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Category: cosmology

How do you study something you can never step outside of?

Studying the thing you can never step outside of and look back at is the fundamental problem facing every cosmologist who has ever looked up at the night sky. The Universe is not a laboratory you can peer into from above, it’s the thing you are already inside. The only way to truly test your ideas about how it works is to build a copy of it, run the clock forward from the Big Bang, and see if what emerges matches what your telescopes are actually telling you.

That is exactly what the FLAMINGO project has been doing. And this week, its creators made the results available to the entire world.

An international team of astrophysicists, led by researchers at Leiden University in the Netherlands, has released one of the largest cosmological simulation datasets ever produced. The archive contains more than 2.5 petabytes of data (roughly equivalent to half a million high definition films) and is free to access for researchers anywhere on the planet.

Is Our Model of Dark Energy WRONG? | New 4.2σ Results

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The biggest news in cosmology in recent years is that the mysterious universe-accelerating entity we call dark energy may be fading away. The evidence for this is now strong enough that enormous effort is going into confirming this result. So what’s it going to take, and when are we going to know?

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Are Cosmic Strings Cracks in the Universe?

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Reality has cracks in it. Universe-spanning filaments of ancient Big Bang energy, formed from topological defects in the quantum fields, aka cosmic strings. They have subatomic thickness but prodigious mass and they lash through space at a close to the speed of light. They could be the most bizarre undiscovered entities that actually exist.

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Topological Origin of Cosmological Constant ( Dark Energy)

Shape of the universe and Cosmological Constant.

🚨 The Biggest Problem in Physics (Cosmological Constant) https://lnkd.in/gt7tEpJw ❓ Problem: Why is the Universe accelerating… and why is the value so unbelievably small? Observations (supernovae, CMB, BAO) show: 👉 The expansion is accelerating 👉 This requires a cosmological constant Λ From Einstein’s equation: Λ = 8πG ρ_Λ 😳 But here’s the crisis: Quantum physics predicts vacuum energy: ρ_vac ≈ M_Pl⁴ But observations give: ρ_Λ ≈ 10⁻¹²⁰ M_Pl⁴ 💥 That’s a mismatch of 120 orders of magnitude This is called the cosmological constant problem 🧠 Standard thinking fails because: We assume: 👉 Energy fills space uniformly 👉 Λ comes from summing quantum fluctuations ρ_vac = (1/V) Σ (½ ℏωₖ) But this diverges → way too large ❌ 💡 A different perspective (EWOG insight): Instead of asking: 👉 “What is the energy of empty space?” Ask: 👉 “What is the geometry of the Universe?

Physicists reveal universal speed limit on quantum information scrambling

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.

What is quantum gravity? Scientists think it could explain the beginning of our universe

“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.”

Netta Engelhardt: Puzzles in the Black Hole Interior: Past, Present and Future (April 22, 2026)

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.

Bizarre Hawking radiation may smooth the jagged hearts of black holes

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.

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