In physics, complementarity is a conceptual aspect of quantum mechanics that Niels Bohr regarded as an essential feature of the theory. The complementarity principle holds that certain pairs of complementary properties cannot all be observed or measured simultaneously. For example, position and momentum or wave and particle properties. In contemporary terms, complementarity encompasses both the uncertainty principle and wave-particle duality. Bohr considered one of the foundational truths of quantum mechanics to be the fact that setting up an experiment to measure one quantity of a pair, for instance...

In the religion of Theosophy and the spiritual movement called Anthroposophy, the Akashic records are believed by Theosophists to be a compendium of all universal events, thoughts, words, emotions, and intent ever to have occurred in the past, present, or future in terms of all entities and life forms, not just human. They are believed by theosophists to be encoded in a non-physical plane of existence known as the mental plane. There is no evidence for the existence of Akashic records, and rigorous scientific research in this field has seen little traction. Akasha (ākāśa आकाश) is the Sanskrit word...

Helena Petrovna Blavatsky (née Hahn von Rottenstern; 12 August [O.S. 31 July] 1831 – 8 May 1891), often known as Madame Blavatsky, was a Russian and American mystic and author who co-founded the Theosophical Society in 1875. She gained an international following as the primary founder of Theosophy as a belief system. Born into an aristocratic family in Yekaterinoslav, then in the Russian Empire (now Dnipro in Ukraine), Blavatsky traveled widely around the empire as a child. Largely self-educated, she developed an interest in Western esotericism during her teenage years. According to her later claims...