| − | The amount of [[isotope]] necessary to cause an explosion due to a chain reaction.<ref>Wile, Dr. Jay L. ''Exploring Creation With Physical Science''. Apologia Educational Ministries, Inc. 1999, 2000</ref> | + | The amount of [[isotopes|isotope]] necessary to cause an explosion due to a chain reaction.<ref>Wile, Dr. Jay L. ''Exploring Creation With Physical Science''. Apologia Educational Ministries, Inc. 1999, 2000</ref> |