The Planck energy is where we can be 100% certain to observe quantum gravity. There are 16 orders of magnitude between the LHC collision energies and the Planck

The Planck energy is where we can be 100% certain to observe quantum gravity. There are 16 orders of magnitude between the LHC collision energies and the Planck scale. That's a humongous energy range in which to look for new physics. You could build a collider that's 10x more powerful than the LHC, but it'd be a stab in the dark, as the new physics may occur at 100x the LHC energy, or much much more. To date there is no indirect evidence (e.g. Particle decay rates that deviate from the standard model predictions) that points to quantum gravity effects occuring below the Planck scale. This indirect evidence is required to make a case for building a super expensive particle collider. For example, the LHC was built because we knew through indirect evidence, that it would either find the higgs boson, or new physics if the higgs wasn't found. Without indirect evidence your experiment is a stab in the dark, which is fine, but for particle physics an insanely expensive stab in the dark. Regarding astronomical evidence, it can give hints on quantum phenomena, but can't shed much light on their cause. For instance, we know dark matter exists via astronomy, but it can't tell us what the stuff actually is, we need laboratory evidence for that, I.e. Produce it in a collider, measure its mass, spin, other quantum properties, and how it interacts with other particles.