Bonn 2020 – scientific programme

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AGPhil: Arbeitsgruppe Philosophie der Physik

AGPhil 2: Space, Time and Symmetry I

AGPhil 2.3: Talk

Tuesday, March 31, 2020, 12:00–12:30, H-HS IV

Measuring expansion of the universe — •Ari Belenkiy — SFU, Vancouver, Canada

Apart from the ongoing debate on who is the discoverer of the Expanding Universe, there is another debate as to whether the space around us is expanding. The debate originated as early as 1933 by G. C. McVittie and the conclusions are swinging since then. In 1973, Misner, Thorne and Wheeler suggested a standard picture for global expansion is that of a rubber balloon being gradually filled in with air. Asking whether atoms expand, whether the meter stick expand, whether the distance between sun and earth expand, Misner et al answer all three questions in negative: "Only distances between clusters of galaxies and greater distances are subject to the expansion. Only at this gigantic scale of averaging does the notion of homogeneity makes sense." This conclusion however left open the question about expansion on smaller scales where homogeneity is absent and Friedman solutions are not necessarily present. In 1998, Cooperstock, Faraoni and Vollick took a contrarian view, claiming that "effects of dark energy are observable not only globally, but also in local systems. These effects can be measured and are comparable with the present value of the Hubble constant." As a result of this uncertainty, as recently as 2008, John Peacock renewed the discussion asking similar questions: "Is the space in my bedroom expanding, and what would this mean? Do we expect the Earth to recede from the Sun as the space between them expands?" All these surprising and often counter-intuitive results ask for an experiment.