An elusive planet Of all the planets of the solar system visible to the naked eye, Mercury is perhaps the most difficult to observe, especially in temperate latitudes. The fact is that the planet can be seen in a relatively short period of time immediately after sunset or before sunrise, and quite low above the horizon. Therefore, there is even a popular astronomical legend, as if at the end of the years, the brilliant Nicholas Copernicus once complained that in his life he had never seen the...