Monica Mazzotto, science writer for the Italian national daily newspaper La Stampa, wrote an article, “Ascolto la sinfonia segreta che fa vibrare il Pianeta Terra” (“I listen to the hidden symphony of Planet Earth’s vibrations”), based on an email interview with me. The article appeared in the Tutto Scienze section of La Stampa on February 13, 2008. Although La Stampa appears not to archive past articles, you can still read it here . (A low-resolution scan of the article is also archived at the University of Pisa.)

The following is the original text of my replies to her ten questions.

1. How did you pass from the geologic studies to the actual "acoustic" studies? What has pushed you to try to give voice to the Earth?

It happened gradually. When I was first studying seismology in California, I spent hours and hours looking at seismograms — those printed recordings of wiggly lines that show the vibrations of the Earth. Every seismologist learns to interpret those wiggles: this one is from a large, deep earthquake in Indonesia; this one is a little earthquake from just a few miles away; this is “noise” from a storm at sea; and so on. That’s what seismologists do. But the wiggles that really interested me were the big, slow waves that arrive long after the earthquake is over. Those are the waves that have traveled the farthest. They take the “scenic route” through the Earth’s crust, bouncing off mountain ranges and deep ocean trenches until they finally arrive at the seismograph. This idea was very exciting to me. It’s just like listening to your echo when you shout into a mountain valley or a cathedral: the sound bounces around and around until it finally reaches your ears a few seconds later. And each echo tells a story about where it traveled during its long journey back to your ears. This suddenly made studying the Earth feel very personal and human. Eventually I began writing computer programs in my spare time to turn seismograms from around the world into sound. I just wanted to hear the Earth, instead of analyzing it with a scientific mind.

I think I’m not the only one these days who’s hungry for this kind of sensual reconnection with the planet. Blind consumerism has numbed us to the miracle right here under our feet. And, as we’ve been learning in recent years, the planet is now on the brink of becoming permanently uninhabitable because of our stupidity. For me, these sounds are a gateway to rediscovering the beauty and wonder of the Earth that we lost somewhere along the way. In listening to these sounds I’ve been learning all over again what a rare and beautiful gift the Earth really is. I hope others will have a similar reaction.

2. What have you felt the first time you heard the "internal voice" of the earth?

It was a very powerful experience. For two years I had been designing a sound installation whose purpose was to create the illusion of standing inside the Earth. The idea was to play back recordings from many seismic stations from around the world, simultaneously, and all speeded up about 250 times. It was a difficult project. But finally I got it to work. I stood at the center of this ring of eight loudspeakers, and listened to the catastrophic Indonesian earthquake of December 2004. I couldn’t believe what I was hearing! For those few minutes, it seemed that my ears were as big as the Earth. I honestly felt that I’d wrapped my arms around the whole planet and around everyone living on it. I was holding it all close to my heart, touching something infinitely more powerful and beautiful than anything I could conceive of. It was a deep and healing experience. Sound has a way of taking us very, very deep inside. Especially the sound of the Earth.

3. You have recorded an infinity of sounds. Which is, so far, the sound that has touched your heart more?

Last year I finally got around to answering a question that had been in the back of my mind for a long time: “What would it be like if we could actually hear the Earth’s tides?” We’ve all seen the ocean rise and fall twice a day, dragged by the gravitational pull of the Sun and Moon. But what most people don’t know is that the solid Earth itself gets pushed around by the Sun and Moon, too. The Earth’s crust rises and falls twice a day, by as much as 40 centimeters. Of course, if we look out the window we don’t actually see the streets, buildings, and mountains moving up and down, because we’re moving up and down right along with them. And the motion happens so slowly that we can’t feel it. But it’s very real — scientists have been measuring it for at least a hundred years. So I wondered to myself, “If this up-and-down vibration of the Earth were turned into sound, what would it sound like?” Last year I assembled several years of measurements of this “solid Earth tide” and, with the help of a computer, sped up the recordings about four million times and fed them into a sound system. The result is magnificent. Behind the loud crackling noise of hundreds of earthquakes, you can hear a beautiful low, pulsating hum. That’s the sound of the whole Earth vibrating under the influence of the gravity of the Sun and Moon. That’s the rhythm to which we’ve all been gently rocked since the day we were born. When I first heard that sound, my ears and mind and heart settled into a very deep place, as if a door had suddenly opened inside. There’s something timeless and universal there, something that all of humanity has in common. It was a transformative moment. I wonder if it’s the true musica universalis — the “music of the spheres” — that the ancient philosophers wrote about.

4. It looks like you are convinced that the human being pays a little attention to senses he is endowed, above all the acoustic one. What do you think we can learn, succeeding to listen what generally we cannot listen?

