That was the subject of our contest at this year's SLAC Summer Institute. It has become a tradition to have the students participate in a contest to make the best prediction of what will happen in our physics future. Ok, so the tradition is not that old, it is the brainchild of Chris Quigg from Fermilab who started it last year. It's great fun and will no doubt continue long in future Summer Institutes. This year's official question was:
What will be the first evidence to demonstrate that Einstein's theory of General Relativity must be revised and when will that be found?
We decided not to ask anything provocative... We had alot of entries, some of which were even serious. Contestents came from near and far in order to vie for the prize - bottle of California's best sparkling wine. None other than George Bush submitted two entries:
GR is perfect, no evidence will ever be found to contradict it. - George Bush.
2013: Blackholes from extra dimensions will be observed at the LHC with long lifetimes, suppressed cross sections and a high mass threshold. These properties will lead to necessary modifications to GR from HEP measurements. - George Bush. Theory has it that W flew his Secretary of Energy, Samuel Bodman, out to SLAC just to submit these entries into the contest box. Secretary Bodman, who was observed hovering around the box, covered up the real mission behind his visit by giving a speech to the lab employees. My personal theory is that Bodman submitted the second entry by himself (note it shows more knowledge than the first), but felt compelled to sign his bosses' name. We also had some humorous entries from the students. One compared Hell to a blackhole, since it is well-known that upon entering Hell, it is impossible to escape. He then calculated the Schwarzschild radius of Hell in his Hell-Freezes-Over Theory. The entries were judged by a panel of distinguished experts:
who decided upon 2 honorable mentions, 1 runner-up, and 1 winner. The first honorable mention noted that recent cosmological measurements have justified the need for a non-vanishing cosmological constant and that was already a modification in a certain sense. The panel had some sympathy for this view. Honorable mention #2 stated "I think that the most likely (first) violation for Einstein's GR will be in terms of Lorentz violation: that is, the existence of a preferred frame in GR." That was cute, but the principle of Lorentz violation was the winning answer to last year's contest, so we couldn't award it again! (Can you just imagine, every year people would be submitting answers with Lorentz violation.) The runner-up was more succinct:
~ 6 weeks.
She is a member of the Eotvos experiment (which tests gravity at short distances) at the University of Washington and we thought maybe she might have some inside information... For the grand prize, the winning entry:
The Cassini spacecraft will also exhibit anomalous acceleration towards the sun ("Pioneer anomaly"). A specifically designed follow-up mission will then confirm this and find oscillating anomalous accelerations out to 5 times Pluto's orbital radius. Taking into account time scales for landing space missions and reaching the outer solar system, this will probably happen ~2050.
The winner was from Zurich and I hope he enjoys his bottle of California's finest!