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A universe that continually expands has long been the dominant cosmological framework. But a universe that undergoes cycles of expansion and contraction, perhaps for all time, has recently been analyzed mathematically, and its proponents claim that it provides a more convincing cosmological paradigm. Join leaders of this renegade approach as they make the case for a new kind of cosmology that reimagines time.

The Big Ideas Series is supported in part by the John Templeton Foundation.

Participants:
Peter Galison.
Anna Ijjas.
Paul Steinhardt.

Moderator:

SN 1,006, a supernova observed over a millennium ago, has been extensively studied using NASA ’s Chandra and IXPE telescopes, revealing critical details about its magnetic field and particle acceleration, contributing to our understanding of cosmic rays.

When the object now called SN 1,006 first appeared on May 1, 1006 A.D., it was far brighter than Venus and visible during the daytime for weeks. Astronomers in China, Japan, Europe, and the Arab world all documented this spectacular sight, which was later understood to have been a supernova. With the advent of the Space Age in the 1960s, scientists were able to launch instruments and detectors above Earth’s atmosphere to observe the Universe in wavelengths that are blocked from the ground, including X-rays. The remains of SN 1,006 was one of the faintest X-ray sources detected by the first generation of X-ray satellites.

Recent observations with nasa’s x-ray telescopes.

In 2022, scientists from Northwestern University presented novel observational data indicating that long gamma-ray bursts (GRBs) might originate from the collision of a neutron star with another dense celestial body, such as another neutron star or a black hole — a finding that was previously believed to be impossible.

Now, another Northwestern team offers a potential explanation for what generated the unprecedented and incredibly luminous burst of light.

After developing the first numerical simulation that follows the jet evolution in a black hole — neutron star merger out to large distances, the astrophysicists discovered that the post-merger black hole can launch jets of material from the swallowed neutron star.

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Observing these types of stars is rare; only one was previously identified. Now, researchers have found a whole population of these stars in the Large and Small Magellanic Clouds, relatively nearby satellite galaxies of the Milky Way. The finding may give insight into hot helium stars, which are thought to be the start of neutron star mergers and hydrogen-poor core-collapse supernovae. The study was published this month in Science.

“Our work sheds light on these fascinating relationships, revealing a universe that is far more interconnected and active than we previously imagined,” says Bethany Ludwig, a PhD candidate at the University of Toronto and coauthor of the study, in a press release. “Just as humans are social beings, stars too, especially the massive ones, are rarely alone.”

In 2015, the LIGO/Virgo experiment, a large-scale research effort based at two observatories in the United States, led to the first direct observation of gravitational waves. This important milestone has since prompted physicists worldwide to devise new theoretical descriptions for the dynamics of blackholes, building on the data collected by the LIGO/Virgo collaboration.

Researchers at Uppsala University, University of Oxford, and Université de Mons recently set out to explain the dynamics of Kerr black holes, theoretically predicted black holes that rotate at a constant rate, using theory of massive high-spin particles. Their paper, published in Physical Review Letters, specifically proposes that the dynamics of these rotating black holes is constrained by the principle of gauge symmetry, which suggests that some changes of parameters of a physical system would have no measurable effect.

“We pursued a connection between rotating Kerr black holes and massive higher-spin particles,” Henrik Johansson, co-author of the paper, told Phys.org. “In other words, we modeled the black hole as a spinning fundamental particle, similar to how the electron is treated in .”

An international team of astronomers has employed a set of space telescopes to observe a peculiar nuclear transient known as AT 2019avd. Results of the observational campaign, presented in a paper published December 21 on the pre-print server arXiv, deliver important insights into the properties and behavior of this transient.

Nuclear astrophysics is key to understanding supernova explosions, and in particular the synthesis of the chemical elements that evolved after the Big Bang. Therefore, detecting and investigating nuclear transient events could be essential in order to advance our knowledge in this field.

At a redshift of 0.028, AT 2019avd is a peculiar nuclear transient discovered by the Zwicky Transient Facility (ZTF) in 2009. The transient has been detected in various wavelengths, from radio to soft X-rays, and has recently exhibited two continuous flaring episodes with different profiles, spanning over two years.

Did you know that Einstein’s most important equation isn’t E=mc^2? Find out all about his equation that expresses how spacetime curves, with Sean Carroll.

Buy Sean’s book here: https://geni.us/AIAOUHn.
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This lecture was recorded at the Ri on Monday 14 August 2023.

When the theoretical physicist Leonard Susskind encountered a head-scratching paradox about black holes, he turned to an unexpected place: computer science. In nature, most self-contained systems eventually reach thermodynamic equilibrium… but not black holes. The interior volume of a black hole appears to forever expand without limit. But why? Susskind had a suspicion that a concept called computational complexity, which underpins everything from cryptography to quantum computing to the blockchain and AI, might provide an explanation.

He and his colleagues believe that the complexity of quantum entanglement continues to evolve inside a black hole long past the point of what’s called “heat death.” Now Susskind and his collaborator, Adam Brown, have used this insight to propose a new law of physics: the second law of quantum complexity, a quantum analogue of the second law of thermodynamics.

Also appearing in the video: Xie Chen of CalTech, Adam Bouland of Stanford and Umesh Vazirani of UC Berkeley.

00:00 Intro to a second law of quantum complexity.