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Posts Tagged ‘Cosmology

“For the moment we might very well can them DUNNOS (for Dark Unknown Nonreflective Nondetectable Objects Somewhere)”*…

When does one give up on a hypothesis?…

In 1969, the American astronomer Vera Rubin puzzled over her observations of the sprawling Andromeda Galaxy, the Milky Way’s biggest neighbour. As she mapped out the rotating spiral arms of stars through spectra carefully measured at the Kitt Peak National Observatory and the Lowell Observatory, both in Arizona, she noticed something strange: the stars in the galaxy’s outskirts seemed to be orbiting far too fast. So fast that she’d expect them to escape Andromeda and fling out into the heavens beyond. Yet the whirling stars stayed in place.

Rubin’s research, which she expanded to dozens of other spiral galaxies, led to a dramatic dilemma: either there was much more matter out there, dark and hidden from sight but holding the galaxies together with its gravitational pull, or gravity somehow works very differently on the vast scale of a galaxy than scientists previously thought.

Her influential discovery never earned Rubin a Nobel Prize, but scientists began looking for signs of dark matter everywhere, around stars and gas clouds and among the largest structures in the galaxies in the Universe…

But… over the past half century, no one has ever directly detected a single particle of dark matter. Over and over again, dark matter has resisted being pinned down, like a fleeting shadow in the woods. Every time physicists have searched for dark matter particles with powerful and sensitive experiments in abandoned mines and in Antarctica, and whenever they’ve tried to produce them in particle accelerators, they’ve come back empty-handed. For a while, physicists hoped to find a theoretical type of matter called weakly interacting massive particles (WIMPs), but searches for them have repeatedly turned up nothing.

With the WIMP candidacy all but dead, dark matter is apparently the most ubiquitous thing physicists have never found. And as long as it’s not found, it’s still possible that there is no dark matter at all. An alternative remains: instead of huge amounts of hidden matter, some mysterious aspect of gravity could be warping the cosmos instead…

Dark matter is the most ubiquitous thing physicists have never found; Ramin Skibba (@raminskibba) wonders if it isn’t time to consider alternative explanations: “Does dark matter exist?” in @aeonmag.

* Bill Bryson on dark matter, in A Short History of Nearly Everything (2003)

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As we interrogate the invisible, we might send observant birthday greetings to Val Logsdon Fitch; he was born on this date in 1923. A particle physicist, he shared the 1964 Nobel Prize in Physics with his collaborator James Cronin for their experiments proving that some subatomic reactions do not adhere to fundamental symmetry principles (and are therefore indifferent to the direction of time).

By examining the decay of K-mesons, they proved that a reaction run in reverse does not retrace the path of the original reaction, which showed that the reactions of subatomic particles are not indifferent to time. Thus the phenomenon of CP violation was discovered… and thus was demolished the faith that physicists had previously had that natural laws were universally governed by symmetry.

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“A mind that is stretched by a new idea can never go back to its original dimensions”*…

Alex Berezow observes (in an appreciation of Peter AtkinsGalileo’s Finger: The Ten Great Ideas of Science) that, while scientific theories are always being tested, scrutinized for flaws, and revised, there are ten concepts so durable that it is difficult to imagine them ever being replaced with something better…

In his book The Structure of Scientific Revolutions, Thomas Kuhn argued that science, instead of progressing gradually in small steps as is commonly believed, actually moves forward in awkward leaps and bounds. The reason for this is that established theories are difficult to overturn, and contradictory data is often dismissed as merely anomalous. However, at some point, the evidence against the theory becomes so overwhelming that it is forcefully displaced by a better one in a process that Kuhn refers to as a “paradigm shift.” And in science, even the most widely accepted ideas could, someday, be considered yesterday’s dogma.

Yet, there are some concepts which are considered so rock solid, that it is difficult to imagine them ever being replaced with something better. What’s more, these concepts have fundamentally altered their fields, unifying and illuminating them in a way that no previous theory had done before…

The bedrock of modern biology, chemistry, and physics: “The ten greatest ideas in the history of science,” from @AlexBerezow in @bigthink.

