Over the last six months, I have come to loathe George Gershwin’s "Rhapsody in Blue." I used to love it. But that was before United Airlines made a tinny, Muzak version its signature theme song. I have now spent so many hours on hold with United’s customer service department, that the merest hint of those opening strains of "Rhapsody" are enough to make me want to gouge out my eyes with a ballpoint pen while grinding my teeth in abject frustration and listening to my ulcer drip. I will spare you my long list of woes; after all, I’m not the only one who has suffered this week. (And really, I should have known better than to fly through O’Hare, a.k.a., the Portal To Hell, but in this instance, I had no choice. So naturally my bag got sucked into its bottomless vortex en route to the APS April Meeting in Jacksonville, and has yet to re-emerge.) Suffice to say that over the last six months, I’ve been traveling an awful lot, almost exclusively on United, and found myself, roughly 60-70% of the time, dealing with lost baggage (even on simple direct flights), rude or indifferent personnel, and constant delays, not just from weather (which is irritating but understandable), but mechanical problems or, say, the crew just not showing up. These days, it’s unusual when the airline actually gets it right.
It’s not just United either; the entire airline industry has begun a slow spiral into chaos, and not in an interesting, nonlinear phenomena kind of way. We are required to practically undress and unpack at security checkpoints, meekly submitting to having a complete stranger paw through our personal belongings at random because the person manning the X-ray machine mistook a few Power Bar Protein Plus food bars for, I dunno, sticks of dynamite or something. When we finally get on the plane, we must squeeze into tiny seats that make even my relatively slim self feel a bit crowded. Hardly any domestic flights serve meals anymore, and those that do ask you to pay through the nose for them (unless you’re First Class, in which case, you’ve already paid for several mediocre meals with the higher fare). And when you arrive at your destination, there’s no guarantee that your bags will arrive with you. When you lodge a complaint, the staff person will first try to blame you for the problem: "Well, did you check your bag 45 minutes prior to the flight? Because we can’t guarantee anything after that." If your bag arrives damaged, the airline swears it isn’t responsible, honestly, because you CHOSE to check your bag with them, after all, and anyway, it was a subpar piece of crap if it couldn’t take a decent beating.
Okay, that last bit exaggerates a little, but I’m sure many people share my impotent rage at how bad air travel has become. Perhaps the most frustrating thing about all these problems is that we are powerless to wage any effective protest or even a boycott, because, well, sometimes you’ve just got to fly. We need another option. It’s time for a revolution, comrades in science — a technological revolution. While loudly venting my rage this morning in the APS press room, I jokingly demanded that these lazy quantum physicists get off their derrieres and make teleportation a practical reality ASAP. (Whenever someone asks the inevitable "What superpower would you choose?" I always pick teleportation, because I waste so much friggin’ time getting from Point A to Point B.) Ben Stein, of AIP’s media relations team, assured me scientists could do it now, "as long as you’re willing to be teleported one atom at a time." I’d be willing, but be forewarned: we’re gonna need an awful lot of bandwidth. The Internets could be down for awhile — like, the remainder of your lifetime and far, far beyond.
So teleportation — not really a viable option as yet. Maybe Madeleine L’Engle had the right idea in A Wrinkle in Time: we should tesseract! Actually a tesseract is a hypercube, whereas L’Engle’s description in the book more closely resembles a wormhole. And when it comes to wormholes, all good sci-fi fans (especially Trekkies) know the drill: under Einstein’s general relativity, it’s theoretically possible to warp spacetime so much (given enough mass/energy) that it can bend in such a way to connect remote points (and times!) in spacetime. Sadly, it would take far too much mass/energy than is available in our solar system, possibly even our entire galaxy, to create such a fold. So I guess we’re stuck with meekly enduring a thousand paper cuts of indignity from the airline industry every time we venture into the not-so-friendly skies.
That’s not stopping physicists from continually testing and refining Einstein’s seminal theory, however, as this morning’s first plenary lecture proved. Francis Everitt of Stanford University was on hand to give a broad overview of the Gravity Probe B experiment
and announce some preliminary results. For people who want the "news nugget" straight away, here’s the gist: after a lot of delays and some unexpected complications, the measurement data indicate that (a) GR correctly predicts the so-called "geodesic effect" (i.e., how much the mass of the Earth is warping local spacetime) to within around 1%; and (b) they’re having a bit more trouble with data analysis to measure the expected "frame-dragging" effect (i.e., whether or not, and by what degree, the Earth drags the fabric of spacetime with it as it rotates). But Everitt, while cautious, is "optimistic" that they have caught "glimpses" of the frame-dragging effect. That caution translates into another eight months of slogging through the data to account for unexpected anomalies and such, but he and his colleagues seem fairly confident that in the end, GP-B’s results will mesh nicely (within the expected error bars) with Einstein’s prediction.
