scholarly journals A climatic thermostat making Earth habitable

2005 ◽  
Vol 4 (1) ◽  
pp. 3-7 ◽  
Author(s):  
Peter D. Ditlevsen
Keyword(s):  
Surface Temperature ◽  
Temperature Control ◽  
Black Body ◽  
Black Body Radiation ◽  
Cold Climate ◽  
Snowball Earth ◽  
Greenhouse Warming ◽  
Radiative Balance ◽  
The Mean ◽  
Warm State

The mean surface temperature on Earth and other planets with atmospheres is determined by the radiative balance between the non-reflected incoming solar radiation and the outgoing long-wave black-body radiation from the atmosphere. The surface temperature is higher than the black-body temperature due to the greenhouse warming. Balancing the ice-albedo cooling and the greenhouse warming gives rise to two stable climate states. A cold climate state with a completely ice-covered planet, called Snowball Earth, and a warm state similar to our present climate where greenhouse warming prevents the total glaciation. The warm state has dominated Earth in most of its geological history despite a 30% fainter young Sun. The warming could have been controlled by a greenhouse thermostat operating by the temperature control of the weathering process depleting CO2 from the atmosphere. This temperature control has permitted life to evolve as early as the end of the heavy bombardment 4 billion years ago.

scholarly journals On phenomena relating to the spectra of hydrogen and helium

1916 ◽  
Vol 93 (646) ◽  
pp. 27-28
Keyword(s):  
Accurate Determination ◽  
Principal Series ◽  
Black Body ◽  
Black Body Radiation ◽  
Balmer Series ◽  
Mean Values ◽  
Carbon Arc ◽  
The Mean ◽  
The Individual

In a previous paper the structure of broadened spectrum lines was investigated by a method involving the use of a neutral-tinted wedge as an accessory to the spectroscope. The present communication deals with a method for the accurate determination of the photographic intensities of spectrum lines and the reduction of such intensities to absolute values by comparison with the continuous black-body radiation of the carbon arc. These methods have been applied to a study of the relative intensity distribution in the spectra of helium and hydrogen under different conditions of excitation. It has been found that under certain specified conditions there is a transfer of energy from the longer to the shorter wave-lengths in any given series, and that, under such conditions, the associated series, and in particular the Diffuse series, are relatively enhanced at the expense of the Principal series. It has also been found that the distribution of intensity found in certain celestial spectra can be approximately reproduced in the laboratory. In any attempt to interpret the phenomena observed in connection with the Balmer series of hydrogen, it is necessary to know the particular type to which this series belongs. In order to decide this point a study has been made of the separations of the components of lines of the Balmer series of hydrogen, and the mean values of the separations of the doublets constituting the lines H a and H β have been found to be respectively 0.132 Å.U. and 0.033 Å.U. These values are consistent with the separations appropriate to a Principal series, and the first is in precise agreement with the value deduced by Buisson and Fabry. These results have been obtained by crossing a Lummer Gehrcke plate with the neutral wedge, and submitting the contours obtained to mathematical analysis, by means of which the distribution of intensity in the individual components, and the separation of the components, can be determined.

scholarly journals Some phenomena connected with the transfer of heat by radiation and turbulence in the lower atmosphere

1930 ◽  
Vol 130 (812) ◽  
pp. 98-104 ◽  
Keyword(s):  
Black Body ◽  
Black Body Radiation ◽  
Mean Value ◽  
Absolute Temperature ◽  
Lower Atmosphere ◽  
Lapse Rate ◽  
A Value ◽  
Radiative Diffusion ◽  
The Mean ◽  
Very High

