“In space no one can hear your screams .” With this disturbing slogan, the classic science fiction film Alien was publicized. Its creators hit the nail on the head: sound needs a material medium to propagate itself, and in the void of space there is nothing it can hold onto. For this reason, almost all films in the genre – except 2001: A Space Odyssey – make the mistake of treating us to explosions and powerful roars from hyperdrive engines. However, silence does not reign in the entire universe . The Huygens probe, which was launched on January 14, 2005 towards the surface of Titan – Saturn’s satellite – carried a pair of tiny microphones. Because it has a dense atmosphere, continents, and a sea of methane, Titan is quite a noisy place. The probe’s microphones recorded wind noise throughout the two-and-a-half-hour descent. Despite the very strong deceleration to which it was subjected – 15 times that of Earth’s gravity – Huygens survived the impact with the ground and transmitted data and images of the surface for more than an hour. Thus, an orange landscape strewn with rocks could be seen, possibly made of solid water and, covering everything, a haze of ethane or methane. The microphone had to register the sound of alien thunder. No luck.
This is not the first time we have sent a microphone to another planet. In 1999, NASA wanted to realize what would be the last dream of astrophysicist and popularizer Carl Sagan, which was none other than recording the sounds of the Martian surface. To do this, they installed a microphone on the Mars Polar Lander, but ten minutes before landing, contact with the probe was lost. Despite this, NASA has not thrown in the towel and hopes to record in future missions scheduled to the red planet the howling of the wind or the machine-gunning whistles of its sandstorms. Obviously, no one thought of equipping the Apollo 11 mission with microphones, except for those necessary so that Neil Armstrong could pronounce his famous phrase after stepping on the firm moon. Do not forget that our satellite lacks an atmosphere.
Venus, a good sound candidate
Venus is a different story, as its dense atmospheric envelope makes it a good sound candidate, but no probe has introduced a microphone into that hell, where the temperature is so high that it melts lead. The Russians claim that in the 1980s they carried one that recorded electric shocks, but they never showed the recordings. Astrophysicists are not complicated by music producers, since all the planets – and many moons – in the solar system have a gaseous envelope, although Mercury’s is very weak. But the same noise would be heard differently depending on where we were. The speed of sound is different on each planet, and depends on both the composition of the atmosphere and its temperature. On Earth, sound travels at 340 meters per second under normal conditions. This means that if lightning strikes the ground 10 kilometers from us, we hear it 29 seconds later. On the Martian surface it would take 44 seconds to hear it, because there the sound propagates 30% slower. On Venus, whose atmosphere is much denser, we would hear thunder 24 seconds after seeing lightning. And for speed, that of Jupiter and Saturn, where it would reach our ears in just 12 and 13 seconds, respectively.
Whispers on mars
If we wanted to talk on Mars – as long as we could breathe its deadly atmosphere of carbon dioxide – we’d have a pretty hard time. Even the loudest scream would be reduced to a low whisper due to its low atmospheric density. In fact, our voice would sound as if we were suffering from laryngitis. Of course, the sounds would not seem as different to us as on Earth, and we could recognize a large number of them. The situation on Venus would be totally different. With an atmospheric pressure 90 times higher than the earth’s pressure – similar to that found a kilometer below the surface of the sea – the almost imperceptible murmur of a library would become the background noise of an office. The next time you turn on your stereo, chew on the table where it is leaning. If you cover your ears, you will hear the music through your bones. Something similar is what Nicholas C. Makris, professor of ocean engineering at MIT, has proposed to study the surface of Europa – a moon of Jupiter – which possibly has between 10 and 100 kilometers of ice and under which an immense sea extends of salty water. His idea is a variant of the acoustic techniques used to study the ice that covers part of the Arctic Ocean. The method consists of introducing microphones sensitive to vibrations due to stresses, compressions and ice fractures, which in theory would produce noise with frequencies between 0.1 and 100 Hz.
Radio Cosmos FM
Titan
Because the Huygens probe was designed to stay on Titan’s surface for two and a half hours, all data transmissions had to be done in real time. And this was a problem for the transmission of pure sounds. The bandwidth used was 480 bits per second, while that used by us to download files from the internet is more than 260 times higher. So the microphone turned the sounds into sonograms, diagrams where time is plotted against the power and frequency of signals. Then they become sounds that we can hear here.