* Oliver Wendell Holmes

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As we forage for first principles, we might send carefully-calcuated birthday greetings to Georgiy Antonovich Gamov; he was born on this date in 1904. Better known by the name he adopted on immigrating to the U.S., George Gamow, he was a physicist and cosmologist whose early work was instrumental in developing the Big Bang theory of the universe; he also developed the first mathematical model of the atomic nucleus. In 1954, he expanded his interests into biochemistry and his work on deoxyribonucleic acid (DNA) made a basic contribution to modern genetic theory.

But mid-career Gamow began to shift his energy to teaching and to writing popular books on science… one of which, One Two Three… Infinity, inspired legions of young scientists-to-be and kindled a life-long interest in science in an even larger number of other youngsters (including your correspondent).

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“The past, like the future, is indefinite and exists only as a spectrum of possibilities”*…

A recent paper by Robert Lanza and others suggests that physical reality isn’t independent of us, “objective,” but is the product of networks of observers…

Is there physical reality that is independent of us? Does objective reality exist at all? Or is the structure of everything, including time and space, created by the perceptions of those observing it? Such is the groundbreaking assertion of a new paper published in the Journal of Cosmology and Astroparticle Physics.

The paper’s authors include Robert Lanza, a stem cell and regenerative medicine expert, famous for the theory of biocentrism, which argues that consciousness is the driving force for the existence of the universe. He believes that the physical world that we perceive is not something that’s separate from us but rather created by our minds as we observe it. According to his biocentric view, space and time are a byproduct of the “whirl of information” in our head that is weaved together by our mind into a coherent experience.

His new paper, co-authored by Dmitriy Podolskiy and Andrei Barvinsky, theorists in quantum gravity and quantum cosmology, shows how observers influence the structure of our reality.

According to Lanza and his colleagues, observers can dramatically affect “the behavior of observable quantities” both at microscopic and massive spatiotemporal scales. In fact, a “profound shift in our ordinary everyday worldview” is necessary, wrote Lanza in an interview with Big Think. The world is not something that is formed outside of us, simply existing on its own. “Observers ultimately define the structure of physical reality itself,” he stated.

How does this work? Lanza contends that a network of observers is necessary and is “inherent to the structure of reality.” As he explains, observers — you, me, and anyone else — live in a quantum gravitational universe and come up with “a globally agreed-upon cognitive model” of reality by exchanging information about the properties of spacetime. “For, once you measure something,” Lanza writes, “the wave of probability to measure the same value of the already probed physical quantity becomes ‘localized’ or simply ‘collapses.’” That’s how reality comes to be consistently real to us all. Once you keep measuring a quantity over and over, knowing the result of the first measurement, you will see the outcome to be the same.

“Similarly, if you learn from somebody about the outcomes of their measurements of a physical quantity, your measurements and those of other observers influence each other ‒ freezing the reality according to that consensus,” added Lanza, explaining further that “a consensus of different opinions regarding the structure of reality defines its very form, shaping the underlying quantum foam,” explained Lanza.

In quantum terms, an observer influences reality through decoherence, which provides the framework for collapsing waves of probability, “largely localized in the vicinity of the cognitive model which the observer builds in their mind throughout their lifespan,” he added.

Lanza says, “The observer is the first cause, the vital force that collapses not only the present, but the cascade of spatiotemporal events we call the past. Stephen Hawking was right when he said: ‘The past, like the future, is indefinite and exists only as a spectrum of possibilities.’”

Could an artificially intelligent entity without consciousness be dreaming up our world? Lanza believes biology plays an important role, as he explains in his book The Grand Biocentric Design: How Life Creates Reality, which he co-authored with the physicist Matej Pavsic.

