(Press-News.org) This news release is available in German.
All the objects around us emit thermal radiation. Usually, this radiation can be described very accurately using Planck's law. If, however, the radiating object is smaller than the thermal wavelength, it behaves according to different rules and cannot emit the energy efficiently. This has now been confirmed by a team of researchers at the Vienna University of Technology. These findings are important for heat management of nano-devices and also for the science of aerosols - microparticles suspended in air, which influence the climate.
Planck's Law
In 1900, the Physicist Max Planck came up with a formula describing the heat radiation of bodies as a function of their temperature. In doing so, he laid down the groundwork for quantum physics. His theory describes the radiation of a wide variety of objects, such as the light emitted by stars, the color of a glowing poker stick, or invisible heat radiation that can be recorded with infrared cameras. But while his theory can be applied to many different systems, Planck himself already knew that it is bound to fail and has to be replaced by a more general theory when very small objects are involved.
This has now been investigated at the Vienna University of Technology by Christian Wuttke and Arno Rauschenbeutel (Vienna Center for Quantum Science and Technology, Institute for Atomic and Subatomic Physics, Vienna University of Technology) by studying the heat radiation of ultra-thin optical fibers.
Absorbing and Emitting Radiation
Max Planck considered bodies which absorb all radiation. Due to the conservation of of energy, radiation has to be re-emitted by the surface. The body's temperature determines at which wavelengths the heat radiation is emitted, and this temperature-dependent wavelength distribution can be predicted with great accuracy using Planck's equations.
"However, things change if the object is smaller than the typical length over which the radiation is absorbed", says Arno Rauschenbeutel. "In that case, the body cannot fully absorb the incoming radiation, part of it can pass through." As a result, the thermal radiation of the body is altered and does not obey Planck's law any more.
Fluctuational Electrodynamics
Christian Wuttke and Arno Rauschenbeutel sent light through ultra-thin optical fibers with a diameter of only 500 nanometers. They measured the amount of optical energy which was converted into heat and subsequently radiated away into the environment. "We could show that the fibers take much longer to reach their equilibrium temperature than a simple application of Planck's law would suggest", says Arno Rauschenbeutel. "However, our findings are in perfect agreement with the more general theory of fluctuational electrodynamics, which allows one to take the geometry and the size of the body into account."
Data Transfer and Soot Particles
Arno Rauschenbeutel's research group is also using ultra-thin optical fibers to transmit quantum information. In this context, a good understanding of the fibers' thermal behavior is very important. A slower cooling process and a less effective heat transport entails a higher risk of the fibers melting and burning out when data is sent through.
More general theories of heat radiation beyond Planck's equations also play an important role in aerosol physics, which deals with tiny particles in the atmosphere. "The thermal radiation of a lump of coal can be described perfectly well by Planck's law, but the behavior of soot particles in the atmosphere can only be described with a more general theory, which we could now further confirm in our experiment", says Arno Rauschenbeutel.
INFORMATION:
The results of the research project have now been published in the scientific journal "Physical Review Letters".
Bilderdownload: http://www.tuwien.ac.at/dle/pr/aktuelles/downloads/2013/strahlen/
Further information:
Prof. Arno Rauschenbeutel
Insitute for Atomic and Subatomic Physics
Vienna Center for Quantum Science and Technology
Vienna University of Technology
Stadionallee 2, 1020 Vienna
T: +43-1-58801-141761
arno.rauschenbeutel@tuwien.ac.at
Heat radiation of small objects: Beyond Planck's equations
Objects that are smaller than the wavelength of thermal radiation cannot radiate heat efficiently. A generalized theory of thermal radiation has now been experimentally confirmed at the level of a single object at the Vienna University of Technology
2013-07-10
ELSE PRESS RELEASES FROM THIS DATE:
Huge iceberg breaks away from the Pine Island glacier in the Antarctic
2013-07-10
On 8 July 2013 a huge area of the ice shelf broke away from the Pine Island glacier, the longest and fastest flowing glacier in the Antarctic, and is now floating in the Amundsen Sea in the form of a very large iceberg. Scientists of the Alfred Wegener Institute - Helmholtz Centre for Polar and Marine Research have been following this natural spectacle via the earth observation satellites TerraSAR-X from the German Space Agency (DLR) and have documented it in many individual images. The data is intended to help solve the physical puzzle of this "calving".
