For a sense of scale at how fast this expansion is going –– our universe came into existence 13.8 billion years ago. Without dark energy and expansion, the diameter of the universe would then be 13.8 billion light-years wide, but, we do have dark energy and because of this expansion the observable universe is now 91.32 billion light-years across. Today’s task was to rebalance the telescope. Because the DESI cables are so heavy, they’ve thrown the balance of the scope out of whack. I stood with David Sprayberry, my host, and onsite manager of the project, while his team strapped themselves into harnesses on a floor elevator 18 stories up. Men my dad’s age slipped their legs into something fit for a person working on the outside of the Empire State Building.
To balance the telescope they have to carry trays of solid lead weights the size of envelopes up into its belly. Two by two they would screw on each weight and then test it, then add more weight to certain spots and test it again. They were just weeks away from collecting what astronomers call “first light.” The lucky first object of DESI’s gaze would be a spiral galaxy called Triangulum, 2.7 million light-years away. This particular galaxy has been studied so much over the years that its spectra are very well known, making it a sort of galactic calibrator.