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January 21, 2015

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Could our galaxy be a wormhole?

Jan. 21, 2015
Courtesy of the In­terna­t­ional 
School for Ad­vanced Stud­ies
and World Science staff

Our gal­axy could conceivably be a huge worm­hole—or short­cut through space and time—a study concludes, though this path may or may not be nav­i­ga­ble.

The stu­dy, pub­lished in the journal An­nals of Phys­ics, looks at a pos­si­bil­ity that phys­i­cists had been toy­ing with for some time and is al­so raised in the re­cent movie In­ter­stel­lar. “Ob­vi­ously we’re not claim­ing that our gal­axy is def­i­nitely a worm­hole, but simply that, ac­cord­ing to the­o­ret­i­cal mod­els, [it] is a pos­si­bil­ity,” said Pa­o­lo Salucci, a co-author of the stu­dy.

The pro­pos­al takes in­to con­sid­era­t­ion the widely ac­cept­ed ex­ist­ence of dark mat­ter—a sub­stance that per­me­ates ga­lax­ies but is in­vis­i­ble, be­ing de­tect­a­ble only through its gravita­t­ional ef­fects. 

It al­so builds on the pre­vail­ing sci­en­tif­ic view that the uni­verse orig­i­nat­ed with a sort of ex­plo­sion, called the Big Bang. It fur­ther­more in­cor­po­rates the idea of worm­holes—tun­nels through space and time that, though nev­er seen be­fore, are al­lowed by Ein­stein’s widely ac­cept­ed the­o­ry of Gen­er­al Rel­a­ti­vity.

Gen­er­al rel­a­ti­vity ex­plains gravita­t­ional ef­fects be­tween ob­jects as re­sult­ing from the way that they bend space­time, space and time being con­si­dered parts of a single thing. The proposed warp­ing ef­fect is great­er the heav­i­er the ob­ject.

“If we com­bine the map of the dark mat­ter in the Milky Way with the most re­cent Big Bang mod­el to ex­plain the uni­verse and we hy­poth­e­size the ex­ist­ence of space-time tun­nels, what we get is that our gal­axy could really con­tain one of these tun­nels, and that the tun­nel could even be the size of the gal­axy it­self,” said Sa­lucci.

“We could even trav­el through this tun­nel, since, based on our cal­cula­t­ions, it could be nav­i­ga­ble. Just like the one we’ve all seen in the re­cent film In­ter­stel­lar,” added Salucci, of the In­terna­t­ional School for Ad­vanced Stud­ies of Tri­este, It­a­ly.

Al­though worm­holes gained pub­lic at­ten­tion thanks to Chris­to­pher Nolan’s sci-fi film, they had been a fo­cus of as­t­ro­phys­i­cists’ at­ten­tion for many years. “What we tried to do in our study was to solve the very equa­t­ion that the as­t­ro­phys­i­cist ‘Mur­ph’ was work­ing on. Clearly we did it long be­fore the film came out,” jokes Salucci. “It is, in fact, an ex­tremely in­ter­est­ing prob­lem for dark mat­ter stud­ies.”

Can it ev­er be tested ex­pe­ri­men­tal­ly? “In prin­ci­ple, we could test it by com­par­ing two ga­lax­ies—our gal­axy and an­oth­er, very close one like, for ex­am­ple, the Mag­el­lanic Cloud,” he said. “But we are still very far from any ac­tu­al pos­si­bil­ity of mak­ing such a com­par­ison.”

Salucci and col­leagues com­bined the equa­t­ions of gen­er­al rel­a­ti­vity with a de­tailed map of the dis­tri­bu­tion of dark mat­ter in the Milky Way. “The map was one we ob­tained in a study we car­ried out in 2013,” said Salucci. “Be­yond the sci-fi hy­poth­e­sis, our re­search is in­ter­est­ing be­cause it pro­poses a more com­plex re­flec­tion on dark mat­ter.”

Salucci not­ed that sci­en­tists have long tried to ex­plain dark mat­ter by hy­poth­e­siz­ing the ex­ist­ence of a par­tic­u­lar par­t­i­cle, the neu­tralino, which, howev­er, has nev­er been de­tected. But al­ter­na­tive the­o­ries al­so ex­ist that don’t rely on the par­t­i­cle, he added: “Dark mat­ter may be ‘an­oth­er di­men­sion,’ per­haps even a ma­jor ga­lac­tic trans­port sys­tem.”


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Our galaxy could be a huge wormhole, or shortcut through space and time, a study proposes, though this wormhole may or may not be navigable. The study, published in Annals of Physics, looks at a possibility that physicists had been toying with for some time and is also raised in the recent film Interstellar. The proposal takes into consideration the widely accepted existence of dark matter—a substance that permeates galaxies but is invisible, being detectable only through its gravitational effects. It also builds on the prevailing scientific view that the universe originated with a sort of explosion, called the Big Bang. It furthermore incorporates the idea of wormholes—tunnels through space and time that, though never seen before, are allowed by Einstein’s widely accepted theory of General Relativity. General relativity explains gravitational effects between objects as resulting from the way that they bend spacetime, a warping effect that’s greater for heavier objects. “If we combine the map of the dark matter in the Milky Way with the most recent Big Bang model to explain the universe and we hypothesize the existence of space-time tunnels, what we get is that our galaxy could really contain one of these tunnels, and that the tunnel could even be the size of the galaxy itself,” said Paolo Salucci, a co-author of the study. “We could even travel through this tunnel, since, based on our calculations, it could be navigable. Just like the one we’ve all seen in the recent film Interstellar,” added Salucci, of the International School for Advanced Studies of Trieste, Italy. Although wormholes gained public attention thanks to Christopher Nolan’s sci-fi film of that name, they had been a focus of astrophysicists’ attention for many years. “What we tried to do in our study was to solve the very equation that the astrophysicist ‘Murph’ was working on. Clearly we did it long before the film came out,” jokes Salucci. “It is, in fact, an extremely interesting problem for dark matter studies.” “Obviously we’re not claiming that our galaxy is definitely a wormhole, but simply that, according to theoretical models, this hypothesis is a possibility.” Can it ever be tested experimentally? “In principle, we could test it by comparing two galaxies—our galaxy and another, very close one like, for example, the Magellanic Cloud, but we are still very far from any actual possibility of making such a comparison,” Salucci said. Salucci and colleagues combined the equations of general relativity with a detailed map of the distribution of dark matter in the Milky Way. “The map was one we obtained in a study we carried out in 2013,” said Salucci. “Beyond the sci-fi hypothesis, our research is interesting because it proposes a more complex reflection on dark matter.” Salucci noted that scientists have long tried to explain dark matter by hypothesizing the existence of a particular particle, the neutralino, which, however, has never been detected. But alternative theories also exist that don’t rely on the particle, he added: “Dark matter may be ‘another dimension,’ perhaps even a major galactic transport system.”