Stable isotopes do not decay into other elements. In contrast, radioactive isotopes (e.g., 14C) are unstable and will decay into other elements. The less abundant stable isotope(s) of an element have ...

But it is well known that the simplest designs are unstable against gravitational ... certain configurations of these objects ...

a wide base a low centre of gravity Objects with a wide base, and a low centre of gravity, are more stable than those with a narrow base and a high centre of gravity. The yellow car has a wider ...