Question: Extract the answer to the question from the following context. Question: What was the logic behind the leap year put forth in 1560? Context: Ancient tables provided the sun's mean longitude. Christopher Clavius, the architect of the Gregorian calendar, noted that the tables agreed neither on the time when the sun passed through the vernal equinox nor on the length of the mean tropical year. Tycho Brahe also noticed discrepancies. The Gregorian leap year rule (97 leap years in 400 years) was put forward by Petrus Pitatus of Verona in 1560. He noted that it is consistent with the tropical year of the Alfonsine tables and with the mean tropical year of Copernicus (De revolutionibus) and Reinhold (Prutenic tables). The three mean tropical years in Babylonian sexagesimals as the excess over 365 days (the way they would have been extracted from the tables of mean longitude) were 14,33,9,57 (Alphonsine), 14,33,11,12 (Copernicus) and 14,33,9,24 (Reinhold). All values are the same to two places (14:33) and this is also the mean length of the Gregorian year. Thus Pitatus' solution would have commended itself to the astronomers.
Answer: 97 leap years in 400 years

Question: Extract the answer to the question from the following context. Question: What led to creation of the electromagnetic self-rotors? Context: In 1827, Hungarian physicist Anyos Jedlik started experimenting with electromagnetic coils. After Jedlik solved the technical problems of the continuous rotation with the invention of the commutator, he called his early devices "electromagnetic self-rotors". Although they were used only for instructional purposes, in 1828 Jedlik demonstrated the first device to contain the three main components of practical DC motors: the stator, rotor and commutator. The device employed no permanent magnets, as the magnetic fields of both the stationary and revolving components were produced solely by the currents flowing through their windings.
Answer: Anyos Jedlik started experimenting with electromagnetic coils

Question: Extract the answer to the question from the following context. Question: What happened in 1857? Context: Punjab during Mahabharata times was known as Panchanada. Punjab was part of the Indus Valley Civilization, more than 4000 years ago. The main site in Punjab was the city of Harrapa. The Indus Valley Civilization spanned much of what is today Pakistan and eventually evolved into the Indo-Aryan civilisation. The Vedic civilisation flourished along the length of the Indus River. This civilisation shaped subsequent cultures in South Asia and Afghanistan. Although the archaeological site at Harappa was partially damaged in 1857 when engineers constructing the Lahore-Multan railroad used brick from the Harappa ruins for track ballast, an abundance of artefacts have nevertheless been found. Punjab was part of the great ancient empires including the Gandhara Mahajanapadas, Achaemenids, Macedonians, Mauryas, Kushans, Guptas, and Hindu Shahi. It also comprised the Gujar empire for a period of time, otherwise known as the Gurjara-Pratihara empire. Agriculture flourished and trading cities (such as Multan and Lahore) grew in wealth.
Answer:
the archaeological site at Harappa was partially damaged