domingo, 27 de maio de 2012

O HÉLIO VAI ACABAR?


Destaque para a coluna What's New do físico Robert Park:

HELIUM CRISIS: THE WORLD IS RUNNING OUT OF HELIUM. 
Physicists, it must be acknowledged, have a certain reverence for "helium," 
the second element in the periodic table, without which the 20th century 
revolution in physics would never have taken place. There is no substitute 
and the supply is nonrenewable. Helium exists on Earth today only as a 
product of radioactive decay of heavy nuclei in the crust of our nascent 
planet.  It accumulated in the same underground geologic formations that 
trap natural gas (methane). At a maximum concentration of 2.7%, natural-gas 
wells represent the only practical large-scale source of helium. North 
America has more helium than any other region of the world, but is also by 
far the biggest consumer.  When it's gone, it will be gone forever – unless 
we succeed in generating power by deuterium fusion. In that case helium may 
again be abundant, but that day is a long way off.  In 1925 a Federal 
Helium Reserve was created in Amarillo, TX as a strategic supply of gas for 
airships. By the 1950s helium had become essential to electronics 
development but huge amounts were being squandered by NASA on low priority 
tasks such as purging the fuel tanks of shuttle rockets. However, most 
members of Congress remain unaware of its use for anything other than 
inflating party balloons. Over the objections of the American Physical 
Society, which urged an increase in the helium reserve, the 1996 Helium 
Preservation Act ordered the Interior Department to liquidate the Federal 
Helium Reserve by 2015. What then?
 
Robert Park 

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