[sovande]

I thought particle physics were coming to an end? After CERN found the Higgs boson then nothing. The ROI of a more powerful accelerator is abysmal. It is impossible to know how large a new collider needs to be and if anything interesting will be found. Use the money on a moon-base instead and then mars.

[ddavis]

"the rumors of my demise have been greatly exaggerated"

There are tens of thousands of us still driving the field (with many open questions) forward.

[rurban]

They still cannot explained gravity, and the standard model is unsatisfactory.

They know exactly what they are searching for, read the paper. Esp. in QCD there's a lot still missing. Sea quarks, gluons.

[thekingofh]

Forgive me for the naive question, but I thought we had proper models for gravity since General Relativity.

[rurban]

At the quantum level gravity is not explained properly yet. My favorite rant is from Heisenberg in his autobiography.

But even on the astronomic level GR leaves the dark matter hole, which is a non-satisfactory explanation to many. Elegant yes, but certainly not proper.

[mhh__]

General Relativity cannot be (yet) quantised in a predictive way.

[whyever]

GR only works at large scales. It is still unclear how gravity at quantum scales should be modeled.

[TangoTrotFox]

How do you propose to measure the ROI of the completely unknown? This is not just related to your comment here, but it's a very general and important part of science. In the early part of the 20th century it was felt that physics was basically 'solved' and the only changes would come in refining values to another decimal point. Of course that was before the discovery of quantum mechanics or the explosion in particle physics. Have we started reach a valley at which point there's nothing but ever more diminishing returns ahead in the future? Or are we just about over the precipice onto a new explosion of revolutionary knowledge? I don't see how you can propose to meaningfully answer this one way or the other.

I'd also prioritize manned exploration above particle physics, but I think they should continue and grow in tandem as I see no way of knowing exactly what the future of these endeavors holds, other than that there is a reasonable argument to be made that either could produce discoveries of tremendous value.

[sovande]

Using probability is a good start I think. As I understand it, CERN should be able to find new particles below about 2–3 TeV in energy. It hasn't and physicists say it’s a reasonable assumption that there might not be anything new to find until energy scales of 100,000,000 TeV or more. You'll need to build and accelerator around the Sun to reach those energy levels. With that in mind, does it make sense to build something slightly larger than LHC? At billions of dollars?

[yoklov]

> physicists say it’s a reasonable assumption that there might not be anything new to find until energy scales of 100,000,000 TeV or more

This is an extremely pessimistic view. Yes, we're almost certainly going to find something there, but that doesn't mean there's nothing before then. I'd bet a reasonably large sum of money that there's something before around 10TeV.

Also, this collider isn't looking for new particles so much as trying to improve our understanding of ones we know about already.

[lovich]

If all the experimentation at the LHC brought up nothing that physicists expect, that would imply that our model of physics is wrong. Now the model can be updated with new theories and tested with new experiments

I wouldn't imagine that particle physics would be coming to an end until we had an experimentally proven model that explained all phenomena we can observe

[danharaj]

There's still a lot to learn about QCD even if new physics seems to be in a rut.

[mng2]

Yes, the EIC is much more about nuclear structure than traditional particle physics.

https://en.wikipedia.org/wiki/Deep_inelastic_scattering

[nikofeyn]

there are other accelerator architectures and approaches that are not just scaled versions of the LHC.

https://en.m.wikipedia.org/wiki/Plasma_acceleration