While a bot could conceivably be an observer, Lanza thinks a conscious living entity with the capacity for memory is necessary to establish the arrow of time. “‘A brainless’ observer does not experience time and/or decoherence with any degree of freedom,” writes Lanza. This leads to the cause and effect relationships we can notice around us. Lanza thinks that “we can only say for sure that a conscious observer does indeed collapse a quantum wave function.”…

Another key aspect of their work is that it resolves “the exasperating incompatibility between quantum mechanics and general relativity,” which was a sticking point even for Albert Einstein.

The seeming incongruity of these two explanations of our physical world — with quantum mechanics looking at the molecular and subatomic levels and general relativity at the interactions between massive cosmic structures like galaxies and black holes — disappears once the properties of observers are taken into account.

While this all may sound speculative, Lanza says their ideas are being tested using Monte Carlo simulations on powerful MIT computer clusters and will soon be tested experimentally.

Is the physical universe independent from us, or is it created by our minds? “Is human consciousness creating reality?@RobertLanza

We might wonder, if this is so, how reality emerged at all. Perhaps one possibility is implied in “Consciousness was upon him before he could get out of the way.”

* Stephen Hawking

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As we conjure with consciousness, we might recall that it was on this date in 1908 (the same year that he was awarded the Nobel Prize in Physics) that Ernest Rutherford announced in London that he had isolated a single atom of matter. The following year, he, Hans Geiger (later of “counter” fame), and Ernest Marsden conducted the “Gold Foil Experiment,” the results of which replaced J. J. Thomson‘s “Plum Pudding Model” of the atom with what became known as the “Rutherford Model“: a very small charged nucleus, containing much of the atom’s mass, orbited by low-mass electrons.

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“Nature is pleased with simplicity”*…

As Clare Booth Luce once said, sometimes “simplicity is the ultimate sophistication”…

… The uniformity of the cosmic microwave background (CMB) tells us that, at its birth, ‘the Universe has turned out to be stunningly simple,’ as Neil Turok, director emeritus of the Perimeter Institute for Theoretical Physics in Ontario, Canada, put it at a public lecture in 2015. ‘[W]e don’t understand how nature got away with it,’ he added. A few decades after Penzias and Wilson’s discovery, NASA’s Cosmic Background Explorer satellite measured faint ripples in the CMB, with variations in radiation intensity of less than one part in 100,000. That’s a lot less than the variation in whiteness you’d see in the cleanest, whitest sheet of paper you’ve ever seen.

Wind forward 13.8 billion years, and, with its trillions of galaxies and zillions of stars and planets, the Universe is far from simple. On at least one planet, it has even managed to generate a multitude of life forms capable of comprehending both the complexity of our Universe and the puzzle of its simple origins. Yet, despite being so rich in complexity, some of these life forms, particularly those we now call scientists, retain a fondness for that defining characteristic of our primitive Universe: simplicity.

The Franciscan friar William of Occam (1285-1347) wasn’t the first to express a preference for simplicity, though he’s most associated with its implications for reason. The principle known as Occam’s Razor insists that, given several accounts of a problem, we should choose the simplest. The razor ‘shaves off’ unnecessary explanations, and is often expressed in the form ‘entities should not be multiplied beyond necessity’. So, if you pass a house and hear barking and purring, then you should think a dog and a cat are the family pets, rather than a dog, a cat and a rabbit. Of course, a bunny might also be enjoying the family’s hospitality, but the existing data provides no support for the more complex model. Occam’s Razor says that we should keep models, theories or explanations simple until proven otherwise – in this case, perhaps until sighting a fluffy tail through the window.

Seven hundred years ago, William of Occam used his razor to dismantle medieval science or metaphysics. In subsequent centuries, the great scientists of the early modern era used it to forge modern science. The mathematician Claudius Ptolemy’s (c100-170 CE) system for calculating the motions of the planets, based on the idea that the Earth was at the centre, was a theory of byzantine complexity. So, when Copernicus (1473-1543) was confronted by it, he searched for a solution that ‘could be solved with fewer and much simpler constructions’. The solution he discovered – or rediscovered, as it had been proposed in ancient Greece by Aristarchus of Samos, but then dismissed by Aristotle – was of course the solar system, in which the planets orbit around the Sun. Yet, in Copernicus’s hands, it was no more accurate than Ptolemy’s geocentric system. Copernicus’s only argument in favour of heliocentricity was that it was simpler.

