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The physics of accretion: How the universe pulled itself together

To form a celestial object, start with a gas cloud and add gravity. Then, it gets complicated.


Accretion is one of the most fundamental processes in the cosmos. It is a universal phenomenon triggered by gravity, and the process by which bits of matter accumulate and coalesce with more bits of matter. It works inexorably on all scales to attract and affix smaller things to bigger things, from the tiniest dust grains to supermassive black holes.

Accretion creates everything there is: galaxies, stars, planets, and eventually, us. It is the reason the universe is filled with a whole bunch of somethings instead of a whole lot of nothing.

The fact that matter tends to glom together may seem intuitive. But to scientists, accretion remains a mysterious topic, filled with unanswered questions.

Weird Energy Beam Just Left A Galaxy Travelling At Five Times the Speed of Light And Hubble Caught It

Science, Technology, Health, Physics, Chemistry stay Updated.


Scientists from The Australian National University (ANU) and James Cook University (JCU) have identified an “exquisite” natural mechanism that helps plants limit their water loss with little effect on carbon dioxide (CO2) intake—an essential process for photosynthesis, plant growth and crop yield.

Artificial intelligence discovers new physics variables!

Analysing pendulum videos, the artificial intelligence tool identified variables not present in current mathematics.


An artificial intelligence tool has examined physical systems and not surprisingly, found new ways of describing what it found.

How do we make sense of the universe? There’s no manual. There’s no prescription.

At its most basic, physics helps us understand the relationships between “observable” variables – these are things we can measure. Velocity, energy, mass, position, angles, temperature, charge. Some variables like acceleration can be reduced to more fundamental variables. These are all variables in physics which shape our understanding of the world.

The Fermi Paradox Revisited and Resolved?

In February 2020, four distinguished astrophysicists — Jonathan Carroll-Nellenback, Adam Frank, Jason Wright, Caleb Scharf suggested that Earth may have remained unvisited by space-faring civilizations all the while existing in a galaxy of interstellar civilizations seeded by moving stars that spread alien life, offering a solution to the perplexing Fermi paradox. They concluded that a planet-hopping civilization could populate the Milky Way in as little as 650,000 years.

“It’s possible that the Milky Way is partially settled, or intermittently so; maybe explorers visited us in the past, but we don’t remember, and they died out,” says Jonathan Carroll-Nellenback, an astronomer at the University of Rochester and his collaborators in a 2019 study that suggests it wouldn’t take as long as thought for a space-faring civilization to planet-hop across the galaxy, because the orbits of stars can help distribute life, offering a new solution to the Fermi paradox. “The solar system may well be amid other settled systems; it’s just been unvisited for millions of years.”

How blue-sky research shapes the future

While driven by the desire to pursue curiosity, fundamental investigations are the crucial first step to innovation.


When scientists announced their discovery of gravitational waves in 2016, it made headlines all over the world. The existence of these invisible ripples in space-time had finally been confirmed.

It was a momentous feat in basic research, the curiosity-driven search for fundamental knowledge about the universe and the elements within it. Basic (or “blue-sky”) research is distinct from applied research, which is targeted toward developing or advancing technologies to solve a specific problem or to create a new product.

But the two are deeply connected.

MIT scientists create color-shifting films inspired by 19th-century holography

Potential applications include pressure-monitoring bandages, shade-shifting fabrics.


The bright iridescent colors in butterfly wings or beetle shells don’t come from any pigment molecules but from how the wings are structured—a naturally occurring example of what physicists call photonic crystals. Scientists can make their own structural colored materials in the lab, but it can be challenging to scale up the process for commercial applications without sacrificing optical precision.

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