The sun is a singular experience in Earthly life. We see it. We feel it. But we can’t seem to hear it.
If we did, would it sound like an explosion? Or a primordial heartbeat? Or just a dull roar, bellowing 93 million miles away? The sun is huge—roughly 100 times wider than Earth, and it’s especially active lately—so much so that its eruptions can distort GPS, degrade communications, and create auroras. So what’s with the silent treatment? These questions and more cascade from a Popular Science reader’s seemingly simple ask: Does the sun make noise?
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“The basic answer is no, not for us,” Chris Impey, an astronomer and professor at the University of Arizona, said in a call with Popular Science. “The sun doesn’t make noise because noise, or sound, needs a medium to carry it,” Impey explained. Essentially, the space “between us and the sun is almost a perfect vacuum, so sound can’t travel through that.” Impey added, “So whatever the sun is doing, it’s not transmitting sound to us.”
Bummer! Or… great! Maybe we’re fortunate to not hear the big plasma ball, but with virtually nothing in the way, how come sound doesn’t travel past the emptiness to our ear drums?
“Sound is so funny. It’s a pressure wave,” explained Shauna Edson, an astronomy educator at the National Air and Space Museum in D.C. “It has to move through something, and our ears are adapted to interpret those pressure waves and turn them into a sound that our brain can understand.” To help people visualize how sound works, Edson said she asks them to imagine a row of beach balls.
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“If you pushed on the ball at the end of the line, it would roll into the next ball, which would bump into the next ball, and they would all kind of—boom, boom, boom,” she explained. “The push would travel from ball to ball, all the way down the line, as a wave. That is what sound does to the molecules of air or liquid or solid that they’re moving through.” In space, the molecules are “so few and far between,” Edson said, “that even if you pushed on one, there’s nothing else nearby for it to push on, so the wave can’t keep going.” (Hence, the famous Alien tagline, “In space no one can hear you scream.”)
So, the sun can’t make sound as we conceptualize it on Earth because of the vacuum of space. But still, given how big and energetic it is, isn’t the sun doing something that’s at least sound-like?
“The sun has oscillations and vibrations,” offered Impey, “so in a sense, it does have some of the elements of sound within it.” But even so, because the sun is so large relative to Earth, “all the activity in [it] is incredibly low-frequency,” Impey said. In other words, sun activity is definitely not the sort of thing human ears evolved to perceive. Cool—but why, then, are there audio clips online offering otherworldly snippets of oscillations or solar winds via Stanford and Johns Hopkins? This is where something called sonification comes in.
“It’s quite a clever idea in science, where you take—in astronomy particularly—you take some distant phenomenon, like a galaxy; or a black hole, you know, sucking in matter; or the atmospheric motions of Jupiter; or the sun itself, and you turn the signals that are happening in that domain into sound waves, just as a way of realizing them in a way that’s not visual,” Impey said. The technique helps scientists represent data, but according to Impey it also “sort of misrepresents the physics. It’s not a real sound.”
Impey elaborated that sonification is sort of like viewing a vivid infrared image from the James Webb Space Telescope on your phone screen. “They’re not real colors because the radiation that was being detected was not visible to the naked eye.”
Back to sonification: “It’s a way of experiencing a phenomenon that’s not really for the human senses at all,” explained Impey.
There are some good reasons why experts turn to sound to help them interpret such raw data. “Sound is one of the ways that humans make sense of our environment,” said Edson.
[ Related: Why can’t we just launch all of Earth’s garbage into the sun? ]
“We might hear raindrops or wind blowing, and that tells us about the weather without us needing to look outside. We hear ambulance sirens that tell us we need to get out of the way.” Edson said, “But sound is also a way of learning.” Like a mechanic listens to an engine, or a doctor listens to a heart, for anomalies, scientists convert and condense data into sound to figure out what’s happening. “You can hear years and years of changes in a few seconds or minutes,” Edson explained, and “sometimes there are patterns that will show up in the sound that you wouldn’t have noticed.”
Like Earth, our sun has its own activity cycle. And it’s been quite busy lately. “Right now we’re in what we call solar maximum,” said Edson. “So there’s a ton of sunspots. There are lots of flares. We’ve been seeing auroras in places we don’t usually.”
If you sonify the sunspot data, “when it gets turned into sound, you can hear the up and down of that 11-year cycle,” explained Edson, “and it does kind of sound like a heartbeat.”
(The expert did not say if it went something like ba boom ba boom, or lub dub lub dub.)
This story is part of Popular Science’s Ask Us Anything series, where we answer your most outlandish, mind-burning questions, from the ordinary to the off-the-wall. Have something you’ve always wanted to know? Ask us.
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