And if Alien was wrong? What if we could be heard screaming in space? The catchphrase of Ridley Scott’s horror film (1) makes sense, because effectively no one can hear you scream if you’re in space without a suit – not that that’s the most immediate problem though. unfortunately you find yourself in this situation.
Sound waves need a medium to propagate: on Earth, they travel through air or water for marine species. But in the vacuum of space, there is nothing to “carry” these waves. So you can shout, make a noise, the person in front of you will not hear them. NASA found the solution, and published last May the sounds of a black hole, which are making news today thanks to a “remix”.
The misconception that there is no sound in space originates because most space is a ~vacuum, providing no way for sound waves to travel. A galaxy cluster has so much gas that we’ve picked up actual sound. Here it’s amplified, and mixed with other data, to hear a black hole! pic.twitter.com/RobcZs7F9e
—NASA Exoplanets (@NASAExoplanets) August 21, 2022
The black hole in question is located at the center of a cluster of galaxies in the constellation Perseus. And this cluster, one of the most massive in the Universe, is bathed in a cloud of hot, dense gases. The pressure waves therefore diffuse in this medium, since it is not empty. Using the Chandra space telescope, the US space agency was able to see them spread.
This scientific data was then transformed into audible sounds for the human ear. The sound wave produced, the “original cry” of the black hole, corresponds to an oscillation every ten million years. For comparison, the lowest note that the human ear can hear corresponds to an oscillation every twentieth of a second! To make this noise audible, the engineers increased it by 57 octaves.
Listen to the sounds of the Universe
In the end, the result gives the impression of listening to a winter wind through an old window. For the curious, NASA has also transformed other waves from the Universe into sounds. It is possible, for example, to listen to the Sun, emissions from Saturn or even the interstellar space that the Voyager probes are still exploring.
For scientists, these sounds are not only a good way to communicate their work to the general public. By observing the propagation of waves, they learn more about the media in which they travel and the energy exchanges that take place there.