Daily Archives: January 11, 2022

Heres a brain teaser for you: scientists are suggesting spacetime may be made out of individual spacetime pixels, instead of being smooth and continuous like it seems.

Rana Adhikari, a professor of physics at Caltech, suggested in a new press blurb that these pixels would be so small that if you were to enlarge things so that it becomes the size of a grain of sand, then atoms would be as large as galaxies.

Adhikaris goal is to reconcile the conventional laws of physics, as determined by general relativity, with the more mysterious world of quantum physics.

Its a seriously mind-bending theory that attempts to explain whether gravity can actually be split up into its individual components, a question that has been keeping quantum physicists up at night for a long time.

Sometimes there is a misinterpretation in science communication that implies quantum mechanics and gravity are irreconcilable, said Cliff Cheung, a Caltech professor of theoretical physics whos working with Adhikari, in the statement. But we know from experiments that we can do quantum mechanics on this planet, which has gravity, so clearly they are consistent.

The devil, as always, is in the detail.

The problems come up when you ask subtle questions about black holes or try to merge the theories at very short distance scales, Cheung added.

In other words, if you were to zoom in on spacetime, would you also find individual photons, which make up light, according to the laws of quantum mechanics? Or would it be a continuous spectrum?

Some scientists suggest individual hypothetical gravitons could make up gravity on the smallest scale. Gravitons are a component of string theory that would resonate at a particular frequency.

But on an even smaller scale than that, scientists are still scratching their heads as to how to unify the laws of general relativity and quantum physics.

If I drop my coffee mug and it falls, Id like to think thats gravity, Adhikari quipped. But, in the same way that temperature is not real but describes how a bunch of molecules are vibrating, spacetime might not be a real thing.

The same may go for spacetime.

It may be that something that arises out of the pixelation of spacetime has just been given the name gravity because we dont yet understand what the guts of spacetime are, he added.

READ MORE: Is Space Pixelated? The Quest for Quantum Gravity [California Institute of Technology]

More on quantum physics: Scientist Claims That Aliens May Be Communicating via Starlight

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Scientists Say the Universe Itself May Be "Pixelated" - Futurism

Jody DruceNews Editor

Some staff in the School of Physics are to call for the Erwin Schrdinger lecture theatre to be renamed in light of revelations about the physicists abuse of young women and girls.

Two staff members in the School confirmed to The University Times that a meeting will be held to discuss the possibility of renaming the theatre, after an Irish Times article published in December detailed Schrdingers record as a sexual predator. The meeting was supposed to be held today but was postponed.

A petition published last month calling for Schrdingers removal from the School of Physics lecture theatres name, has garnered 51 signatures. The petition is being shared among staff in the school, but it was not created by a staff member.

The physicist, known for his contributions to quantum theory, worked in Trinity for nearly 20 years and became a naturalised Irish citizen.

The article names three girls who were teenagers or pre-adolescents when Schrdinger became infatuated with them.

According to the 2012 biography Erwin Schrdinger and the Quantum Revolution by John Gribbin, which is cited in the article, Schrdinger groomed a 14-year-old girl named Itha Junger after he became her mathematics tutor. Schrdinger, then in his mid forties, wrote that he fell in love with the girl and admitted to having intercourse with her when she was 17.

In the same year, Junger became pregnant and had a disastrous abortion that left her sterile according to the Irish Times. The relationship ended soon after.

In Schrdinger, Life and Thought, Walter Moore describes how Schrdinger became infatuated with a 12-year-old girl named Barbara. While Schrdinger agreed not to pursue the child after one of her family members raised concerns, he wrote in his diaries that she was among the unrequited loves of his life.

Moore wrote that the physicists attitude towards women was essentially that of a male supremacist.

The petition said: It seems in bad taste that a modern college such as Trinity one that holds lectures to both men and women, one that (hopefully) rejects the abuse of women, of young girls or, indeed, of anyone would honour this man with an entire building.

It added: The School of Physics is, and always should be, a welcoming, inclusive place of learning. Who we choose to honour our places of study with should reflect that.

We can acknowledge the great mark Schrodinger has left on science through our study, and this petition does not wish to diminish the impact his lectures or ideas had in physics.

