The so-called gauge hierarchy fine‑tuning problem is the difficulty of explaining why the electroweak scale (≈ 100 GeV) is so much smaller than the Planck scale (≈ 10¹⁹ GeV) without extremely unnatural parameter adjustments, and it is a specific instance of a much broader so-called hierarchy/fine‑tuning problem in particle physics. In the Standard Model, the Higgs boson mass (and thus the electroweak scale) is sensitive to quantum corrections from all higher energy scales. Radiative corrections tend to push the Higgs mass up toward the highest scale in the theory, so to keep it at the observed 125 GeV requires an impossibly delicate cancellation between the bare mass parameter and these corrections. This cancellation has to be “fine‑tuned” to many decimal places, by hand, which is “unnatural” in the absence of a physical mechanism which would naturally bring this about.

From the very beginning, supersymmetry has failed all experimental tests. Not a single one of the predictions of supersymmetry has been found to be correct.  Yet the idea is so vital to efforts to go beyond the Standard Model that theorists have been inexcusably slow to let go of it!

Supersymmetry solves a large number of highly technical problems occurring in the application of quantum field theory to particle physics.

Virtual particles, including matter-antimatter pairs, allow what would have been infinite “bare” charges and masses to be renormalized and replaced with measured masses. However, a mass problem still remains since the correct masses have to be inserted “by hand.”  Fundamental considerations indicate that masses should still be many orders of magnitude larger than observed. A solution that has worked before might work again, so it was suggested to double the number of particles by having the distinction between bosons and fermions be a broken symmetry. Then all fermions should have boson counterparts, and vice versa. However, these “superpartners” have never been observed, although most experts think they almost certainly should have shown up at energy levels already probed. When the LHC came back on-line at double the previous center-of-momentum energy, and much greater luminosity, many physicists thought that this would be the last chance to confirm supersymmetry. No superpartners were seen and it is looking very much as if it will probably be necessary to abandon this idea or modify it beyond recognition. The LHC is currently shut down for another large upgrade but virtually nobody expects that the upgraded accelerator will suddenly be able to make superpartners.

Many superpartners should have appeared between 800 and 2500 GeV, in almost all versions of supersymmetry, thus filling in the lower part of the Energy Desert and solving the hierarchy problem.  But absolutely nothing has ever appeared in this energy region, experimentally, despite many decades of searching with continual upgrades to beam energy and luminosity.  Before the current shutdown the LHC reached 13,600 GeV cm collision energy (13.6 TeV). While believers continue to move the goalposts, the vast majority of physicists now admit that supersymmetry in particle physics is not a possibility.

The biggest problem resulting from the failure of supersymmetry is that, as we shall see later, supersymmetry is intimately embedded in String Theory. Strings are inherently bosonic in nature, and so the only way to get String Theory to describe fermions is via making String Theory supersymmetric! But essentially ALL suggested approaches going beyond the Standard Model also incorporate supersymmetry. That's not good... in any way.