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Category: cosmology – Page 132

Theoretical physicists have a lot in common with lawyers. Both spend a lot of time looking for loopholes and inconsistencies in the rules that might be exploited somehow.

Valeri P. Frolov and Andrei Zelnikov from the University of Alberta in Canada and Pavel Krtouš from Charles University in Prague probably couldn’t get you out of a traffic fine, but they may have uncovered enough wiggle room in the laws of physics to send you back in time to make sure you didn’t speed through that school zone in the first place.

Shortcuts through spacetime known as wormholes aren’t recognized features of the cosmos. But for the better part of a century, scientists have wondered if the weft and warp instructed by relativity prescribe ways for quantum ripples – or even entire particles – to break free of their locality.

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Are back holes related to dark matter? Do the observations of black holes by LIGO hint at a signature of quantum gravity? Can we find evidence of black holes from a previous universe?

In 2019 second place in the Buchalter Cosmology Prize was awarded to two of the speakers you will see in this film which explores some of the above themes. We filmed this at the Loop Quantum Gravity Conference in 2019 and plan to make a follow up film exploring the latest ideas in the field.

Look out for the optical illusion around 8:12–8:25.

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Penn State researchers have recently characterized over a hundred blazars – far-off, dynamic galaxies hosting a central supermassive black hole.

A black hole is a place in space where the gravitational field is so strong that not even light can escape it. Astronomers classify black holes into three categories by size: miniature, stellar, and supermassive black holes. Miniature black holes could have a mass smaller than our Sun and supermassive black holes could have a mass equivalent to billions of our Sun.

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The Fine-Tuning Argument is often seen as the best argument for the existence of God. Here we have assembled some of the world’s top physicists and philosophers to offer a reply. Not every critic of the argument comes from the same perspective. Some doubt there is a problem to be solved whilst others agree it is a genuine problem but think there are better solutions than the God hypothesis. Some like the multiverse and anthropics other don’t. We have tried to represent these different approaches and so it should be taken as given, that not all of the talking heads agree with each other. Nevertheless, they all share the view that the fine-tuning argument for God does not work. Nor are all the objectors atheist, Hans Halvorson offers what we think is a strong theological objection to the argument. This film does not try to argue that God doesn’t exist only that the fine-tuning argument is not a good reason to believe in God. Most of the footage was filmed exclusively for this film with some clips being re-used from our Before the Big Bang series, which can be viewed here: https://www.youtube.com/watch?v=Ry_pILPr7B8&list=PLJ4zAUPI-q…4hnojoCR4m All of the critics of the fine tuning argument that appear were sent a draft of the film more than a month before release and asked for any objections either to their appearance, the narration or any other aspect of the film. No objections were raised, and many replies were extremely positive and encouraging. A timeline of the subjects covered is below:
(We define God as a perfect Omni immaterial mind as for example modern Christians and Muslims advocate, there are other conceptions of God which our video does not address).
Just to be clear, this is a polemical film arguing against the fine tuning argument.

Timecodes.

0:00 Introduction.

Continue reading “Physicists & Philosophers critique The Fine Tuning Argument” | >

Patreon: https://www.patreon.com/seanmcarroll.
Blog post with audio player, show notes, and transcript: https://www.preposterousuniverse.com/podcast/2022/06/06/200-…ultiverse/

The 200th episode of Mindscape! Thanks to everyone for sticking around for this long. To celebrate, a solo episode discussing a set of issues naturally arising at the intersection of philosophy and physics: how to think about probabilities and expectations in a multiverse. Here I am more about explaining the issues than offering correct answers, although I try to do a bit of that as well.

Mindscape Podcast playlist: https://www.youtube.com/playlist?list=PLrxfgDEc2NxY_fRExpDXr87tzRbPCaA5x.
Sean Carroll channel: https://www.youtube.com/c/seancarroll.

#podcast #ideas #science #philosophy #culture

Continue reading “Mindscape 200 | Solo: The Philosophy of the Multiverse” | >

But in black holes, where a lot of mass is crammed into a very small region of space, these worlds collide and there is no theoretical framework that unifies the two.

“We have a great understanding of both individually, but it turns out extremely hard to combine these two theories,” says Weinfurtner. “The idea is that we want to understand how quantum physics behaves, on what we call a curved space time geometry.”

In the new setup, the black hole is represented by a tiny vortex inside a bell jar of superfluid helium, cooled to-271C. At this temperature, helium begins to demonstrate quantum effects. Unlike water, which can spin at a continuous range of speeds, the helium vortex can only swirl at certain fixed values. Ripples sent across the surface of the helium, tracked with nanometre precision by lasers and a high-resolution camera, represent radiation approaching a black hole.

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Patreon: https://www.patreon.com/seanmcarroll.
Blog post with audio player, show notes, and transcript: https://www.preposterousuniverse.com/podcast/2023/05/15/236-…al-theory/

Is there a multiverse, and if so, how should we think of ourselves within it? In many modern cosmological models, the universe includes more than one realm, with possibly different laws of physics, and these realms may or may not include intelligent observers. There is a longstanding puzzle about how, in such a scenario, we should calculate what we, as presumably intelligent observers ourselves, should expect to see. Today’s guest, Thomas Hertog, is a physicist and longstanding collaborator of Stephen Hawking. They worked together (often with James Hartle) to address these questions, and the work is still ongoing.

Thomas Hertog received his Ph.D. in physics from Cambridge University. He is currently a professor of theoretical physics at KU Leuven. His new book is On the Origin of Time: Stephen Hawking’s Final Theory.

Mindscape Podcast playlist: https://www.youtube.com/playlist?list=PLrxfgDEc2NxY_fRExpDXr87tzRbPCaA5x.

Continue reading “Mindscape 236 | Thomas Hertog on Quantum Cosmology and Hawking’s Final Theory” | >

A trio of astrophysicists, two from Colgate University and the third from the University of Texas, has found evidence of dark stars courtesy of data from the James Webb Space Telescope. In their study, reported in Proceedings of the National Academy of Sciences, Cosmin Ilie, Jillian Paulin and Katherine Freese, analyzed three galaxies spotted by the JWST and how they might relate to dark stars.

Back in 2007, Freese, along with Douglas Spolyar and Paolo Gondolo, proposed the idea of a dark star —rather than nuclear fusion, these theorized dark stars are powered by dark matter. Since that time, researchers have continued to study the idea of such a star, built models to show what they might look like and derived a list of characteristics that such a star might have. In the current study, Ilie, Paulin and Freese have found three candidates in Webb data that fit the bill.

Dark stars, the team suggests, likely could have been born during the early days of the universe—like other stars, they would have been made mostly of helium and hydrogen. But they would also contain dark matter—enough to provide a heat source. Such stars would not then be lit by nuclear fusion. If such stars did exist, they would be much larger than other types of stars that have been observed—so large that they might look like galaxies from Earth-based telescopes.

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Our universe could be twice as old as current estimates, according to a new study that challenges the dominant cosmological model and sheds new light on the so-called “impossible early galaxy problem.”

“Our newly-devised model stretches the galaxy formation time by a several billion years, making the universe 26.7 billion years old, and not 13.7 as previously estimated,” says author Rajendra Gupta, adjunct professor of physics in the Faculty of Science at the University of Ottawa.

For years, astronomers and physicists have calculated the age of our universe by measuring the time elapsed since the Big Bang and by studying the oldest stars based on the redshift of light coming from distant galaxies. In 2021, thanks to new techniques and advances in technology, the age of our universe was thus estimated at 13.797 billion years using the Lambda-CDM concordance model.

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