Scientists from ...
ALMA prenatal scan reveals embryonic monster star
2013-07-10
The most massive and brightest stars in the galaxy form within cool and dark clouds but the process remains not just shrouded in dust, but also in mystery [1]. An international team of astronomers has now used ALMA to perform a microwave prenatal scan to get a clearer look at the formation of one such monster star that is located around 11 000 light-years away, in a cloud known as the Spitzer Dark Cloud (SDC) 335.579-0.292.
There are two theories on the formation of the most massive stars. One suggests that the parental dark cloud fragments, creating several small cores ...
Astronomers witness birth of Milky Way's most massive star
2013-07-10
Scientists have observed in unprecedented detail the birth of a massive star within a dark cloud core about 10,000 light years from Earth.
The team used the new ALMA (Atacama Large Millimetre/submillimetre Array) telescope in Chile – the most powerful radio telescope in the world – to view the stellar womb which, at 500 times the mass of the Sun and many times more luminous, is the largest ever seen in our galaxy.
The researchers say their observations – to be published in the journal Astronomy and Astrophysics – reveal how matter is being dragged into the centre of ...
Bacteria from Salar de Uyuni in Bolivia conceal bioplastic
2013-07-10
In Bolivia, in the largest continuous salt desert in the world, researchers from the Polytechnic University of Catalonia have found a bacterium that stores large amounts of PHB, a prized polymer. This biodegradable plastic is used by the food and pharmaceutical industries, for example to produce nanospheres to transport antibiotics.
In the quest for natural polymers to substitute for petroleum-based plastics, scientists have recently discovered that a microorganism in South America produces poly-beta-hydroxybutyrate (PHB), a biodegradable compound of great utility for ...
Calculating the value of effortful behavior: A clue to schizophrenia-related disability?
2013-07-10
Philadelphia, PA -- Many people with schizophrenia have marked problems with motivation, failing to initiate and persist in goal-directed behavior. These negative symptoms of schizophrenia can be disabling and prevent individuals from realizing their potential.
For many years it was thought this was due to an inability to experience pleasure associated with successful goal attainment. However, recent laboratory studies have shown that hedonic experience is actually intact in people with schizophrenia, calling for new approaches to better understand these motivational ...
Photosynthesis: Membranes in tight corners
2013-07-10
Photosynthesis takes place in specialized membrane systems, made up of stacked disks linked together by unstacked planar leaflets. A team of Ludwig-Maximilians-Universitaet (LMU) in Munich has now identified a protein that tucks the membrane in at the edge of each stack.
Scanning electron microscopy (SEM) micrograph of a chloroplast in maize (Zea mays) showing thylakoids (green) and assimilation starch granules (grey). (Prepared by freeze fracturing; micrograph is pseudo-colored.) (Source: G. Wanner LMU)
By making use of sunlight to generate molecular oxygen and other ...
Inscription from time of David & Solomon found near Temple Mount in Hebrew University excavation
2013-07-10
Working near the Temple Mount in Jerusalem, Hebrew University of Jerusalem archaeologist Dr. Eilat Mazar has unearthed the earliest alphabetical written text ever uncovered in the city.
The inscription is engraved on a large pithos, a neckless ceramic jar found with six others at the Ophel excavation site. According to Dr. Mazar, the inscription, in the Canaanite language, is the only one of its kind discovered in Jerusalem and an important addition to the city's history.
Dated to the tenth century BCE, the artifact predates by two hundred and fifty years the earliest ...
Stanford researchers say 'peak oil' concerns should ease
2013-07-10
Fears of depleting the Earth's supply of oil are unwarranted, according to new research, which concludes that the demand for oil – as opposed to the supply – will reach its own peak and then decline.
"Peak oil" prognosticators have painted pictures of everything from a calm development of alternatives to calamitous shortages, panic and even social collapse as the world reaches its peak of oil production – and then supplies fall.
