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"Beyond the Elements" host David Pogue and chemical and environmental engineer Ruoxue Yan illustrate how the molecular bonds around us actually make sounds—even if we can’t hear them.

In the atomic world, everything is in motion, vibrating because of thermal energy.

Yes, Molecules Do Make Sounds

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"Beyond the Elements" host David Pogue and chemical and environmental engineer Ruoxue Yan illustrate how the molecular bonds around us actually make sounds — even if we can’t hear them.

In the atomic world, everything is in motion, vibrating because of thermal energy.

Physics & Math

Yes, Molecules Do Make SoundsPublished: May 28, 2021DAVID POGUE: So the story is bonds...atomic bonds. But the thing to remember is that in the atomic world, everything is in motion, vibrating because of thermal energy, heat. And that includes the bonds between atoms. They’re more like springs, oscillating. And according to a University of California at Riverside scientist, Ruoxue Yan, all that atomic vibration plays a specific tune, shaped by the atoms and the bonds between them, the Song of the Molecule.DAVID POGUE: So what do you mean when you talk about the song of the molecules?RUOXUE YAN: So, we’ve all seen the stick and ball model of molecules in science class, right? They tell you what the molecules look like, how the atoms are arranged in the molecule, but what it didn’t show is the atoms in the molecules, they’re not stationary. They’re constantly moving. They can stretch, they can bend, and those vibrations make sounds.DAVID POGUE: But they’re actual notes? I mean obviously not this high, but –RUOXUE YAN: Way over there, yes.DAVID POGUE: – but it’s real sound?RUOXUE YAN: So it’s like when you play a high note, you will see it’s always associated with a string that is both short and thin.DAVID POGUE: Right, these short thin ones make…[plays notes]RUOXUE YAN: It’s the same thing in molecular vibrations. So if the two atoms that make up the bond are light, like oxygen and hydrogen, then they move very violently, very quickly. So they give out high pitched sound.DAVID POGUE: So lighter things would be higher notes.RUOXUE YAN: Yes, higher frequency.DAVID POGUE: Alright, so like [singing] hydrogen.RUOXUE YAN: Yes, but hydrogen molecules, not atoms.DAVID POGUE: [singing] Molecules. Nitrogen, oxygen...molecules.RUOXUE YAN: Exactly.DAVID POGUE: OK, what are some middle range ones?RUOXUE YAN: Like alumina.DAVID POGUE: [singing] Alumina.RUOXUE YAN: Titania.DAVID POGUE: [singing] Titania.RUOXUE YAN: Silica.DAVID POGUE: [singing] Silica. [speaking] Okay, and then what’s a low one?RUOXUE YAN: Like silver oxide.DAVID POGUE: [singing] Silver oxide.RUOXUE YAN: Lead oxide.DAVID POGUE: [singing] Lead oxide.RUOXUE YAN: Radium permanganate.DAVID POGUE: [singing] Radium permanganate. [speaking] Song of the Molecules. By Ruoxue Yan...and David Pogue.DAVID POGUE: The song of the molecules isn’t a metaphor. In her lab, Ruoxue uses the vibrations of atoms and their bonds to identify a molecule’s structure. She isn’t the first to use the technique, but she and her team have developed an inexpensive and portable way to detect the faint signals. It uses light sent down a glass optical fiber which gradually narrows. At the fiber’s end, a silver nanowire focuses the light even more until it reaches the tip where it’s just a few nanometers across… about the width of a DNA molecule. The light it emits interacts with the vibrating target molecule, revealing its structure. Here, Ruoxue has used the system to analyze carbon nanotubes that are made of a single sheet of carbon atoms, rolled up into a cylinder. This is the tip of the device, scanning across the surface.RUOXUE YAN: Once you hit the carbon nanotube, you suddenly see these strong peaks coming up.DAVID POGUE: The tallest peak represents the atomic vibration perpendicular to the length of the carbon nanotube.RUOXUE YAN: All of the carbon atoms are going up and down. You go here at a higher frequency, what happens is all of the carbon molecules are going left and right. That’s a different motion at that different frequency.DAVID POGUE: Ruoxue thinks her system will give more labs around the world a chance to examine the atomic structure of molecules in the kind of detail that has been limited to expensive facilities.RUOXUE YAN: Those vibrations, those sounds, are too faint. They’re very weak. So the secret to hear those whispers is to shine lights on them. Because light can turn them on, and their voices can be enlarged to several orders of magnitude so that you can actually hear them.

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Yes, Molecules Do Make Sounds

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