- based ▁g amma - ray ▁observations ▁from ▁the ▁Very ▁Ener get ic ▁Rad iation ▁Im aging ▁T eles cope ▁Array ▁( VER IT AS ) ▁show ▁that ▁spac etime ▁is ▁uniform ▁down ▁to ▁distances ▁ 1 0 0 0 ▁times ▁smaller ▁than ▁the ▁nucle us ▁of ▁a ▁hydro gen ▁atom . ▁ ▁Observ ations ▁of ▁radiation ▁from ▁nearby ▁qu as ars ▁by ▁F loyd ▁Ste cker ▁of ▁NASA ' s ▁God d ard ▁Space ▁Fl ight ▁Center ▁have ▁placed ▁strong ▁experimental ▁limits ▁on ▁the ▁possible ▁viol ations ▁of ▁Ein stein ' s ▁special ▁theory ▁of ▁relativ ity ▁imp lied ▁by ▁the ▁existence ▁of ▁quantum ▁fo am . ▁Thus ▁experimental ▁evidence ▁so ▁far ▁has ▁given ▁a ▁range ▁of ▁values ▁in ▁which ▁scient ists ▁can ▁test ▁for ▁quantum ▁fo am . ▁ ▁Random ▁diffusion ▁model ▁ ▁Ch andra ' s ▁X - ray ▁detection ▁of ▁qu as ars ▁at ▁distances ▁of ▁bill ions ▁of ▁light ▁years ▁rules ▁out ▁the ▁model ▁where ▁phot ons ▁diff use ▁randomly ▁through ▁spac etime ▁fo am , ▁similar ▁to ▁a ▁light ▁diff using ▁by ▁passing ▁through ▁the ▁fog . ▁ ▁H olog raph ic ▁model ▁ ▁Me asure ments ▁of ▁qu as ars ▁at ▁shorter , ▁g amma - ray ▁w avel ength s ▁with ▁F erm i , ▁and , ▁shorter ▁w avel ength s ▁with ▁V ER IT AS ▁rule ▁out ▁a ▁second ▁model , ▁called ▁a ▁h olog raph ic ▁model ▁with ▁less ▁diffusion . ▁ ▁Rel ation ▁to ▁other ▁theories ▁The ▁vac u um ▁fl