You see, wire telegraph is a kind of a very, very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? And radio operates exactly the same way: you send signals here, they receive them there. The only difference is that there is no cat. -Albert Einstein
One of the most exciting parts of any scientific field is to imagine what the next big discovery is going to be. In the late 1800s, we thought we were almost at the end of physics. We had Newton’s laws for gravity, our entire system of classical mechanics for describing force and motion, and all of electricity and magnetism figured out thanks to Maxwell. There were just a few small problems.
1.) When things moved close to the speed of light, our old laws of force and motion didn’t work any more. Of course, this was a very, very fast speed, and while you could fix it by adding in the Lorentz-Fitzgerald factor, it took the revolutionary new physics of Special Relativity to explain mechanics successfully at high speeds.
2.) When things are deep inside of strong gravitational fields, Newton’s laws of gravity don’t hold anymore. The orbit of Mercury was problematic, for one, but it was the observation of stars during an eclipse in 1919 that sealed the deal on this one. It turned out that Newton’s law of gravity needed to be replaced by a new theory of gravity in many situations, known as General Relativity.
3.) Stars of different temperatures emit different wavelengths of light. So what, right? Like that could possibly be a big, unexpected deal. But in order to explain this, you need to understand blackbody radiation, and in order to do that, you need to develop quantum theory and quantum mechanics.
There are plenty of other examples: the discovery of antimatter and a successful explanation for it led to the development of relativistic quantum mechanics and quantum field theory, the entire zoo of baryons and mesons combined with deep inelastic scattering led to the development of the quark theory of matter and the standard model, and on my frontier, a myriad of observations have led to the understanding that our Universe is filled with dark matter and dark energy.
So what are some things that people are looking for today to usher in new laws of nature?
Can the proton decay? If we observe proton decay, it is some pretty strong evidence that there exists a Grand Unified Theory, where the strong force, the electromagnetic force and the weak force all become the same thing at a high enough energy.
Mind you, we’ve been looking for this since the 1980s, and all that we’ve discovered is that if the proton can decay, it has a half-life of at least 1034 years, a factor 1024 larger than the current lifetime of the Universe.
Does supersymmetry exist? One of the things people don’t like about the Standard Model (above) is that there are different numbers of fermions and bosons, the two fundamental types of particles. There’s a theory that states that these two types should be equivalent, so that for every fermion, there’s a bosonic super-partner, and for every boson, there’s a fermionic super-partner.
We’ve been searching for these since the 1980s as well, and we’ve found that if these superpartners do exist, they’re all significantly heavier (by many orders of magnitude in most cases) than their “normal” counterparts. If the LHC fails to find them, we’re going to need to seriously consider alternatives.
(Supersymmetry and Grand Unification, by the way, are fairly general predictions of string theory. If these fail to pan out, it will be a significant blow to string theory’s viability.)
Why do neutrinos have mass? This is, arguably, the only non-astrophysical discovery that we’ve made that the Standard Model cannot explain: the massiveness of neutrinos. Is there a super-heavy particle out there to give our plain-old neutrino some mass? If so, we have a mechanism to explain it, but we have no further evidence for this phenomenon.
Can quarks be made up of even tinier particles? This possibility, known generally as technicolor, is one of the most exciting alternatives to the existence of the Higgs. In fact, if the Higgs doesn’t exist, many theorists believe that technicolor is the only other viable options, which itself is highly constrained based on numerous observations.
So these are some of the trees we’re barking up. Personally, I think that — with the exception of neutrinos — these are all likely to not pan out the way we expect. But this is the frontier of modern physics, and at this point, we simply don’t know until we do the necessary experiments. The proton could live for 1035 years, for 10350 years, or — in principle — forever; we simply haven’t tested it that far. So what’s going to come next?