ocr: TODAY The actual model of the universe still cannot be given with any cer- tainty. The current view is that the universe began from the big bang about 12 billion years ago, when it began expanding into the emptiness. (There are two alternatives for the expansion: closed universe or open uni- verse, the latter being more popular.) In both cases there are maybe more than a billion galaxies, Solarand and in galaxies there are bil- Heliospheric lions of stars, some of them Obseryatory more or less like our Sun. The more we know about our cen- Observatoire tral star, the more we under- Hehesphériqu ...
