Imagine observing a clear glass pot of milk boiling — a common everyday process. Interestingly, this simple phenomenon can serve as an analogy to some of the most fundamental processes in cosmology. Researchers study such behaviors to gain insights into the early universe’s rapid expansion and structure formation.
Figure 1. The void-dominated structure in the milk bubbles and cosmic simulation.
When milk is heated, bubbles form, foam rises, and eventually, the liquid overflows. This process can be viewed as a metaphor for cosmic inflation, a theory proposing that in the first fractions of a second after the Big Bang, space underwent exponential expansion at a rate faster than the speed of light. This rapid expansion smoothed out initial irregularities and set the stage for the large-scale structure of the universe.
Why Does Milk Overflow But Water Does Not?
The physical properties of different substances influence their boiling behavior. Milk contains proteins and fats that lower surface tension and form large, unstable bubbles that burst quickly, leading to overflow. In contrast, water’s higher surface tension results in smaller, more stable bubbles that prevent sudden spillovers. These differences in fluid dynamics have cosmological implications, helping researchers understand how different fields and matter distributions affected the universe’s evolution. Inspired by the surface tension observed in milk bubbles, our paper, “Surface Tension of Cosmic Voids as a Possible Source of Dark Energy,” employed heuristic calculations to estimate the cosmological constant and dark energy.
Researchers posit that early universe fluctuations—analogous to foam in boiling milk—were seed perturbations. Small quantum fluctuations in the density of matter and energy were amplified during inflation, eventually leading to the formation of galaxies and cosmic filaments observed today. Understanding these initial irregularities is key to understanding structure formation on the largest scales.
Studying everyday fluid behaviors offers models for understanding dark energy and the influence of large-scale voids—vast empty regions in space—on cosmic expansion. Just as bubbles influence the behavior of boiling liquids, the distribution and properties of space’s large-scale structures could impact the accelerated expansion of the universe.
Next time you observe boiling milk, consider the profound physical processes at play. These simple phenomena serve as valuable models for understanding the universe’s earliest moments and its long-term evolution, advancing our comprehension of fundamental cosmology.