There are mistaken ideas out there that planets make sounds , for example. What's 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 aren't making sounds. 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 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.
And, guess what? There's 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 wouldn't 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. Light waves that aren't radio waves are different. They do not require the existence of a medium in order to propagate.
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 can't hear any sounds they might make. Our ears are what pick up sound waves, and for a variety of reasons, our unprotected ears aren't going to be in space.
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. But because the "space roar" is caused by synchrotron radiation, a type of emission from high-energy charged particles in magnetic fields, and because every source has the same characteristic spectrum, pinpointing the origin of this intense signal is difficult.
One reason it probably isn't coming from within our galaxy is because the roar doesn't seem to follow the spatial distribution of Milky Way radio emission. But nobody is saying for certain that the signal isn't from a source closer to home — only that the smart money is on it coming from elsewhere. This article is brought to you by All About Space. All About Space magazine takes you on an awe-inspiring journey through our solar system and beyond, from the amazing technology and spacecraft that enables humanity to venture into orbit, to the complexities of space science.
There are other issues as well, such as that it would require a complete rethinking of our models of the galactic magnetic field. Fixsen agrees wholeheartedly. For those reasons, experts think the signal is primarily extragalactic in origin. But since the universe is so vast this doesn't exactly narrow things down that much, which is why scientists have been working hard to come up with multiple theories for the signal's source. Related: Mysterious deep-space flashes repeat every days.
American physicist David Brown, for example, said the space roar could be "the first great empirical success of M-theory , " a broad mathematical framework encompassing string theory. What this supposes is that the early universe had much more real matter than today, accounting for the powerful radio signal.
The space roar could be "the first great empirical success of M-theory," a broad mathematical framework encompassing string theory. But if that is too far out, there are other theories to get your teeth into. Synchrotron radiation is easy to make, he said.
It is also known that synchrotron radiation is associated with star production. Or perhaps there is some process that we haven't thought of yet. So what does this leave us with? Some scientists have suggested gases in large clusters of galaxies could be the source , although it's unlikely ARCADE's instruments would have been able to detect radiation from any of them.
Similarly, there is a chance that the signal was detected from the earliest stars or that it is originating from lots of otherwise dim radio galaxies, the accumulative effect of which is being picked up. But if this was the case then they'd have to be packed incredibly tightly, to the point that there is no gap between them, which appears unlikely.
Whatever the signal is, it's also causing issues when it comes to detecting other space objects. As NASA has pointed out in the past, the earliest stars are hidden behind the space roar, and that is making them more difficult to detect. It's as if the universe is giving with one hand and taking with another, but to have uncovered something so unusual is immensely exciting. When you're ruling out an origin from primordial stars and known radio sources such as gas in the outermost halo of our galaxy, it's a mystery any scientist would savour with relish.
In any gas with a mean free path larger than 17 m the wavelength of sounds with a frequency of 20 Hz , the waves that propagate will be too low-frequency for us to hear them. These sound waves are called infrasound.
Ripples in interstellar gas, produced by sound waves from a supermassive black hole. Image credit: NASA. About million light years away, at the center of a cluster of thousands of galaxies, a supermassive black hole is humming to itself in the deepest note the universe has ever heard as far as we know.
The darker rings are the troughs of the sound waves, where the pressure is lower. Hot, magnetized gas rotates around the black hole, more or less like water swirling around a drain. All that magnetized material in motion generates a powerful electromagnetic field. The field is strong enough to accelerate material away from the brink of the black hole at nearly the speed of light, in huge bursts called relativistic jets.
These relativistic jets force gas in their path out of the way, and that disturbance produces deep cosmic sound waves. Closer to home, our planet makes a deep groan every time its crust shifts, and sometimes those low-frequency sounds carry all the way into space.
If the earthquake is strong enough, it can send infrasound waves up through the atmosphere to the edge of space. From about 80 to about kilometers above the surface, the mean free path of a molecule is about a kilometer. That means the air at this altitude is about 59 times too thin for audible sound waves to travel through, but it can carry the longer waves of infrasound. When a magnitude 9. And the satellite recorded those sound waves - sort of.
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