nature.net 



Noble Gas 



By Robert Anderson 



Ever wondered how many helium 

 balloons it would take to lift your- 

 self off the ground? If sanity has kept 

 you from finding out, you'll enjoy Jeff 

 Whitehead's video of a safely tethered 

 helium flyer in the crucial experiment 

 (humanbeingcurious.com/page17/page16/ 

 page16.html). The results would have 

 been more dramatic, however, if the 

 pilot had cut her tethers to drift free, 

 as "Lawn-Chair Larry" did in 1982 (go 

 to markbarry.com or to darwinawards.com/ 

 darwin to read that remarkable story). 

 More recently, John Ninomiya, a li- 

 censed hot-air balloon pilot, has made 

 about forty such free-flying helium- 

 powered flights (go to clusterballoon.org 

 to find out more). 



Given the rarity of helium on earth, 

 using the noble gas for filling a party 

 balloon seems just, well, frivolous. 



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Making up just 0.0005 percent of the 

 atmosphere, helium is so diffuse it was- 

 n't detected until 1868, and then only 

 from a mysterious line in the solar spec- 

 trum. For that reason, Sir J. Norman 

 Lockyer, a British astronomer, named 

 it after Helios, the Greek sun god. Go 

 to "Astronomy Picture of the Day" at 

 antwrp.gsfc.nasa.gov/apod/ap960520.html 

 to see our star glowing in the light 

 emitted from hot, ionized helium. 



Modern astronomy has revealed that 

 helium is the second most common el- 

 ement in the universe, after hydrogen, 

 making up nearly a quarter of the mass 

 of visible matter. An entertaining Web 

 site called "The Big Bang Time Ma- 

 chine" (schoolscience.co.uk/flash/bang. 

 htm) takes you back to the earliest mo- 

 ments of the universe, when, among 

 other things, hydrogen and helium 

 condensed into being after the big 

 bang's burst of incredible heat. (Use the 

 time machine's green joystick to go 

 back and forth.) A Web page at the 

 University of Tennessee Astrophysics 

 Group (csepl 0. phys.utk.edu/astr1 62/lect/ 

 cosmology/hotbb.html) details how the 

 formation of helium supports the big 

 bang model. For basic information 

 about helium, go to theodoregray.com/ 

 PeriodicTable/#tabletop and click on the 

 symbol "He" at the upper right. In ad- 

 dition to making the most beautiful pe- 

 riodic table on the Internet, Theodore 

 Gray has collected fascinating specimens 

 of the elements, which you can view by 

 scrolling down the page for each one. 



For eighty years almost all of the 

 world's extracted helium has come 

 from the natural-gas fields around the 

 Oklahoma panhandle. Compared with 

 the cosmic helium, the Oklahoma he- 

 lium is relatively young, a by-product of 

 radioactive decay deep within the earth. 

 Until recently the U.S. government 

 stockpiled excess helium in an under- 

 ground reservoir near Amarillo, Texas. 

 The National Academy of Science has 

 an excellent overview of the helium sup- 

 ply — past, present, and future — in an 

 online report at darwin.nap.edu/books/ 

 0309070384/html titled "The Impact of 

 Selling the Federal Helium Reserve." 



Chapter three describes the unique 

 properties that make the gas indis- 

 pensable to modern technology. Re- 

 maining liquid down to absolute zero 

 (at least at ordinary pressures), helium 

 is critical to many devices that require 

 extreme cold — such as the powerful 

 superconducting magnets in MRI 

 imaging machines, which consume 

 about a third of the gas now collected. 

 And because helium does not react 

 with other elements, it is used for mak- 

 ing controlled atmospheres, for pres- 

 surizing, and for purging in many in- 

 dustrial processes, as well as for weld- 

 ing and for gas mixtures that deepwater 

 divers can breathe safely. 



Because pure helium gas can slip 

 through holes that would stop any 

 other gas (that's the reason helium bal- 

 loons go flat so quickly), it is a com- 

 mon leak detector. An article from the 

 Houston Geological Society (hgs.org/ 

 en/art/?162), titled "Helium Explo- 

 ration — A 21st Century Challenge," 

 gives more insight on meeting the 

 growing demand for this noble gas. 



In the more distant future, helium 

 might help solve one of humanity's 

 most pressing problems: how to sup- 

 ply abundant energy without increas- 

 ing greenhouse gases or poisoning the 

 environment with radiation. The key 

 may be helium-3, a rare isotope on 

 Earth, but which occurs in abundance 

 in lunar soil (see the article in Wired 

 magazine titled "A Helium Shortage?" 

 at wired.com/wi red/a rchive/8.08/helium. 

 html). As a fuel for fusion reactors, he- 

 lium-3 could, in principle, provide 

 limitless energy, with little residual ra- 

 diation. Harrison H. Schmitt, the only 

 geologist to step on the Moon, is a pro- 

 ponent of returning there someday to 

 mine it for helium. To listen to him 

 lecture on the subject, go to Google's 

 video search engine (video.google.com) 

 and type in "Schmitt helium," or try 

 mitworld.mit.edu/video/159 for a more 

 lengthy presentation. If his dreams are 

 ever realized, helium will be a noble 

 element indeed. 



Robert Anderson is a freelance science 

 writer living in Los Angeles. 



60 



NATURAL HISTORY September 2006 



