A Big Change Is Happening in Physics

Physics is entering a post-speculation phase: once-dominant ideas like supersymmetry, string theory, multiverses, and invented new particles and forces have largely lost momentum, largely because the Large Hadron Collider failed to turn up evidence that requires physics beyond the Standard Model. That absence of new discoveries at higher energies has effectively removed the field’s most convenient justification for endlessly proposing new high-energy mechanisms—at least until experiments reach vastly higher energy scales. The shift matters because it changes what “progress” looks like: fewer sweeping theoretical bets, more emphasis on experiments that can actually confirm or falsify specific claims.

The change is also cultural, not just experimental. Popular science coverage and online audiences have grown tired of a familiar cycle: proposed anomalies are treated as evidence for a new theory, then follow-up results never arrive—or the claims quietly fade. Hossenfelder argues that this repeated pattern has damaged physics’ reputation and helped drive the speculative era to stall. In her view, the most dramatic “end” is not that physicists stopped working, but that many now recognize the trajectory isn’t going anywhere.

A new paper by three philosophers frames the same pivot in institutional terms: particle physics, once guided by theory, is giving way to a period where pioneering experimental research becomes more crucial. That sounds like a corrective—measure first, theorize second—but it creates a practical problem: deciding which experiments deserve funding. Hossenfelder suggests that stagnation in foundational physics stems from misallocated resources, especially an overemphasis on pushing to higher energies rather than addressing open questions at accessible scales.

Her prescription is specific. She has long argued that foundational physics should focus on testing quantum gravity and the quantum measurement problem at low energies. There are already experimental avenues—using massive objects in quantum superpositions to probe quantum-gravity effects, or testing whether Penrose’s gravitationally induced collapse is real—but comparatively little effort goes into them. She contrasts this with the scale of funding for a bigger collider, estimating that redirecting tens of billions toward low-energy experiments targeting these two problems could produce tangible, technologically relevant progress within about 20 years.

The caution is that abandoning high-energy speculation may not automatically improve the field. Hossenfelder worries that researchers will simply relocate pseudoscientific theory production to astrophysics and cosmology, where “dark sectors” and modified gravity frameworks can be tuned to explain little without decisive tests. She points to the GRQC archive as a place where modified-gravity ideas proliferate.

Finally, she notes that collider expansion plans may be constrained by reality and politics. The Chinese have reportedly decided not to build a larger particle collider, which she calls a smart move given that the next major machine is likely to deliver another null result. Whether Europe will invest heavily anyway remains uncertain—though, in her framing, pouring money into experiments that keep failing to find new physics would repeat the same pattern that helped end the speculative era in the first place.