Subhash Kak (born 26 March 1947, Srinagar, Jammu and Kashmir) is an Indian-American computer scientist, historian of science, and Vedic scholar whose work spans two largely distinct fields: technical contributions to quantum information, cryptography, and neural computing; and Indological arguments about the scientific content of ancient Vedic texts. He holds the rank of Regents Professor of Electrical and Computer Engineering at Oklahoma State University, Stillwater, is an honorary visiting professor of engineering at Jawaharlal Nehru University, and has served on India's Prime Minister's Science, Technology and Innovation Advisory Council (PM-STIAC). In 2019 the Government of India awarded him the Padma Shri, the fourth highest civilian honor. His Indological work - particularly his Astronomical Code of the Rigveda and related arguments for the antiquity and scientific sophistication of Vedic civilization - has been broadly contested by mainstream Indologists, archaeoastronomers, and historians of science, while finding an audience among scholars and writers sympathetic to the Indigenous Aryans hypothesis and the broader Vedic science movement.

Kak completed his undergraduate engineering degree at the Regional Engineering College, Srinagar (now the National Institute of Technology, Srinagar) and his doctorate at the Indian Institute of Technology Delhi in 1970. He subsequently taught at IIT Delhi, spent 1975-1976 as a visiting faculty member at Imperial College London and a guest researcher at Bell Laboratories, Murray Hill, and held a position at Louisiana State University before joining Oklahoma State University's Computer Science department in 2007.

Kak's peer-reviewed technical work is concentrated in three areas: neural network architectures, quantum information, and cryptography. He developed an efficient three-layer feed-forward neural network architecture and associated training algorithms, and proposed instantaneously trained neural networks as a method for faster computation. In 1995 he published one of two independent papers - alongside Ron Chrisley's contemporaneous work - credited with founding the field of quantum neural computing, which applies quantum-mechanical principles to the modeling of neural computation. He has subsequently argued that biological intelligence involves three distinct computational modes: associative, reorganizational, and quantum. His cryptographic work includes a three-stage quantum cryptography protocol and contributions to quantum key distribution. His technical publications have appeared in IEEE journals, Foundations of Physics, Information Sciences, and other peer-reviewed venues.

Kak's Indological publications argue that ancient Indian texts - primarily the Rigveda, the Vedic altar literature (Shulbasutras), and the Siddhantas - encode sophisticated astronomical knowledge that has been systematically underestimated by Western scholarship. His central claim, developed in The Astronomical Code of the Rigveda (1994; revised 2000), is that the organization of hymns in the Rigveda's ten books encodes numbers corresponding to astronomical periods and distances, reflecting an astronomical knowledge base extending back to approximately the 7th millennium BCE. This chronological claim, if accepted, would place Vedic civilization far earlier than the dates accepted by mainstream Indo-Aryan migration scholarship and would support the view that Indo-Aryan speakers were indigenous to South Asia rather than migrants from the Eurasian steppe.

Kak has also argued that Vedic ritual structures - particularly the five-layered fire altar (vedi) described in the Shatapatha Brahmana - embed precise astronomical ratios, including the approximate 108:1 ratio of the Earth-Sun and Earth-Moon distances to the respective diameters of those bodies. He prepared the section on archaeoastronomical sites in India for the thematic study on Heritage Sites of Astronomy and Archaeoastronomy prepared for UNESCO by ICOMOS and the International Astronomical Union (IAU).

Kak is also associated with arguments about ancient Indian computing and mathematics, developed in Computing Science in Ancient India (2001), and with broader claims about Indian civilizational priority in works co-authored with Georg Feuerstein and David Frawley, including In Search of the Cradle of Civilization (1995).

The reception of Kak's Indological work divides sharply between specialist academic communities and popular or Hindu nationalist audiences. Within mainstream Indology, historical linguistics, and the history of science, his archaeoastronomical claims have been broadly rejected. Critics argue that his numerical analyses of the Rigveda's structure involve post hoc selection of sums and differences to fit astronomical targets; that his proposed Vedic chronology conflicts with convergent evidence from comparative linguistics, genetics, and archaeology bearing on the Indo-Aryan migration; and that his treatment of Vedic texts as repositories of encoded scientific knowledge conflates ritual and cosmological functions that the tradition itself kept distinct.

Contributors to A House Built on Sand (ed. Noretta Koertge) characterized aspects of the broader movement in which Kak's work participates as a “social constructivist and postmodern attack on modern science.” Historian of religion Meera Nanda has placed Kak within the broader tradition of Hindu nationalist historiography. Alan Sokal described him as one of the leading intellectual figures of the Hindu-nationalist diaspora. Edwin Bryant, more sympathetic to arguments for Vedic antiquity, characterized Kak as a well-read and articulate spokesman for the Indigenous Aryans position and for issues concerning ancient Indian science.

Defenders of Kak's Indological work argue that mainstream scholarship has systematically undervalued ancient Indian scientific achievements under the influence of colonial-era assumptions, and that his computational and textual analyses deserve engagement on their merits. Whether his methods constitute legitimate archaeoastronomy or retrospective pattern-matching is a subject of ongoing dispute.

The mainstream scholarly consensus in Indology, historical linguistics, and the history of science rejects Kak's chronological claims for Vedic astronomy and his arguments for the Indigenous Aryans hypothesis. His technical contributions to quantum neural computing and cryptography are accepted within their respective fields.

• Vedic Science Viewpoint - Kak and allied scholars argue that ancient Indian texts encode genuine scientific knowledge and that Vedic civilization is significantly older and more scientifically sophisticated than mainstream scholarship holds.
• Mainstream Indology Viewpoint - The predominant position among Indologists and historians of science holds that Kak's archaeoastronomical claims are methodologically unsound and his chronological conclusions unsupported by available evidence.
• Hindu Nationalist Viewpoint - Within Hindu nationalist discourse, Kak is regarded as a significant intellectual figure whose work establishes the priority and independence of Indian scientific traditions against what is framed as colonial distortion of the historical record.

• Subhash Kak - Debate
• Vedic Science
• The Astronomical Code of the Rigveda
• Indo-Aryan Migration
• Indigenous Aryans Hypothesis
• Vedic Astronomy
• Heliocentrism - Hindu Viewpoint
• David Frawley
• History of Science - Indo-Aryan Consensus

1. Subhash Kak. The Astronomical Code of the Rigveda. Aditya Prakashan, 1994; revised Munshiram Manoharlal, 2000. ISBN 81-215-0986-6.
2. S. Kak, “Quantum neural computing.” Advances in Imaging and Electron Physics, vol. 94, pp. 259-313. Academic Press, 1995.
3. Georg Feuerstein, Subhash Kak, David Frawley. In Search of the Cradle of Civilization. Quest Books, 1995. ISBN 0-8356-0741-0.
4. Subhash Kak. Computing Science in Ancient India. Munshiram Manoharlal, 2001.
5. S. Kak, “Astronomy of the Vedic altars.” Vistas in Astronomy, 36 (1993): 117-140.
6. S. Kak, “A three-stage quantum cryptography protocol.” Foundations of Physics Letters, vol. 19 (2006): 293-296.
7. Noretta Koertge, ed. A House Built on Sand: Exposing Postmodernist Myths About Science. Oxford University Press, 1998.
8. Meera Nanda. Prophets Facing Backward: Postmodern Critiques of Science and Hindu Nationalism in India. Rutgers University Press, 2003.
9. Edwin Bryant. The Quest for the Origins of Vedic Culture. Oxford University Press, 2001.
10. Government of India, Ministry of Home Affairs. Padma Awards 2019.