Space is not homogeneous nothing. Between various objects there are clouds of gas and dust. They are the remnants of a supernova explosion and a place for the formation of stars. In some areas, this interstellar gas is dense enough to propagate sound waves, but they are not susceptible to human hearing.
Is there a sound in space?
When an object moves - whether it is a vibration of a guitar string or an exploding firework - it acts on nearby air molecules, as if pushing them. These molecules crash into their neighbors, and those, in turn, into the next. Movement travels through the air like a wave. When it reaches the ear, a person perceives it as a sound.
When a sound wave passes through airspace, its pressure fluctuates up and down, like sea water in a storm. The time between these vibrations is called the frequency of sound and is measured in hertz (1 Hz is one oscillation per second). The distance between the peaks of the highest pressure is called the wavelength.
Sound can propagate only in an environment in which the wavelength is not greater than the average distance between particles. Physicists call this "conditionally free road" - the average distance that a molecule travels after a collision with one and before interacting with the next. Thus, a dense medium can transmit sounds with a short wavelength and vice versa.
Sounds with long waves have frequencies that the ear perceives as low tones. In a gas with an average mean free path exceeding 17 m (20 Hz), sound waves will be too low-frequency for a person to perceive. They are called infrasounds. If there were aliens with ears perceiving very low notes, they would know for sure whether sounds are heard in outer space.
Black hole song
At a distance of about 220 million light-years, in the center of a cluster of thousands of galaxies, a supermassive black hole sings the lowest note the universe has ever heard. 57 octaves below the average “do,” which is about a million billion times deeper than the sound of the frequency that a person can hear.
The deepest sound that can be caught by people has a cycle of about one swing every 1/20 second. In a black hole in the constellation Perseus, the cycle is about one oscillation every 10 million years.
This became known in 2003 when the NASA Chandra space telescope discovered something in the gas filling the Perseus cluster: concentrated rings of light and darkness, similar to ripples in a pond. Astrophysicists say these are traces of incredibly low-frequency sound waves. Brighter - these are the tops of the waves, where the greatest pressure on the gas. The rings are darker - these are troughs where the pressure is lower.
Sound that can be seen
Hot, magnetized gas revolves around a black hole, similar to the water circulating around a drain. Moving, it creates a powerful electromagnetic field. Strong enough to accelerate the gas near the edge of the black hole almost to the speed of light, turning it into huge bursts called relativistic jets. They force the gas to turn on its way to the side, and this effect causes eerie sounds from space.
They are transported through the Perseus cluster for hundreds of thousands of light-years from their source, but sound can travel only as long as there is enough gas to transport it. Therefore, it stops at the edge of a gas cloud filling the cluster of Perseus galaxies . This means that it is impossible to hear its sound on Earth. You can only see the effect on the gas cloud. It looks like if you look through the space at a soundproofed camera.
Strange planet
Our planet makes a deep moan every time its crust moves. Then there is no doubt: whether sounds propagate in space. An earthquake can create vibrations in the atmosphere with a frequency of one to five Hz. If it is strong enough, it can send infrasound waves through the atmosphere into outer space.
Of course, there is no clear boundary where the Earth’s atmosphere ends and space begins. The air simply gradually becomes thinner, until in the end it disappears completely. From 80 to 550 kilometers above the surface of the Earth, the mean free path of a molecule is about a kilometer. This means that the air at this height is approximately 59 times thinner than that at which it would be possible to hear sound. It can only carry long infrasound waves.
When an earthquake of magnitude 9.0 shook the northeast coast of Japan in March 2011, seismographs all over the world recorded how its waves passed through the Earth and vibrations caused low-frequency vibrations in the atmosphere. These vibrations went all the way to where the spacecraft of the European Space Agency (Gravity Field) and the stationary satellite Ocean Circulation Explorer (GOCE) compare the gravity of the Earth in low orbit with a mark of 270 kilometers above the surface. And the satellite managed to record these sound waves.
GOCE has very sensitive onboard accelerometers that control the ion engine. This helps maintain the satellite in a stable orbit. On March 11, 2011, GOCE accelerometers detected vertical displacement in a very thin atmosphere around the satellite, as well as wave-like shifts in air pressure at the time of the propagation of sound waves from an earthquake. The satellite’s engines corrected the displacement and stored data, which became similar to earthquake infrasound recordings.
This record was kept secret in satellite data until a group of scientists led by Rafael F. Garcia published this document.
First sound in the universe
If there was an opportunity to return to the past, approximately in the first 760,000 years after the Big Bang, one could find out if there is sound in space. At this time, the universe was so dense that sound waves could freely propagate.
Around the same time, the first photons began to travel in space as light. After that, everything was finally cooled enough so that subatomic particles condense into atoms. Before cooling took place, the Universe was filled with charged particles - protons and electrons - which absorbed or scattered photons, particles that make up light.
Today it reaches the Earth as a faint glow of the microwave background, visible only by very sensitive radio telescopes. Physicists call this relict radiation. This is the oldest light in the universe. He answers the question if there is sound in space. Relic radiation contains a record of the most ancient music of the universe.
Light to help
How does light help to know if there is sound in space? Sound waves travel through air (or interstellar gas) as pressure fluctuations. When the gas is compressed, it gets hotter. On a cosmic scale, this phenomenon is so intense that stars form. And when the gas expands, it cools. Sound waves propagating through the early universe caused slight pressure fluctuations in the gaseous medium, which in turn left slight temperature failures reflected in the cosmic microwave background.
Using temperature changes, University of Washington physicist John Kramer was able to recover these eerie sounds from space - the music of an expanding universe. He multiplied the frequency by 10 26 times so that human ears could hear him.
So no one will really hear a scream in space, but there will be sound waves moving through the clouds of interstellar gas or in the rarefied rays of the Earth’s outer atmosphere.