Of course, there’s a whole lotta backstory and other details to take in before one can truly appreciate the significance of that tidy little summation. First, non-scientist readers mostly likely had no idea that there was a satellite called Gravity Probe B circling the earth for the last three years, collecting data in hopes of confirming a couple of key Einsteinian predictions. Stanford’s official press release calls it "the most sophisticated orbiting laboratory ever created."
Per Sir Isaac Newton, the spin axis of a perfect gyroscope (assuming such a thing existed, which it didn’t in the late 1600s) orbiting the earth would remain unchanged for all eternity. But Newton saw gravity as a force between objects. Einstein re-envisioned gravity as arising from the warping, or curvature, of spacetime. The earth orbits the sun because the sun’s mass causes spacetime to curve and dip, and the earth’s motion merely follows that curvature. That’s the central tenet of General Relativity, and Einstein made several predictions that could be used to test the accuracy of his theory.
One was confirmed almost immediately: Einstein said that a ray of light passing near the sun would be deflected by a certain degree, because the sun’s mass would warp the surrounding spacetime and the light ray would follow that curvature. This effect would be observable during a solar eclipse, when the sun’s light was temporarily blocked. And indeed, two years later, in May 1919, two separate scientific expeditions — one in Brazil and another on an island off the coast of West Africa — observed just such a deflection during a solar eclipse.
Einstein also predicted that the earth’s mass would warp its surrounding spacetime, and that it would "drag" the fabric of spacetime by a certain degree as it rotates. Those last two predictions are the reason Gravity Probe B was first conceived in 1959 by two Stanford scientists named George Pugh and Leonard Schiff. The idea was to precisely measure the displacement angles of the spin axes of four different gyroscopes-in-space over the course of a year and then compare that data with Einstein’s predictions. But the instrumentation and associated technologies just didn’t exist back then to build such a complicated system. Here’s just a few things they needed:
- Wobble-free gyroscopes. These are much larger versions of the spinning toys many of us played with as kids. (You can still buy them in science-type stores.) GP-B scientists did this by creating the world’s smoothest, most perfect spheres, only surpassed in their perfect roundness by very dense neutron stars.
- Incredibly sensitive and precise sensors capable of measuring something the width of a human hair from about a mile away, because that’s how tiny Einstein’s predicted frame-dragging effect is expected to be. So they had to wait for the invention and subsequent development of Superconducting Quantum Interference Device (SQUID) based sensors to measure those tiny magnetic variations.
- A really, really big thermos. Seriously. They call it a "dewar," and it’s roughly the size of a minivan, only it’s a minivan filled with liquid helium to ensure that the entire gyroscope assembly housed within stays cold enough to function properly for the full 16 months with the needed precision: 1.8 degrees Kelvin.
- There’s so much more technological development that had to be developed to make the mission remotely feasible (never mind successful), including the entire Global Positioning System; a souped-up telescope to get the most precise focus on the orienting star; a suspension system capable of keeping the gyroscopes’ spinning rotors from making contact with the walls (which would naturally destroy the equipment); and a technology capable of tracking the path of the equipment inside the probe itself rather than the path of the orbiting spacecraft. (Basically, the gyroscope orbits the earth in a state of perfect free-fall because the body of the craft shields it from outside disturbances like friction and magnetic fields.)
So, 40-odd years and some $700 million after it was first proposed, Gravity Probe B has returned with some preliminary answers. There’s really little doubt about the confirmation of the geodesic effect, according to Everitt: "[It] is clearly seen even in the unprocessed scientific data." (For hard-core types who want the numbers, Einstein predicted that geodetic warping around the earth would cause the spin axes of each gyroscope to shift by 6.606 arc-seconds, or 0.0018 degrees.) But frame-dragging is a much tinier effect; the prediction is that the twisting of earth’s local spacetime would cause the spin axis to shift by 0.039 arc-seconds, or 0.000011 degrees. That’s much harder to measure accurately — particularly since the "signal" indicating relativistic effects of gravity around the earth must be extracted from a bunch of background noise. Ergo, that’s where the biggest delays have occurred in terms of analyzing the data.
