According to a theorist from Duke University, the reason objects in the universe come in various sizes has to do with the process of how paint cracks after it dries.
In a study published in the Journal of Applied Physics, Adrian Bejan and R.W. Wagstaff explained that the universe known today was shaped by the need to release tension from the inside. While it is vast and spread out, the early universe had a finite number of suspended particles. When all these particles exert gravitational force on everything else, internal tension was created.
According to Bejan, the easiest way to explain the process is to think of paint drying. Paint shrinks as it dries, building tension all over the entire system. And then suddenly, it cracks, relieving built-up tension. The resulting release follows a hierarchical design, which means some large, and then many small structures are formed.
This relief pattern follows what is called constructal law, which states that any kind of flowing system allowed to freely change over time will experience a tendency toward easier flowing architectures. In the case of a young universe - with particles pulling at it in every direction - internal tension had to be released in the quickest way possible.
Using simple physics equations and thought experiments, Bejan and Wagstaff showed that the fastest means possible for tension relief is by forming bodies hierarchically. Had all celestial bodies formed at the same size, the universe would not have been able to release internal tension as effectively as when some large bodies had formed alongside smaller other ones.
Much like what you see in paint cracking.
Bejan added that all volumetric cracking is hierarchical, so no cracks will ever be uniform. There's an old idea in celestial mechanics that says bodies combine and grow because of gravity.
"Growth is one thing, but growing hierarchically rather than all in the same size is another, which is called nature."
The study was supported by the National Science Foundation.
Photo: Curran Kelleher | Flickr