Some 500,000 asteroids are circulating near-Earth space and some of them may pose a real danger to our planet. But a US company says it plans to build a telescope that will be able to watch them. ­Some asteroids may collide with Earth between 2020 and 2030, and only about 10,000 out of half a million have been catalogued to date – so time is of the essence. But the B612 Foundation is certain its...