Nearly all the great scientists who followed Copernicus retained Occam’s preference for simple solutions. In the 1500s, Leonardo da Vinci insisted that human ingenuity ‘will never devise any [solutions] more beautiful, nor more simple, nor more to the purpose than Nature does’. A century or so later, his countryman Galileo claimed that ‘facts which at first seem improbable will, even on scant explanation, drop the cloak which has hidden them and stand forth in naked and simple beauty.’ Isaac Newton noted in his Principia (1687) that ‘we are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances’; while in the 20th century Einstein is said to have advised that ‘Everything should be made as simple as possible, but not simpler.’ In a Universe seemingly so saturated with complexity, what work does simplicity do for us?

Part of the answer is that simplicity is the defining feature of science. Alchemists were great experimenters, astrologers can do maths, and philosophers are great at logic. But only science insists on simplicity…

Just why do simpler laws work so well? The statistical approach known as Bayesian inference, after the English statistician Thomas Bayes (1702-61), can help explain simplicity’s power. Bayesian inference allows us to update our degree of belief in an explanation, theory or model based on its ability to predict data. To grasp this, imagine you have a friend who has two dice. The first is a simple six-sided cube, and the second is more complex, with 60 sides that can throw 60 different numbers. Suppose your friend throws one of the dice in secret and calls out a number, say 5. She asks you to guess which dice was thrown. Like astronomical data that either the geocentric or heliocentric system could account for, the number 5 could have been thrown by either dice. Are they equally likely? Bayesian inference says no, because it weights alternative models – the six- vs the 60-sided dice – according to the likelihood that they would have generated the data. There is a one-in-six chance of a six-sided dice throwing a 5, whereas only a one-in-60 chance of the 60-sided dice throwing a 5. Comparing likelihoods, then, the six-sided dice is 10 times more likely to be the source of the data than the 60-sided dice.

Simple scientific laws are preferred, then, because, if they fit or fully explain the data, they’re more likely to be the source of it.

In my latest book, I propose a radical, if speculative, solution for why the Universe might in fact be as simple as it’s possible to be. Its starting point is the remarkable theory of cosmological natural selection (CNS) proposed by the physicist Lee Smolin. CNS proposes that, just like living creatures, universes have evolved through a cosmological process, analogous to natural selection.

Smolin came up with CNS as a potential solution to what’s called the fine-tuning problem: how the fundamental constants and parameters, such as the masses of the fundamental particles or the charge of an electron, got to be the precise values needed for the creation of matter, stars, planets and life. CNS first notes the apparent symmetry between the Big Bang, in which stars and particles were spewed out of a dimensionless point at the birth of our Universe, and the Big Crunch, the scenario for the end of our Universe when a supermassive black hole swallows up stars and particles before vanishing back into a dimensionless point. This symmetry has led many cosmologists to propose that black holes in our Universe might be the ‘other side’ of Big Bangs of other universes, expanding elsewhere. In this scenario, time did not begin at the Big Bang, but continues backwards through to the death of its parent universe in a Big Crunch, through to its birth from a black hole, and so on, stretching backward in time, potentially into infinity. Not only that but, since our region of the Universe is filled with an estimated 100 billion supermassive black holes, Smolin proposes that each is the progenitor of one of 100 billion universes that have descended from our own.