The solar system
The Cassini spacecraft, as it got closer to Jupiter, has detected ripples in the faint gas of charged particles that fills the solar system. These waves are low radio frequency and have been converted into sound waves so that you can hear them.
Jupiter
The gas giant’s magnetosphere produces radio waves that are captured by the Juno space probe. Conveniently treated, we can hear how the music of this planet sounds.
Mars
NASA’s InSight lander, which scans underground on Mars, is equipped with a very special ‘ear’. The seismometer, called the Seismic Experiment for Interior Structure (SEIS), can pick up vibrations as subtle as the breeze.
Scientists want to study how seismic waves from earthquakes move through the interior of the planet, revealing the deep internal structure of Mars.
Sun
To hear the continuous bubbling of the Sun’s surface and its oscillations, just enter here.
Pulsars
Imagine a star four times the mass of our Sun but all of it packed together inside a sphere only three kilometers in diameter. They got it? Now put it to rotate on itself so that in a second it rotates a thousand times. The light of a star in such extraordinary conditions does not come out of its surface in all directions, as happens with the Sun or a light bulb, but in two privileged directions, coinciding with the magnetic poles of the star. What we have is a kind of galactic beacon in the range of radio waves. When we observe it, we will see a star that turns on and off about five hundred times per second. Hence they are known by the name of pulsar, from the English pulsating star. In this direction we will be able to hear how the brightest pulsars would sound in the sky.
Something similar happens on Earth. After analyzing 10 years of seismic data, the research group led by Kiwamu Nishida, a geophysicist at the University of Tokyo, has found inaudible vibrations that travel through the lower atmosphere and cause weak seismic waves inside the Earth “that make it sing like a canary, “ according to Nishida. If we could hear it, this murmur would silence the noise of a hundred television talk-shows. But where do those waves come from? It is not known for sure. They may have their origin in variations in atmospheric pressure.
The Universe is an immense organ
After centuries of discoveries, scientists have agreed with Plato, at least in part. The Greek philosopher affirmed that the planets moved on spheres that emitted continuous music. Now cosmologists have come to the conclusion that the universe is like a huge organ. Apparently, the galaxies are distributed like the matter of a sponge, leaving huge voids between them. In 2002 the astrophysicist Jaan Einasto, from the Tartu Observatory in Toravere (Estonia), discovered that galaxies and voids repeat every 390 million light-years and give rise to a cellular structure. It was a shocking find. Why is there that order? One possible interpretation is that “the early universe was full of sound waves that compressed and rarefied matter and light in the same way that happens with air inside a flute or a trumpet,” according to the Italian cosmologist Paolo de Bernardis. If this assumption is true, it means that the microscopic murmurs generated when the universe was 300,000 years old caused matter to condense and give rise to the seeds from which, many millions of years later, galaxies would form.
If we compare the universe to an organ pipe, we can say that the stars look like bells. Sound waves travel on its surface, with which astronomers intuit what is happening inside. This peculiar branch of modern astrophysics is known as astroseismology. The first star where these faint oscillations were discovered was our Sun. In the 1960s solar telescopes revealed that its surface is covered by acoustic waves similar to those of earthquakes, and these vibrations are related to the superenergetic reactions that take place in inside the star. The energy produced in the Sun’s nuclear furnace is transmitted to the surface by convection, the same mechanism that causes water to begin to boil when it is boiled in a pot: hot matter rises while cold matter falls. In the Sun, gas bubbles rise to the surface at a speed close to that of sound. Unfortunately, we are not able to hear its gurgling because it does not propagate through space. And even if these waves were transmitted, we could not hear anything, since their frequency is below the threshold of human hearing. What scientists do is analyze how this cosmic bell vibrates, which provides valuable information about the physical conditions of the solar heart.
