FRED AN­SWERS YOUR QUES­TIONS

Australian Geographic - - Geo Buzz - If you have a space ques­tion for Fred, email it to ed­i­to­rial@aus­geo.com.au

If, as cur­rent thought dic­tates, the Uni­verse be­gan as a grape-sized ‘sin­gu­lar­ity’, where did the mat­ter and en­ergy for 2 tril­lion gal­ax­ies, each of 100 bil­lion stars, come from? Did the Uni­verse: cre­ate it­self as it ex­panded; sweep up mat­ter al­ready nearby; or was it all once squeezed into a grape-sized area? Doug Hurst, Chap­man, ACT The last al­ter­na­tive is what’s usu­ally ac­cepted. By def­i­ni­tion, space and time don’t ex­ist within a sin­gu­lar­ity that has in­fi­nite den­sity, mean­ing the en­ergy of the ini­tial sin­gu­lar­ity is un­known. Ob­ser­va­tions of the

Big Bang ‘flash’ (see this col­umn in AG 146) tell us the Uni­verse was ex­tremely hot and dense shortly af­ter form­ing. We can thus ex­trap­o­late back in time, pro­vid­ing the best ob­ser­va­tional ev­i­dence for the ini­tial sin­gu­lar­ity’s ex­treme en­ergy.

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