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On this day, April 25, in 1929, the world learned how astronomer Edwin Hubble had discovered that the universe was much larger than we had believed. On this day in 2025, you can preorder a book and on the 29th learn about this and four other Astrophysics discoveries that changed how we see the universe — and ourselves — in The Story of Astrophysics in Five Revolutions.

By Ersilia Vaudo, translated by Vanessa Di Stefano. If you use this link we get a penny or something.

He had published his seminal paper in the March issue of Astrophysical Journal but on April 25th in Proceedings of the National Academy of Sciences he published the how, and people began to think about what it meant. He had discovered that the collection of gas and dust we call Andromeda was actually another galaxy.

Criegee intermediates (CIs)—highly reactive species formed when ozone reacts with alkenes in the atmosphere—play a crucial role in generating hydroxyl radicals (the atmosphere’s “cleansing agents”) and aerosols that impact climate and air quality. The syn-CH3CHOO is particularly important among these intermediates, accounting for 25%–79% of all CIs depending on the season.

Until now, scientists have believed that syn-CH3CHOO primarily disappeared through self-decomposition. However, in a study published in Nature Chemistry, a team led by Profs. Yang Xueming, Zhang Donghui, Dong Wenrui and Fu Bina from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences has uncovered a surprising new pathway: syn-CH3CHOO’s reaction with is approximately 100 times faster than previously predicted by theoretical models.

Using advanced laser techniques, the researchers experimentally measured the reaction rate between syn-CH3CHOO and water vapor, and discovered the faster reaction time. To uncover the reason behind this acceleration, they constructed a high-accuracy full-dimensional (27D) potential energy surface using the fundamental invariant-neural network approach and performed full-dimensional dynamical calculations.

When Albert Einstein introduced his theory of general relativity in 1915, it changed the way we viewed the universe. His gravitational model showed how Newtonian gravity, which had dominated astronomy and physics for more than three centuries, was merely an approximation of a more subtle and elegant model.

Einstein showed us that gravity is not a mere force but is rather the foundation of cosmic structure. Gravity, Einstein said, defined the structure of space and time itself.

But in the past century, we have learned far more about the cosmos than even Einstein could have imagined. Some of our observations, such as gravitational lensing clearly confirm general relativity, but others seem to poke holes in the model. The rotational motion of galaxies doesn’t match the predictions of gravity alone, leading astronomers to introduce .

Scientists in Germany have crafted “skyrmion bags” of light—complex vortex-like structures—on the surface of gold by cleverly manipulating how laser beams interact with nano-etched patterns.

This unusual feat not only adds a surprising twist to the physics of light but also hints at future technologies that could break the limits of current microscopes.

Skyrmion light bags: a new breakthrough

An avalanche is caused by a chain reaction of events. A vibration or a change in terrain can have a cascading and devastating impact.

A similar process may happen when living tissues are subject to being pushed or pulled, according to new research published in Nature Communications, by Northeastern University doctoral student Anh Nguyen and supervised by Northeastern physics professor Max Bi.

As , Bi and Nguyen use and mathematics to understand the mechanical processes that organisms undergo on a cellular level. With this more recent work, they have observed that when subjected to sufficient stress, tissues can “suddenly and dramatically rearrange themselves,” similar to how avalanches are formed in the wild.

Found in everything from kitchen appliances to sustainable energy infrastructure, stainless steels are used extensively due to their excellent corrosion (rusting) resistance. They’re an important material in many industries, including manufacturing, transportation, oil and gas, nuclear power and chemical processing.

However, stainless steels can undergo a process called sensitization when subjected to a certain range of high temperatures—like during welding—and this substantially deteriorates their resistance. Left unchecked, corrosion can lead to cracking and structural failure.

“This is a major problem for stainless steels,” says Kumar Sridharan, a professor of nuclear engineering and engineering physics and materials science and engineering at the University of Wisconsin–Madison. “When gets corroded, components need to be replaced or remediated. This is an expensive process and causes extended downtime in industry.”