The Sun is not the only singing star; the same type of oscillations are also generated in the rest of the stars. The problem is that they are very weak and difficult to detect. It was in 2001, thanks to the Swiss astronomers François Bouchy and Fabien Carrier, from the Geneva Observatory (Switzerland), when the tolling of another star was observed for the first time. It was Alpha Centauri A, only 4 light-years from us and visible to the naked eye from the southern hemisphere. His measurements have shown that this star, very similar to ours, pulses with a 7-minute cycle. The passage of time is not only marked by our clock.
Discoveries like these have led to a curious twinning between astrophysicists and musicians. Why not turn these sounds into melodies? That is the commitment of the members of the Stellar Music Project or Brian May himself, founder of the Queen group, who abandoned his doctorate in astrophysics 35 years ago to lead the mythical rock formation.
As if that weren’t enough, even the death of a star has its own funeral march. In 2006, a research group made up of astrophysicists from the Steward Observatory of the University of Arizona, the Hebrew University and the Max Planck Institute in Potsdam (Germany), discovered that sound is the engine of supernova explosions. Thanks to its internal nuclear reactions, in a star of this type chemical elements are generated: oxygen, nitrogen, carbon, iron … The end of its life is approaching when iron is formed inside, since in the reactions of Nuclear fusion with atoms of this metal does not release energy, but is consumed. In this situation, with nothing to support its own weight, the star collapses and becomes a supernova. The explosion is impressive. For a couple of seconds, this celestial body shines as bright as a billion stars.
Well, the team of astrophysicists has developed a computer model that simulates the last seconds of the life of supernovae, from the collapse of the nucleus to the explosion. And they have discovered that sound governs their last gasp. Calculations indicate that dying stars pulse at audible sound frequencies for a fraction of a second before bursting. “The innermost core begins to vibrate vigorously and, after 700 milliseconds, the oscillation becomes so intense that it begins to generate sound waves of frequencies between 200 and 400 Hz, located in a half octave of the scale. These waves reinforce the wave of shock created by the collapse of the star, which ends up exploding, “explains one of the researchers, Adam Burrows.
Definitely, although our screams cannot be heard in space, sound governs many of the most incredible processes in the universe.
The Sun is not the only singing star; the same type of oscillations are also generated in the rest of the stars. The problem is that they are very weak and difficult to detect. It was in 2001, thanks to the Swiss astronomers François Bouchy and Fabien Carrier, from the Geneva Observatory (Switzerland), when the tolling of another star was observed for the first time. It was Alpha Centauri A, only 4 light-years from us and visible to the naked eye from the southern hemisphere. His measurements have shown that this star, very similar to ours, pulses with a 7-minute cycle. The passage of time is not only marked by our clock.
Discoveries like these have led to a curious twinning between astrophysicists and musicians. Why not turn these sounds into melodies? That is the commitment of the members of the Stellar Music Project or Brian May himself, founder of the Queen group, who abandoned his doctorate in astrophysics 35 years ago to lead the mythical rock formation.
As if that weren’t enough, even the death of a star has its own funeral march. In 2006, a research group made up of astrophysicists from the Steward Observatory of the University of Arizona, the Hebrew University and the Max Planck Institute in Potsdam (Germany), discovered that sound is the engine of supernova explosions. Thanks to its internal nuclear reactions, in a star of this type chemical elements are generated: oxygen, nitrogen, carbon, iron … The end of its life is approaching when iron is formed inside, since in the reactions of Nuclear fusion with atoms of this metal does not release energy, but is consumed. In this situation, with nothing to support its own weight, the star collapses and becomes a supernova. The explosion is impressive. For a couple of seconds, this celestial body shines as bright as a billion stars.
Well, the team of astrophysicists has developed a computer model that simulates the last seconds of the life of supernovae, from the collapse of the nucleus to the explosion. And they have discovered that sound governs their last gasp. Calculations indicate that dying stars pulse at audible sound frequencies for a fraction of a second before bursting. “The innermost core begins to vibrate vigorously and, after 700 milliseconds, the oscillation becomes so intense that it begins to generate sound waves of frequencies between 200 and 400 Hz, located in a half octave of the scale. These waves reinforce the wave of shock created by the collapse of the star, which ends up exploding, “explains one of the researchers, Adam Burrows.
Definitely, although our screams cannot be heard in space, sound governs many of the most incredible processes in the universe.
