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Category: cosmology

We’ve misunderstood the physics of our universe | Sabine Hossenfelder, Ivette Fuentes, James Ladyman

Sabine Hossenfelder, Ivette Fuentes and James Ladyman discuss the scaling laws of the universe and the fundamental nature of reality.

Is the universe one thing, or many things?

With a free trial, you can watch the full debate NOW at https://iai.tv/video/the-one-and-the–… central question in ancient Greek philosophy was the problem of the One and the Many. It is a question that has echoed across Western culture and is still with us today. Should we see the world as a coherent whole or a multitude of separate parts? The puzzle is that we need both the whole and the parts, but an explanation of the relationship between them has proved problematic and perhaps unknowable. In contemporary physics, the parts are the teeming world of particle physics, and these should make up the cosmological world of the universe as a whole and the overall framework of Einsteinian space-time. But as yet we have not been able to combine the two coherently. Is looking at the universe from the small scale and the large always going to be incompatible? Does it mean a theory of everything is an illusion and the attempt to combine quantum mechanics and Einstein’s general relativity a forlorn project? Or is the parallel with the ancient Greek puzzle accidental and the current challenge one that might be overcome? #quantumphysics #universe #philosophy #fundamentalunits #theoryofeverything Sabine Hossenfelder is a theoretical physicist and acclaimed science communicator, known for her sharp critiques of the scientific mainstream. She is also a best-selling author and YouTuber. Ivette Fuentes is a theoretical quantum physicist at the University of Southampton and Emmy Fellow at the University of Oxford. James Ladyman is a philosopher of science at the University of Bristol. He is best known for his book Every Thing Must Go, calling for a metaphysics grounded in physics and complexity science. Hosted by Jack Symes. 00:40 James Ladyman on the different notions of scale 02:39 Sabine Hossenfelder on energy in the universe 05:19 Ivette Fuentes on unifying quantum mechanics and general relativity 09:00 Is the universe “One” or “Many”? 17:15 Particles are not fundamental The Institute of Art and Ideas features videos and articles from cutting edge thinkers discussing the ideas that are shaping the world, from metaphysics to string theory, technology to democracy, aesthetics to genetics. Subscribe today! https://iai.tv/subscribe?utm_source=Y… For debates and talks: https://iai.tv For articles: https://iai.tv/articles For courses: https://iai.tv/iai-academy/courses.

A central question in ancient Greek philosophy was the problem of the One and the Many. It is a question that has echoed across Western culture and is still with us today. Should we see the world as a coherent whole or a multitude of separate parts? The puzzle is that we need both the whole and the parts, but an explanation of the relationship between them has proved problematic and perhaps unknowable. In contemporary physics, the parts are the teeming world of particle physics, and these should make up the cosmological world of the universe as a whole and the overall framework of Einsteinian space-time. But as yet we have not been able to combine the two coherently.

Is looking at the universe from the small scale and the large always going to be incompatible? Does it mean a theory of everything is an illusion and the attempt to combine quantum mechanics and Einstein’s general relativity a forlorn project? Or is the parallel with the ancient Greek puzzle accidental and the current challenge one that might be overcome?

#quantumphysics #universe #philosophy #fundamentalunits #theoryofeverything.

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Heisenberg Made a Discovery in 1925. We Still Can’t Explain It

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2025 is … was the international year of quantum science and technology. Yes because quantum tech is increasingly important, but especially because quantum mechanics was invented 100 years ago this year. In 1925, our strangest true theory went from being a peculiar set of ideas to describe some funny results from experiments, to a full-blown theoretical framework that overturned how we think reality really works. So today, as the centenary year approaches its end I want to take you on a little journey through what may be the most paradigm-destroying several months in scientific history.

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What Happens When A Black Hole Dies and the End of the Universe

An exploration of the question of what happens when a back hole evaporates and ultimately what that means for the end of the universe, and what that end might be like.

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The Physicist Who Proved Entropy = Gravity

What if gravity is not fundamental but emerges from quantum entanglement? In this episode, physicist Ted Jacobson reveals how Einstein’s equations can be derived from thermodynamic principles of the quantum vacuum, reshaping our understanding of space, time, and gravity itself.

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Gravitational waves leave imprints on light emitted by atoms, theoretical study predicts

Gravitational waves are ripples in spacetime produced by violent cosmic events, such as the merging of black holes. So far, direct detections have relied on measuring tiny distance changes over kilometer-scale instruments. In a new theoretical study published in Physical Review Letters, researchers at Stockholm University, Nordita, and the University of Tübingen propose an unconventional approach: tracking how gravitational waves reshape the light emitted by atoms. The work describes a possible detection route, but an experimental demonstration remains for the future.

