Is Space Completely Silent?
Sound is a mechanical, longitudinal wave of energy emerging from a vibration. For instance, when a guitar string vibrates, the atoms of the metal string hit the atoms around it, and that vibration is passed along to the following and further until it gets to your ear. Once you get there, the tympanic membrane, or eardrum vibrates at the same frequency, and therefore, the tiny bones in your middle and inner ear transmit the movement to the energy that your brain can interpret. Since all atoms can vibrate this way, sound can travel through solids, liquids, and gases. On the opposite hand, the outer spaces are assumed of like a vacuum, the absence of matter. Thus, without any matter, no sound will be heard. NASA also says that there’s about one atom per cubic centimeter!
Basically, sound waves are oscillations in pressure that travel through the medium that they’re in. In most cases, this can be a series of compressions where molecules are closer together, and rarefactions, where they are further apart and this is caused by the molecules themselves moving backward and forward.
As we all are aware of the fact that there is sound on planets and moons in the solar system—places where there’s a medium through which sound waves can be transmitted, such as an atmosphere or an ocean. However, what about the empty space?
If you take all those free-floating atoms into consideration, you would have 90 percent hydrogen, 9 percent helium, and fewer than one percent of common fraction for other stuff which makes sense considering the makeup of everything we know in the universe. While one atom per cubic centimeter might sound like more than you thought, considering it’s a vacuum.
So, with such a low density the energy of sound waves cannot jump from one atom to another atom. Therefore, no atoms mean no waves, and no waves mean no sound!
However, sound travels at a faster rate on Venus as compared to that on earth, and that is because the atmosphere of Venus is “thick and soupy” says Tim Leighton of the University of Southampton. This means if you could talk on Venus, the sound would zoom through your vocal cords, but deepen in pitch because of the makeup of the air.
Many would have heard the explanation that in space, nobody can hear you shout. In the same way as others before you, you may have simply accepted this as the truth without thinking much more about the topic. Some may have even delved further and learned that space is silent because sound cannot travel through a vacuum. While both of these things are valid, have you at any point asked why?
To get to the base of this we need to explore the science behind it all. Some may have even dove further and discovered that, despite being loaded up with stars, planets, asteroids, rocks, and so on, space is attributed to as a vacuum. All in all, space is a vacuum, however what does that actually mean?
A vacuum technically implies an area completely without matter. Inside a vacuum, there’s literally nothing. No particles, no air, nothing. So how is space a vacuum, if there are so significant numbers of cosmic bodies filling the night sky? Well! All things considered, notably, space isn’t really a true vacuum at all.
Well, it turns out that space isn’t actually a real vacuum. It’s referred to as such for our comfort, as space is such an enormous place, the most by far of it really is a vacuum. On account of sound waves, these mechanical waves come as a vibrating wave and it transports energy as it moves to start with one place then onto the next.
This wave needs to go through what we call a medium, which in this case is through particles. Notice how we say protons because space which constitutes 99.9 percent of the entire universe isn’t filled with gas but with plasma–a different state of matter made of charged particles.
Let’s look at an instance though, to make it a little clearer.
Sound cannot travel through space though, because it is a vacuum. If you played the guitar in space, you wouldn’t hear it. If you play the strings of a guitar, then the strings will begin to vibrate. This vibration formed at the beginning creates a chain reaction in the particles around it, in such a way that it is not too different from the ripples from a pebble dropped into a pond. Each particle affected then transfers the vibrations onto those around it, transferring the energy. The further the sound wave travels, the weaker the vibration becomes. This happens until the sound wave ceases to exist, due to a small amount of energy being lost in each transfer between particles. So, for sound to travel, we need particles. These particles can make up a whole range of things including water, gas, liquids, or even solids.
There aren’t any particles between the enormous gaps of nothingness between cosmic bodies in space to vibrate, and thus the initial vibrations of the guitar string wouldn’t have anything to transfer to, and no one would ever hear it.
Throughout the universe clouds of dust and gas can be found. These can be the remains of long-dead stars or even regions where a matter is being pulled together to create a new one. In these space-faring clouds, it is possible for the gas and dust to form clusters and thus can become denser. What this means is that it’s actually possible for there to be enough particles close enough together for sound to occur, and to even travel a small distance.
Do astronauts talk in Space?
Astronauts in space do talk to each other. In the spacecraft, there is plenty of air, so they just talk normally. When they are spacewalking, they talk by means of radios in their helmets. The radio waves, again, have no problem in space, but they’re not sound. They’re radio, which has to be converted into sound by the astronauts using their headsets.
Can gases propagate sound?
True that there are gases in space and it’s true that these gasses can propagate sound waves just like Earth’s air lets the sound to travel. The only dissimilarity is that interstellar gas clouds are less dense than the Earth’s atmosphere. They have fewer atoms per cubic foot. So, if a sound wave was traveling through a big gas cloud in space and if we are able to hear the same, only a few atoms per second would impact our eardrum, and we wouldn’t be able to hear the sound because our ears aren’t sensitive enough.
There can even be vibrations in the matter that’s not gaseous. For instance, the Earth or the Sun. But although sound can travel through Earth, it can’t travel from Earth to Mars because there’s no matter such as gases, liquids, solids in between the two planets for it to travel through.
So it’s not strictly true that no sound vibrations can travel through space at all, but it is true that humans would not be able to hear any sounds in space.
Could a human hear large explosions?
In movies, it is often shown that a large space ship has exploded with another spaceship nearby, playing a large exploding sound. So, while a large explosion takes place, say in a supernova, could a person hear the sound because possibly the explosion releases gases?
As we discussed before, space is a vacuum, and the gases released into space expand rapidly, and as they keep on expanding, their density decreases. So let’s say you were in a spaceship in the middle of a big space battle and a nearby ship exploded. The exploding ship would release gases and accordingly, the sound could travel along with them. However, since space is a vacuum, these gases will spread out very rapidly and the density will drop off very fast with distance from the explosion. So by the time the explosion reached your ship nearby, any sounds carried by the gas would still be too faint to hear.
Conclusion
While space is more silent than you could ever imagine, it’s not completely devoid of sound. No, you cannot hear any sounds in near-empty regions of space. Sound travels through the vibration of atoms and molecules in a medium such as air or water. In space, where there is no air, there’s no way sound can travel.
Sound waves cannot travel through space, but there are some small regions where sound can exist, that too when given very specific conditions.
In empty space, there is no air, and what we call “sound” is actually vibrations in the air. There are indeed light waves and radio waves in space, but these waves are not sound, but light. Light does not need air to travel, but then you don’t hear it; you see it, or it is interpreted by your radio set and then translated into sound.
