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Public Radio's Environmental News Magazine (follow us on Google News)

The Sound of Solar

Air Date: Week of

If you’ve ever seen the aurora borealis, you’ve seen evidence of the solar wind - the constant stream of hot, charged particles flowing into space from the atmosphere of the sun. Now you can listen to it, too. Members of The Solar and Heliospheric Research Group at the University of Michigan are using the solar wind as musical inspiration. Host Jeff Young speaks with composer Robert Alexander and space science research fellow Jason Gilbert about how to make music from celestial data.


YOUNG: If you’ve ever been to the far north, you may have seen the aurora borealis, those dancing, leaping lights in the northern sky. What we see in the northern lights is the effect of the solar wind. But we haven’t been able to hear those electrically charged particles streaming through space from the sun. Until now:

[MUSIC: drumbeats, whooshing sounds, and vocals]

YOUNG: The men behind this music are Jason Gilbert, a research fellow in space science, and Robert Alexander, a composer and media artist. They’re part of the Solar and Heliospheric Research Group at the University of Michigan. Welcome to the program!

GILBERT: How are you doing?


YOUNG: Jason, what is that we were listening to?

GILBERT: What you were hearing was data from the advanced composition explorer, the ACE spacecraft. It’s measuring the solar wind. It’s essentially a stream of numbers that are coming down, which give us information on the temperature, the density, the charged state of the atoms in the wind.

YOUNG: What is solar wind?

GILBERT: Solar wind is essentially the atmosphere of the sun as it expands out into space. It goes streaming by the Earth very fast, and we catch it with our instruments, we measure what it is, what it’s made of, where it’s coming from, how fast and how hot it is.

YOUNG: So, obviously, pretty important to study this, but why is it important to take that data and turn it into music?

GILBERT: We wondered if there was a chance that there were things in the data that we just weren’t seeing as we look at it visually. Perhaps there was some pattern or some artifact that we could hear audibly instead. And so, we decided to sonify our data just to see if there was some other interesting piece of the puzzle that we could work out.

YOUNG: And Robert, that was your job, to take this raw data and make it into music. Where do you even start with that?

ALEXANDER: Well, I think that the things I noticed right off the bat just looking at the data is that some things were changing very rapidly – you’d get this really chaotic, sort of turbulent behavior with some of the data entries, while other points of data were happening much more smoothly. And some of the data points, such as the speed of helium as it was moving by the satellite. I was thinking that this would translate directly to something that might be similar to the sound of wind blowing here on earth.


ALEXANDER: I thought, well, what does wind sound like in our ears, and I thought that, hey, the pitch of wind as it goes by is in part determined by the speed at which it goes by. So that’s the approach that I took.

YOUNG: So this almost tribal drum beat that we hear…


YOUNG: What is that in terms of the data?


ALEXANDER: So, that’s a grandiose metronome. They’re actually representing the rotation speed of the sun on something… it’s known as the Carrington rotation.

YOUNG: And the swelling, sort of, symbol crashes?


ALEXANDER: So, you’ve got this whooshing sort of sweeping sound and that relates directly back to the helium velocity and density.

YOUNG: And then the sort of constant tones, almost like a choir or a string section – what’s that?


ALEXANDER: So, I actually recorded my sister, Amanda Alexander, and I layered her voice such that at different charge states of carbon the prevalence of different layers of her voice changed just based on the charged state.

YOUNG: So, what we’re actually hearing here is the carbon in different charged states, the helium, and the speed that the sun is doing all this, right?

ALEXANDER: That’s correct.

YOUNG: And it comes together like music. It’s amazing.

ALEXANDER: [Laughs] Yeah.


YOUNG: And your – what it’s all about – your subject matter here is, it’s the sun. You’re giving voice to the sun, essentially.

ALEXANDER: Yeah, the source of all life on Earth. It’s pretty humbling to have that as source material.

YOUNG: Jason, is there a scientific benefit for this, or is this purely art, or does this affect the way you view what you study now?

GILBERT: In its current stage, this is purely an artistic production, but one of the things that we envision is perhaps having a graphical interface on your screen where you can check a box to turn on the carbon, or turn on the iron, or see how much this element is compared to this one. If we can make it an interactive tool like that, a researcher can use it find the science that they’re most interested in.

YOUNG: And does the finished product sound anything like what you had imagined when you first thought this up?

GILBERT: To be honest, I didn’t know what to expect. When we first started this I didn’t know if it was just going to sound like dropping a handful on needles onto a piece of steel. You know, random noise everywhere, but when we first started to listen to what Robert had been able to sonify, we were able to recognize, oh, that was a coronal mass ejection that just went by; oh, I can hear the wind getting faster here.

And the first time he showed it to us, we actually had the data on the screen, so we were watching it go by and so we knew what was coming, and then when it went by we knew how to recognize it in the future. So it turned out to be much more than what I expected.

YOUNG: And Robert did this end up sounding like what you thought it might sound like when you started out with that stream of data?

ALEXANDER: When I first started out I was extremely aware of wanting this data to be scientifically accurate, so most of my sonification work was extremely restrained and it sounded like really simple tones, and the scientists they kept prodding me like really, be more adventurous, and take more risks here, and really go out and try using a beat rather than a metronome.

YOUNG: And Jason, has this affected the way you now look at your data, listen to your data, the kind of questions you might ask of the data?

GILBERT: I think this is definitely given me a new appreciation for how things work out in space. You know, we can watch our satellites and see visually how the solar wind affects them and how this space weather affects them, but to hear it sort of gives it a new dimension, one that I hadn’t considered before. It’s opened my mind.

YOUNG: Jason Gilbert and Robert Alexander who collaborated on putting the solar wind to music. Thank you both very much.

GILBERT: Thank you.

ALEXANDER: Thank you so much for having us.



The Solar and Heliospheric Research Group at University of Michigan.

Composer Robert Alexander’s website


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