The 'day of Brahma' is the basic cycle called Kalpa. Each kalpa lasts for 4,320,000,000 years. The 'night of Brahma' is as long as the day. 360 such days and nights form one 'year of Brahma'. Brahma's life span lasts for 100 such years. The currentkalpa, called the Varaha kalpa, is the first day of Brahma's 51st year. During the day of Brahma, creation is in its active phase. During the night there is a cosmic calm and life is at a standstill.

Each Kalpa is divided into 14manvantaras (or secondary cycles, each lasting 306,720,000 years). In each manvantara the world is entirely recreated with a new Manu as its progenitor. Currently we are in the seventh manvantara of the kalpaand Manu Vaivasvata is its progenitor.

Each manvantara in turn contains 71 mahayugas or eons, of which 1000 form akalpa (each lasting 4,320,000 years). Each mahayuga is further divided into four ages called yugas, namely Krta, Treta, Dvapara and Kali: the first lasting 1,728,000 years, the second 1.296,000, the third 864,000 and the last for 432,000. We are now in the 5,102nd year of the Kali Yuga of the 28th mahayuga of the 7th manvantara of theVaraha kalpa. This Yuga is said to have begun in the year of the Mahabharata war. Another reference quotes the commencement of the current kali Yuga to coincide with the day of the death of Krishna.

At the beginning of each kalpa or the Day of Brahma, when he wakes the 'Three Worlds' (referred to often in the myths) are manifested afresh, according to the individual karma. Only the ones who passed beyond the Three Worlds in the previouskalpa are released from the cycle (nirvana, moksha). At the end of Brahma's day, the Three Worlds resolve into chaos with great floods (pralaya). The Night of Brahma, again lasting for the same 4.32 billion years, when there is no life from in the universe, follows this. Sleeping Narayana is now resting on the cosmic ocean, supported by Ananta (Infinity), the seven-hooded snake, with Brahma seated on the lotus arising from his navel. After one hundred Brahma years, the creation resolves into great chaos (mahapralaya) and a new Brahma does not appear for another hundred Brahma years.

The time span of each kalpa is remarkably close to the life span of our star, the sun, at least in terms of billions of years. Upon the death of our sun (supernova), life as we know it, comes to an end. The ancient thinkers seemed to have grasped the enormous and infinite scale of the universe and the only way to measure the scale of time is in terms of light years.

The geography of the mythological era is also fascinating. There are seven continents with seven seas in concentric circles, the innermost of which is the Jambu-dvipa (continent with a rose-apple tree). In the center is the golden mountain called Meru, rising 84,000 leagues above the earth. In the southern part of Jambu-dvipa is the Himalayas, south of which is the 'land of sons of Bharata', called Bharatavarsha (India). The ocean next to Jambu-dvipa has salt water. The next concentric land is called the Paksha-dvipa and beyond that are the remaining continents. The oceans surrounding each are made of treacle, wine, ghee, milk, curds and fresh water respectively. One of the mountains surrounding the Mount Meru is the mountain of Mandara, the mythical mountain used by the gods as a pivot for the churning of the ocean. There are four such mountains buttressing Meru, each 10,000 leagues high.

Brahmagupta in the 7th century proposed that the earth was spherical and gave its circumference as 5000 yojanas (each yojana is 4.5 miles). This figure is quite accurate for an ancient astronomer. In his book Brahmasphutasiddhanta he defined the concept of the number zero. When he was 67 years old he wrote his second book on mathematics called Khandakadhyaka. Bhaskara (12th century, his famous work called Siddhanta Shiromani) reaffirmed that infinity, however divided, remains infinite, which had been established more than a thousand years earlier by the Indian theologians. It is little wonder that medieval mathematicians understood the implications of zero (shunya) and infinity (ananta), long before the rest of the world had.

However, for religious purposes the earth was thought to be flat, in the shape of an egg, hence the reference to Brahmanda or the Egg of Brahma. Eight elephants support the earth, one on each of the eight quarters. On the summit of Meru is the city of Brahma. The Three Worlds or Triloka are the physical plane (Bhur), astral plane (Bhuvar) and the Heaven (Swarga). The Hindus believed that Brahma's world is divided into 21 zones. The earth is the seventh from the top. Above the earth are six heavens called Swarga, with increasing beatitude as one ascends. Below the earth are seven layers of the nether worlds called the Patala that are the abode of Nagas, the mythical serpents. This underworld is filled with riches and wealth guarded by the semi-human Nagas. Under Patala is another seven zones called Naraka, with increasing misery and inhabited by tormented souls of sinners.

Astronomy, Astrology and the Calendar

Jyotisha is a subsidiary of Vedic studies classified under the heading of Vedanga. Like most Indian texts, no true Vedic texts are available but it is clear that an adequate knowledge of the astrology was available to set proper dates and times for religious sacrifices. The Greeks and the Romans profoundly influenced later Indian astronomical ideas. Varahamihira, a sixth century astronomer (505-587 C.E.) enumerated five astronomical systems, one of which is called Romika Siddhanta(referenced to Romans) and another Paulisa Siddhanta, referenced to the classical astronomer Paul of Alexandria. Varahamihira wrote the Pancha-siddhanta that included five treatises. The other three are Surya, Vasishta and Paitamaha Siddhantas.

Astrology gained in status during the Gupta period and moved beyond mere prognostication of birthmarks and foretelling of the future by interpretation of dreams and facial features. Astronomy also modernized with the assimilation of the knowledge of the Greeks. With the achievements in mathematics, the Indian astronomers gained a reputation in the medieval Europe and the Arabic nations.

