Friday, December 12, 2003
Cold molecules
"Using a method usually more suitable to billiards than atomic physics, researchers from Sandia National Laboratories and Columbia University have created extremely cold molecules that could be used as the first step in creating Bose-Einstein molecular condensates." in Physlink.com
Tuesday, December 02, 2003
History of the 2.7 K temperature prior to Penzias and Wilson
I've found an article ( Apeiron 2, 79 (1995)) by A. K. T. Assis and M. C. D. Neves that reveals the history of the prediction of the temperature of the Universe. I'll try to give some main points:
1879 - Stefan found experimentaly that the total bolometric flux of radiation emitted by a black body is proportional to the 4th power of its temperature.
1884 - Boltzmann derived theoretically Stefan's law.
1896 - Guillaume estimated the temperature of "space" to be between 5 K and 6 K. This estimate is restricted to the effect due to stars belonging to our own galaxy.
1924 - Hubble established that the nebulae are stellar systems outside the Milky Way.
1926 - Eddington, also restricting himself to stars belonging to our own galaxy, estimated a temperature of 3.18 K
1928 - R. A. Millikan and Cameron found that the total energy of cosmic rays at the top of the atmosphere was one-tenth of that due to starlight and heat.
They also infered that the major part of the cosmic rays components originated from outside our galaxy.
1928 - Walther Nernst developed the idea of an Universe in a stationary state: " The Universe is in a stationary condition, that is, the present fixed stars cool continually and new ones are being formed".
1929 - Hubble obtained his redshift-distance law
1933 - Regener estimated that the charateristic temperature of the intergalatic space would be 2.8 K.
1937 - Nernst developed his model of a Universe in a stationary state and proposed a tired light explanation of the cosmological redshift.
1938 - Nernst discusses the radiation temperature in the Universe arriving at a temperature in intergalatic space as 0.75 K.
1941 - Herzberg based on the observations made by A. McKellar found a temperature of 2.3 K characterizing the observed degree of excitation of the cyanogen molecules if they were in equilibrium in a heat bath.
1953 - Gamow, using the Big Bang model, predicted that the temperature of the Universe should be 7 K.
1953-1954 - Finlay-Freundlich proposed a tired light model to explain the redshift of solar lines and some anomalous redshifts of several stars, as wel as the cosmological redshift. According to his theory the redshift is proportional to the 4th power of the temperature and inverselly proportional to the length of path traversed through the radiation field. By proposing an alternative to the Doppler interpretation of the cosmological redshift he arrived at 1.9K < T < 6.0K for the temperature of the intergalatic space.
1954 - Max Born discussing Finlay-Freundlich's proposal that this new effect might be due to a photon-photon interaction predicted that the resulting radiation should be of the order of radar waves.
1961 - Gamow in his book The Creation of the Universe predicts a present temperature of the Universe of 50 K.
1965 - Penzias and Wilson discovered the Cosmic Background Radiation using a horn reflector antenna built to study radio astronomy. They found a temperature of 3.5+/- 1.0K observing background radiation at 7.3 cm wavelength.
1879 - Stefan found experimentaly that the total bolometric flux of radiation emitted by a black body is proportional to the 4th power of its temperature.
1884 - Boltzmann derived theoretically Stefan's law.
1896 - Guillaume estimated the temperature of "space" to be between 5 K and 6 K. This estimate is restricted to the effect due to stars belonging to our own galaxy.
1924 - Hubble established that the nebulae are stellar systems outside the Milky Way.
1926 - Eddington, also restricting himself to stars belonging to our own galaxy, estimated a temperature of 3.18 K
1928 - R. A. Millikan and Cameron found that the total energy of cosmic rays at the top of the atmosphere was one-tenth of that due to starlight and heat.
They also infered that the major part of the cosmic rays components originated from outside our galaxy.
1928 - Walther Nernst developed the idea of an Universe in a stationary state: " The Universe is in a stationary condition, that is, the present fixed stars cool continually and new ones are being formed".
1929 - Hubble obtained his redshift-distance law
1933 - Regener estimated that the charateristic temperature of the intergalatic space would be 2.8 K.
1937 - Nernst developed his model of a Universe in a stationary state and proposed a tired light explanation of the cosmological redshift.
1938 - Nernst discusses the radiation temperature in the Universe arriving at a temperature in intergalatic space as 0.75 K.
1941 - Herzberg based on the observations made by A. McKellar found a temperature of 2.3 K characterizing the observed degree of excitation of the cyanogen molecules if they were in equilibrium in a heat bath.
1953 - Gamow, using the Big Bang model, predicted that the temperature of the Universe should be 7 K.
1953-1954 - Finlay-Freundlich proposed a tired light model to explain the redshift of solar lines and some anomalous redshifts of several stars, as wel as the cosmological redshift. According to his theory the redshift is proportional to the 4th power of the temperature and inverselly proportional to the length of path traversed through the radiation field. By proposing an alternative to the Doppler interpretation of the cosmological redshift he arrived at 1.9K < T < 6.0K for the temperature of the intergalatic space.
1954 - Max Born discussing Finlay-Freundlich's proposal that this new effect might be due to a photon-photon interaction predicted that the resulting radiation should be of the order of radar waves.
1961 - Gamow in his book The Creation of the Universe predicts a present temperature of the Universe of 50 K.
1965 - Penzias and Wilson discovered the Cosmic Background Radiation using a horn reflector antenna built to study radio astronomy. They found a temperature of 3.5+/- 1.0K observing background radiation at 7.3 cm wavelength.
