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There are many sources of knowledge of physics in ancient Indian texts and a wide range of topic they dealt with.  

There are many sources of knowledge of physics in ancient Indian texts and a wide range of topic they dealt with.  

# [[Vedas (वेदाः)|Vedas]] - They were the earliest texts that deal with the [[Srshti Siddhanta (सृष्टिसिद्धान्तः)|concepts of cosmology]], creation  of the universe and cosmic cycles. Sutra granthas specifically the [[Shulbasutras (शुल्बसूत्राणि)|Shulbasutras]] gave the fundamentals of mathematics and their application in geometry and architecture.  

# [[Vedas (वेदाः)|'''Vedas''']] - They were the earliest texts that deal with the [[Srshti Siddhanta (सृष्टिसिद्धान्तः)|concepts of cosmology]], creation  of the universe and cosmic cycles. Sutra granthas specifically the [[Shulbasutras (शुल्बसूत्राणि)|Shulbasutras]] gave the fundamentals of mathematics and their application in geometry and architecture.

# [[Upanishads (उपनिषदः)|Upanishads]] - They explain interconnectedness of matter-energy, their relationship and unity, the chemical qualities such as solubility, viscosity etc. Physical

# [[Upanishads (उपनिषदः)|'''Upanishads''']] - They explain interconnectedness of matter-energy, their relationship and unity, the chemical qualities such as solubility, viscosity etc. Physical

# Darshanas - They put forth the earliest atomic theory, defined matter, their interactions and attributes. [[Vaiseshika Darshana (वैशेषिकदर्शनम्)|Vaiseshika darshana]] elaborates the atomic theory (Paramanu), classified reality into seven padarthas and explained their characteristics.

# '''Darshanas''' - They put forth the earliest atomic theory, defined matter, their interactions and attributes. [[Vaiseshika Darshana (वैशेषिकदर्शनम्)|Vaiseshika darshana]] elaborates the atomic theory (Paramanu), classified reality into seven padarthas and explained their characteristics.

# Puranas - A great deal of information on light, cosmology is specifically noted in Vishnu, Vayu and Matsya puranas.<ref>Kak, S. (1999). The Speed of Light and Puranic Cosmology. In ''Annals of Bhandarkar Oriental Research Institute,'' vol. 80, pp. 113-123, 1999. arXiv:physics/9804020v3 [physics.hist-ph] 15 Jan 2001</ref>  

# '''Puranas''' - A great deal of information on light, cosmology is specifically noted in Vishnu, Vayu and Matsya puranas.<ref>Kak, S. (1999). The Speed of Light and Puranic Cosmology. In ''Annals of Bhandarkar Oriental Research Institute,'' vol. 80, pp. 113-123, 1999. arXiv:physics/9804020v3 [physics.hist-ph] 15 Jan 2001</ref>

# Vaastu shastra, Shilpa shastra - They discuss the principles of structure, geometry, acoustics, and materials.

# '''Vaastu shastra, Shilpa shastra''' - They discuss the principles of structure, geometry, acoustics, and materials.

# Siddhanta granthas - Surya siddhanta for example describes the planetary motion, eclipses, calculation of time (concept of cyclic time, yugas, kalpas) and trignometric functions.  

# '''Siddhanta granthas''' - Surya siddhanta for example describes the planetary motion, eclipses, calculation of time (concept of cyclic time, yugas, kalpas) and trignometric functions.

# Commentaries - Astronomical texts such as [[Aryabhata (आर्यभट्ट)|Aryabhata's]] Aryabhatiya gave the foundational concepts such as rotational motion of earth, celestial body calculations, correct order of planetary orbits and the infiniteness of the universe. Bhaskara II's Siddhanta Shiromani deals with advanced astronomical principles, mechanics and planetary equations. A commentary of Kamasutra by Visvakarma details design of machines.