One of the most outstanding facts of observation of the distribution of temperature in the atmosphere is the constancy of the mean lapse-rate of temperature at all heights within the troposphere and in all latitudes. The variation about the mean value, which is roughly one-half of the dry adiabatic lapse-rate, is very slight at all heights greater than a few hundred metres above the ground, but in the layer nearest the ground the extent of the variation is very considerable. At night, and particularly during clear nights in winter, the sign of the lapse-rate in the lowest layer is changed, and the temperature increases with height instead of decreasing. On sunny summer afternoons the lapse-rate in the lowest layers attains very high values, the change of temperature from 1/2 metre to 1 metre above the ground amounting to the equivalent of 100 to 200 times the dry adiabatic lapse-rate. Observations in the layers still nearer to the ground are not yet available, but the nature of the values hitherto observed suggests that the lapse-rate increases in a marked manner as we approach the surface. This raises a very natural question. Is there any limit to the lapse-rate which physically capable of foundation in the atmosphere immediately above the ground? In an earlier paper, I have shown that the outward flux of heat (W-radiation) by radiation can be represented by — k ∂͞T/∂͞z calories/cm. 2 /min., where k is 115/ p m at a temperature of 275° A., p w being the vapour pressure in millibars, and T representing the absolute temperature at a height z above the ground. The average amount of incoming radiation which has to be disposed of is given ( loc. cit .) as 0∙275 calories/cm. 2 /min. This, however, is the average over all latitudes, and over day and night, and is too low a value for our present purposes. We shall adopt instead an amount equal to black body radiation at 280° A. amounting to 0∙509 calories/cm. 2 /min. Of this, an amount 0∙290 calories/cm. 2 /min. leaves the ground as W-radiation. These figures would roughly correspond with afternoon sunshine in the British Isles. If we assume the temperature gradient in the layer near the ground to be ∂͞T/∂͞z, then it has been shown ( loc. cit .) that in this layer the amount of W-radiation transported outward by radiative diffusion is —1/2 k ∂͞T/∂͞z. If the lapse-rate has the value given by the equation.

The Physical World

2017 ◽  
Author(s):  
Nicholas Manton ◽  
Nicholas Mee
Keyword(s):  
Quantum Mechanics ◽  
Particle Physics ◽  
Variational Principles ◽  
Black Body ◽  
Black Body Radiation ◽  
Physical World ◽  
Atomic Scale ◽  
Solid State Physics ◽  
Least Action ◽  
Dimensional Spacetime

The book is an inspirational survey of fundamental physics, emphasizing the use of variational principles. Chapter 1 presents introductory ideas, including the principle of least action, vectors and partial differentiation. Chapter 2 covers Newtonian dynamics and the motion of mutually gravitating bodies. Chapter 3 is about electromagnetic fields as described by Maxwell’s equations. Chapter 4 is about special relativity, which unifies space and time into 4-dimensional spacetime. Chapter 5 introduces the mathematics of curved space, leading to Chapter 6 covering general relativity and its remarkable consequences, such as the existence of black holes. Chapters 7 and 8 present quantum mechanics, essential for understanding atomic-scale phenomena. Chapter 9 uses quantum mechanics to explain the fundamental principles of chemistry and solid state physics. Chapter 10 is about thermodynamics, which is built around the concepts of temperature and entropy. Various applications are discussed, including the analysis of black body radiation that led to the quantum revolution. Chapter 11 surveys the atomic nucleus, its properties and applications. Chapter 12 explores particle physics, the Standard Model and the Higgs mechanism, with a short introduction to quantum field theory. Chapter 13 is about the structure and evolution of stars and brings together material from many of the earlier chapters. Chapter 14 on cosmology describes the structure and evolution of the universe as a whole. Finally, Chapter 15 discusses remaining problems at the frontiers of physics, such as the interpretation of quantum mechanics, and the ultimate nature of particles. Some speculative ideas are explored, such as supersymmetry, solitons and string theory.

Constructing Quantum Mechanics

2019 ◽  
Author(s):  
Anthony Duncan ◽  
Michel Janssen
Keyword(s):  
Quantum Mechanics ◽  
Quantum Theory ◽  
Stark Effect ◽  
Zeeman Effect ◽  
Black Body ◽  
Black Body Radiation ◽  
Wave Mechanics ◽  
Specific Heats ◽  
Old Quantum Theory ◽  
Upper Level

