The physics of the universe
The collapsing stars Eddington swore couldn't exist turned out to be everywhere, and half a century later the world handed Chandrasekhar his Nobel. How the 1.4 solar mass limit became one of the most important numbers in modern astronomy.
Driven from Europe by the feud, Chandrasekhar rebuilt his life in America and turned mastery-and-move-on into an art form. On his conviction that beautiful physics is true physics, and the two students he drove through blizzards to teach.
In 1935 the most eminent astronomer alive stood up in a packed room and called Chandrasekhar's discovery "stellar buffoonery." The story of Arthur Eddington's years-long campaign against a result that everyone privately knew was correct.
The story of Subrahmanyan Chandrasekhar, who as a teenager on an ocean voyage worked out that white dwarf stars have a maximum mass of 1.4 Suns. A tour of degeneracy pressure, the relativistic insight everyone else missed, and the number that would define his life.
An accelerating observer finds their empty vacuum glowing with real particles, a bizarre effect called Unruh radiation. It's a cousin to Hawking radiation, but with no black hole required, just a rocket and its throttle.
Constant acceleration builds a horizon out of nothing but motion, walling off part of the universe forever. Meet Wolfgang Rindler, the coffee date you'll never reach, and the light that can chase you for infinite time without ever catching up.
Move fast enough and the entire universe compresses into a searing, blueshifted cone of light aimed at your face. How relativistic aberration and the Doppler effect warp your view of the cosmos as you approach lightspeed.
You can't ride alongside a beam of light, and the reason why opens a door onto the strangest parts of relativity. A tour of rest frames, why a photon has no point of view, and how your speed reshapes reality itself.
Researchers at the Advanced Science Research Center at the CUNY Graduate Center have demonstrated a new approach to wave amplification through interaction with rotating bodies. Rather than mechanically rotating matter, however, the team engineered a radio-frequency device with properties modulated in space and time to mimic spinning.
Europe's CERN physics research center bids 'Farewell' to the Large Hadron Collider, but it's actually more like 'See You Later, Accelerator!' The new, improved High-Luminosity LHC is due to make its debut in 2030.
Switch off fusion and, for ten thousand years, nothing happens. Then the Sun begins a slow, strange death: shrinking, briefly brightening, and coasting on gravitational heat for tens of millions of years. And the neutrinos give the whole thing away in just eight minutes.
A photon born in the Sun's core takes around 100,000 years to fight its way to the surface, bouncing through a random walk so inefficient that the light on your face is older than human civilization. Why the Sun's surface is a hundred-millennia-delayed broadcast.
How can the Sun keep shining with its furnace switched off? Two nineteenth-century aristocrats, Helmholtz and Lord Kelvin, worked out the answer mostly by accident. It comes down to stored heat, gravitational shrinking, and the strange self-regulating thermostat of hydrostatic equilibrium.
If the Sun's fusion shut off right now, you would not notice for a very long time. The first stop is understanding the Sun itself: a vast pile of gravitating matter where fusion is so absurdly inefficient that, pound for pound, a compost heap beats it.
The ekpyrotic universe is a beautiful idea that runs headlong into the data. From hand-waved singularities and assumed dark energy to the killer blow from Planck and WMAP measurements of the cosmic microwave background, here is why nature has so far voted against it.
The ekpyrotic theory tries to beat inflation with bouncing higher-dimensional branes, no singularity, and a universe that has always existed. A tour of the prettiest version of the idea and how it claims to handle flatness, dark energy, and the entropy that doomed earlier cyclic models.
An international team led by astronomers at the University of Sydney has uncovered the clearest evidence yet for the origin of an unusual class of cosmic signals. In doing so, they have identified a rare stellar system that is providing scientists with a natural laboratory to study extreme physics.
Inflation is awkward, possibly not even a proper theory, and it has reigned over cosmology for forty years anyway. Here is what it claims, the flatness, horizon, and monopole problems it solves, the structure-formation prediction it nailed, and the deep problems it still cannot escape.
A look at why a cyclic, eternally repeating universe is such an appealing idea, and why the first serious attempt to build one, Richard Tolman's 1930s model of endless big bangs and big crunches, collapsed under the weight of entropy. The Big Bang keeps demanding a beginning.
The LIGO–Virgo–KAGRA (LVK) detector network has a new trick up its sleeve to improve the instruments’ sensitivity to gravitational waves: it’s called Astrophysical Calibration and it plays a role similar to auto-tune in music production.
Universe Today