Dark mat­ter ‘smoother’ than first thought, study dis­cov­ers

China Daily (Hong Kong) - - WORLD - By AGENCE FRANCEPRESSE in Paris

Dark mat­ter, the mys­te­ri­ous sub­stance be­lieved to com­prise a quar­ter of our uni­verse, is spread out more smoothly than pre­vi­ously thought, said a study on Wed­nes­day that may chal­lenge some tenets of physics.

The find­ing may throw into ques­tion what lit­tle we know about the birth and growth of the cos­mos, as­tronomers said.

“All we can say for now is that some­thing ap­pears to be not quite right,” study co-au­thor Kon­rad Kui­jken of the Lei­den Ob­ser­va­tory in the Nether­lands told AFP.

Study­ing the light of some 15 mil­lion dis­tant gal­ax­ies with Europe’s Very Large Tele- scope in Chile, Kui­jken and a team found dark mat­ter to be sig­nif­i­cantly “less clumpy” than pre­vi­ously shown by the Euro­pean Space Agency’s Planck satel­lite.

Dark mat­ter is a mys­te­ri­ous sub­stance not vis­i­ble to tele­scopes and per­ceived only through its grav­i­ta­tional pull on other ob­jects in the uni­verse.

Planck stud­ied ra­di­a­tion rem­nants from the Big Bang that cre­ated the uni­verse about 14 bil­lion years ago.

The new study, in turn, ex­am­ined how the light from dis­tant gal­ax­ies is bent through the grav­i­ta­tional in­flu­ence of mat­ter.

“The sur­prise re­sult ... has im­pli­ca­tions for our un­der­stand­ing of the uni­verse, and how it has evolved dur­ing its al­most 14-bil­lion-year his­tory,” the Royal Astro­nom­i­cal So­cie- ty and the Euro­pean South­ern Ob­ser­va­tory, which hosts the VLT, said in a state­ment.

This could mean re­think­ing the very essence of dark en­ergy — an un­ex­plained force thought re­spon­si­ble for ac­cel­er­at­ing the ex­pan­sion of the uni­verse.

In­stead of the sin­gle “cos­mo­log­i­cal con­stant” sug­gested by Al­bert Ein­stein, there could be sev­eral dif­fer­ent forms of dark en­ergy, said Kui­jken.

“Another ex­cit­ing pos­si­bil­ity is that this is a sign that the laws of grav­ity on the scale of the uni­verse are dif­fer­ent from gen­eral rel­a­tiv­ity” — Ein­stein’s grav­ity the­ory which un­der­pins much of physics to­day.

The Planck satel­lite found that “nor­mal mat­ter” — which makes up hu­mans, plan­ets, stars and gal­ax­ies — com­prises 4.9 per­cent of the uni­verse.

Dark mat­ter makes up sig­nif­i­cantly more than thought — 26.8 per­cent of the uni­verse in to­tal. Dark en­ergy ac­counts for the rest at 68.3 per­cent.

Another ex­cit­ing pos­si­bil­ity is that this is a sign that the laws of grav­ity on the scale of the uni­verse are dif­fer­ent from gen­eral rel­a­tiv­ity.” Kon­rad Kui­jken, of the Lei­den Ob­ser­va­tory in the Nether­lands

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