Scientists Unveil the Mind-Blowing Phenomenon of 'Second Sound'
- Typically, when an object heats up, the warmth spreads outwards and gradually disperses. However, this conventional behavior doesn't apply to superfluid quantum gases.
- For the first time, researchers from MIT have managed to capture images of how heat moves in a wavelike manner, referred to as "second sound," through this unusual liquid.
- Grasping this dynamic might aid in unraveling mysteries surrounding high-temperature superconductors and neutron stars.
In the realm of ordinary, day-to-day substances, heat generally disperses from a specific origin point. Toss a glowing ember into a container of water, and that liquid will gradually increase in temperature before its warmth ultimately fades away. However, the world is home to many unusual, rare substances that do not exactly adhere to these thermal guidelines.
Rather than dispersing as anticipated, these superfluid quantum gases exhibit "heat sloshing" from side to side; this process effectively spreads as waves. wave Scientists refer to this behavior as a material's "second sound" (with the "first sound" being conventional sound through a density wave). Despite previous observations of this effect, capturing an image of it had not been achieved until now. However, researchers from the Massachusetts Institute of Technology (MIT) have successfully visualized the flow of pure heat using a novel technique known as thermography (or heat mapping).
The findings of this research were released in the journal Science , and in an university press release emphasizing the accomplishment, MIT Assistant Professor and co-author Richard Fletcher extended the boiling pot metaphor to illustrate the intrinsic peculiarity of "second sound within these exotic superfluids.
It's like having a tank full of water And heated one half almost to boiling," Fletcher explained. "Once you observed it, the water would appear completely tranquil, yet abruptly one end would become scorching hot, followed by the opposite end heating up. The warmth would shift back and forth, even as the surface of the water remained utterly motionless.
These superfluids emerge when a group of atoms is exposed to extremely low temperatures nearing absolute zero (-459.67 °F). At this extreme temperature, atoms exhibit different behavior, forming a nearly frictionless liquid. This frictionless condition allows heat to potentially travel in waves according to theoretical predictions.
Second sound is characteristic of superfluidity; however, in ultracold gases up until now, it has only been observable as a subtle fluctuation in density. ripples As stated by lead author Martin Zwierlein in a press release, "These findings come alongside it," he noted. "We were unable to confirm the nature of the heatwave prior to this."
To ultimately capture this second sound in action, Zweierlein and his team needed to look beyond the conventional thermal box since tracking the heat of an extremely cold object poses a significant challenge; these objects do not produce typical infrared radiation. Therefore, MIT researchers developed a method using radio frequencies to monitor specific subatomic particles called "lithium-6 fermions," which can be detected through various means. frequencies In connection with their temperature (that is, higher temperatures correspond to higher frequencies, and lower temperatures to lower frequencies). This innovative method enabled the scientists to focus on the "warmer" frequencies (even though they were still quite cool) and monitor the subsequent second wave as it progressed over time.
This could seem like a significant "who cares?" After all, when was the last time you experienced something similar to a superfluid? quantum Sure? However, pose this question to a materials scientist or an astronomer, and you'll receive quite a different response.
Although exotic superfluids might not dominate our daily experiences (just yet), comprehending the characteristics of second-sound propagation could aid in addressing inquiries about high-temperature phenomena. superconductors (again, still at very low temperatures) or the complex physics that lie at the core of neutron stars .
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