Helium: filler of floating balloons, maker of high-pitched voices. But there are a lot of other interesting things about helium too!
First, helium makes our voices high because it is less dense than air, and thus the vocal chords vibrate more quickly. (Also fun: higher density gases, like sulfur hexafluoride, will correspondingly make the voice become very low. In this case, the practitioner must be upside-down, because right-side-up the gas will settle in the lungs, potentially causing asphyxiation.)
Helium is the second most common elements in the universe, but it’s pretty rare on earth. We get pretty much all of our helium during natural gas extraction, when it is trapped underground. Because it has such a low density, it basically escapes the atmosphere once it gets into the air. Helium is very common in the universe because it is formed by the fusion of hydrogen. Our sun and other stars are hydrogen to helium engines, pumping out tons os helium per second, though it doesn’t come to Earth. Most helium on earth comes from the radioactive decay of uranium, which emits helium.
Helium is a noble gas. This means that it naturally has the number of electrons to be stable without interactions with other atoms. Helium has the lowest boiling and melting points of any element, at 4K and 1K respectively. This is due to its stability. Liquids and solids are formed when atoms energetically interact with one another; helium has very little tendency toward this. Because of its stability, helium is used as a cryogenic gas. Helium is an essential part of an MRI machine, shown below. The helium is required to supercool the magnets, which increases the magnetic field and thus the resolution.
MRI for medical imaging.
The US is the largest supplier of hydrogen in the world. This is partially because congress signed an act to bleed down our helium reserve by 2015. However, some scientists have pointed out that helium is hard to come by, and we should conserve our helium. One source estimates that helium balloons should cost $100 dollars each, based upon the scarcity of helium. Another says they should be illegal.
So the next time you look at a blimp or a balloon, marvel at the substance that fills it. It’s really star stuff, and rare to boot!