# '''Commentaries''' - Astronomical texts such as [[Aryabhata (आर्यभट्ट)|Aryabhata's]] Aryabhatiya gave the foundational concepts such as rotational motion of earth, celestial body calculations, correct order of planetary orbits and the infiniteness of the universe. Bhaskara II's Siddhanta Shiromani deals with advanced astronomical principles, mechanics and planetary equations. A commentary of Kamasutra by Visvakarma details design of machines.

# Other works - Many texts were lost but we find their references in major texts such as Mahabhashya, Mahabharata, Puranas, [[Arthashastra (अर्थशास्त्रम्)|Arthashastra]] and Samarangana Sutradhara.   

# '''Other works''' - Many texts were lost but we find their references in major texts such as Mahabhashya, Mahabharata, Puranas, [[Arthashastra (अर्थशास्त्रम्)|Arthashastra]] and Samarangana Sutradhara.   

## Samarangana Sutradhara - Yantras or contrivances useful in creating mechanical objects such as birds, fountains are described in this text. It also describes yantras used in war machines, water-lifting instruments for agricultural uses, and time devices such as water clocks for astronomical measurements.

## '''Samarangana Sutradhara''' - Yantras or contrivances useful in creating mechanical objects such as birds, fountains are described in this text. It also describes yantras used in war machines, water-lifting instruments for agricultural uses, and time devices such as water clocks for astronomical measurements.

## Yantrarnava - describes physical concepts such as generation of power/energy or motion through the continuous movement of lever/pulley.

## '''Yantrarnava''' - describes physical concepts such as generation of power/energy or motion through the continuous movement of lever/pulley.

## Natyashastra - describes various musical instruments and their acoustical characteristics  

## '''Natyashastra''' - describes various musical instruments and their acoustical characteristics

## Agasthya Samhita - describes electrical cells  

## '''Agasthya Samhita''' - describes electrical cells

== Matter and Mass in Vaiseshika Darshana ==

== Padarthas in Vaiseshika Darshana ==

In order to define and distinguish matter, Kanāda divides matter, or substance into [[Padarthas (पदार्थाः)|padarthas]] or six categories (Vais. Sutr. 1.1.4)<ref name=":0" />

In order to define and distinguish matter, Kanāda divides matter, or substance into [[Padarthas (पदार्थाः)|padarthas]] or six categories (Vais. Sutr. 1.1.4)<ref name=":0" />

=== Dik (Space) and Kala (Time) ===

=== Dik (Space) and Kala (Time) ===

Vaisheshika principles approach basic concepts in a characteristic manner. In these sutras we find the basic definitions of dravyas or categories of time and space. <blockquote>तत्त्वम्भावेन । वैशेषिक-२,२.८ ।</blockquote>Meaning: Time, like Existence, is One (unity), because, in spite of their multiplicity, the marks of Time, namely the cognition (example - "it is slow or late") are the same in all places and because there is no distinguishing mark like the Atman, which is Existence.  

Vaisheshika principles approach fundamental scientific concepts in a characteristic manner. In these sutras we find the basic definitions of dravyas or categories of time and space. <blockquote>तत्त्वम्भावेन । वैशेषिक-२,२.८ ।</blockquote>Meaning: Time, like Existence, is One (unity), because, in spite of their multiplicity, the marks of Time, namely the cognition (example - "it is slow or late") are the same in all places and because there is no distinguishing mark like the Atman, which is Existence.  

Time which is said to be One, however, is manifold, hours, moments, days, days and nights, seasons and years. The reason for this is explained as due to the external condition or Upadhi - the indivisible time appears to be different according to the limit set by the moverment of the Sun as well as the limit imposed by the effects of sun.<ref name=":3">Basu, B. D. (Ed.). (1923). ''The Vaisesika Sutras of Kanada'' (N. Sinha, Trans.; 2nd ed.). The Panini Office. (pp.172)</ref> The division of time as past, present and future as understood by the observer is said to be a consequence of the fact that time is a function of movement.<blockquote>