There’s a whole host of reasons for this, but one of the most certain things about space-based missions is that, no matter how thoroughly you try to predict every conceivable complication, something unexpected is bound to happen. (I’d wager United Airlines can relate.) That’s what happened with Gravity Probe B. First, the initial in-flight verification phase of the project took twice as long as expected. Then, as the experiment was running, random protons from a solar flare damaged some cells in the on-board computer memory, so the system automatically switched to the backup computer. Ensuing computer reboots in response to random radiation strikes meant there were interruptions in the data streams. (Segmented data is much harder to analyze; you’ve got to account for the breaks in data and so forth.)
The GP-B scientists also overlooked a tiny electrostatic "patch" effect in the gyroscopes. These patches can cause the gyroscope to "wobble" a bit as it spins, much like a football that isn’t thrown in a perfect spiral. The scientists were able to model and predict that wobble. What they didn’t expect was that the pattern/motion would subtly shift over time. They accounted for electrostatic patches on the rotor, said Everitt, but forgot about the housing, and it turned out to be significant enough a discrepancy to add those 8 months to the data analysis. Those same electrostatic patches also caused small torques in the gyroscopes’ spin axes, and the resulting slight changes in orientation could be mistaken for the relativity "signal" that GP-B is designed to measure. Nobody wants to announce a "false positive," so the collaboration is taking its time and being extra careful to ensure they’re seeing what’s really there, not an anomaly masquerading as a frame-dragging effect.
Gravity Probe B has taken some flak lately for the long delays and high cost of the project: when the government spends $700 million, gosh darn it, they want answers quickly. But science doesn’t always proceed according to a predetermined schedule (in fact, it rarely does). That’s just not the nature of the beast. Personally, if I spent $700 million on an experiment, I would want the scientists involved to take as much time as they think they need with the data before announcing an official final result. No point spending all that cash if you’re not going to get a reliable result.
Everitt, not surprisingly, agreed with that assessment when I brought up during a brief discussion with him after his talk, pointing out that the folks who worked on GP-B’s predecessor (Gravity Probe A, natch) had expressed surprise that the B team expected to publish their results so soon after collecting the raw data. "This is a very different game from pure astronomy, not better, not worse, just different," he said, citing the fact that astronomers can quickly publish their images from the Hubble Space Telescope and worry about more specific analysis later. The GP-B, on the other hand, is looking for two very small numbers given a very small margin for error. "So we’d better not get either one wrong," said Everitt. "Deliberateness is the name of the game."
So, okay, we got some interesting new insights into general relativity, and as a bonus, some nifty new technological toys out of it for future missions. It’s still a fair question to ask, if there’s already strong evidence supporting GR’s predictions, why continue testing it at all? Well, because that’s pretty much what science is about — a theory is only as good as its last experimental confirmation. Einstein was brilliant, but he wasn’t infallible. It’s perfectly plausible that there could be an error in one of his predictions, and that Gravity Probe B or subsequent experiments could find it. And if/when that happens, a lot of newspaper headlines will scream, "EINSTEIN WAS WRONG!" while crackpots everywhere secretly feel vindicated because, heck, they’ve been saying this for decades and now maybe someone will consider their wacky alternative theory.
The very British and wryly laconic Everitt declined to comment directly on the implications — best case scenario or worst case scenario — of GP’B’s expected final results. "I don’t believe in worst case scenarios," he said in answer to the the latter, adding, "We have only one job: to do the experiment right. It’s not my job to worry about the implications." But I’ll go out on a limb here and predict that, should the worst case scenario transpire and Einstein had a wrong prediction for the frame-dragging effect, all it will actually mean is that one aspect of GR needs to be fine-tuned/corrected in light of experimental data unavailable to Good Ol’ Al back in 1917. The theory itself will survive quite intact, because so many other predictions have been experimentally confirmed already. It’s not the proverbial house of cards; by now, GR is pretty darn robust as scientific theories go.
About the only place it doesn’t work is at the subatomic scale, and, well, a lot of very smart people are working on reconciling that problem even as I type. Once they get a handle on that whole Theory of Everything problem, I hope they’ll turn their attention to the much tougher task of fixing the airline industry.