If you have been affected by, or would like to discuss issues concerning sexual assault or non-consensual behaviour, you can contact the Welfare Officer of Trinity College Dublin Students Union by emailing [emailprotected] Emergency appointments with the Student Counselling Service are also available. You can phone Niteline, the student listening service, every night of term from 9pm2:30am on 1800 793 793, or the Samaritans at any time on 116 123. The Dublin Rape Crisis Centre can be reached at 1800 778 888.

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Physics Staff to Call for Schrdinger Theatre to be Renamed - The University Times

Winter/Spring2022Virtual Science Inquiry Lecture SeriesExplore cutting-edge science topics, their latest developments, and their relevance to society. Sponsored by the Gallatin Valley Friends of the Sciences, and co-sponsored by the non-profit community service organization Hopa Mountain andMuseum of the Rockies, talks for the 2022 winter/spring serieswill be presented virtually via the Zoom video conferencing platformon Wednesday evenings at 7 pm, followed by a brief question-and-answer period using the Zoom chat function.

Quantum Materials and the MonArk Quantum FoundryHow does quantum mechanics work, and how can it be applied to practical, everyday use?Dr. Yves Idzerda, MSU Professor of Physics and Dean of the College of Letters and Science, will discuss the latest advances in quantum technology and how MSUs NSF-funded quantum foundry will research and develop quantum materials and devices that will connect science and industry.

Free and open to the public via Zoom.Visit theGallatin Valley Friends of the Sciences websitefor the Zoom link for this lecture.

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Science Inquiry Lecture: Quantum Materials and the MonArk Quantum Foundry - Montana State University

The last star will slowly cool and fade away. With its passing, the universe will become once more a void, without light or life or meaning. So warned the physicist Brian Cox in the recent BBC series Universe. The fading of that last star will only be the beginning of an infinitely long, dark epoch. All matter will eventually be consumed by monstrous black holes, which in their turn will evaporate away into the dimmest glimmers of light. Space will expand ever outwards until even that dim light becomes too spread out to interact. Activity will cease.

Or will it? Strangely enough, some cosmologists believe a previous, cold dark empty universe like the one which lies in our far future could have been the source of our very own Big Bang.

But before we get to that, lets take a look at how material physical matter first came about. If we are aiming to explain the origins of stable matter made of atoms or molecules, there was certainly none of that around at the Big Bang nor for hundreds of thousands of years afterwards. We do in fact have a pretty detailed understanding of how the first atoms formed out of simpler particles once conditions cooled down enough for complex matter to be stable, and how these atoms were later fused into heavier elements inside stars. But that understanding doesnt address the question of whether something came from nothing.

So lets think further back. The first long-lived matter particles of any kind were protons and neutrons, which together make up the atomic nucleus. These came into existence around one ten-thousandth of a second after the Big Bang. Before that point, there was really no material in any familiar sense of the word. But physics lets us keep on tracing the timeline backwards to physical processes which predate any stable matter.

This takes us to the so-called grand unified epoch. By now, we are well into the realm of speculative physics, as we cant produce enough energy in our experiments to probe the sort of processes that were going on at the time. But a plausible hypothesis is that the physical world was made up of a soup of short-lived elementary particles including quarks, the building blocks of protons and neutrons. There was both matter and antimatter in roughly equal quantities: each type of matter particle, such as the quark, has an antimatter mirror image companion, which is near identical to itself, differing only in one aspect. However, matter and antimatter annihilate in a flash of energy when they meet, meaning these particles were constantly created and destroyed.

But how did these particles come to exist in the first place? Quantum field theory tells us that even a vacuum, supposedly corresponding to empty spacetime, is full of physical activity in the form of energy fluctuations. These fluctuations can give rise to particles popping out, only to be disappear shortly after. This may sound like a mathematical quirk rather than real physics, but such particles have been spotted in countless experiments.

The spacetime vacuum state is seething with particles constantly being created and destroyed, apparently out of nothing. But perhaps all this really tells us is that the quantum vacuum is (despite its name) a something rather than a nothing. The philosopher David Albert has memorably criticised accounts of the Big Bang which promise to get something from nothing in this way.