Time which is said to be One, however, is manifold, hours, moments, days, days and nights, seasons and years. The reason for this is explained as due to the external condition or Upadhi - the indivisible time appears to be different according to the limit set by the movement of the Sun as well as the limit imposed by the effects of sun.<ref name=":3">Basu, B. D. (Ed.). (1923). ''The Vaisesika Sutras of Kanada'' (N. Sinha, Trans.; 2nd ed.). The Panini Office. (pp.172)</ref> The division of time as past, present and future as understood by the observer is said to be a consequence of the fact that time is a function of movement.<blockquote>

इत इदमिति यतस्तद्दिश्यं लिङ्गम् । वैशेषिक-२,२.१० ।</blockquote>

इत इदमिति यतस्तद्दिश्यं लिङ्गम् । वैशेषिक-२,२.१० ।</blockquote>

- That which gives rise to such (cognition and usage) as "This (is remote, etc) from this" is the mark of space.  

- That which gives rise to such (cognition and usage) as "This (is remote, etc) from this" is the mark of space.  

Time, space, Atma and mind are the eternal or nitya dravyas and none of them are perceivable by any of the sense organs is a basic definition in Vaisesika. Although, these four eternal entities can only be conceived by the mind, they are real existent dravyas or entities. Time, space and akasa are incapable of motion and it is only the earth, water, fire and air (the four dravyas) and mind which are capable of motion.<blockquote>

Time, space, Atma and mind are the eternal or nitya dravyas and none of them are perceivable by any of the sense organs is a basic definition in Vaiseshika. Although, these four eternal entities can only be conceived by the mind, they are real existent dravyas or entities. Time, space and akasa are incapable of motion and it is only the earth, water, fire and air (the four dravyas) and mind which are capable of motion.<blockquote>

दिक्कालावाकाशं च क्रियावद्वैधर्म्यान्निष्क्रियाणि । वैशेषिक-५,२.२१ ।</blockquote>

दिक्कालावाकाशं च क्रियावद्वैधर्म्यान्निष्क्रियाणि । वैशेषिक-५,२.२१ ।</blockquote>

Meaning: Space, time, Akasa and Atman (indicated by the word "Cha") are void of action because of their difference from that which possesses activity.<ref name=":3" />

Meaning: Space, time, Akasa and Atman (indicated by the word "Cha") are void of action because of their difference from that which possesses activity.<ref name=":3" />

Space is identified through the fact that it can provide the context to describe objects as

Space is identified through the fact that it can provide the context to describe objects as being separated spatially.

 

being separated spatially.

== Universal Vedic Conceptions ==

== Universal Vedic Conceptions ==

These universal conceptions laid the foundations for newer formulations which are holistic in nature and structure.  

These universal conceptions laid the foundations for newer formulations which are holistic in nature and structure.  

==== Visvajyoti or Cosmic Light ====

=== Visvajyoti or Cosmic Light ===

A striking feature of the Rigvedic texts is the attempt to discover the essence or power that is behind all manifestations. In the [[Rigveda (ऋग्वेदः)|Rigveda]], the concept of the unmanifested is cosmic energy, and the manifested is cosmic light, which is referred to as Visvajyoti, a positive unitary principle, pure and sublime. One can conceive the cosmic light as the principle of life and longevity, and it is the ‘soul of all gods’ and the ‘womb’ of all created things. Sri Aurobindo explains the symbolism of Aditi as 'the boundless' or 'the unbounded'. According to the [[Rigveda (ऋग्वेदः)|Rigveda]], Aditi is the substratum (pure consciousness of infinite existence) of all that is here and beyond. Aditi is Light-Infinite, and the deities who are born of Aditi are manifestations of the Infinite Light. Mundaka Upanishad (2.20.10) refers to Brahman as the Self-Luminous Light.<ref name=":1">Bose, D. M., Sen, S. N., & Subbarayappa, B. V. (1971). A concise history of science in India. New Delhi: Indian National Science Academy. pp. 453-459</ref>

