Shortly after 1pm today, the planet Jupiter and the Sun will line up, with the Earth directly in between ... and pretty much nothing will happen. 'I don't think [gravitational force] will exert any influence on us,' said Chan Ying-wa, a scientific officer at the Hong Kong Observatory. 'This happens every 399 days and is the time that Jupiter is brightest in the sky. 'During opposition [the technical name for the event] is the best time to observe Jupiter because it will [also] be in the night sky the longest. It will move directly from west to east.' The phenomenon has been building up for the past two weeks and will continue for another two, making it fairly easy to spot the planet or one of its moons: stargazers need only point their telescopes at the second-brightest star. The regularity of Jupiter's opposition means it has been one of the better observed planets throughout human history, said Mr Chan. 'In ancient China, people used the position of Jupiter in the celestial sphere to tell how many years had passed.' It takes Jupiter 11.86 years to orbit the Sun once. 'That is why they called it the Age Star,' Mr Chan said.