Nuclear suns

Cerenkov radiation emission of blue hght by particles moving faster than light in a medinm other than the vacuum (note that in a medinm with refrachve index n, hght moves with speed v = cjn) 

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Europium has been identified spectroscopically in the sun and certain stars. Seventeen isotopes are now recognized. Europium isotopes are good neutron absorbers and are being studied for use in nuclear control applications. 

If possible comparisons are focused on energy systems, nuclear power safety is also estimated to be superior to all electricity generation methods except for natural gas (30). Figure 3 is a plot of that comparison in terms of estimated total deaths to workers and the pubHc and includes deaths associated with secondary processes in the entire fuel cycle. The poorer safety record of the alternatives to nuclear power can be attributed to fataUties in transportation, where comparatively enormous amounts of fossil fuel transport are involved. Continuous or daily refueling of fossil fuel plants is required as compared to refueling a nuclear plant from a few tmckloads only once over a period of one to two years. This disadvantage appHes to solar and wind as well because of the necessary assumption that their backup power in periods of no or Httie wind or sun is from fossil-fuel generation. Now death or serious injury has resulted from radiation exposure from commercial nuclear power plants in the United States (31). 

In fact, the sun is not a first-generation main-sequence star since spectroscopic evidence shows the presence of many heavier elements thought to be formed in other types of stars and subsequently distributed throughout the galaxy for eventual accretion into later generations of main-sequence stars. In the presence of heavier elements, particularly carbon and nitrogen, a catalytic sequence of nuclear reactions aids the fusion of protons to helium (H. A. Bethe... 

Because the steam engine described is a heat engine of the external-combustion type, the cycle experienced by the working medium can be executed without combustion. In some steam engines, for example, the required input heat is supplied by a nuclear reactor. Stirling engines have been operated on radiant energy supplied by the sun. 

The most important contribution I lertz made in this inaugural lecture was his prediction, based on his estimates of the energy sources available, that ultimately the Earth was completely dependent on the Sun for the light and heat it needed to support life. Of course, this picture would change after Henri Becquerel discovered radioactivity in 1896, and thus introduced the nuclear age of physics. 

Th ese manufactured light sources are, perhaps ironically, largely dependent on the Sun. The radiant energy from the Sun has been stored in the fossilized remains of billions of creatures over millions of years and is used to power the electric light sources created by modern humans. The power generated by hydroelectric sources also is a result of solar evaporation and subsequent rainfall. Only nuclear reactors provide power independent of the Sun, which is, of course, the largest nuclear reactor in the solar system. 

The composition of the Earth was determined both by the chemical composition of the solar nebula, from which the sun and planets formed, and by the nature of the physical processes that concentrated materials to form planets. The bulk elemental and isotopic composition of the nebula is believed, or usually assumed to be identical to that of the sun. The few exceptions to this include elements and isotopes such as lithium and deuterium that are destroyed in the bulk of the sun s interior by nuclear reactions. The composition of the sun as determined by optical spectroscopy is similar to the majority of stars in our galaxy, and accordingly the relative abundances of the elements in the sun are referred to as "cosmic abundances." Although the cosmic abundance pattern is commonly seen in other stars there are dramatic exceptions, such as stars composed of iron or solid nuclear matter, as in the case with neutron stars. The... 

Unlocking the secrets of the nucleus was a mixed blessing, for in addition to our understanding of the sun, we also acquired nuclear weapons of immense desfructive potential. The bombing of Hiroshima and Nagasaki with nuclear weapons was one of the last acts of the Second World War but the beginning of the nuclear dilemma More than 50 years later, controversies still rage over how society should use the fruits of nuclear science. 

The sun and all other stars produce energy at a huge rate from sustained nuclear fusion. Over time, stars evolve through several stages, including stellar explosions. The products of a stellar explosion can form stars of more complex composition. Three distinct generations of stars have been identified, each fueled by a different set of fusion reactions. 

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