A striking feature of the Rigvedic texts is the attempt to discover the essence or power that is behind all manifestations. In the [[Rigveda (ऋग्वेदः)|Rigveda]], the concept of the unmanifested is cosmic energy, and the manifested is cosmic light, which is referred to as Visvajyoti, a positive unitary principle, pure and sublime. One can conceive the cosmic light as the principle of life and longevity, and it is the ‘soul of all gods’ and the ‘womb’ of all created things. Sri Aurobindo explains the symbolism of Aditi as 'the boundless' or 'the unbounded'. According to the [[Rigveda (ऋग्वेदः)|Rigveda]], Aditi is the substratum (pure consciousness of infinite existence) of all that is here and beyond. Aditi is Light-Infinite, and the deities who are born of Aditi are manifestations of the Infinite Light. Mundaka Upanishad (2.20.10) refers to Brahman as the Self-Luminous Light.<ref name=":1">Bose, D. M., Sen, S. N., & Subbarayappa, B. V. (1971). A concise history of science in India. New Delhi: Indian National Science Academy. pp. 453-459</ref>

==== Rta ====

=== Rta ===

[[Rta (ऋतम्)|Rta]] is the cosmic law of harmony. ‘Rta’ means ‘the course of things’, order or law, and the primal principle, which is non-temporal and cohesive. It is a natural law which even the Vedic deities have to follow; they are often described as the "guardians of rta" and "practicers of rta" in the Rigveda (1.23.5). The natural phenomena, such as the flow of rivers, change of seasons, and day and night, are stated to be in accordance with this natural law (Rig. Veda. 4.3.8-12; 5.80.1). Aditya, or Surya, is the all-pervading light extolled as the dweller in eternal law and, eventually, the eternal law itself (Rig Veda 4.40.5). The Rigvedic seers were convinced that nature is not as heterogeneous as it seems to us and that all types of natural motions are traceable to rta, which, according to them, is self-existent and ever extending. Symbolically, rta was also conceived by the Rigvedic seers as Varuna, who was supposed to have determined the laws of the physical universe. Rta helps Indra "light up and energize the whole world" and Ushas to "illumine the universe". As eternal order, it is transcendental, signifying uniformity of nature or an ordered course in a cosmic sense.<ref name=":1" />

[[Rta (ऋतम्)|Rta]] is the cosmic law of harmony. ‘Rta’ means ‘the course of things’, order or law, and the primal principle, which is non-temporal and cohesive. It is a natural law which even the Vedic deities have to follow; they are often described as the "guardians of rta" and "practicers of rta" in the Rigveda (1.23.5). The natural phenomena, such as the flow of rivers, change of seasons, and day and night, are stated to be in accordance with this natural law (Rig. Veda. 4.3.8-12; 5.80.1). Aditya, or Surya, is the all-pervading light extolled as the dweller in eternal law and, eventually, the eternal law itself (Rig Veda 4.40.5). The Rigvedic seers were convinced that nature is not as heterogeneous as it seems to us and that all types of natural motions are traceable to rta, which, according to them, is self-existent and ever extending. Symbolically, rta was also conceived by the Rigvedic seers as Varuna, who was supposed to have determined the laws of the physical universe. Rta helps Indra "light up and energize the whole world" and Ushas to "illumine the universe". As eternal order, it is transcendental, signifying uniformity of nature or an ordered course in a cosmic sense.<ref name=":1" />

Rta and satya were the successive manifestations of Prakriti after the commencement of the process of creation. While rta is the cosmic order, Satya, the Sanskrit term, is synonymous with 'Truth' in English, but in physics ''''satya' denotes 'reality'''<nowiki/>'. Verma mentions that in Yaskacharya's Nirukta, rta has been stated to denote '''electricity'''.

Rta and satya were the successive manifestations of Prakriti after the commencement of the process of creation. While rta is the cosmic order, Satya, the Sanskrit term, is synonymous with 'Truth' in English, but in physics ''''satya' denotes 'reality'''<nowiki/>'. Verma mentions that in Yaskacharya's Nirukta, rta has been stated to denote '''electricity'''.