The model Smolin proposed includes a kind of universal self-replication process, with black holes acting as reproductive cells. The next ingredient is heredity. Smolin proposes that each offspring universe inherits almost the same fundamental constants of its parent. The ‘almost’ is there because Smolin suggests that, in a process analogous to mutation, their values are tweaked as they pass through a black hole, so baby universes become slightly different from their parent. Lastly, he imagines a kind of cosmological ecosystem in which universes compete for matter and energy. Gradually, over a great many cosmological generations, the multiverse of universes would become dominated by the fittest and most fecund universes, through their possession of those rare values of the fundamental constants that maximise black holes, and thereby generate the maximum number of descendant universes.

Smolin’s CNS theory explains why our Universe is finely tuned to make many black holes, but it does not account for why it is simple. I have my own explanation of this, though Smolin himself is not convinced. First, I point out that natural selection carries its own Occam’s Razor that removes redundant biological features through the inevitability of mutations. While most mutations are harmless, those that impair vital functions are normally removed from the gene pool because the individuals carrying them leave fewer descendants. This process of ‘purifying selection’, as it’s known, maintains our genes, and the functions they encode, in good shape.

However, if an essential function becomes redundant, perhaps by a change of environment, then purifying selection no longer works. For example, by standing upright, our ancestors lifted their noses off the ground, so their sense of smell became less important. This means that mutations could afford to accumulate in the newly dispensable genes, until the functions they encoded were lost. For us, hundreds of smell genes accumulated mutations, so that we lost the ability to detect hundreds of odours that we no longer need to smell. This inevitable process of mutational pruning of inessential functions provides a kind of evolutionary Occam’s Razor that removes superfluous biological complexity.

Perhaps a similar process of purifying selection operates in cosmological natural selection to keep things simple…

It’s unclear whether the kind of multiverse envisaged by Smolin’s theory is finite or infinite. If infinite, then the simplest universe capable of forming black holes will be infinitely more abundant than the next simplest universe. If instead the supply of universes is finite, then we have a similar situation to biological evolution on Earth. Universes will compete for available resources – matter and energy – and the simplest that convert more of their mass into black holes will leave the most descendants. For both scenarios, if we ask which universe we are most likely to inhabit, it will be the simplest, as they are the most abundant. When inhabitants of these universes peer into the heavens to discover their cosmic microwave background and perceive its incredible smoothness, they, like Turok, will remain baffled at how their universe has managed to do so much from such a ‘stunningly simple’ beginning.

The cosmological razor idea has one further startling implication. It suggests that the fundamental law of the Universe is not quantum mechanics, or general relativity or even the laws of mathematics. It is the law of natural selection discovered by Darwin and Wallace. As the philosopher Daniel Dennett insisted, it is ‘The single best idea anyone has ever had.’ It might also be the simplest idea that any universe has ever had.

Does the existence of a multiverse hold the key for why nature’s laws seem so simple? “Why simplicity works,” from JohnJoe McFadden (@johnjoemcfadden)

* “Nature does nothing in vain when less will serve; for Nature is pleased with simplicity and affects not the pomp of superfluous causes.” – Isaac Newton, The Mathematical Principles of Natural Philosophy

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As we emphasize the essential, we might spare a thought for Martin Gardner; he died on this date in 2010. Though not an academic, nor ever a formal student of math or science, he wrote widely and prolifically on both subjects in such popular books as The Ambidextrous Universe and The Relativity Explosion and as the “Mathematical Games” columnist for Scientific American. Indeed, his elegant– and understandable– puzzles delighted professional and amateur readers alike, and helped inspire a generation of young mathematicians.

Gardner’s interests were wide; in addition to the math and science that were his power alley, he studied and wrote on topics that included magic, philosophy, religion, and literature (c.f., especially his work on Lewis Carroll– including the delightful Annotated Alice— and on G.K. Chesterton).  And he was a fierce debunker of pseudoscience: a founding member of CSICOP, and contributor of a monthly column (“Notes of a Fringe Watcher,” from 1983 to 2002) in Skeptical Inquirer, that organization’s monthly magazine.

