While the eye is sensitive only to the light perceived instantly, the silver medium (photo plate and films) that was still used until the 1980s can record the light received during a long exposure. A camera equipped with an ordinary emulsion can detect very weak objects that the eye as exercised will never see, even …
It is enough to have spent a few seconds on the eyepiece of a so-called azimuthal instrument, mounted on a tripod, to be aware of the sidereal movement which causes the whole celestial vault in the opposite direction to the rotation of the Earth, causing all the stars from east to west. With manual retraction …
Around the world, about thirty observatories have dedicated at least one telescope to the study of the Sun. Given the atmospheric turbulence, it is almost impossible to use instruments over one meter in diameter unless you have a high altitude site or install adaptive optics. Also for the time being, the largest solar telescope is …
Since the manufacture of the 5 m diameter mirror of the Mount Palomar Observatory in 1939, because of their gross mass exceeding 40 tons, the mirrors of the large telescopes have been hollowed out, which allowed them to be lightened by 50 %. But beyond 5 meters, it becomes very difficult to manufacture them in …
At the turn of the twentieth century, Lorentz understood the futility of mechanical support to explain the propagation of the electromagnetic field. He also discovered the theory of electrons. Meanwhile, the mathematicians Gauss, Lobatchevski, Bolyai and Riemann created the concept of curved space and endeavored to define the peculiarities of coordinate systems relative to each …
A decisive step was taken in the seventeenth century by Johannus Kepler in Germany, a renowned mathematician, the founding father of modern astronomy. Protestant of confession and thus little concerned by the recommendations of Rome which was in a blind alley, Kepler did not seek to “save the phenomena” while maintaining at any cost the …
In China, the greatest astronomer of the Middle Kingdom was Tcheou Kong, the brother of Emperor Wou Wang who lived in the eleventh century before our era. He built an observatory in the city of Honan-fu, determined the position of the solstices, discovered the latitude, and deduced the inclination of the axis of the Earth …