With the rumors of a Higgs Boson detected at Fermilab now getting the sort of official denial that in politics would mean the rumors were about to be confirmed in spectacular fashion, it's looking like we'll have to wait a little while longer before the next "Holy Grail" of physics gets discovered.
Strictly speaking, the only thing I recall being officially dubbed a "Holy Grail" that's been discovered was Bose-Einstein Condensation (BEC), first produced by eventual Nobelists Carl Wieman and Eric Cornell in 1995. Somebody, I think it was Keith Burnett of Oxford, was quoted in the media calling BEC the Holy Grail of atomic physics, which drew a bit of eye-rolling mockery at the time (but thankfully not the sort of overreaction that "God particle" for the Higgs gets). It's a little overwrought, but not a completely terrible analogy: BEC in dilute atomic vapors was something that had been predicted 70-ish years previously, and actively sought for something like 20 years (depending on who you ask) before its discovery, so it had a decent quest aspect to it.
Of course, the problem with the analogy is that in Arthurian mythology, there was one and only one Holy Grail. In physics, there are lots of them, or at least lots of things that might fairly be called the Holy Grail of one subfield or another. The Higgs is probably the best known one currently being sought, and almost certainly the most expensive, but it's far from the only one.
The Holy Grail of solid-state physics is a working theory of high-temperature superconductivity. The phenomenon was discovered in the mid-1980's, to the delight of physics demo shows everywhere, who can now levitate magnets with just a little liquid nitrogen and a chunk of ceramic, but as yet we do not have a comprehensive theory of how these systems work comparable to the BCS theory that explains normal superconductivity. Lots of people are looking, and whoever comes up with one is more or less assured of a trip to Stockholm the next December, but for now, it remains out of reach.
Positive detection of gravitational waves has most of the characteristics of a Holy Grail. Despite an early claim by Weber that basically nobody believes, nobody has ever definitively detected a gravitational wave passing by. Their effects have been observed indirectly in the behavior of pulsars and the like, but a clear and unambiguous signal from one of the gravity-wave detectors now working or in development would be pretty spectacular.
Similarly, dark matter remains a Holy Grail, despite a few tantalizing hits that there might be something peeking out of the CDMS data, or one of the other experiments that have sorta-kinda-maybe seen something. Explaining the nature of dark energy would be an even bigger accomplishment, though that particular quest might be too recent in origin for it to count as a Grail.
Closer to the areas that I follow closely, the best current Grail candidate would be an electric dipole moment of the electron or another fundamental particle. In the cold-atom world, a degenerate Fermi gas might've been a good candidate to follow BEC as a cold-atom Grail, but it was achieved a little too quickly-- Deb Jin and colleagues at JILA reached Fermi degeneracy five-ish years after BEC-- and while it's proven to be a rich source of physics (dozens of DAMOP talks on the subject), it never had the sense of suspense about it that BEC did. I'm not sure there is a cold-atom Grail at present, actually.
Those are the Holy Grails of the moment, at least the ones I can think of. What am I missing in physics? What are the Holy Grails of other areas of science?
Anything in the supersymmetric particle zoo would do....
The Annals of Improbable Research ran a whole article a few years back about things the press calls "holy grails" of science -- here's the abridged online version.
I would say an excellent candidate for "Grail" status would be a magnetic monopole
Also maybe proton decay for those desperately seeking a GUT symmetry.
For chemistry, at least from my perspective, I would say the Holy Grails are artificial photosynthesis and a much more efficient artificial nitrogen fixation process (the Haber Bosch process takes up somewhere between 1 and 3% of all the energy produced worldwide).
I'm sure there are others but those involve the environmental, energy, bio, and inorganic disciplines of chemistry.
For the analytical-chem minded, a Grail would be the artificial nose with levels of detection we see in the natural world.
fundamental theory of turbulence with solutions...
In cosmic microwave background cosmology, probably the biggest target right now is the measurement of so-called B-mode polarization of the CMB. Detecting/measuring B-modes would be a huge win for comfirming the inflationary model of the Universe's evolution.
asad, I hear a lot of cosmology types say that, but I don't understand why. The Lyth bound makes it pretty difficult to imagine a tensor component large enough to be observable. Why do so many people talk about it as if it's a generic prediction of inflation?
The analogy is apt in that just like the Holy Grail the Higgs boson doesn't even exist, it's just a popular fable. As far as I am concerned spin 0 fundamental particles cannot exist and the Higgs mechanism is just a mix of speculations and hand weaving. The same goes for most of the other examples cited above - magnetic monopole, proton decay, electric dipole moment of electron and probably dark matter particle too (dark matter is almost certainly an issue of interpretation not of an undetected particle).
The achievable holy grails of science are:
Theoretical Physics: Grand unification/self-consistent and complete theory of matter fields/correct interpretation of QM/explanation why SM is what it is and why it's parameters are what they are... which as all just different aspects of the same story - the quest for a more fundamental and better physical theory.
Experimental Physics: Fusion energy.
Biology: Understanding of the mechanics of aging and cancer, and more generally complete understanding of the biology of human cells and human life. Life extension, aging reversal, medicine.
Nanotechnology: Fully controlled nano-assembly of atoms and molecules - creating materials designed and built with atomic precision and at the same time with enough parallelism to produce them in practical amounts. Soon to follow by technologies minimizing negative impact of nanotechnology on human life and environment.
Philosophy: Explanation of consciousness, what is really behind our consciousness? Explanation of why Universe exists at all, why something exists at all, how is it all even possible and why it is the way it is...
Well, there's always the Holy Grail of archaeology -- it's a vessel believed to have been used to collect the blood of the crucified Jesus.
What is the Spear of Destiny of physics?
Well, the last two - consciousness and existence - are BIG Problems(tm) and it's far from clear if they can ever be solved in a satisfactory way, but the solution of all the others is almost certainly only a matter of time (though possibly quite substantial).
The holy grail for archeology is The Holy Grail.
I think you meant abiogenesis.
Energy related ones:
Plasma Physics - Sustained fusion yield greater than input energy (Q>1)
Fission- A _politically viable_ closed nuclear fuel cycle.
Chemistry - High energy density battery or safe non-petroleum liquid fuel.
Solid State- Viable HTSC wires for lossless transmission.
There's also the Millenium problems,
most notable P=NP? and the Riemann Hypothesis.
There is no such thing as holy grail of science
There is no such thing as holy grail of science
Are you looking for a grail? Look only if you are men of valour. For the entrance to these grails is guarded by a monster, a creature so foul and cruel that no man yet has fought with it and lived. Bones of full fifty men lie strewn about its lair ... therefore sweet physicists, if you may doubt your strength or courage come no further, for death awaits you all with nasty pointy teeth....