miércoles, 16 de noviembre de 2016

If they're lower frequency and moving more slowly, the brain interprets it as a drum or a boom or a low voice. Here's the important thing to remember: without anything to compress, sound waves can't be transmitted. In the vacuum of space there is no medium to compress, therefore you would not be able to hear anything. Of course, if you were in space without any protection against the vacuum, hearing sound waves would be the least of your problems. What About Light? Light 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 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. Haven't 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 none too specific about how the sounds were made exactly. It turns out the recordings weren't 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 your radio captures the radio waves (which are long-wavelength light waves) from radio stations and converts those signals into sound. About those Apollo Astronauts Reports of Sounds On and Around 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 didn't propagate through the vacuum of space. Why Do the Movies Have Spacecraft Making Sounds? Since we know that you can't physically hear sounds in the vacuum of space, the best explanation for sound effects in TV and movies is this: if producers didn't make the rockets roar and the spacecraft go "whoosh", the soundtrack would be boring. And, that's true. But, it doesn't mean there's sound in space. All it means is that sounds are added to give the scenes a little drama. That's perfectly fine as long as you understand that it doesn't happen in reality.

Updated November 11, 2016.
Is it possible to hear sounds in space? That's a question astronomers and astronauts often get asked. The short answer is "No." Yet, the misconception of sound in space continues to exist, mostly due to the sound effects used in sci-fi movies and TV. How many times have you "heard" the starship Enterprise or the Millennium Falcon whoosh through space?  It's so ingrained our idea about space that people are often surprised to find out that it doesn't work that way.

The Physics of Sound

Sound travels through through the air (and space) as waves. They require a medium, like air or water, to travel though. 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 they're lower frequency and moving more slowly, the brain interprets it as a drum or a boom or a low voice. 
Here's the important thing to remember: without anything to compress, sound waves can't be transmitted. In the vacuum of space there is no medium to compress, therefore you would not be able to hear anything. Of course, if you were in space without any protection against the vacuum, hearing sound waves would be the least of your problems. 

What About Light?

Light 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 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 planetsstars, and galaxies.

Haven't 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 none too specific about how the sounds were made exactly. It turns out the recordings weren't 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 your radio captures the radio waves(which are long-wavelength light waves) from radio stations and converts those signals into sound.

About those Apollo Astronauts Reports of Sounds On and Around 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 15astronauts 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 didn't propagate through the vacuum of space. 

Why Do the Movies Have Spacecraft Making Sounds?

Since we know that you can't physically hear sounds in the vacuum of space, the best explanation for sound effects in TV and movies is this: if producers didn't make the rockets roar and the spacecraft go "whoosh", the soundtrack would be boring. And, that's true. But, it doesn't mean there's sound in space. All it means is that sounds are added to give the scenes a little drama. That's perfectly fine as long as you understand that it doesn't happen in reality. 

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