Highways in the Sky

Calculation of orbits of members of the solar systemSolar system started early but was hampered by the idea of a static Earth. In modern times, CopernicusCopernicus, Nicolaus first suggested that the Earth actually moves round the Sun. Galileo’sGalilei, Galileo discovery of the Jovian satellites played an important role in general acceptance of the heliocentric system; it later also allowed the first measurement of the velocity of light. Once the heliocentric system was accepted, progress was swift. KeplerKepler, Johannes postulated elliptical orbits which led to Newton’s law of universal gravitation. Measurement of the size of the solar system followed immediately. The discovery of the planet NeptuneNeptune discovery from calculation of the orbit of Uranus was a triumph of Newton’s law. Later, deviation of the orbit of Mercury from the prediction of Newton’s law paved the way to the General Theory of RelativityGeneral relativity. Observation of motion of binary starsBinarystars allowed us to measure their masses contributing significantly to understanding them. The same approach also led tho the discovery of exoplanetsExoplanet. Finally, the motion of the stars in galaxies has been instrumental in deducing the property of the black holesBlack hole at their centres, at the same time it has also thrown up a puzzle that still remains to be solved.