Juin 2005

eN0 1HING is more captivatingthanatotal eclipse ofthe sun. Darkness meesacross the surfaceofthe EarthThe skytums sta1eblue. Temperaturesdrop.Dogs bark And then,of COllISe, there is thealien beautyofthe sun's pearly white coronasurrounding the black silhouette ofthe moon.But there may be more to an eclipse thanmeets the eye. Swinging pendulums go wild10 as ifsornemysterious force were tuggingon them. Sensitivegravimetersgivereadingsthat fluctuate violently. Gravity itselfseemsto quiver a bit Or so say a smallbaudofphysicists who c1aimthat these mysteriousphenomena hint at a fundaruental flaw inEinstein's general theory ofrelativity,Need1ess to say, such c1aimshaveproved coutroversial. Celestial aliguments,peudulum experiments, Einstein bashing ­62.0 it ail smacksof fringe science that deservesto be iguored Surely there must hesorneconventional explanation.(1) whenphysicist Chris DuifofDelftUniversity ofTechnology in the Netherlandspublished a review in August!his year ofthe varions explanations that physicists haveput forward, he couc1uded that they all failto make sense ofthe bizarre findings.So now researchers are planning to pack up3::> their pendulums and chase eclipses acrossShadowover 9ravityWatch your grandfather clock next timethere's an eclipse. Il might be trying to tellyou something, says Govert SchillingCover featurethe globein the hope ofsettlingthe debate (see Graphie, page 31). It vcered Iiuthest off light waves were once thought to propagate.once and for ail. course 20 minutes before "maximum eclipse". Beliefin the ether was widespreadThe first indication that something might when the m0011 smothered a large fraction of la::> amongphysicists in the late 19th century.be wrong came 50 years ago, in the summer the sun's surtace. Afterwards the penduhun's Butexperimenters were unable to prove itsof1954. At the School ofMining inParis, .::ra swing went back ta normal. lt was as if the existence and Einstein builthis theory ofengineer, economist and would-be physicist pendulum had somehow been influenced bv the relativity on the asswnption that theMaurice Allais carried out an impressive series alignment of the Enrth the 11100n and the sun. invisible substance does not existofpendulum experiments. Allais's original In an iruproved version ofhis experunem Yet Allais has never given up on the etheraim was to investigate a possible linkbetween tour vears later. Anais placcd t\-VO pcndulums and believes that it somehow affeets swinging4D magnetism and gravitation. What he found 6 kilometres apart. Dnring June and July pendulums on Earth, (3) he offersuowas much stranger. that year. both 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 "In the history ofswingîng because gravity tugs down on it, ofWcmhcr von BraLU1. the pionccring rocket \(0 science, every revolutionary result meets withEinstein's general theory ofrelativity explains engineer. Spellbound by these apparent very strong opposition," Allais says.this relentless tugging geometrica1ly: $"0 gravitational anomalies, he urged Allais to "Relativists say I'm wrong without providingevery mass bends the fabrie ofspace-time publish his results in English and Ilotjust in any demonstration. Most ofthem haven't evenaround it, so other masses slide clown into French oïeroSpccelingincenng. vol 9. P46). read what I wrote. li Given the faet that the vastthe dimple in space-time, Walk into a roommajority ofhis publications are in French,and you subtly distort space-lime, pullingthat may not be too surprising.50 everything gently towards YOll. Einstein ecllpsed Still, a small uumber ofseientists didLeftto swing freely, a pendulwn will The scene was set tor a repeot experiment read whatAllais wrote and tried to repeathisalways trace the same path through spaee. during the partial solar eclipse or 22 October experiment. In 1970EIWinSaxi, who foundedBut because of our planet's rotation, the plane 1959- Again Allais saw bis pendulum swing 1070 the company Tensitron, and Mildred Allen ofin which the pendulum swings appears to wildlv. (2) ~ similar etTeets were Mount Holyoke College, Massachusetts,rotate slowly with respect to a laboratory on observed during an eclipse in 1961 by threc studied the behaviour of a pendulwn before,Earth. This effect was first demonstrated by Romanian scientists who \Verecompletelv during and aftera total eclipse. Like Allais,French physicistLéonFoucaultin 1851. unaware of Allais's results. they noted large irregularities at the onset ofSurprisingly, Allais saw the pendulum's "'10 To Allais"the mvsterious behaviour the eclipse. And in a paperthey coucluded thatrotation rate mcreasmg and decreasmg ID the soundec as If it could SIgnal the collapse of "gravitational theory needs to be modified"6:J course ofaday, which was mysterious enough. Ëinstein's general theorv of relativitv - a view (Physical Review D, vol 3, P 823).Then, during a partial eelipse of the sun he still holds todsy at the age 01'93 and with Saxi and Allen used a completely differenton 30 June 1954, one ofAllais's assistants the 1988Nobel prize for economies under his setup from Allais. He hadmeasured changesnoted that the pendulum went mad. At the belt. In particular, he claims that the pendulum \3?in the swing direction ofa "paraconical"start ofthe eclipse, the pendulum's swing resulrs point to the existence orthe ether. pendulum, a short, stiffversion ofthe famousplane sudden1ystarted to rotate backwards the hvpothetical substance through which Foucault pendulum. (4) , Saxi and281 NevScientist 127 November 2004 V'NIW,newscîentist,com