The Helium Conundrum (3)
Helium even has a role in the visual arts, where it is responsible for the distinctive voices of some cartoon characters. Sound travels three times faster in this light gas, Wikipedia reports, than in the air we breathe—enabling He-4 to change the resonant frequency of the human vocal tract.
Hence some actors who do cartoon voice-overs, inhale small amounts of helium, to affect the quality of speech that fit their characters. Says Wikipedia: “The higher resonant frequencies cause a change in timbre, resulting in a reedy, duck-like vocal quality”.
Because it’s so hard to contain, helium is also the gas of choice for many leak detection systems. “If a system has a leak,” King notes, “helium will escape. [It] is therefore used to test high vacuum systems, fuel systems and other containments for leaks”.
According to APS, roughly 25 percent of all helium consumption is for the creation of inert welding environments, to prevent fires, explosions and corrosion. In addition, liquid helium cools infrared telescopes to reduce internally generated noise.
But while helium is a handy resource for humans, it has a hidden chemical and physical persona. First, its role in early cosmic history (just after the big bang) is less than complimentary: Helium nearly derailed the evolution of carbon-based life in the universe, by gobbling up most of the free neutrons.
“The unusual stability of the helium-4 nucleus is…important cosmologically” Wikipedia reports. “It explains the fact that in the first few minutes after the Big Bang,…almost all first compound atomic nuclei to form were helium-4 nuclei”.
So tight was helium-4 binding, it continued, “that helium-4 production [quickly] consumed nearly all of the free neutrons… leaving few to form heavier atoms such as lithium [atomic number ‘3’], beryllium , or boron ”.
The copious production of elements “3,” “4” and “5,” during this primordial process, would have made the synthesis of element “6” a piece of cosmic cake: Lithium, beryllium and boron being conveniently available, to combine into carbon atoms.
But this was not to be. Instead, nature created a game of cosmic billiards, whose outcome hinged on a trick-shot, which astronomers call “triple alpha”: An unlikely collision between three helium nuclei was necessary to synthesize a carbon atom.
Wikipedia: “All heavier elements (including those necessary for rocky planets like the Earth and for carbon-based or other life) have thus been created since the Big Bang, in stars which were hot enough to fuse helium itself”.
In its other persona, helium has two protons but only one neutron’ and it is wreaking geological havoc. This ionized variant, an isotope known as “helium-3,” is also strategically important, as a future energy source. (But we will table this aspect, until another time.)
Small amounts of He-3 are being produced through the natural neutron bombardment of lithium and the radioactive decay of tritium. Some, especially in old surface rocks, is cosmogenic—derived from interplanetary dust and cosmic ray collisions. But most of the He-3 in Earth’s mantle and crust is primordial.
In “Helium Fundamentals,” posted on Mantle Plumes.Org, Don L. Anderson of the California Institute of Technology’s Seismological Laboratory, and his collaborators, explains that He-3 “was made in the Big Bang and incorporated into Earth during its initial accretion and in the subsequent long-term acquisition of “late veneer” material”.
This residual helium-3, geologists have found, is implicated in a “superplume” of heat, welling up from Earth’s interior, that is tearing Africa apart: Separating two tectonic plates and pushing up plateaus on either side of a rift that runs between Kenya and Ethiopia. Millions of years hence, they say, an ocean will form in the rift..
To be continued.