<P> Liquid helium is used in cryogenics (its largest single use, absorbing about a quarter of production), particularly in the cooling of superconducting magnets, with the main commercial application being in MRI scanners . Helium's other industrial uses--as a pressurizing and purge gas, as a protective atmosphere for arc welding and in processes such as growing crystals to make silicon wafers--account for half of the gas produced . A well - known but minor use is as a lifting gas in balloons and airships . As with any gas whose density differs from that of air, inhaling a small volume of helium temporarily changes the timbre and quality of the human voice . In scientific research, the behavior of the two fluid phases of helium - 4 (helium I and helium II) is important to researchers studying quantum mechanics (in particular the property of superfluidity) and to those looking at the phenomena, such as superconductivity, produced in matter near absolute zero . </P> <P> On Earth it is relatively rare--5.2 ppm by volume in the atmosphere . Most terrestrial helium present today is created by the natural radioactive decay of heavy radioactive elements (thorium and uranium, although there are other examples), as the alpha particles emitted by such decays consist of helium - 4 nuclei . This radiogenic helium is trapped with natural gas in concentrations as great as 7% by volume, from which it is extracted commercially by a low - temperature separation process called fractional distillation . Previously, terrestrial helium--a non-renewable resource, because once released into the atmosphere it readily escapes into space--was thought to be in increasingly short supply . However, recent studies suggest that helium produced deep in the earth by radioactive decay can collect in natural gas reserves in larger than expected quantities, in some cases having been released by volcanic activity . </P> <P> The first evidence of helium was observed on August 18, 1868, as a bright yellow line with a wavelength of 587.49 nanometers in the spectrum of the chromosphere of the Sun . The line was detected by French astronomer Jules Janssen during a total solar eclipse in Guntur, India . This line was initially assumed to be sodium . On October 20 of the same year, English astronomer Norman Lockyer observed a yellow line in the solar spectrum, which he named the D Fraunhofer line because it was near the known D and D lines of sodium . He concluded that it was caused by an element in the Sun unknown on Earth . Lockyer and English chemist Edward Frankland named the element with the Greek word for the Sun, ἥλιος (helios). </P> <P> In 1881, Italian physicist Luigi Palmieri detected helium on Earth for the first time through its D spectral line, when he analyzed a material that had been sublimated during a recent eruption of Mount Vesuvius . </P>

Which noble gas was the first observed in india during a solar eclipse