The Heisenberg Limit at Cosmological Scales

International audienceFor an observation time equal to the universe age, the Heisenberg principle fixes the value of the smallest measurable mass at mH=1.35 ×10-69 kg and prevents to probe the masslessness for any particle using a balance. The corresponding reduced Compton length to mH is [inline-graphic not available: see fulltext], and represents the length limit beyond which masslessness cannot be proved using a metre ruler. In turns, [inline-graphic not available: see fulltext] is equated to the luminosity distance dH which corresponds to a red shift zH. When using the Concordance-Model parameters, we get dH=8.4 Gpc and zH=1.3 . Remarkably, dH falls quite short to the radius of the observable universe. According to this result, tensions in cosmological parameters could be nothing else but due to comparing data inside and beyond zH. Finally, in terms of quantum quantities, the expansion constant H0 reveals to be one order of magnitude above the smallest measurable energy, divided by the Planck constant