[...] astronomers estimate that the sun will be around for another several billion years - that's just about forever. 2. The world will eventually reach "peak oil" - the point of maximum global petroleum extraction, after which extraction will begin a permanent decline. Because it's exceedingly difficult to know when that peak will occur, this is a hotly debated topic. [...] access to petroleum has been a factor in military conflicts since the 20th century, including both world wars.