Suppose we ask: where did spacetime itself arise from? Then we can go on turning the clock yet further back, into the truly ancient Planck epoch a period so early in the universes history that our best theories of physics break down. This era occurred only one ten-millionth of a trillionth of a trillionth of a trillionth of a second after the Big Bang. At this point, space and time themselves became subject to quantum fluctuations. Physicists ordinarily work separately with quantum mechanics, which rules the microworld of particles, and with general relativity, which applies on large, cosmic scales. But to truly understand the Planck epoch, we need a complete theory of quantum gravity, merging the two.

We still dont have a perfect theory of quantum gravity, but there are attempts like string theory and loop quantum gravity. In these attempts, ordinary space and time are typically seen as emergent, like the waves on the surface of a deep ocean. What we experience as space and time are the product of quantum processes operating at a deeper, microscopic level processes that dont make much sense to us as creatures rooted in the macroscopic world.

In the Planck epoch, our ordinary understanding of space and time breaks down, so we cant any longer rely on our ordinary understanding of cause and effect either. Despite this, all candidate theories of quantum gravity describe something physical that was going on in the Planck epoch some quantum precursor of ordinary space and time. But where did that come from?

Even if causality no longer applies in any ordinary fashion, it might still be possible to explain one component of the Planck-epoch universe in terms of another. Unfortunately, by now even our best physics fails completely to provide answers. Until we make further progress towards a theory of everything, we wont be able to give any definitive answer. The most we can say with confidence at this stage is that physics has so far found no confirmed instances of something arising from nothing.

Paradoxical though it might seem, a total absence of matter might have managed to give rise to all the matter we see around us in our universe

To truly answer the question of how something could arise from nothing, we would need to explain the quantum state of the entire universe at the beginning of the Planck epoch. All attempts to do this remain highly speculative. Some of them appeal to supernatural forces like a designer. But other candidate explanations remain within the realm of physics such as a multiverse, which contains an infinite number of parallel universes, or cyclical models of the universe, being born and reborn again.

The 2020 Nobel Prize-winning physicist Roger Penrose has proposed one intriguing but controversial model for a cyclical universe dubbed conformal cyclic cosmology. Penrose was inspired by an interesting mathematical connection between a very hot, dense, small state of the universe as it was at the Big Bang and an extremely cold, empty, expanded state of the universe as it will be in the far future. His radical theory to explain this correspondence is that those states become mathematically identical when taken to their limits. Paradoxical though it might seem, a total absence of matter might have managed to give rise to all the matter we see around us in our universe.

In this view, the Big Bang arises from an almost nothing. Thats whats left over when all the matter in a universe has been consumed into black holes, which have in turn boiled away into photons lost in a void. The whole universe thus arises from something that viewed from another physical perspective is as close as one can get to nothing at all. But that nothing is still a kind of something. It is still a physical universe, however empty.

How can the very same state be a cold, empty universe from one perspective and a hot dense universe from another? The answer lies in a complex mathematical procedure called conformal rescaling, a geometrical transformation which in effect alters the size of an object but leaves its shape unchanged.

Penrose showed how the cold dense state and the hot dense state could be related by such rescaling so that they match with respect to the shapes of their spacetimes although not to their sizes. It is, admittedly, difficult to grasp how two objects can be identical in this way when they have different sizes but Penrose argues size as a concept ceases to make sense in such extreme physical environments.

In conformal cyclic cosmology, the direction of explanation goes from old and cold to young and hot: the hot dense state exists because of the cold empty state. But this because is not the familiar one of a cause followed in time by its effect. It is not only size that ceases to be relevant in these extreme states: time does too. The cold dense state and the hot dense state are in effect located on different timelines. The cold empty state would continue on forever from the perspective of an observer in its own temporal geometry, but the hot dense state it gives rise to effectively inhabits a new timeline all its own.

It may help to understand the hot dense state as produced from the cold empty state in some non-causal way. Perhaps we should say that the hot dense state emerges from, or is grounded in, or realised by the cold, empty state. These are distinctively metaphysical ideas which have been explored by philosophers of science extensively, especially in the context of quantum gravity where ordinary cause and effect seem to break down. At the limits of our knowledge, physics and philosophy become hard to disentangle.