But according to the study by researchers at Stanford University and the University of California-Santa Cruz, those scenarios assume that ...
A Malaysian beauty: Newly described endemic herb species under threat of extinction
2013-07-10
A new species of rare and beautiful plant has been described from the biodiversity rich Peninsular Malaysia. Ridleyandra chuana is endemic to the region and only known from two small montane forest populations. The conservation status of this recently described delicate flower is assessed as Endangered due to its restricted distribution. The new species was described and illustrated in the open access journal PhytoKeys.
Ridleyandra chuana is a perennial herb with a woody usually unbranched stem crowned by an asymmetrical rosette of dark green leaves covered in fine hairs. ...
Cigarette smoke impacts genes linked to health of heart and lungs
2013-07-10
New insights into why obese cigarette smokers experience a high risk of heart disease suggest that cigarette smoke affects the activity of hundreds of key genes that both protect the heart and lungs and expose them to damage. The study, published in ACS' Chemical Research in Toxicology, suggests that the effects may be especially profound in obese nonsmokers who inhale "sidesteam smoke" from cigarettes smoldering nearby.
Diana J. Bigelow and colleagues point out that active smoking doubles the risk of heart disease, while second-hand smoke exposure increases this risk ...
LAST 30 PRESS RELEASES:
Elucidating liquid-liquid phase separation under non-equilibrium conditions
Fecal microbiome and bile acid profiles differ in preterm infants with parenteral nutrition-associated cholestasis
The Institute of Science and Technology Austria (ISTA) receives €5 million donation for AI research
Study finds link between colorblindness and death from bladder cancer
Tailored treatment approach shows promise for reducing suicide and self-harm risk in teens and young adults
Call for papers: AI in biochar research for sustainable land ecosystems
Methane eating microbes turn a powerful greenhouse gas into green plastics, feed, and fuel
Hidden nitrogen in China’s rice paddies could cut fertilizer use
Texas A&M researchers expose hidden risks of firefighter gear in an effort to improve safety and performance
Wood burning in homes drives dangerous air pollution in winter
The Journal of Nuclear Medicine Ahead-of-Print Tip Sheet: January 23, 2026
ISSCR statement in response to new NIH policy on research using human fetal tissue (Notice NOT-OD-26-028)
Biologists and engineers follow goopy clues to plant-wilting bacteria
What do rats remember? IU research pushes the boundaries on what animal models can tell us about human memory
Frontiers Science House: did you miss it? Fresh stories from Davos – end of week wrap
Watching forests grow from space
New grounded theory reveals why hybrid delivery systems work the way they do
CDI scientist joins NIH group to improve post-stem cell transplant patient evaluation
Uncovering cancer's hidden oncRNA signatures: From discovery to liquid biopsy
Multiple maternal chronic conditions and risk of severe neonatal morbidity and mortality
Interactive virtual assistant for health promotion among older adults with type 2 diabetes
Ion accumulation in liquid–liquid phase separation regulates biomolecule localization
Hemispheric asymmetry in the genetic overlap between schizophrenia and white matter microstructure
Research Article | Evaluation of ten satellite-based and reanalysis precipitation datasets on a daily basis for Czechia (2001–2021)
Nano-immunotherapy synergizing ferroptosis and STING activation in metastatic bladder cancer
Insilico Medicine receives IND approval from FDA for ISM8969, an AI-empowered potential best-in-class NLRP3 inhibitor
Combined aerobic-resistance exercise: Dual efficacy and efficiency for hepatic steatosis
Expert consensus outlines a standardized framework to evaluate clinical large language models
Bioengineered tissue as a revolutionary treatment for secondary lymphedema
Forty years of tracking trees reveals how global change is impacting Amazon and Andean Forest diversity
[Press-News.org] Heat radiation of small objects: Beyond Planck's equationsObjects that are smaller than the wavelength of thermal radiation cannot radiate heat efficiently. A generalized theory of thermal radiation has now been experimentally confirmed at the level of a single object at the Vienna University of Technology