This is the first of two volumes on the genesis of quantum mechanics. It covers the key developments in the period 1900–1923 that provided the scaffold on which the arch of modern quantum mechanics was built in the period 1923–1927 (covered in the second volume). After tracing the early contributions by Planck, Einstein, and Bohr to the theories of black‐body radiation, specific heats, and spectroscopy, all showing the need for drastic changes to the physics of their day, the book tackles the efforts by Sommerfeld and others to provide a new theory, now known as the old quantum theory. After some striking initial successes (explaining the fine structure of hydrogen, X‐ray spectra, and the Stark effect), the old quantum theory ran into serious difficulties (failing to provide consistent models for helium and the Zeeman effect) and eventually gave way to matrix and wave mechanics. Constructing Quantum Mechanics is based on the best and latest scholarship in the field, to which the authors have made significant contributions themselves. It breaks new ground, especially in its treatment of the work of Sommerfeld and his associates, but also offers new perspectives on classic papers by Planck, Einstein, and Bohr. Throughout the book, the authors provide detailed reconstructions (at the level of an upper‐level undergraduate physics course) of the cental arguments and derivations of the physicists involved. All in all, Constructing Quantum Mechanics promises to take the place of older books as the standard source on the genesis of quantum mechanics.

Successive Modulation of ENSO to the Future Greenhouse Warming

2008 ◽  
Vol 21 (1) ◽  
pp. 3-21 ◽  
Author(s):  
Soon-Il An ◽  
Jong-Seong Kug ◽  
Yoo-Geun Ham ◽  
In-Sik Kang
Keyword(s):  
General Circulation ◽  
Southern Oscillation ◽  
General Circulation Models ◽  
Tropical Pacific ◽  
Greenhouse Warming ◽  
Delayed Response ◽  
Subsurface Temperature ◽  
Climate System Model ◽  
The Mean ◽  
The Tropical Pacific

Abstract The multidecadal modulation of the El Niño–Southern Oscillation (ENSO) due to greenhouse warming has been analyzed herein by means of diagnostics of Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) coupled general circulation models (CGCMs) and the eigenanalysis of a simplified version of an intermediate ENSO model. The response of the global-mean troposphere temperature to increasing greenhouse gases is more likely linear, while the amplitude and period of ENSO fluctuates in a multidecadal time scale. The climate system model outputs suggest that the multidecadal modulation of ENSO is related to the delayed response of the subsurface temperature in the tropical Pacific compared to the response time of the sea surface temperature (SST), which would lead a modulation of the vertical temperature gradient. Furthermore, an eigenanalysis considering only two parameters, the changes in the zonal contrast of the mean background SST and the changes in the vertical contrast between the mean surface and subsurface temperatures in the tropical Pacific, exhibits a good agreement with the CGCM outputs in terms of the multidecadal modulations of the ENSO amplitude and period. In particular, the change in the vertical contrast, that is, change in difference between the subsurface temperature and SST, turns out to be more influential on the ENSO modulation than changes in the mean SST itself.

Ocular surface temperature differences in glaucoma

2021 ◽  
pp. 112067212110237
Author(s):  
Ari Leshno ◽  
Ori Stern ◽  
Yaniv Barkana ◽  
Noa Kapelushnik ◽  
Reut Singer ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Thermal Imaging ◽  
Ocular Surface ◽  
Open Angle Glaucoma ◽  
Tissue Temperature ◽  
Body Temperatures ◽  
Current Thinking ◽  
Imaging Camera ◽  
The Mean ◽  
The Difference

Purpose: Accumulating evidence suggests that neuroinflammation and immune response are part of the sequence of pathological events leading to optic nerve damage in glaucoma. Changes in tissue temperature due to inflammation can be measured by thermographic imaging. We investigated the ocular surface temperature (OST) profile of glaucomatous eyes to better understand the pathophysiology of these conditions. Methods: Subjects diagnosed with glaucoma (primary open angle glaucoma [POAG] or pseudo exfoliation glaucoma [PXFG]) treated at the Sam Rothberg Glaucoma Center (11/2019–11/2020.) were recruited. Healthy subjects with no ocular disease served as controls. The Therm-App thermal imaging camera was used for OST acquisition. Room and body temperatures were recorded, and the mean temperatures of the medial cantus, lateral cantus, and cornea were calculated with image processing software. Results: Thermographic images were obtained from 52 subjects (52 eyes: 25 POAG and 27 PXFG) and 66 controls (66 eyes). Eyes with glaucoma had a significantly higher OST compared to controls (mean 0.9 ± 0.3°C, p < 0.005). The difference between the two groups remained significant after adjustment for age, sex, intraocular pressure (IOP) and room and body temperatures. Lens status and topical IOP-lowering medication did not significantly affect OST. A subgroup analysis revealed that the OST was higher among eyes with POAG compared to eyes with PXFG, but not significantly. Conclusions: Differences in the OST between glaucomatous and normal eyes strengthens current thinking that inflammation affects the pathophysiology of glaucoma. Longitudinal studies are warranted to establish the prognostic value of thermographic evaluations in these patients.

