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Bismuth No Longer the Heaviest Stable Element
forii writes "Bismuth-209 was commonly thought to be the heaviest stable element. But now Physicists have discovered that Bi-209 actually is unstable and decays with a halflife of 2*10^19 years. This means that the average 8oz (237ml) bottle of Pepto-Bismol contains one decay event every 36 hours or so."
Bismuth-209 was commonly thought to be the heaviest stable element.
Actually, most of the scientists believed it was stable, however not everyone. (Some of them were considered "crackpots" by the rest of the community, but the point remains valid, even if somewhat less so.) Try a Google search.
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That's a really long time. I mean, really long. The universe is considered to be 15 to 20 billion years by most who decide to actually guess. That means that, if the universe is 20 billion years old... and 1 g of Bi-209 was produced at the beginning of the universe, it would take another 1.999999998*10^19 years before half of the Bi-209 was left. I wonder if our universe will even reach that age, if the big bang 'cycle' theory holds to be true.
Does 'stable' mean that decay hasn't been observed, or that it NEVER occurs?
How does quantum mechanics apply to decay?
Does an atom decay when a certain set of positions occur within it, and if so why can't the frequency that this would occur at be calculated?
A pizza of radius z and thickness a has a volume of pi z z a
Not only that, he never said "it's" when he meant "its".
My favorite element, by the way, is Osmium. It sublimates dreadfully toxic fumes from a solid state at room temperature, and nobody knows exactly what its specific gravity is, nor whether it or Iridium is the heaviest element.
This could prove to be the most important use of this technique, as most proposed Grand Unified Theories have interactions that can turn quarks into leptons, so that a proton would be expected to eventually decay into a positron and a meson. Unfortunately, this process has never been observed (well, only somewhat unfortunately, as high proton stability is definitely a Good Thing in most ways), and experiment and theory have thus set a lower bound on the lifetime of a proton of roughly 10^33 years, about 23 orders of magnitude greater than the estimated current age of the universe.
As you can see, compared to the suggested lifetime of a proton, even Bi-209 seems unstable. The expected extreme rarity of a proton decay event, however, is somewhat balanced by the overwhelming abundance of protons in the universe.The "lifetime" for an individual proton is more like a life expectancy, an average figure- given a suitably large collection of protons, odds are good that at least one would decay in a reasonable timeframe. If you carefully watch 10^33 protons for a year, for example, and reality agrees with theory (big if), then it is likely (certainly not guaranteed though) you will see at least one decay event. Now, 10^33 may sound like a tremendous amount, but remember that each proton has a mass of only 1.67*10^-27 kilograms, so that 10^33 protons would have a mass of about 1,600 metric tons- a lot, but not outrageous.
The real problem lies in that "carefully watching" part. So many other forms of radiation are much more prevalent, and so might mask the signature of proton decay. Cosmic rays, naturally occuring radioisotopes in places you'd never think to look, solar neutrinos, that sort of thing. Ah, why yes, this is one of those experiments they do in a salt mine and uses a gigantic tank of ultrapure water (your proton source). However, as of yet, no one has found concrete evidence for proton decay from one of these experiments. Go here for a excellent site about a proton decay detector that ran in the 80s, and here for one currently in use.
Perhaps this process will detect this very rare event, lending profound support to one of the many supersymmetric models out there. Unfortunately, if it does not detect proton decay, it will be much more difficult to say just what the result means, it being difficult to prove a negative and all.
"FDA staff reviewers expressed concern about the number of patients who were left out of the study because they died."
Since there are likely to be a number of people teading this that have good command of the topic, let me ask a question on isotopes. All through school I was taught that different isotopes of an element have the same chemical property. That information is still found in most articles on the subject. Yet I recently found a reference that Heavy Water was poisonous. Since there is no radiation danger, how can heavy water be poisonous if isotopes are chemically identical? What is going on here? And what are the indications of heavy water poisoning?
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