Solar eclipse

Gr. helios, the sun). Janssen obtained the first evidence of helium during the solar eclipse of 1868 when he detected a new line in the solar spectrum. Lockyer and Frankland suggested the name helium for the new element. In 1895 Ramsay discovered helium in the uranium mineral clevite while it was independently discovered in cleveite by the Swedish chemists Cleve and Langlet at about the same time. Rutherford and Royds in 1907 demonstrated that alpha particles are helium nuclei. 

In November 1919 Einstein became the mythical figure he is to this day. In May of that year two solar eclipse expeditions had (in the words of the astronomer Eddington) confirm[ed] Einstein s weird theory of non-Euclidean space. On November 6 the president of the Royal Society declared in London that this was the most remarkable scientific event since the discoveiy [in 18461 of the predicted existence of the planet Neptune. ... 

You would see the three groups like this, and you would not see the back carbon atom, because the carbon atom in front would be covering it up (again, like the moon covers the sun during a solar eclipse). Let s try to draw that back carbon that we cannot see, and by convention, we will draw it as a big circle ... 

Astronomers use spectroscopy to identify the composition of the sun and other stars. A striking example is the discovery of the element helium. In 1868, astrono-mers viewing a solar eclipse observed emission lines that did not match any known element. The English astronomer Joseph Lockyer attributed these lines to a new element that he named helium, from hellos, the Greek word for the sun. For 25 years the only evidence for the existence of helium was these solar spectral lines. 

In 1894, the Scottish chemist William Ramsay removed nitrogen and oxygen from air through chemical reactions. From the residue, Ramsay Isolated argon, the first noble gas to be discovered. A year after discovering argon, Ramsay obtained an unreactive gas from uranium-containing mineral samples. The gas exhibited the same spectral lines that had been observed in the solar eclipse of 1868. After helium was shown to exist on Earth, this new element was studied and characterized. 

In 1908, Kamerling-Onnes got the liquefaction of helium (discovered by Janssen e Lockyer during the solar eclipse of 18 August 1868). Kamerlingh-Onnes obtained in Leiden 60 cc of liquid helium extracted from several tons of monazite sable imported from India. Kamerlingh-Onnes himself discovered the X-transition and the superfluidity in 4He and in 1911 the superconductivity of Hg, a particularly pure substance at that time. In the race towards lower and lower temperatures, Kamerling-Onnes, pumping on liquid 4He, obtained 0.7K in 1926. 

Hydrogen in the uncombined state exists in enormous masses upon the sun, and is present in the "prominences observed in solar eclipses, while by optical means it may also be detected in many stars and nebulae. 

Helium - the atomic number is 2 and the chemical symbol is He. The name derives from the Greek helios for sun . The element was discovered by spectroscopy during a solar eclipse in the sun s chromosphere by the French astronomer Pierre-Jules-Cesar Janssen in 1868. It was independently discovered and named helium by the English astronomer Joseph Norman Lockyer. It was thought to be only a solar constituent until it was later found to be identical to the helium in the uranium ore cleveite by the Scottish chemist William Ramsay in 1895. Ramsay originally called his gas krypton, until it was identified as helium. The Swedish chemists Per Theodore Cleve and Nils Abraham Langet independently found helium in cleveite at about the same time. 

It would be hard to argue with that decision. But I recall a less-obvious version of the same basic problem. A rare solar eclipse was soon to occur, and our newspaper was flooded with urgent messages from individuals and organizations dedicated to the prevention of blindness. We were urged to tell our readers there was no safe way to look directly at the eclipse. It so happens that a safe eclipse viewer can be made with exposed photographic negatives, but the anti-blindness lobby said the procedure was too complicated, and many people undoubtedly would botch the job. Well, what should we... 

You can see why the conformations have these names by looking at the end-on views in the diagram. In the eclipsed case the near C-H bonds completely block the view of the far bonds, just as in a solar eclipse the moon blocks the sun as seen from the Earth, In the staggered conformation, the far C-H bonds appear in the gaps between the near C-H bonds—the bonds are staggered. 

Helium was discovered during a solar eclipse as an orange line in the spectrum of the sun s atmosphere. Physically, helium is colorless odorless, and tasteless and it is the second lightest element, second only to hydrogen. Helium, is chemically inert and has only a 5 part-per-million (ppm) concentration in the atmosphere. 

The Russian peasant of his day never heard of the Periodic Table, but he remembered Dmitri Mendel eft for another reason. One day, to photograph a solar eclipse, he shot into the air in a balloon, flew on a bubble and pierced the sky. And to every boy and girl of the Soviet Union today Mendel eff is a national hero. 

As a result, the lens and macula are prone to damage, especially without adequate eye protection. In addition to appropriate external protection (e.g., sunglasses), the eye requires an efficient internal antioxidant system. In this regard, Galileo apparently became blind after repeatedly observing the sun. Centuries later, in 1912, an estimated 3500 Germans suffered visual impairment after watching a solar eclipse. 

The ftrst noble gas to be discovered was hehum (Lockyer, 1869). Spectroscopic investigations of the Sun s chromosphere during a solar eclipse in India in 1868 revealed a previously unobserved line, close in wavelength to the Dj and D2 Fraunhofer lines of sodium. The new line was designated D3 and the element it represented helium ( = sun). 

During a solar eclipse in 1868, a new emission line, matching no known element, was found in the spectrum of the solar corona. J. N. Locklear and E. Frankland proposed the existence of a new element named, appropriately, helium (Greek, helios, sun). The same spectral line was subsequently observed in the gases of Mount Vesuvius. 

Helium was first discovered not on Earth, but in the sun. In 1868 French astronomer Pierre Janssen (1824-1907) studied light from the sun during a solar eclipse. He found proof that a new element existed in the sun. He called the element helium. 

An Element on the Sun This principle led to the discovery of helium. In 1868, Pierre Janssen visited India in order to observe a full eclipse of the sun. A solar eclipse occurs when the Moon comes between the sun and Earth. The Moon blocks nearly all of the sun s light. All that remains is a thin outer circle (corona) of sunlight around the dark Moon. Solar eclipses provide scientists with an unusual chance to study the sun. 

Pierre Janssen, studies the spectra of a solar eclipse and finds evidence of a new element. Edward Frankland, an English chemist, and Joseph Lockyer, an English astronomer, suggest the name helium. 

Helium derives its name from the Greek word helios, sun. The first evidence for helium was discovered in the solar spectrum taken during a solar eclipse in 1868. Helium is the second most abundant element in the universe after hydrogen. Helium atoms are light and travel at velocities sufficient to escape from the earth s atmosphere. 

Stratospheric intrusion. Solar eclipse. Photochemical O3 formation... 

Figure 4. Behaviour of the surface ozone concentration during the 94% solar eclipse in Sofia on August 11 1999 (curve B) and on August 18th 1999, a control day with close meteorological conditions (curve A).

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