Theoretical physicists in the US have discovered a “speed limit” on the time taken for quantum information to spread through larger systems. Publishing their results in Physical Review Letters, Amit Vikram and colleagues at the University of Maryland have proved for the first time that this minimum time is closely linked with a system’s entropy and temperature, perhaps paving the way for a deeper understanding of quantum information across a wide range of physical settings.
In 1974, Stephen Hawking proposed for the first time that black holes aren’t entirely black. As well as emitting thermal radiation (now known as “Hawking radiation”), they also exhibit thermodynamic properties including temperature and an entropy proportional to their surface area.
Since entropy is a measure of the information carried by a system, this means a black hole’s surface effectively stores a finite number of “qubits”: the quantum equivalent of classical bits, each capable of storing quantum information as a superposition of two states simultaneously. In this way, the black hole’s temperature as described by Hawking governs how these qubits interact and evolve over time.
“General relativity works extraordinarily well in many settings, but when we run it back to the Big Bang, and apply it to the inside of black holes, it predicts a singularity: a moment where density, curvature and temperature formally become infinite. That is usually a sign that the theory is being pushed beyond where it can be trusted,” Afshordi told Space.com. “In other words, general relativity is likely incomplete for describing the very first moments of the universe, when quantum effects should also matter.”
Afshordi explained that in the standard picture of the Big Bang, scientists usually start with Einstein’s theory of gravity, then add extra ingredients to explain the earliest moments of the universe, most notably a hypothetical “inflation field” to account for the initial rapid expansion of the cosmos.”
In this Presidential Lecture, Netta Engelhardt will (metaphorically!) dive straight into the black hole interior to explain the origin of this puzzle and its significance in modern physics. The lecture will then turn to the recent revolution in physicists’ understanding of the black hole information paradox and the current state of the resolution. She will conclude with a discussion of where these new insights may lead, what questions remain outstanding and how this may all fit into the universe at large.
It’s a longstanding pain point for physicists: Their theory of gravity, general relativity, predicts that a black hole must contain a singularity, a point where space and time are infinitely warped and the laws of physics break down.
Many researchers hope that a theory combining gravity and quantum mechanics—if it can ever be discovered—will someday remove the thorn. However, a full-fledged theory of quantum gravity may not be necessary, two theorists argue independently.
A pinch of quantum mechanics—in the form of an effect called Hawking radiation—may suffice, enabling a black hole to form, age, and evaporate without creating a singularity.
Hawking’s signature prediction may prevent vexing singularities from forming.
In the chaotic first moments after the Big Bang, ripples in spacetime may have done more than just echo through the cosmos—they could have helped create dark matter itself. New research suggests that faint, ancient gravitational waves might have transformed into particles that eventually became the invisible substance shaping galaxies today.
A scientist from Tokyo Metropolitan University has proposed using safety monitoring at synchrotron facilities to study the properties of dark photons, hypothetical particles proposed to explain dark matter. Calculations show that the X-ray source at these sites and a Geiger-Muller counter behind safety shielding could be used to propose limits on how strongly dark photons interact with normal photons. The experiment would not involve a dedicated facility and could run alongside other experiments.
Experimental particle physics is often a world of enormous collaborations, multinational funding, and dedicated sites and facilities, yielding groundbreaking triumphs such as the discovery of the Higgs boson.
The community has now turned its attention to the hunt for dark matter, some of which might account for the “missing” portion of mass in the known universe eluding detection by conventional means.
The detection and study of isotopes, atoms of the same element that have different numbers of neutrons, could expand the scope of physics research and enable new scientific discoveries. So far, rare isotopes have been primarily detected using a technique known as accelerator mass spectrometry (AMS), which accelerates atoms, to then measure their mass and charge.
Despite its widespread use, AMS is not always precise at the ultra-rare level, as it is susceptible to what is known as background interference. This essentially means that similar atoms or neighboring isotopes can produce misleading signals that reduce the accuracy and precision of measurements.
Researchers at the University of Science and Technology of China and the Chinese Academy of Sciences recently developed a new technique for detecting and counting individual atoms called Atom Trap Trace Analysis (ATTA).
Ultra-faint dwarf galaxies—tiny satellite galaxies orbiting the Milky Way—have long been seen as cosmic fossils. Now, a new study published today in Monthly Notices of the Royal Astronomical Society uses an unprecedented set of simulations to show just how powerfully these faint systems can reflect the conditions of the early universe and tell us why some galaxies grew and others did not.
They could also reveal what the universe’s earliest “climate” was like—for example, the level of radiation and how this impacted whether and where stars formed.
Dwarf galaxies are often described as small cousins of the Milky Way. They form in small dark matter halos which are predicted by the standard model of cosmology. The faintest examples of such systems are extreme in both size and fragility, and lie on the boundary of our knowledge about galaxy formation and dark matter.
