The accelerator would be built in two stages. Stage one proposes a 500 m vertical accelerator, starting from the base of the LHC shafts. An exciting collaboration with NASA may come to fruition by utilising detectors on the International Space Station (ISS) to detect beams of particles fired by the accelerator every time the ISS is overhead. This "reverse cosmic-ray" experiment would allow the measurement of Earth's gravity on particle trajectories at unprecedented levels. Stage one will seek to match the roughly 1% precision on measurements of the gravitational constant "g," which is currently being targeted in parallel by experiments with antihydrogen at the Laboratory's Antimatter Factory. This moderate build will also allow engineers and physicists to understand the intricacies of running a vertical accelerator in preparation for stage two -- the space elevator. "If built, however, this advanced particle accelerator would nevertheless be three times taller than the Burj Khalifa in Dubai, which has been the tallest structure in the world since 2009."
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