Does Sound Travel Through Space

Is it possible to hear sounds in space? The short answer is No.  Yet, misconceptions about sound in space continue to exist, mostly due to the sound effects used in sci-fi movies and TV shows. How many times have we heard  the starship Enterprise or the Millennium Falcon whoosh through space? Its so ingrained our ideas about space that people are often surprised to find out that it doesnt work that way. The laws of physics explain that it cant happen, but often enough producers dont really think about them.  Theyre going for effect. We often hear ships in movies going into warp or FTL drive, when, if we were outside a ship in space, we wouldnt hear a thing. People INSIDE the ship might hear something, but thats not the same as hearing sounds in the vacuum of space. NASA Plus, its not just a problem in TV or movies. There are mistaken ideas out there that planets make sounds, for example. Whats really happening is that specific processes in their atmospheres (or rings) are sending out emissions that can be picked up by sensitive instruments. In order to understand them, scientists take the emissions and heterodyne them (that is, process them) to create something we can hear so they can try to analyze what they are. But, the planets themselves arent making sounds. Voyager and Cassini spacecraft spotted spokes in Saturns rings. Spokes are the ghostly radial markings discovered in the rings by NASAs Voyager spacecraft 25 years ago. When observed using a radio astronomy receiver, the process of the spokes rotation gave off radio emissions, which astronomers processed to create ghostly sounds, although no such sound was heard in space. NASA/JPL/Space Science Institute The Physics of Sound It is helpful to understand the physics of sound. Sound travels through the air as waves. When we speak, for example, the vibration of our vocal cords compresses the air around them. The compressed air moves the air around it, which carries the sound waves. Eventually, these compressions reach the ears of a listener, whose brain interprets that activity  as sound. If the compressions are high frequency and moving fast, the signal received by the ears is interpreted by the brain as a whistle or a shriek. If theyre lower frequency and moving more slowly, the brain interprets it as a drum or a boom or a low voice. Heres the important thing to remember: without anything to compress, sound waves cant be transmitted. And, guess what? Theres no medium in the vacuum of space itself that transmits sound waves. There is a chance that sound waves can move through and compress clouds of gas and dust, but we wouldnt be able to hear that sound. It would be too low or too high for our ears to perceive. Of course, if someone were in space without any protection against the vacuum, hearing any sound waves would be the least of their problems.   What About Light? Light waves (that arent radio waves) are different. They  do not require the existence of a medium in order to propagate. (Though the presence of a medium does affect the light waves. In particular, their path changes when they intersect the medium, and they also slow down.) So light can travel through the vacuum of space unimpeded. This is why we can see distant objects like planets, stars,  and galaxies. But, we cant hear any sounds they might make. Our ears are what pick up sound waves, and for a variety of reasons, our unprotected ears arent going to be in space. Havent Probes Picked Up Sounds From the Planets? This is a bit of a tricky one. NASA, back in the early 90s, released a five-volume set of space sounds. Unfortunately, they were not too specific about how the sounds were made exactly. It turns out  the recordings werent actually of sound coming from those planets. What was picked up were interactions of charged particles in the magnetospheres of the planets — trapped radio waves and other electromagnetic disturbances. Astronomers  then took these measurements and converted them into sounds. It is similar to the way that a radio captures the radio waves (which are long-wavelength light waves) from radio stations and converts those signals into sound. Why Did Apollo Astronauts Reports of Sounds Near the Moon? This one is truly strange. According to NASA transcripts of the Apollo moon missions, several of the astronauts reported hearing music when orbiting the Moon. It turns out that what they heard was entirely predictable radio frequency interference between the lunar module and the command modules. The most prominent example of this sound was when the Apollo 15 astronauts were on the far side of the Moon. However, once the orbiting craft was over the near side of the Moon, the warbling stopped. Anyone who has ever played with a radio or done HAM radio or other experiments with radio frequencies would recognize the sounds at once. They were nothing abnormal and they certainly didnt propagate through the vacuum of space.   Why Do the Movies Have Spacecraft Making Sounds? Since we know that no one can physically hear sounds in the vacuum of space, the best explanation for sound effects in TV and movies is this: if producers didnt make the rockets roar and the spacecraft go whoosh, the soundtrack would be boring. And, thats true. But, it doesnt mean theres sound in space. All it means is that sounds are added to give the scenes a little drama. Thats perfectly fine as long as people understand it doesnt happen in reality.   Updated and edited by Carolyn Collins Petersen.