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“See the turtle of enormous girth, on his shell he holds the earth”*…

An illustration of the “Hindu Earth” from 1876

On the roots of a surprisingly wide-spread– and durable– image…

Anyone who’s ever heard the expression “it’s turtles all the way down” is probably familiar with the image of the world being carried on the back of a giant turtle. While that philosophical one-liner is of relatively modern vintage, the cosmic turtle mytheme has appeared in disparate cultures across the globe for millennia. In honor of everyone’s favorite intellectual quandary, let’s take a moment to celebrate the tortoises that hold up the world.

In his book Researches Into the Early History of Mankind and the Development of Civilization, the turn-of-the-20th-century anthropologist Edward Burnett Tylor writes that the world turtle concept likely first appeared in Hindu mythology. In one Vedic story, the form of the god Vishnu’s second avatar, Kurma, is a great turtle, which provides a celestial foundation upon which a mountain is balanced.

Over in China, part of the traditional creation mythology involves a giant turtle named Ao, although the image in this case is a bit different. According to the legend, the creator goddess cut off the legs of the cosmic turtle and used them to prop up the heavens, which had been damaged by another god. It’s not quite carrying the world on its back, but it still puts a terrapin at the center of the universe, making sure that the very sky doesn’t fall down.

The concept of a world turtle seems to have arisen independently within Native American myth and legend. In the creation stories of the Lenape and Iroquois people, the Earth is created as soil is piled on the back of a great sea turtle that continues to grow until it is carrying the entire world. Many indigenous tribes in North America refer to the continent as Turtle Island to this day.

The image of the world being carried through space by an ancient, impossibly massive tortoise is evocative, so it’s not hard to imagine why it has survived for so long in so many different cultures. But in the end, why turtles?

In a 1974 issue of the anthropological journal Man, the scholar Jay Miller provides some thoughts on what makes the turtle such a popular world bearer, writing, “I viewed the turtle as a logical choice for such an atlantean because its shape and appearance were suited to this role.” But he goes on to write, specifically of the Lenape belief in a world turtle, that the creature also mirrored aspects that they valued in their culture, such as perseverance and longevity. And that idea doesn’t just apply to the cosmic turtle in Lenape culture. “With intensive research, the above analysis should also apply for other societies that place the earth on the back of a turtle.” Most turtles and tortoises are also famously long-lived, giving them a wise, ancient quality that lends itself to mythologizing.

World turtles appear in more modern pop culture as well, from the Great A’Tuin of the late Terry Pratchett’s Discworld franchise, to the all-knowing Maturin of Stephen King’s metaverse. Clearly, it remains cool to imagine that our world is being led through space by a being that actually knows where we’re headed.

Why Is the World Always on the Back of a Turtle?” As Eric Grundhauser (@OMGrundhauser) explains, it’s mythology all the way down.

* Stephen King

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As we contemplate cosmological chordates, we might recall that it was on this date in 762 that Baghdad was founded. After the fall of the Umayyads, the first Muslim dynasty, the victorious Abbasid rulers wanted their own capital from which to rule. They chose a site north of the Sassanid capital of Ctesiphon— a site especially blessed as it had control over strategic and trading routes along the Tigris, and it had an abundance of water in a dry climate. The caliph Al-Mansur commissioned the construction of the city– in the round, a deliberate reminder of an expression in the Qur’an, when it refers to Paradise.

Within a short time, Baghdad evolved into a significant cultural, commercial, and intellectual center of the Muslim world. This, in addition to housing several key academic institutions, including the House of Wisdom (see also here), as well as hosting a multi-ethnic and multi-religious environment, earned the city a worldwide reputation as the “Center of Learning.”

Baghdad was the largest city in the world for much of the Abbasid era during the Islamic Golden Age, peaking at a population of more than a million. But the city was largely destroyed at the hands of the Mongol Empire in 1258, resulting in a decline– fueled by frequent plagues and the turmoil of multiple successive empires– that lingered through many centuries.

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Written by (Roughly) Daily

July 30, 2021 at 1:00 am

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