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Category: cosmology – Page 261

An international team of astronomers led by researchers from the Netherlands has found no trace of dark matter in the galaxy AGC 114,905, despite taking detailed measurements over a course of forty hours with state-of-the-art telescopes. They will present their findings in Monthly Notices of the Royal Astronomical Society.

When Pavel Mancera Piña (University of Groningen and ASTRON, the Netherlands) and his colleagues discovered six galaxies with little to no dark matter, they were told “measure again, you’ll see that there will be dark matter around your galaxy.” However, after forty hours of detailed observations using the Very Large Array (VLA) in New Mexico (United States), the evidence for a dark matter-free galaxy only became stronger.

The galaxy in question, AGC 114,905, is about 250 million light-years away. It is classified as an ultra-diffuse dwarf galaxy, with the name ‘dwarf galaxy’ referring to its luminosity and not to its size. The galaxy is about the size of our own Milky Way but contains a thousand times fewer stars. The prevailing idea is that all galaxies, and certainly ultra-diffuse dwarf galaxies, can only exist if they are held together by dark matter.

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If someone told you that the world’s biggest laser was in California that has something to do with space and national defence, you might imagine it was a super-weapon designed to blast enemy satellites out of the sky. But the reality is quite different. The new laser is a unique research tool for scientists, capable of creating the extreme conditions that exist inside stars and nuclear explosions.

The giant laser is located at the Lawrence Livermore National Laboratory (LLNL) in Livermore, California, and it goes by the rather cryptic name of the National Ignition Facility (NIF). That’s because, in the context of nuclear science, “ignition” has a very specific meaning according to the Lawrence Livermore National Laboratory. It refers to the point at which a fusion reaction becomes self-sustaining – a condition that is found inside the sun and other stars, but is extremely difficult to achieve in an earthbound laboratory. Triggering nuclear fusion requires enormously high temperatures and pressures, and that’s where NIF’s giant laser comes in.

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Theoretical physicist Sean Carroll joins us to discuss whether it make sense to think of consciousness as an emergent phenomenon, and whether contemporary physics points in this direction.

We discussed Sean’s essay responding to Philip’s book ‘Galileo’s Error,’ and Philip’s counter-response essay. Both are available here: https://conscienceandconsciousness.com/2021/08/01/19-essays-on-galileos-error/

We also discussed Philip’s Scientific American article making the case that the move from the fine-tuning to the multiverse commits the ‘inverse gambler’s fallacy’: https://www.scientificamerican.com/article/our-improbable-ex…20we%20are, with%20the%20existence%20of%20life.

Finally, Keith and Philip discussed the PhilPapers 2020 survey of philosophers’ opinions on philosophical questions, which is linked to from this blog post of Philip’s: https://conscienceandconsciousness.com/2021/11/01/materialis…only-just/

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Astronomers from the University of Texas have spotted a gigantic black hole at the heart of our galaxy’s many dwarf satellite galaxies — meaning that, in intergalactic terms, it’s just a stone’s throw away from our own Solar System.

The newly discovered black hole, dubbed Leo I, is roughly the same size as the suspected black hole at the center of the Milky Way.

It also appears to be a bit of an oddball. By measuring the gravitational pull it has on the stars surrounding it, the researchers found that it’s absolutely massive compared to the size of its host galaxy.

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Astronomers at The University of Texas at Austin’s McDonald Observatory have discovered an unusually massive black hole at the heart of one of the Milky Way ’s dwarf satellite galaxies, called Leo I. Almost as massive as the black hole in our own galaxy, the finding could redefine our understanding of how all galaxies — the building blocks of the universe — evolve. The work is published in a recent issue of The Astrophysical Journal.

