In a groundbreaking experiment, a team of scientists from the Massachusetts Institute of Technology (MIT) has discovered an unusual behavior of heat in a super-cool liquid, revealing that heat can move in waves, similar to how sound travels through the air.
This fascinating finding changes our understanding of heat movement and could have implications for a wide range of scientific fields.
Typically, when you warm up a part of a material, the heat spreads out slowly, warming up the surrounding areas.
However, in some very special conditions, heat doesn’t just spread out; it moves back and forth in a wave.
Imagine throwing a stone into a pond and watching the ripples travel across the water; now, picture heat doing something similar in a super-cool liquid.
Scientists call this wave-like heat movement “second sound,” because it’s reminiscent of the way sound waves move.
Until now, this wave-like behavior of heat was mostly a theoretical idea, observed indirectly in very few materials.
But the MIT team, led by Martin Zwierlein and Richard Fletcher, managed to capture direct images of this phenomenon for the first time, using a superfluid—a kind of fluid that flows without any friction at extremely low temperatures.
To picture this, Fletcher uses the analogy of heating half a tank of water until it’s nearly boiling, while the other half remains cool.
In normal conditions, the heat would slowly spread from the hot side to the cool side.
But in their experiment with superfluid, the heat “sloshed” back and forth between the two sides without actually moving the water itself. It’s as if the heat has a life of its own, bouncing back and forth while the water stays perfectly still.
The team achieved this by cooling a cloud of atoms to a temperature so low that it becomes a superfluid. At these temperatures, atoms behave differently, allowing heat to move in this unique wave-like manner.
This super-cool state of matter and the behavior of heat within it are not just scientific curiosities. They hold clues to understanding how heat moves in other complex systems, such as superconductors and even neutron stars.
To observe this phenomenon, the researchers used a clever technique. Instead of trying to “see” the heat directly, they used radio frequencies to track how the heat moved through the superfluid.
By applying a specific radio frequency, they could make the atoms at different temperatures “ring” differently, allowing them to create a sort of movie showing how heat waves move through the superfluid.
This breakthrough is not just about observing a curious form of heat movement. It opens up new ways to understand and manipulate heat in materials.
For example, it could help scientists design better superconductors—materials that conduct electricity without any loss, which could revolutionize how we use and distribute power.
It might even help us understand the extreme conditions inside neutron stars, where matter is squeezed into incredibly dense forms.
By capturing the first images of second sound, the MIT researchers have taken a significant step forward in our understanding of superfluids and the bizarre but fascinating ways that heat can behave.
Their work promises to unlock new discoveries in physics, engineering, and materials science, helping us to design better technologies and solve mysteries of the cosmos.
The study was published in the journal Science.
