THE LOUDEST SOUND IN THE UNIVERSE
Sound is a mechanical wave, meaning it disperses its energy through matter. Meaning, in space, sound starves without touch. You could wail and wail into the empty black of space until your spit froze to your throat, but no one would ever hear it. Silence is golden. Silence is fundamental—gravity, entropy, quiet.
In 1964, Arno Penzias and Robert Wilson work on an experiment collecting radio signals from balloon satellites at the Bell Laboratory in New Jersey. They direct a twenty-foot horn antenna in a slow sweep of the heavens, trying to capture the messages bounced from the upper atmosphere. However, the two scientists find a constant, low noise in all their recordings. Morning, afternoon night, from all corners of the sky comes a mysterious groan, something massive and unnamed unfurling itself behind the stars
Sound needs to travel through matter. Electromagnetic radiation, however, can travel through the vacuum of space. Radio, x-ray, gamma, microwave, visible light can be caught in the hoop of satellite dishes, transformed into a form the human mind can understand. We can trade photons for waves, turn the bashing of electrons into songs. If our ears can’t hear it, we’ll build ones that can.
Most of the planets are wrapped in a magnetosphere, a system of magnetic fields stretching out far from the planet’s surface. These magnetic fields trap solar wind in protective bubbles, preventing most of the violent energy of the sun from reaching the surface. Without the magnetosphere, life would not be able to survive on Earth.
The excited particles occasionally reach Earth in the form of northern lights, painting the high-latitude skies in flickering lights and radio waves. With the right receiver, the evening sky chirps, whistles, hisses. Like frogs, katydids and the distant rush of cars on a rural highway. Safety is the unending sound of a summer night far above our heads.
Unable to figure out the source of the strange background noise, Penzias and Wilson do everything they can think of to account for this unexpected intrusion. They recalibrate, adjust their systems, make sure that the antenna is still running at its super-cooled temperatures. They even clamber into the horn to clear away pigeon nests and droppings. Still, nothing changes. Penzias and Wilson theorize that the sound is not from within our solar system, or even the Milky Way, but farther out.
It’s not until a friend of theirs mentions a paper being published by astrophysicist Tim Peebles on the suspected enduring radiation of the Big Bang that the sound is pinned to a source. The pair contact the team, inviting them to listen in on what will be declared the strongest evidence of the Big Bang theory. Penzias and Wilson earn a Nobel Prize for their discovery, stumbling into cosmological fame purely by chance.
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The sun beats a steady rhythm, a rise and fall of heat and light bubbling to the surface. All the planets, moons, named and unnamed rocks float on its ebb and flow.
Yet, the sun, our heart, is a small one. There are stars so bright and huge their very pulse picks them apart layer by layer until all that’s left is the bitter shell of their core. It shines, a haunted skeleton, shambling, refusing to die. We call these undead stars white dwarves, neutron stars, pulsars. But sometimes the death is too catastrophic. There will be no body to make a tombstone of. Even the core becomes too heavy, collapsing into itself until not even the fabric of space-time can hold it, the inescapable maw of a black hole.
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The magnetosphere of the planets is created by their rotation, the churning of their guts. Jupiter, with a nine-hour day, has a magnetosphere 20,000 times stronger than Earth’s. There is no place to rest here, spinning so fast its clouds pool ragged against each other. So fast the planet’s center bulges, fighting to keep its own viscera contained.
When the JUNO probe crossed into Jupiter’s magnetic fields, it recorded the sounds of the bow shock and magnetopause, the places where the sun and Jupiter meet. There is no protection here. Radiation wreathes the Jupiter system, annihilating anything that would dare to live on its satellites, creating thin atmospheres around its largest moons as it tears into the surface of Ganymede, Io, Callisto, and Europa. As it rips the rind from its humble moons, Jupiter roars.
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What is the loudest sound? A thunder clap? A rocket? Or something else? Something that shakes the very structure of space? In 2015, LIGO detectors pick up the gravitational waves of two black holes colliding over a billion light years away. These husks of stars, circle each other until they merge. Ironically, in that moment, the two black holes generate more than they ever did in life, radiating out more energy than all the living stars in the universe. The loudest thing is a graveyard
Penzias and Wilson’s noise is now known as the cosmic microwave background radiation. Radio telescopes map the microwave into a globe splattered in blues and greens, yellows and reds, all the minute variations in temperature where matter clung together during the first years of the universe. This radiation is the oldest relic, the farthest we can peer back into time.
Did you know you can hear it? It’s the simplest thing. Adjust an old radio or analog TV; listen for the static between channels. There, nestled in the white noise between the country music station and talk radio, are the echoes of creation.
Sound is a mechanical wave, meaning it cannot travel through space. Still, we shout out into the black. Sometimes, in the hope that someone out there is listening, despite all the time and all the distances. Sometimes, for ourselves, just to mark ourselves against the vastness of the universe.
Inside the Voyager space probes are golden records containing 115 images and sounds of Earth, inscribed with what we hope are universal symbols of life. A small voice amongst the cacophony of the cosmos.
Voyager 1 entered the interstellar medium in 2012 and is currently the most distant man-made object from Earth. As it left, it recorded the sounds of plasma vibrating around its sensors. We listen to our own goodbye, two whistles as we slip further from home.