Dark Matter Hunter Captures The 'Rarest Thing Ever Recorded' In A Process 1 Trillion Times Longer Th
Dark Matter Hunter Captures The ‘Rarest Thing Ever Recorded’ In A Process 1 Trillion Times Longer Than The Age Of The Universe
24 April 2019, 11:55 pm EDT By Naia Carlos Tech Times
The universe is more than 13 billion years old. Multiply this number by a trillion and that is the half-life of a xenon-124 atom, which is the time it takes for a group of xenon-124 to diminish by half.
For the first time ever, scientists were able to observe this decaying process in a near-impossible feat.
"We actually saw this decay happen. It's the longest, slowest process that has ever been directly observed, and our dark matter detector was sensitive enough to measure it," said Ethan Brown, coauthor and an assistant professor of physics at Rensselaer Polytechnic Institute, in a report from the university. "It's an amazing to have witnessed this process, and it says that our detector can measure the rarest thing ever recorded."
Amazingly, the scientists were able to pull it off using an instrument that's designed to search the universe for another elusive sight: dark matter.
More:
https://www.techtimes.com/articles/242225/20190424/dark-matter-hunter-captures-the-rarest-thing-ever-recorded-in-a-process-1-trillion-times-longer-than-the-age-of-the-universe.htm
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So in one year, i.e. about 1 / 10^22 half-life, you should expect several dozen atoms to decay. If your detectors are very sensitive and heavily shielded, you can pick up each of these decays as an individual event.
Ain't technology wonderful ? 
Even if it's very unlikely that any one atom will decay at any given time, and it will take Brazillions of years for all to decay, if the sample is large enough and your instruments sensitive enough you can monitor a sample for months and get enough recorded decay events to extrapolate the half-life -- the longer you take measurements, the more precise the extrapolation. Also, the larger your sample, the faster you accumulate data -- these guys used 3,200 kg of liquid xenon. 
They should have observed a pretty large number of decay events -- enough to lower the statistical uncertainty pretty quickly. Oh, and placing the experiment inside a mountain helped shield the detectors from cosmic rays and other background radiation.
(In small amounts, Xe costs ~ $1.20/g, or $1200/kg, for anyone who's thinking of repeating this experiment.)