==== Yajna ====

=== Yajna ===

Yajna is referred to as the navel of the universe (vishvanabhi) round which the latter turns, and as the unifying principle which expands and contracts in accordance with the happenings in the universe. For, the Rgvedic seers believed that yajna is the instrument for preserving the cycle of cosmic events in harmony. The act of yajna is for the protection of rta. It also has the connotation of dynamism too.<ref name=":1" />  

Yajna is referred to as the navel of the universe (vishvanabhi) round which the latter turns, and as the unifying principle which expands and contracts in accordance with the happenings in the universe. For, the Rgvedic seers believed that yajna is the instrument for preserving the cycle of cosmic events in harmony. The act of yajna is for the protection of rta. It also has the connotation of dynamism too.<ref name=":1" />  

==== Ap (Water) ====

=== Ap (Water) ===

The famous Nasadiya Sukta in the tenth Mandala of the Rigveda, speaks of water as the supra-sensible First Cause or the primeval world-ground; and water is the first "element" to be conceived in this manner, without any mythological association. In the Brhadaranyaka Upanishad (5.5.1), it is stated: ‘In the beginning this world was just water.’<ref name=":1" />

The famous Nasadiya Sukta in the tenth Mandala of the Rigveda, speaks of water as the supra-sensible First Cause or the primeval world-ground; and water is the first "element" to be conceived in this manner, without any mythological association. In the Brhadaranyaka Upanishad (5.5.1), it is stated: ‘In the beginning this world was just water.’<ref name=":1" />

==== Panchamahabhutas ====

=== Panchamahabhutas ===

The Indian doctrine of five elements, or [[Panchamahabhutas (पञ्चमहाभूतानि)|Panchamahabhutas]], it must be emphasised, is a part of the philosophical ideas. In other words, it does not have an independent standing apart from its being an integrated component of the leading systems of Indian thought.<ref name=":1" /> It accounts for the apparently unordered, diverse world of matter and qualities. Also known as Pancabhutas (mahabhutani), the five elements are prthvi, ap, tejas, vayu, and akasa, which are loosely translated respectively as earth, water, fire, air and a non-material ubiquitous substance. Since they are interrelated, they have to be viewed in totality.  

The Indian doctrine of five elements, or [[Panchamahabhutas (पञ्चमहाभूतानि)|Panchamahabhutas]], it must be emphasized, is a part of the philosophical ideas. In other words, it does not have an independent standing apart from its being an integrated component of the leading systems of Indian thought.<ref name=":1" /> It accounts for the apparently unordered, diverse world of matter and qualities. Also known as Pancabhutas (mahabhutani), the five elements are prthvi, ap, tejas, vayu, and akasa, which are loosely translated respectively as earth, water, fire, air and a non-material ubiquitous substance. Since they are interrelated, they have to be viewed in totality.  

 

The concept of Heliocentrism, i.e., the sun is central planetary body around which the planets revolve, is as old as the Rigveda.   

The Indian traditional astronomy is essentially geo-centric and geo-static inasmuch as the Earth is considered to be a stationary sphere at the centre of the solar system. The Sun, the Moon and the planets have a motion of their own from west to east while the asterisms or the stellar sphere is considered to have their motion from east to west, as a result of which the former are supposed to fall behind the latter. This geocentric and geo-stationary view was for the first time modified by Aryabhata I who, while maintaining the geo-centric idea, conceived of a direct rotation of the Earth about its axis, and even gave a precise rate of rotation stating that the Earth rotates through an angle of one second in one prana of time.<ref>Subbarayappa, B. V., & Sarma, K. V. (1985). ''Indian Astronomy: A Source-book: Based primarily on Sanskrit texts''. Nehru Centre. <nowiki>http://ci.nii.ac.jp/ncid/BA10111373</nowiki></ref>  

== Light ==

== Light ==