Here’s visible proof for the first time
ever.
StudioM1//Getty
Images
- Usually, when something gets warmed up, heat tends to spread outward before eventually dissipating. But things are a little different in the world of superfluid quantum gas.
- For the first time, MIT scientists have successfully imaged how heat actually travels in a wave, known as a “second sound,” through this exotic fluid.
- Understanding this dynamic could help answer questions about high-temperature superconductors and neutron stars.
In
the world of average, everyday materials, heat tends to spread out from a
localized source. Drop a burning coal into a pot of water, and that liquid will
slowly rise in temperature before its heat eventually dissipates. But the world
is full of rare, exotic materials that don’t exactly play by these
thermal rules.
Instead
of spreading out as one would expect, these superfluid quantum gasses “slosh”
heat side to side—it essentially propagates as a wave. Scientists call
this behavior a material’s “second sound” (the first being ordinary sound via a
density wave). Although this phenomenon has been observed before, it’s never
been imaged. But recently, scientists at the Massachusetts Institute of Technology
(MIT) were finally able to capture this movement of pure heat by developing a
new method of thermography (a.k.a. heat-mapping).
The
results of this study were published last week in
the journal Science, and in an university press release highlighting the achievement,
MIT assistant professor and co-author Richard Fletcher continued the boiling
pot analogy to describe the inherent strangeness of “second sound” in
these exotic superfluids.
MIT
Simplified example of
"sloshing" heat in a superfluid compared to a normal fluid.
“It’s
as if you had a tank of water and made one half nearly boiling,”
Fletcher said. “If you then watched, the water itself might look totally calm,
but suddenly the other side is hot, and then the other side is hot, and the
heat goes back and forth, while the water looks totally still.”
These
superfluids are created when a cloud of atoms is subjected to ultra-cold
temperatures approaching absolute zero (−459.67 °F). In this rare
state, atoms behave differently, as they create an essentially friction-free
fluid. It’s in this frictionless state that heat has been theorized to
propagate like a wave.
“Second
sound is the hallmark of superfluidity, but in ultracold gases so far you could
only see it in this faint reflection of the density ripples that go
along with it,” lead author Martin Zwierlein said in a press statement. “The
character of the heat wave could not be proven before.”
To
finally capture this second sound in action, Zweierlein and his team had to
think outside the usual thermal box, as there’s a big problem trying to track
heat of an ultracold object—it doesn’t emit the usual infrared radiation. So,
MIT scientists designed a way to leverage radio frequencies to track certain
subatomic particles known as “lithium-6 fermions,” which can be captured via
different frequencies in relation to their temperature (i.e. warmer
temperatures mean higher frequencies, and vice versa). This novel technique
allowed the researchers to essentially zero in on the “hotter” frequencies
(which were still very much cold) and track the resulting second wave over
time.
This
might feel like a big “so what?” After all, when’s the last time you had a
close encounter with a superfluid quantum gas? But ask a materials
scientist or astronomer, and you’ll get an entirely different answer.
While
exotic superfluids may not fill up our lives (yet), understanding the
properties of second wave movement could help questions regarding high-temperature superconductors (again,
still at very low temperatures) or the messy physics that lie at the
heart of neutron stars.
Source
of the information: popularmechanics.com
Post a Comment