It was not until 1997, however, that a direct experiment, by S. Lamoreaux, described above, quantitatively measured the force ( to within 15 % of the value predicted by the theory ), although previous work van Blockland and Overbeek ( 1978 ) had observed the force qualitatively, and indirect validation of the predicted Casimir energy had been made by measuring the thickness of liquid Helium films by Sabisky and Anderson in 1972.

Helium was also isolated by the American geochemist William Francis Hillebrand prior to Ramsay's discovery when he noticed unusual spectral lines while testing a sample of the mineral uraninite.

Helium use following World War II was depressed but the reserve was expanded in the 1950s to ensure a supply of liquid helium as a coolant to create oxygen / hydrogen rocket fuel ( among other uses ) during the Space Race and Cold War.

Helium use in the United States in 1965 was more than eight times the peak wartime consumption.

Helium produced between 1930 and 1945 was about 98. 3 % pure ( 2 % nitrogen ), which was adequate for airships.

But Dalton and other chemists of the time had not considered that some elements occur in monatomic form ( like Helium ) and others in diatomic form ( like Hydrogen ), or that water was H < sub > 2 </ sub > O, not the simpler and more intuitive HO — thus the atomic weights presented at the time were varied and often incorrect.

* Helium was first detected during the total solar eclipse of August 18, 1868 in parts of India.

Helium was first found on Earth in uraninite after having been discovered spectroscopically in the Sun's atmosphere.

* The Helium Centennial Time Columns Monument is expected to be opened 50 years after the time capsule was locked in 1968.

* The Helium Centennial Time Columns Monument is expected to be opened 100 years after the time capsule was locked in 1968.

He tried to liquefy the last remaining gas, Helium, which condenses into a liquid at − 268. 9 ° C, but owing to a number of factors, including a lack of Helium with which to work, Dewar was preceded by Heike Kamerlingh Onnes as the first person to produce liquid helium, in 1908.

Helium was rare in most parts of the world, but large amounts were discovered in the USA.

Helium did not have any practical applications at the time, but by 1917 the federal government was sponsoring extensive research into the possibility of using helium in airships.

Helium was previously used, but it was less suitable because it diffuses out of the case more quickly than argon.

* The Helium Centennial Time Columns Monument in Amarillo, Texas, contains four separate time capsules, the last of which is intended to be opened 1000 years after the Time Columns Monument was locked in 1968.

Helium was first liquefied on July 10, 1908, by the Dutch physicist Heike Kamerlingh Onnes in Holland.

Helium was used to pressurize the fuel tanks but should not have been in the combustion chamber.

For example, the element Helium was first identified through its spectroscopic signature in the Sun before it was isolated as a gas on Earth.

Helium was routed to hold the propellant bleed valves closed and to purge the thrust chamber LOX dome, the LOX pump intermediate seal, and the gas generator oxidizer passage.

A variation of the Geiger tube is used to measure neutrons, where the gas used is boron trifluoride or Helium 3 and a plastic moderator is used to slow the neutrons.

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.

Hubbert models have been used to predict the production trends of various resources, such as natural gas ( Hubbert's attempt in the late 1970's resulted in an inaccurate prediction that natural gas production would fall dramatically in the 1980's ), Coal, fissionable materials, Helium, transition metals ( such as copper ), and water.

Unlike the thermonuclear bomb contained in the Pod ( which is used to destroy the Barrier ) they can become temporarily disabled by " concentrated disbelief " in the reaction " When Hydrogen One and Hydrogen Two are in the presence of Mu Mesons, they fuse into Helium Three, with an energy yield in electron volts of 5. 4 times ten to the fifth power ".

In the case of compressed air, or Nitrox mixtures, the exhaled gas is not valuable enough to justify the expense of recycling, but Helium based mixtures are considerably more expensive, and as the depth increases, the amount of gas used ( in terms of mass, or number of molecules ) increases in direct proportion to the ambient pressure.

* Helium is used in helium-neon lasers and in some thyratrons rated for high currents and high voltages.

Helium provides about as short deionization time as hydrogen, but can withstand lower voltage, so it is used much less often.

Analysis instruments commonly used by recreational / technical diving gas blenders are typically capable of a resolution of 0. 1 % for both Oxygen and Helium.

Helium and carbon dioxide were the first shielding gases used, since the beginning of World War 2.

Helium is used as a shield gas in laser welding for carbon dioxide lasers.

* 1947 — 1948 Introduced kinetic equations in the theory of superfluidity, computed the excitation spectrum for a weakly imperfect Bose gas, showed that this spectrum has the same properties as spectrum of Helium II, and used this analogy for a theoretical description of superfluidity of Helium II.

Gas chromatography ( GC ) is based on a partition equilibrium of analyte between a solid stationary phase ( often a liquid silicone-based material ) and a mobile gas ( most often Helium ).

After the " Helium Acts Amendments of 1960 " ( Public Law 86 – 777 ), the U. S. Bureau of Mines arranged for five private plants to recover helium from natural gas.

Helium is the least reactive noble gas after neon and thus the second least reactive of all elements ; it is inert and monatomic in all standard conditions.

Helium is the least water soluble monatomic gas, and one of the least water soluble of any gas ( CF < sub > 4 </ sub >, SF < sub > 6 </ sub >, and C < sub > 4 </ sub > F < sub > 8 </ sub > have lower mole fraction solubilities: 0. 3802, 0. 4394, and 0. 2372 x < sub > 2 </ sub >/ 10 < sup >− 5 </ sup >, respectively, versus helium's 0. 70797 x < sub > 2 </ sub >/ 10 < sup >− 5 </ sup >), and helium's index of refraction is closer to unity than that of any other gas.

Helium is typically separated from natural gas, and radon is usually isolated from the radioactive decay of dissolved radium compounds.

Helium conducts heat six times faster than air ; often helium breathing divers carry a separate supply of a different gas to inflate drysuits.

Helium is the gas thought to be most active in the process.

Helium is almost always placed above neon ( which is in the p-block ) in the periodic table as a noble gas, although it is occasionally placed above beryllium due to their similar electron configuration.

( 1990 ), Helium and carbon fluxes in Lake Nyos, Cameroon: constraint on next gas burst, Earth and Planetary Science Letters, v. 99, p. 303-314

* Helium gas has a specific gravity of 0. 000179, so it is 179 one-millionths as dense as water, and less dense than air.

He joined Bell Telephone Laboratories in 1958 shortly after he conceived the working principle of his gas discharge Helium Neon laser device and predicted its significance.

( PI: Vance Oyama, NASA Ames ) The Gas Exchange ( GEX ) experiment looked for gases given off by an incubated soil sample by first replacing the Martian atmosphere with the inert gas Helium.