Juin 2005

eNOTIllNGismore captivatingthanatotal eclipse ofthe sun. Darkness racesacross the surfuce ofthe Earth.Theskytums staleblue. Temperaturesdrop.Dogs bark And then, ofcourse, there isthea1ienbeauty ofthe sun's pearly wbite coronasurrounding the black silhouette ofthe moon.But there may be more to an eclipse thanmeels the eye. Swinging pendulums go wild10 as ifsornemysterious forcewere tuggingonthem Sensitive gravimeters givereadingsthat fluctuate violently. Gravity itselfseemsto quiver a bit. Or so say a smallband ofphysicists who claim that these mysteriousphenomena hint at a fundaruental flaw inEinstein's general theory of relativity.Needless te say, such claims haveproved conlroversial. Celestial alignments,penduhun expenments, Einstein bashing ­~O it all smacks offringe science!hat deservesto be ignored. Surely there must be sorneconventional explanation(1) whenphysicist Chris DuifofDelftUniversity ofTechnology in the Netherlandspublished a review in August this year ofthe various explanatious thatphysicisls beveput forward, he concluded tbat they ail l'ailto make sense ofthe bizarre findings.So now researchers are planning to pack up~ their pendulumsand chase eclipsesacrossShadowover gravityWalch your grandfalher clock nexllimelhere's an eclipse. Il mighl be lrying 10 lellyou something, says Govert SchillingCoyer featurethe globe in the hope ofsettJing the debate (sec Graphie, page 31). It veered furthest off light waves were once thought to propagate,once and for all. course 20 minutes before "maXi111LUl1 eclipse". Beliefin the etherwas widespreadThe first indication that something might when the mOOH smothered a large fractionof 1et> among physicists in the late 19thcentury,he wrong came 50 years age. in the summer the sun's surface.Aûcrwards. the pendulum's Butexperimenters were unable to prove itsof1954. At the School ofMining in Paris, .::Jo swing went back to normal. Jtwas as Ifthe existence and Einstein built his theory ofengineer, economist and would-be physicist pendulum had somehow becn influenced lw the relativity on the assumption that theMaurice Allais carried out an impressive series alignment of the Earth,the 11100n and the sun. invisible substance does not exist.ofpendulum experiments. Allais's original ln an improved version ofhis experiment Yet Allais bas never given up on the etheraimwas to investigate a possible link between four years later, Allais placed two pendulums and believes that it somehow affects swinging4D magnetism and gravitation. Whathe found 6 kilometres epart. During June and JlÙY pendulums on Earth, (3) he offers nowas much stranger. that vear, bath displaved the same erratic explanation why. Hardly anyone agrees withLet go ofa pendulum and itwill start rotation. 111e work caught the attention him.Still, he remains defiant. "Inthe history ofswinging beeause gravity tugs down on it, ofWernher von Braun. the pioneering rocket HO science. every revolutionary result meets withEinstein's general theory ofrelativity explains engineer. Spellbound by these apparent very strong opposition," Allais says.this relentless tugging geometrically: ~O grevitational anomalies, he urged Allais to "Relativists say l'rn WTOng without providingevery mass bends the fabric ofspace-tirne publish his rcsults in Englîsh and 110t just B1 any demonstration. Most of them havent evenaround it, so other masses slide down into French tAero'Spocelingmecnng. vol 9, l' 46) read what 1wrote. Il Given the fact that the vastthe dimple in space-lime. Walk into a roommajority ofbis publications are in French,and you subtly distort space-lime, pullingthat may not be too surprising.SOeverything gently towards you. Einstein eclipsee Still, a small number ofscientiste didLeft 10swing freely, a pendulum will The seene was set for a repeat expcriment read what Allais wrote and tried to repeat hisalways trace the sarne path through space. during the partial solar eclipse of22 October experiment. In 1970Erwin Saxl, who foundedBut because ofour plenet's rotation, the plane 1959 - Again Allais &'1'1,',- his pendulum swing \&'0 the company Tensitron, and Mildred. Allen ofin wbich the pendulum swings appears to wildly. (2) . similar effects were Mount Holyoke College, Massachusetts,rotate slowly with respect to a laboratory on observed during an eclipse in 1961 by three studied the behaviour ofa pendulum before,Earth. This effect was fust demonstrated by Romanian scientists who were completef, during and after a total eclipse. Like Allais,French physicist Léon Foucault in 1851. unaware of Allais's results, they noted large irregularities at the onset ofSurprisingly, Allais saw the pendulum's q() To Allais, the mysterious behaviour the eclipse. And in a paperthey concluded thatrotation rate mcreasmg and decreasing ID the sounded as Ifrt could signal the collapse of "gravitational theory needs to he rnodified"6::J course ofa day, wbich wasmysterious enough. Einstein's general theory ofrelativitv - a view (Physical Review D, vol 3, p 823).Then, during a partial eclipse of the sun he still holds today at the age of93 and with Saxi and Allen used a completely differenton 30 June 1954, one ofAllais's assistants the 1988 Nobel prize for economies under his setup from Allais. He had measured changesnoted that the pendulum went mad. At the belt. In particuler. he daims thar the pendulum\3?in the swing direction ofa "paraconical"start ofthe eclipse, the pendulum's swing results point to the existence of the ether- pendulum, a short, stiffversion of the famousplane suddenly started to relate backwards the hypothetical substance through which Foucault pendulum. (4) , Saxi and281 Nev.Scientist 127 November 2004 www.newscientist.com