Why is calcium-48 considered stable for practical purposes?

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A labeled diagram of the periodic table entry for calcium, showing its atomic number 20, symbol Ca, atomic weight 40.078, electron configuration, and classification as an alkaline-earth metal. Icons indicate calcium is a solid with a face-centered cubic crystal structure and strongly basic oxides at room temperature. — calcium The chemical element calcium is the most abundant metallic element in the human body.

Calcium-48 is considered stable for practical purposes because its half-life is approximately $4 \times 10^{19}$ years, an incredibly long duration that far exceeds the age of the universe.1

While it does undergo double beta decay, this process occurs so slowly that the isotope is effectively stable in any standard context. Furthermore, calcium-48 is classified as a "doubly magic" nucleus, meaning it possesses both full proton shells and full neutron shells, which grants it a high degree of nuclear stability. Because it is particularly neutron-rich, it is also highly valued by scientists for use in particle accelerators to synthesize new heavy nuclei.12