It’s taken 25 years to build, has faced long delays, and cost many billions of dollars more than expected, but the countdown is finally on to launch the James Webb telescope, the successor to the Hubble Space Telescope. In just six weeks, a powerful rocket is expected to carry into space the most ambitious space telescope ever built, one promising to revolutionize how we see the universe. At a news conference this week, scientists said that after more than a decade of delays, the James Webb telescope is finally ready to fly.