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I never re­ally ‘got’ grav­ity at school. I knew grav­ity was what made ap­ples fall to the ground and plan­ets loop around the Sun, but I could never sat­is­fac­to­rily get my head around how it ac­tu­ally worked. It wasn’t un­til uni­ver­sity, when I walked into a class­room with ny­lon stretched out be­tween some ta­bles like a badly made tram­po­line, that I re­ally un­der­stood. The ny­lon, my friend ex­plained, was space-time, the fab­ric of the Uni­verse. The weight in the cen­tre, stretch­ing the fab­ric to­wards the floor, was the Sun. This was what huge ob­jects like stars did to space-time: they warped it, only in three di­men­sions rather than just two. Throw some mar­bles in and they be­came recog­nis­able as small plan­ets or­bit­ing a large sun. Throw in dozens, and you soon saw why so­lar sys­tems tend to or­bit stars in one di­rec­tion. Physi­cists will be fa­mil­iar with the demon­stra­tion I’m talk­ing about, but luck­ily for ev­ery­one else, I re­cently came across a much bet­ter re­cre­ation of it on YouTube – search for ‘grav­ity vi­su­al­ized’ (they’re Amer­i­can) to see it for your­self.

My point is, grav­ity is an elu­sive con­cept. The ny­lon anal­ogy demon­strates Ein­stein’s take on grav­ity, the Gen­eral The­ory of Rel­a­tiv­ity, but un­for­tu­nately these neat, sim­ple ‘rules’ can’t be rec­on­ciled with quan­tum me­chan­ics, the other cornerstone of mod­ern physics. It also leaves us with some big ques­tions about the way our Uni­verse works, such as why it seems to be ex­pand­ing at an ever in­creas­ing speed. But one the­o­ret­i­cal physi­cist, Erik Ver­linde thinks he might have a so­lu­tion – and it’s one that could re­write the laws of physics as we know them. Turn to p40 to find out more…

En­joy the is­sue!

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