When atoms are excited, they naturally relax by emitting light at a characteristic frequency—a quantum process known as spontaneous emission. This happens through their interaction with the quantum electromagnetic field.

“Gravitational waves modulate the quantum field, which in turn affects spontaneous emission,” said Jerzy Paczos, a Ph.D. student at Stockholm University. “This modulation can shift the frequencies of emitted photons compared with the no-wave case.”

DESI maps C-19, an extremely metal-poor Milky Way stellar stream

Using the Mayall 4-meter telescope at Kitt Peak National Observatory, an international team of astronomers has observed C-19—an extremely metal-poor stellar stream in the Milky Way’s halo. Results of the observational campaign, published March 11 on the arXiv pre-print server, provide crucial insights into the properties of this stellar stream.

Stellar streams are remnants of dwarf galaxies or globular clusters (GCs) that once orbited a galaxy but have been disrupted and stretched out along their orbits by tidal forces of their hosts. Observations show that many stellar streams are elongated debris of tidally disrupted globular clusters.

Studies of galactic stellar streams could answer some crucial questions about the Milky Way. For instance, they could help us understand the large-scale mass distribution of the galactic dark matter halo. Moreover, the investigation of stellar streams could confirm whether or not our galaxy contains low-mass dark matter subhalos.

Inside the Gigantic Universe

Physicist Jim Al-Khalili explores the incomprehensible scale of the universe. A cosmic journey into the laws of gravity, relativity, and the formation of supergalaxies. Discover how the largest structures shape our understanding of the cosmos itself.

Director: Tim Usborne.
Writers: Jim Al-Khalili, Tim Usborne.
Stars: Prof. Jim Al-Khalili (Physicist, Presenter)
Genre: Science Documentary, Physics, Cosmology.
Country: United Kingdom.
Language: English Also Known As: Secrets of Size: Going Big (BBC)
Release Date: 2022
Filming Location: United Kingdom / Various International Locations.

Synopsis:

In this second episode of the fascinating series Secrets of Size, Professor Jim Al-Khalili takes us on a cosmic journey into the immensity, exploring the largest scale of the universe.

We leave behind the quantum realm to focus on the forces that govern the largest structures: gravity and relativity. Al-Khalili explains how these laws shape the existence of galaxies, galaxy clusters, and the immense supergalaxies.

The episode reveals the incomprehensible scale of the cosmos, where time and space are distorted, and how the study of these giants allows us to understand the origin, evolution, and perhaps the ultimate destiny of the universe itself.

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Quantum entanglement and the illusion of time, in 79 minutes

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Up next.
Brian Cox: The quantum roots of reality | Full Interview ► • Brian Cox: The quantum roots of reality |…

Time feels obvious, but physics tells a stranger story about its existence: Theoretical physicist Jim Al-Khalili explores why our sense of time may be incredibly misleading, including the idea that past, present, and future might all exist at once.

0:00 Chapter 1: Does time flow?
2:42 Why Time Feels Faster as We Age.
3:56 Time and Change in Philosophy and Physics.
5:28 Einstein and the End of Absolute Time.
6:19 Time in the Equations of Physics.
7:50 Chapter 2: How do we reconcile quantum field theory with the general theory of relativity?
12:10 Evidence for Time Dilation: Muons.
14:29 Gravity Slows Time: General Relativity.
19:22 Space-Time and the Block Universe.
21:55 Does Time Really Exist?
26:33 The Debate: Eternalism vs Presentism.
34:12 Chapter 3: Is There a “Now”?
40:40 Chapter 4: Why Does Thermodynamics Have a Direction in Time?
49:38 Quantum Entanglement and the Direction of Time.
55:10 Did Time Begin at the Big Bang?
45:00 Will Time End?
1:05:40 Chapter 5: Is Time Travel Possible?

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Dark matter experiment reaches ultracold milestone

An international collaboration, including Northwestern University, has reached a critical milestone in the search for dark matter, the mysterious substance that makes up about 85% of all matter in the universe. Located two kilometers below ground in Canada, the Super Cryogenic Dark Matter Search (SuperCDMS) at SNOLAB has cooled to its operating temperature, the collaboration announced on March 17.

Just thousandths of a degree above absolute zero, the cryogenic experiment is about 100 times colder than the temperature of deep space. This extreme cold enables scientists to eliminate thermal noise from vibrating atoms, potentially isolating dark matter’s incredibly tiny signals.

With this milestone, the project transitions from building the experiment to preparing for the search. Researchers can now turn on the dark matter detectors, whose superconducting sensors only function when cooled to extremely low temperatures. If the equipment operates correctly, it should achieve the highest level of sensitivity yet for detecting low-mass particles, which have about half the mass of a single proton.

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