The team decided to study Leo I because of its peculiarity. Unlike most dwarf galaxies orbiting the Milky Way, Leo I does not contain much dark matter. Researchers measured Leo I’s dark matter profile — that is, how the density of dark matter changes from the outer edges of the galaxy all the way into its center. They did this by measuring its gravitational pull on the stars: The faster the stars are moving, the more matter there is enclosed in their orbits. In particular, the team wanted to know whether dark matter density increases toward the galaxy’s center. They also wanted to know whether their profile measurement would match previous ones made using older telescope data combined with computer models.

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Let me back up a moment. I recently concurred with megapundit Steven Pinker that over the last two centuries we have achieved material, moral and intellectual progress, which should give us hope that we can achieve still more. I expected, and have gotten, pushback. Pessimists argue that our progress will prove to be ephemeral; that we will inevitably succumb to our own nastiness and stupidity and destroy ourselves.

Maybe, maybe not. Just for the sake of argument, let’s say that within the next century or two we solve our biggest problems, including tyranny, injustice, poverty, pandemics, climate change and war. Let’s say we create a world in which we can do pretty much anything we choose. Many will pursue pleasure, finding ever more exciting ways to enjoy themselves. Others may seek spiritual enlightenment or devote themselves to artistic expression.

No matter what our descendants choose to do, some will surely keep investigating the universe and everything in it, including us. How long can the quest for knowledge continue? Not long, I argued 25 years ago this month in The End of Science, which contends that particle physics, cosmology, neuroscience and other fields are bumping into fundamental limits. I still think I’m right, but I could be wrong. Below I describe the views of three physicists—Freeman Dyson, Roger Penrose and David Deutsch—who hold that knowledge seeking can continue for a long, long time, and possibly forever, even in the face of the heat death of the universe.

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Because leviathan black holes would never fit in a lab, Jeff Steinhauer and his research team created a mini one right here on Earth.

When something rips physics apart, you cross over into the quantum realm, a place inhabited by black holes, wormholes and other things that have been the stars of multiple sci-fi movies. What lives in the quantum realm either hasn’t been proven to exist (yet) or behaves strangely if it does exist.

Black holes often venture into that realm. With these collapsed stars — at least most of them are — being impossible to fly a spacecraft into (unless you never want to see it again), one physicist decided that the best way to get up close to them was under a literal microscope. Jeff Steinhauer wanted to know whether black holes radiate particles like the late Stephen Hawking theorized they would. Because one of these leviathans would never fit in a lab, he and his research team created one right here on Earth.

“We have to understand how we see the Hawking radiation sound waves falling in and coming out,” Steinhauer, who co-authored a study recently published in Nature Physics, told SYFY WIRE. “They should be very slight. Seeing this radiation from a real black hole is too weak and would be totally overpowered by other sources of radiation, which is why we want to see it in an analog system.”

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Blackholes are a breakdown in the equations of spacetime. This means both space and time no longer behave the way we would expect of them.
Today we explore the breakdown in time around blackholes and what it means to interact with the event horizon, or the place where time appears to stand still.

Further Reading/Consumption:

Black holes & time warps: einstein’s outrageous legacy — kip thorne.

Your Daily Equation #31: BLACK HOLES: And Why Time Slows Down When You Are Near One — https://youtu.be/qph51qUgwgU

What happens to you if you fall into a black hole? — https://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/fall_in.html.

Physics Beyond the Event Horizon — https://knotphysics.net/black-holes

Continue reading “Why Time “Stops” in a Black Hole” | >

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At 2 mins 26 seconds when I say “Peter” I meant “Paul”. Sorry!

Dark energy has got something to do with quantum vacuum fluctuation, whoa, physics. You have probably heard something like that. Alas, that isn’t quite right. In this video I clear up the confusion. Vacuum energy is much easier to understand than you might have been told. And it doesn’t fluctuate.

You can support us on Patreon: https://www.patreon.com/Sabine.

0:00 Intro.
0:27 Vacuum Energy according to Scientific American.
2:07 Vacuum Energy according to Sabine.
7:11 The Gas Analogy for Dark Energy.
10:04 Sponsor Message.

#physics #science

Continue reading “Physicist Despairs over Vacuum Energy” | >