Electromagnetic fluctuations from energetic particles in plasmas

1988 ◽  
Vol 40 (3) ◽  
pp. 407-417 ◽  
Author(s):  
Cheng Chu ◽  
J. L. Sperling
Keyword(s):  
Distribution Function ◽  
Velocity Distribution ◽  
Charged Particles ◽  
Velocity Distribution Function ◽  
Black Body ◽  
Black Body Radiation ◽  
Specific Model ◽  
Magnetized Plasma ◽  
Plasma Power ◽  
Correlation Techniques

Electromagnetic fluctuations, induced by energetic charged particles, are calculated using correlation techniques for a uniform magnetized plasma. Power emission in the ion-cyclotron range of frequencies (ICRF) is calculated for a specific model of velocity distribution function. The emissive spectra are distinct from that of the black-body radiation and have features that are consistent with experimental observation.

DOES LIOUVILLE'S THEOREM IMPLY QUANTUM MECHANICS?

1999 ◽  
Vol 13 (02) ◽  
pp. 161-189
Author(s):  
C. SYROS
Keyword(s):  
Quantum Mechanics ◽  
Radiation Spectrum ◽  
Black Body ◽  
Boltzmann Distribution ◽  
Black Body Radiation ◽  
Planck Constant ◽  
Klein Gordon ◽  
Energy Variable ◽  
Liouville’S Theorem ◽  
Liouville’S Equation

The essentials of quantum mechanics are derived from Liouville's theorem in statistical mechanics. An elementary solution, g, of Liouville's equation helps to construct a differentiable N-particle distribution function (DF), F(g), satisfying the same equation. Reality and additivity of F(g): (i) quantize the time variable; (ii) quantize the energy variable; (iii) quantize the Maxwell–Boltzmann distribution; (iv) make F(g) observable through time-elimination; (v) produce the Planck constant; (vi) yield the black-body radiation spectrum; (vii) support chronotopology introduced axiomatically; (viii) the Schrödinger and the Klein–Gordon equations follow. Hence, quantum theory appears as a corollary of Liouville's theorem. An unknown connection is found allowing the better understanding of space-times and of these theories.

Effect of Surface Roughness on the Total Hemispherical and Specular Reflectance of Metallic Surfaces

1964 ◽  
Vol 86 (2) ◽  
pp. 193-199 ◽  
Author(s):  
R. C. Birkebak ◽  
E. M. Sparrow ◽  
E. R. G. Eckert ◽  
J. W. Ramsey
Keyword(s):  
Surface Roughness ◽  
Black Body ◽  
Black Body Radiation ◽  
The Other ◽  
Angle Of Incidence ◽  
Metallic Surfaces ◽  
Specular Reflectance ◽  
Other Hand ◽  
Hemispherical Reflectance ◽  
Effect Of Surface

Measurements have been made of the hemispherical and specular reflectance of metallic surfaces of controlled roughness. The surfaces, which were ground nickel rectangles, were irradiated at various angles of incidence by a beam of black-body radiation, the temperature of which was also varied. The instrumentation which was devised to perform the experiments is described. The measurements show that beyond a certain surface roughness, the hemispherical reflectance is virtually independent of further increases in roughness. On the other hand, the specular reflectance decreases steadily with increasing roughness. Additionally, the hemispherical reflectance is found to be quite insensitive to the angle of incidence, while the specular reflectance increases with angle of incidence for the rougher surfaces.

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