Is space completely silent?

 

Is space completely silent?

Many will have heard the expression that no one can hear you scream in space, and like many others before you, you may have simply accepted this as the truth without thinking much further on the subject. Some may have even delved further and learned that space is silent because sound cannot travel through a vacuum, and while both of these things are true, have you ever wondered why, to get to the bottom of it all, we need to take a closer look at the science behind it all? A vacuum technically means a space entirely devoid of matter; inside a vacuum, there is absolutely nothing: no particles, no air, nothing.

So how is space a vacuum? If there are so many cosmic bodies filling the night sky, it turns out that space isn't actually a true vacuum. It's called that for convenience because space is so vast that the vast majority of it is a vacuum. How does sound travel in the first place, and why can't it travel through space like lying? Unlike light waves, sound travels in waves; however, sound waves are referred to as mechanical waves because they take the form of a vibrating wave that transports energy as it moves from one location to another; this wave must travel through what we call a medium, which in this case is particles. Let's look at an example though, to make it a little clearer.

                                                   

 If you play a string on a guitar, the string vibrates. This initial vibration creates a chain reaction in the particles around it in a way not too dissimilar from the ripples from a pebble dropped into a pond. Each particle affected then transfers the vibrations to those around it, transferring 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, and even solids. Because space is a vacuum, sound cannot travel through it; if you played a guitar in space, you would not hear it. There are no particles in the enormous gaps of nothingness between cosmic bodies in space to cause them to vibrate, so the initial vibrations of the guitar string would have nothing to transfer to, and no one would ever hear it.

How can space be silent if it's not a true vacuum? While the vast majority of space is a vacuum and thus completely silent, there are still some areas where sound can be heard. But wait, doesn't this go against everything I've said so far? Well, not quite throughout the universe, but clouds of dust and gas can be found. These can be the remains of long-dead stars or even regions where matter is being pulled together to form a new one. It is possible for the gas and dust to become clustered and thus tense. What this means is that it's actually possible for there to be enough particles close enough together for sound to occur and even travel a small distance. The sound was measured to be a b-flat, but at a frequency billions of times lower than what humans can hear. Sound waves cannot travel through space, but there are some very small regions where sound can exist under very specific conditions.