emphasised. “And so it’s really hard to get people excited about stuff that you can’t see.” 

But now we can actually listen to what’s happening in outer space. Not only does this technique conveniently allow researchers to get through years’ worth of data in just a few minutes, but it’s also much easier to detect patterns with our ears in the midst of noisy data than it is to do so visually on cluttered line plots with massive quantities of information.  

The NASA-piloted HARP Project was thus designed to allow citizens to participate in space science research via a web-based interface that presents the audio data captured by satellites. Interestingly, borrowing techniques from music was fundamental to the project. Dr Archer credits this imaginative approach to his background in radio and DJing. “I think that my background in radio is kind of what drove me to even think about using sound,” Dr Archer shares.  

The magnetosphere also seems to act like a giant musical instrument. “The guitar is a really good analogy,” he explains. “One of the types of these waves that can happen in the plasma is driven by the tension of bending a magnetic field line. The activity of these waves is completely analogous to the tension in a guitar string or harp string. They do kind of get ‘plucked’ by processes in the solar wind that can excite them, and that can give you a spectrum of different frequencies.” 

Space weather and citizen science

By having lots of people listening, we should be able to come to a consensus of what’s actually there. Dr Martin Archer Department of Physics

Why should this research concern us back here down on Earth? While some plasma waves are responsible for the beautiful auroras we see in the north and south poles of the planet, they can also negatively impact our lives and technology. Known as space weather, certain phenomena from space, including plasma waves, can damage GPS and weather satellites. This can be quite dangerous as many of our transportation infrastructures, including flights, depend on this communication. The idea is that if scientists can first understand the underlying physics of the waves, then they can start to consider what impact they might have on us. 

One really exciting aspect of this project is that it calls on the public to help out. Dr Archer explains that not only does the audification of the data make it more manageable for the scientists to analyse, but it also gives citizens a chance to contribute to the scientific process. “It seemed like an obvious way to get people to contribute to our science without having a barrier to entry in terms of learning to code or interpret line plots,” Dr Archer explains. “Instead, we’re just asking, can you hear a swooshing sound and where is it?”  

Public contribution also increases objectivity when it comes to analysing the data. “With this project, we’re trying to tease out patterns or signals in very noisy environments, which our standard computational methods can really struggle with,” says Dr Archer. “By having lots of people listening, we should be able to come to a consensus of what’s actually there.” 

The team hopes to initiate similar citizen science campaigns in the future now that they’ve created the audio software and made it accessible to the public. “Hopefully this is the start of a whole load of listening to space science that people can get involved with,” Dr Archer shares. 

He stresses that researchers need your help to answer questions about these mysterious waves.

Join the project

If you want to get involved in cutting-edge space research, go to listen.spacescience.org, where anyone at home can participate just by using their ears. Give it a go and the team will let you know if you make a discovery.