The movements of the moon in relation to fixed stars formed the basis of astronomical knowledge. Twenty-eight stars were recognized, one for each day of the lunar month. Some of the stars or Nakshatras were more auspicious than others and astrology was closely tied in with astronomy. Thus Bharani and Krttika were inauspicious and a girl born under the sign of Mula found it difficult to find a suitor. The Nakshatra forms part of the horoscope of a person, which is used even today to form alliances for matrimony. Astrology also correlated diseases and ailments according to an individual's Nakshatra. Born under certain Nakshatra, one is more prone to certain diseases.

With their naked eye, Indian astronomers knew of seven planets (graha), in which they included the sun and the moon. Thus Ravi (Sun), Chandra (Moon), Budha(Mercury), Shukra (Venus), Mangala (Mars), Brahaspati (Jupiter) and Shani(Saturn) were the seven planets to which were added Rahu and Ketu. The last two are the ascending and descending nodes of the moon.

Astrologically every individual had influences bestowed upon him by most of the planets through his life span. Thus the influence of Shukra can be good fortune and health, whereas the effects of Shani can be detrimental.

Aryabhata in the 5th century suggested that the earth revolved around the sun and rotated on its axis. He wrote the masterpiece Aryabhatta (499 C.E), an astronomical treatise written in a collection of 118 verses giving a summary of Hindu mathematics until that time. Eclipses were forecast accurately and the equinoxes were well known to the Indian astronomers. They also borrowed, from the West, the ideas of the signs of the zodiac, seven-day week and the hour and made significant advances in the knowledge of astronomy. Another ancient astronomer, Dirghatamas is said to have devoted fifty years of his life to the study of the earth, sun and the moon.

The lunar calendar is followed for most religious purposes. The lunar day is the thithiand approximately thirty of them form a lunar month. The month is divided into two halves called paksha. The full moon (purnimavasya) marks the beginning of the month and the new moon is called amavasya or bahulavasya. The fortnight of the waxing moon is the bright half and called the Shuklapaksha. The waning moon is the dark half and called Krishnapaksha.

The twelve lunar months are Chaitra (March-April), Vaishaka (April-may), Jyaishta(May-June), Ashada (June-July), Sravana (July_August), Bhadrapada (August-September), Ashvina or Ashvayuja (September-October), Karttika (October-November), Pausha or Taisha (December-January), Magha (January-February), andPhalguna (February-March).

There are six seasons with a group of two months each called Ritu. Thus Vasanta is the spring season, Grishma is the summer, Varsha is the rainy season, Sarad is the autumn, Hemanta is the winter and Sisira is the cool season.

During the Gupta period a solar calendar was imported from the Western astrology and this has replaced the lunar calendar for most purposes, though not until recent years. The months are exact translations of the Greek signs of the zodiac. Included in the horoscopes as Rashi, the months of the solar year are: Mesha (Aries), Vrshaba(Taurus), Mithuna (Gemini), Karkataka (Cancer), Simha (Leo), Kanya (Virgo),Tula (Libra), Vrschika (Scorpio) Dhanus (Sagittarius), Makara (Capricornus),Kumbha (Aquarius) and Mina (Pisces).

The seven-day week was also introduced according to their presiding planets similar to the Greco-Roman system. Thus the use of Ravivara or Adityavara (Sunday),Somavara (Monday), Mangalavara (Tuesday), Budhavara (Wednesday),Brahaspativara or Guruvara (Thursday), Shukravara (Friday) and Shanivara(Saturday) became routine in India.

Medicine and Surgery

An earlier state of the practice of medicine during the Vedic period is not known but the medical advances were evident as early as 1st century. By the time of Charaka(1st and2nd century) and Sushruta (4th century) the medical practice was quite sophisticated. Both these physicians are credited with possessing more than one hundred types of surgical instruments and conducting more than a dozen major surgical procedures. The ethics of practice of medicine resembled those of Hippocrates. Practices of yoga as well as the mystical experiences were directed towards personal health. Ayurveda, considered as a subsidiary of the Smriti literature under the heading of Upa-vedas, was at the heart of the medical practice. Vakbhatawas the first to discover bacterium as the causative factor of diseases.

The basic concept of Indian medicine is the recognition of certain faults or humours called Dosha. Three main vital fluids had to be in balance for good health. They areVayu (wind), Pittha (gall) and Kapha (mucous, phlegm). The heart is at the center of intelligence and the ancient Indians did not understand the function of the nervous system. Though medical knowledge was limited because of inaccurate understanding of physiology, surgical skills were surprisingly superior to any contemporary civilization. Plastic surgery, bone setting and cesarean sections were routinely practiced with great success. Rhinoplasty (repair of nose) was first recorded to have been performed by Indian surgeons and was later carried to the West by East India Company. Though antisepsis was not an established form of science, Indian surgeons saw the importance of meticulous cleanliness and the healing powers of fresh air and sunlight.

Charaka is on record in Charaka Samhita, advising his students about the codes of ethics for physicians (Vaidya). Charaka Samhita also mentions a 'medical symposium' presided over by sage Bharadwaja around year 700 B.C.E. The Vedas refer to many medicinal plants, mineral, and animal products as treatment for many ailments. The respected Vaidya is asked never to betray his patient and respect medical privacy. He is also told to strive to improve his own knowledge at all times. Free hospitals for the poor were abundant during Ashoka's reign as recorded in the rock and pillar edicts scattered around India. Veterinary medicine was also practiced and doctors of large animals like horses and elephants were in great demand.