Over millions of years of evolution, human beings have developed exquisitely sensitive eyes and ears. We can hear everything from a mosquito’s wing to a thunderclap. We can recognize a tiny dot of light in the night sky a billion kilometers away, and also grasp the meaning of a smile on a baby’s face. But there is so much more going on around us that we cannot see or hear. Our senses are “tuned” only to a thin sliver of what’s really out there. Just imagine if your eyes could see not only visible light, but every other kind of electromagnetic radiation that is racing through you right now: TV shows, radio sports programs, pop music, a thousand cellphone conversations, ultraviolet light from the sun, radio waves from Jupiter, X-rays from collapsing stars on the other side of the galaxy, etc., etc. If we could really see it all, we’d probably all go mad! Likewise, our ears can hear only one little corner of the spectrum of physical vibration. Just imagine if your ears could hear everything that’s vibrating around you: the ultrasonic sounds of insects and bats; the humming of the molecules of which your desk is made; the sound of the atmosphere swelling and contracting from passing weather systems; the low vibrations of the ground right under your feet, from earthquakes, from the pull of the Moon and Sun, from waves breaking on the coast a hundred kilometers away. The world is a much, much more interesting place than we think. If we can learn to experience more fully the complete spectrum of activity around us, the better we’ll understand what it means to be a human being living on this fragile planet. The more we understand this, the better we’ll know how to safeguard the future of our planet.

5. Can you describe to me how you could obtain those sounds from apparently dumb phenomena as the seismic waves?

It’s a very simple idea. Remember those old vinyl LP records? The wiggling groove that spirals in towards the center of a record represents the sounds that the microphone captured in the recording studio. When you play the record, the needle wiggles from side to side, the wiggling is turned into electricity, and the electricity is amplified and played through a loudspeaker. If you play the record faster, the wiggles go past the needle in a shorter time, and the pitch (frequency) of the music goes up. (As a boy, I remember playing 45 rpm pop records at 78 rpm. The Beatles sounded like chipmunks!) This is exactly what I do with the recordings of the Earth. A seismograph records the wiggles, and I play them back using a computer program that speeds everything up. If I play it back twice as fast, 2 seconds of real Earth time goes by in 1 second, and the sounds are all shifted up by one octave. If I play it back 4 times as fast, it’s shifted up by two octaves. And so on. It gets really interesting when you start speeding things up thousands or even millions of times: you start hearing sounds that most human ears have never heard before.

6. The sound of the Earth is only given from the seismic waves or also from other geologic phenomena?

The surface of the Earth is always moving. The most obvious source of these vibrations is earthquakes. And there are hundreds of measurable earthquakes occurring every day. Large earthquakes make the entire planet jiggle like a bowl of pudding. Ocean storms are shaking the continental shelves. Surf is pounding on the world’s beaches. Gravity is pushing entire countries up and down, twice a day. The atmosphere presses down and pulls up on the oceans as weather systems pass by, causing the whole planet to “hum” at a very low pitch. And then there are the man-made sounds: the vibrations from trains, automobiles, rock quarries, underground explosions, billions of footsteps. It all adds up to a tremendously rich stew of vibration. Some of it we can already hear. Some must be shifted to make it audible. But it’s all very real.

7. What do you think "to discover" in the sounds that you produce?

I don’t expect to discover anything new. I’m just trying to find new ways to experience things that are already very familiar to us. Like the tides: we’ve all “experienced” them by watching the water go in and out at the beach. But have you ever experienced it as sound? Probably not. That’s a very different experience. We’ve all heard crickets singing on summer nights. But have you ever heard those songs slowed down, at a time scale at which the crickets themselves might experience them? The songs turn into the most delicate, beautiful little performances. When you take any familiar sound and change its scale of time and space, you don’t really create anything new; you just experience it from a radically new perspective. That can be a very profound experience.

8. Do you think that any thing can "emit" a sound if listened with the just techniques?

Oh, yes. Every physical object has its own natural frequencies of vibration. If you tap a wine glass, it rings. If you knock on a door, it rumbles. Every physical object has something to tell us. Atoms and molecules vibrate, too. I know of an artist who invented a “sound microscope” for listening to the tiny noises that bacteria make. And big things vibrate, too. Astronomers recently found a black hole that causes an interstellar gas cloud to vibrate at something like 57 octaves below middle “C”. Of course, we’ll never actually hear that particular sound, because it can’t travel all those millions of kilometers through empty space to Earth and into our ears. But if it could get here, all we’d have to do is speed it up a few dozen octaves. It’s all possible.

9. You said that your work is a bridge between science and art. Can you explain better?

Did I say that? I’m not really trying to bridge science and art. I just like to borrow tools from both worlds in my work. The really interesting questions are the ones that artists and scientists have been asking forever, in different ways: What is Time? What is Space? What is Consciousness? What is Life? What is Death? What is Love? They are interesting because, after all these thousands of years, it seems that we’re no closer to finding the answers. We might think we know the answer, until we’re challenged to explain them to someone else. If a child asks you, “What is Time?”, what can you honestly tell them? What do you really know? We might think we know it, but we really don’t. We’re all standing shoulder-to-shoulder in the middle of a breathtaking mystery, and we don’t even notice it. If people could only begin to know less and wonder more, I think we’d all get along a lot better. If we could just begin to appreciate the mystery and beauty of our situation, I think we’d all be better equipped to make peace with ourselves and with the planet.

10. I have read of your new plans on internal sound of the human body and also on the sounds of the underwater world. In what they consist? What are you trying to make and what do you think to find?

These projects are still in their early stages, so I honestly don’t know yet what they’re all about. But I can tell you that they are both based on the same kind of question: “What would it sound like if…?” For example, if you could actually travel inside the heart, what would you hear? If you were the size of a starfish, and you lived in a coral reef, what would you hear? It will take me some time to discover the answers to these questions. It’s a wonderful adventure.