Conformal cyclic cosmology offers some detailed, albeit speculative, answers to the question of where our Big Bang came from. But even if Penroses vision is vindicated by the future progress of cosmology, we might think that we still wouldnt have answered a deeper philosophical question a question about where physical reality itself came from. How did the whole system of cycles come about?Then we finally end up with the pure question of why there is something rather than nothing one of the biggest questions of metaphysics.

But our focus here is on explanations which remain within the realm of physics. There are three broad options to the deeper question of how the cycles began. It could have no physical explanation at all. Or there could be endlessly repeating cycles, each a universe in its own right, with the initial quantum state of each universe explained by some feature of the universe before. Or there could be one single cycle, and one single repeating universe, with the beginning of that cycle explained by some feature of its own end. The latter two approaches avoid the need for any uncaused events and this gives them a distinctive appeal. Nothing would be left unexplained by physics.

Penrose envisages a sequence of endless new cycles for reasons partly linked to his own preferred interpretation of quantum theory. In quantum mechanics, a physical system exists in a superposition of many different states at the same time, and only picks one randomly, when we measure it. For Penrose, each cycle involves random quantum events turning out a different way meaning each cycle will differ from those before and after it. This is actually good news for experimental physicists, because it might allow us to glimpse the old universe that gave rise to ours through faint traces, or anomalies, in the leftover radiation from the Big Bang seen by the Planck satellite.

Penrose and his collaborators believe they may have spotted these traces already, attributing patterns in the Planck data to radiation from supermassive black holes in the previous universe. However, their claimed observations have been challenged by other physicists and the jury remains out.

Endless new cycles are key to Penroses own vision. But there is a natural way to convert conformal cyclic cosmology from a multi-cycle to a one-cycle form. Then physical reality consists in a single cycling around through the Big Bang to a maximally empty state in the far future and then around again to the very same Big Bang, giving rise to the very same universe all over again.

Some people believe parallel universes may be observable in cosmological data, as imprints caused by another universe colliding with ours

This latter possibility is consistent with another interpretation of quantum mechanics, dubbed the many-worlds interpretation. The many-worlds interpretation tells us that each time we measure a system that is in superposition, this measurement doesnt randomly select a state. Instead, the measurement result we see is just one possibility the one that plays out in our own universe. The other measurement results all play out in other universes in a multiverse, effectively cut off from our own. So no matter how small the chance of something occurring, if it has a non-zero chance then it occurs in some quantum parallel world. There are people just like you out there in other worlds who have won the lottery, or have been swept up into the clouds by a freak typhoon, or have spontaneously ignited, or have done all three simultaneously.

Some people believe such parallel universes may also be observable in cosmological data, as imprints caused by another universe colliding with ours.

Many-worlds quantum theory gives a new twist on conformal cyclic cosmology, though not one that Penrose agrees with. Our Big Bang might be the rebirth of one single quantum multiverse, containing infinitely many different universes all occurring together. Everything possible happens then it happens again and again and again.

For a philosopher of science, Penroses vision is fascinating. It opens up new possibilities for explaining the Big Bang, taking our explanations beyond ordinary cause and effect. It is therefore a great test case for exploring the different ways physics can explain our world. It deserves more attention from philosophers.

For a lover of myth, Penroses vision is beautiful. In Penroses preferred multi-cycle form, it promises endless new worlds born from the ashes of their ancestors. In its one-cycle form, it is a striking modern re-invocation of the ancient idea of the ouroboros, or world-serpent. In Norse mythology, the serpent Jrmungandr is a child of Loki, a clever trickster, and the giant Angrboda. Jrmungandr consumes its own tail, and the circle created sustains the balance of the world. But the ouroboros myth has been documented all over the world including as far back as ancient Egypt.

The ouroboros of the one cyclic universe is majestic indeed. It contains within its belly our own universe, as well as every one of the weird and wonderful alternative possible universes allowed by quantum physics and at the point where its head meets its tail, it is completely empty yet also coursing with energy at temperatures of a hundred thousand million billion trillion degrees Celsius. Even Loki, the shapeshifter, would be impressed.

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How could the Big Bang arise from nothing? - TechCentral