Startling Exception Discovered to 200-Year-Old Law of Physics
Scientists have discovered an exception to a 200-year-old scientific law that governs how heat diffuses through solid materials
Known as Fourier’s law, it describes how heat is transferred, or conducted, through solid materials.
As molecules vibrate and electrons shuttle about, the heat diffuses from the hotter end of an object to the colder end, at a rate that is proportional to that temperature difference and the area through which the heat flows.
However, in the past few decades, researchers have found that on the nanoscale, this model of diffusion doesn’t work; Fourier’s law breaks down and no longer predicts how fast or slow heat will move through a solid material.
Being translucent, these materials let some wavelengths of light pass through. Although the light doesn’t get totally absorbed like in opaque materials, it does scatter, bouncing off impurities in the material structure.
Radiant heat is carried through the air as electromagnetic waves, mainly infrared radiation, and an example is the heat we feel from the Sun’s rays.
So the researchers clamped strips of test materials and suspended them, one by one, inside a custom-made vacuum chamber. The vacuum removed the possibility of heat dissipating from the materials through air.
The team fired split-second pulses of laser at the materials to heat them up, and measured how heat spread through each of the materials using three methods: a temperature sensor placed directly on the material surface; measuring the color change of a temperature-sensitive coating painted onto the sample; and an infrared camera.
“The data show heating [occurred] faster than can be attributed to diffusion,” the researchers write, “indicating that radiation contributes significantly to heat flux during early times after a heat pulse, though the relative contribution of radiation diminishes as diffusion becomes dominant at later times.”
“It’s not that Fourier’s Law is wrong,” Granick clarifies, “just that it doesn’t explain everything we see when it comes to heat transmission.”
The team suggests that translucent materials radiate heat internally because structural imperfections act as heat absorbers and sources, allowing the heat to propagate from point to point rather than diffusing slowly.
They add that their findings could help engineers design new strategies for heat management in translucent materials, now that their study provides an expanded understanding of how heat spreads in solids – some 200 years after this phenomenon was first described in mathematical terms.
Source: Science Alert
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Herb Rose
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Could it be that it is not “heat” but energy that is being transferred and what energy different materials absorb depends on the bonds in their structure. In the ideal gas law the r stands for the different properties of different gases that produce different reactions to energy.
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Jerry Krause
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Hi JaKo,
Did you read Herb’s first comment? I did. It’s right on. I didn’t comment before because I considered the scientific law to be the MORE fundamental issue.
Diamond is an atomic solid of carbon. Coal is an impure solid carbon. Ice is a molecular solid of water. Salt (NaCl) is an ionic solid. Copper is a metallic solid. In what solid does diffusion ever become “dominant at later times.”?
When one refers to solids I do not believe one is referring to “nanoscale” dust
Have a good day
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Jerry Krause
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Hi PSI Readers and Herb,
This article is about the critically important Scientific Law which is not an idea nor a theory. It is merely a summary of measured data of similar cases like an atmosphere’s temperature has never been observed to lie less than the atmosphere’s dew-point temperature when both of these temperatures are measured at the same place and same time at weather stations.
Hence when I read: “Scientists have discovered an exception to a 200-year-old scientific law that governs how heat diffuses through solid materials,” I Know that both Clare Watson, this article’s author, and Steve Granick, the research paper’s senior author, evidently do not understand what a Scientific Law actually is.
Have a good day
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JaKo
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Hi Jerry,
Here is an idea: What if many of the “old scientific laws,” as usually based on superficial observations and measurements, just would not work well on nanoscale? As this “radiation seems to be the initial mechanism for the heat transfer in solids before the diffusion takes over.”
Don’t you “feel” that many of these, originally thought of as solid LAWS, are suddenly being limited to the scope / scale of observation? I do.
And further, no pun intended, similar limitations are also recognized in some LAWS on hyper-scale.
Or, maybe, I’m just into an “intensive dislike of dogma”…
Cheers, JaKo
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Herb Rose
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You have been told many times that the dew point is not a measured temperature but is a calculation of the amount of water in the air like relative humidity. No matter how many times your stupid comments are corrected you continue to repeat them.
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sunsettommy
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I decided to end his banning, LOL@Klimate Katastrophe Kooks is now allowed to post again.
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MattH
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You good boy Sunset . Good boy.
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MattH
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Fetch it here, LOL@Klimate Katastrophe Kooks. Fetch it ere.
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Wisenox
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It’s electric.
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