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REFERENCES How black holes may be responsible for Dark Energy • How BLACK HOLES May be Responsible for DAR… Is Dark Energy made of particles? • Is Dark ENERGY made of PARTICLES? The Quin… What is Dark Energy made of? • What is Dark Energy made of? Quintessence?… CHAPTERS 0:00 The 70% mystery 0:58 How Dark Energy was discovered? 4:26 What could be causing Dark Energy? 6:58 Repulsive Gravity? 10:16 What is the energy made of? 11:56 Evolving Dark energy? Quintesssence 14:18 Could Dark Energy be a particle? 16:43 Could Black Holes cause Dark Energy? SUMMARY Dark energy is one of the greatest mysteries in modern physics. It appears to make up nearly 70% of the universe, yet scientists still do not know what it is. Unlike matter, it does not clump together. Unlike radiation, it does not dilute as space expands. Instead, it causes the expansion of the universe to accelerate, pushing galaxies apart faster over time. The discovery of this acceleration came in the late 1990s when astronomers measured distant Type Ia supernovae, which act as reliable “standard candles.” By comparing their brightness and redshift, researchers could determine how fast the universe expanded at different points in cosmic history. Instead of finding that gravity slowed expansion—as expected—they discovered the opposite: the universe was expanding faster and faster. This unexpected result led to the concept of dark energy, the unknown driver behind cosmic acceleration. One possible explanation is that dark energy is a cosmological constant, represented by the Greek letter lambda in Einstein’s equations. In this model, empty space itself contains a constant energy density known as vacuum energy. Quantum mechanics predicts that empty space is not truly empty; quantum fields constantly fluctuate, producing short-lived “virtual particles.” These fluctuations create energy even in a vacuum. Experiments like the Casimir effect provide evidence that vacuum energy is real. However, this explanation has a major problem. When physicists calculate vacuum energy using quantum theory, the predicted value is about 10¹²⁰ times larger than what observations of the universe allow. This enormous mismatch is widely considered the worst prediction in physics. In general relativity, cosmic acceleration can occur if the universe contains energy with negative pressure. In the Friedmann equation, expansion accelerates when pressure is sufficiently negative relative to energy density. Dark energy appears to have exactly this property, effectively producing a form of repulsive gravity that stretches spacetime. Another possibility is that dark energy is not constant but comes from a dynamic field known as quintessence. In quantum theory, fields can have particle-like excitations, meaning dark energy might correspond to extremely weakly interacting particles. If the strength of this field changes over time, the acceleration of the universe could grow stronger. In extreme scenarios, this could eventually lead to a catastrophic future known as the Big Rip, where galaxies, stars, atoms, and even spacetime itself are torn apart. A more speculative idea suggests a connection between supermassive black holes and dark energy. Some recent studies have observed that black holes appear to grow more massive over billions of years than expected from normal matter accretion alone. Researchers have proposed that black holes might somehow be linked to dark energy, though current evidence only shows a correlation and not a confirmed causal explanation. #darkenergy For now, dark energy remains an observed phenomenon with multiple possible explanations. Whether it is a property of empty space, a new field of physics, or something even deeper, it stands as one of the most profound open questions in cosmology.
CHAPTERS 0:00 The 70% mystery 0:58 How Dark Energy was discovered? 4:26 What could be causing Dark Energy? 6:58 Repulsive Gravity? 10:16 What is the energy made of? 11:56 Evolving Dark energy? Quintesssence 14:18 Could Dark Energy be a particle? 16:43 Could Black Holes cause Dark Energy?
SUMMARY Dark energy is one of the greatest mysteries in modern physics. It appears to make up nearly 70% of the universe, yet scientists still do not know what it is. Unlike matter, it does not clump together. Unlike radiation, it does not dilute as space expands. Instead, it causes the expansion of the universe to accelerate, pushing galaxies apart faster over time.
The discovery of this acceleration came in the late 1990s when astronomers measured distant Type Ia supernovae, which act as reliable “standard candles.” By comparing their brightness and redshift, researchers could determine how fast the universe expanded at different points in cosmic history. Instead of finding that gravity slowed expansion—as expected—they discovered the opposite: the universe was expanding faster and faster. This unexpected result led to the concept of dark energy, the unknown driver behind cosmic acceleration.
One possible explanation is that dark energy is a cosmological constant, represented by the Greek letter lambda in Einstein’s equations. In this model, empty space itself contains a constant energy density known as vacuum energy. Quantum mechanics predicts that empty space is not truly empty; quantum fields constantly fluctuate, producing short-lived “virtual particles.” These fluctuations create energy even in a vacuum. Experiments like the Casimir effect provide evidence that vacuum energy is real.
