Do Atoms Last Forever?

Despite what you may have heard, diamonds are not forever. Given enough time, your sparkling rock will degrade into common graphite. The carbon atoms that constitute that diamond, however, are forever, or close enough. Stable isotopes of carbon are thought to enjoy lifetimes that extend far longer than the estimated age of the universe But not every atom of carbon lives forever.

Radioisotopes are forms of chemical elements with unstable nuclei and emit radiation during their decaying process to a stable state. Carbon-14, a radioisotope, is unstable, with a half-life of less than 6,000 years; after 5,730 years, there is a 50 percent chance that a carbon-14 atom will lose an electron and become nitrogen-14 (which is itself stable and the most common form of nitrogen on Earth).

Carbon-14 is the key element in carbon dating: Since radioactive carbon is only absorbed through respiration by living creatures, the date of their death can be determined by measuring the remaining carbon-14 in the specimen.

In addition to carbon-14, there are scores of other naturally occurring radioisotopes and more than a thousand manmade. Each of these radioisotopes tends to decay into another isotope: some in a matter of days, others in hundreds of millions of years. In this sense, these atoms do in fact die. In another way, however,they are simply reborn as different isotopes.

There is one mechanism by which even stable atoms might "die." Some exotic models of physics hypothesize that protons (which along with electrons and neutrons constitute atoms) can decay into lighter subatomic particles. Even if protons do decay, they are nevertheless incomprehensibly durable. Experiments put the lower bound of a proton half-life at 10^33 to 10^34 years, or 23 orders of magnitude longer than the current age of the universe. In conclusion, atoms are forever on just about any relevant timescale.

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