Dark bubble and microcosm: gravity at millionths of a meter express
The Universe behaves like a soap bubble swelling in a multidimensional foam. The dark bubble model explains why it's expanding ever faster: the spacetime bubble grows, and its membrane gains a tiny thickness — about a micron, like a bacterium. At such distances, gravity 'blurs' across this thickness and weakens.
We can test this by measuring the attraction between microscopic particles. At a distance of a micron, the force would be a couple of percent weaker than Newton's textbook law predicts. This weakening is inextricably linked to the accelerated expansion of the cosmos — both are manifestations of the same phenomenon. The model also points to a slight curvature of space, which astronomers hope to detect.
Original abstract
as written by the authors arXiv:2606.20942
The dark bubble model explains the existence of a positive cosmological constant by making explicit use of the instabilities underlying the de Sitter swampland conjectures to make the accelerated expansion of the universe inevitable. A distinctive consequence of the construction is a unique hierarchy connecting cosmological, gravitational, string, and higher-dimensional scales. In particular, the model naturally predicts the existence of a dark dimension of micron size, an idea that has been argued for on independent grounds in the literature. The same framework also predicts a weakening of gravity at distances of order the dark-dimension scale, leading to a fading of the gravitational force at micron distances. We argue that the dark bubble therefore provides a concrete realization of both the dark dimension proposal and Sundrum's fat graviton scenario, in which gravity effectively ceases to probe shorter distances. Additional predictions include a string scale of order tens of TeV and a measurable positive spatial curvature of the universe. We review these key aspects of the model, discuss their implications for gravity and cosmology, and highlight its key predictions.
A micron (one millionth of a meter) is the typical size of a bacterium. If such a dimension existed, it would literally be under our microscope.