Posts Tagged ‘Cosmology’
“The Universe is under no obligation to make sense to you”*…
Uppsala University researchers have devised a new model for the Universe – one that may solve the enigma of dark energy. Their new article, published in Physical Review Letters, proposes a new structural concept, including dark energy, for a universe that rides on an expanding bubble in an additional dimension.
We have known for the past 20 years that the Universe is expanding at an ever accelerating rate. The explanation is the “dark energy” that permeates it throughout, pushing it to expand. Understanding the nature of this dark energy is one of the paramount enigmas of fundamental physics.
It has long been hoped that string theory will provide the answer. According to string theory, all matter consists of tiny, vibrating “stringlike” entities. The theory also requires there to be more spatial dimensions than the three that are already part of everyday knowledge. For 15 years, there have been models in string theory that have been thought to give rise to dark energy. However, these have come in for increasingly harsh criticism, and several researchers are now asserting that none of the models proposed to date are workable.
In their article, the scientists propose a new model with dark energy and our Universe riding on an expanding bubble in an extra dimension. The whole Universe is accommodated on the edge of this expanding bubble. All existing matter in the Universe corresponds to the ends of strings that extend out into the extra dimension. The researchers also show that expanding bubbles of this kind can come into existence within the framework of string theory. It is conceivable that there are more bubbles than ours, corresponding to other universes.
The Uppsala scientists’ model provides a new, different picture of the creation and future fate of the Universe, while it may also pave the way for methods of testing string theory…
(For a different emerging new theory– that may or may not be contradictory– see “Our universe has antimatter partner on the other side of the Big Bang.”)
* Neil deGrasse Tyson
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As we fumble with the fundamentals, we might send carefully-deduced birthday greetings to Richard Bevan Braithwaite; he was born on this date in 1900. A Cambridge philosopher who specialized in the philosophy of science, he focused on the logical features common to all sciences. Braithwaite was concerned with the impact of science on our beliefs about the world and the appropriate responses to that impact. He was especially interested in probability (and its applications in decision theory and games theory) and in the statistical sciences. He was president of the Aristotelian Society from 1946 to 1947, and was a Fellow of the British Academy.
It was Braithwaite’s poker that Ludwig Wittgenstein reportedly brandished at Karl Popper during their confrontation at a Moral Sciences Club meeting in Braithwaite’s rooms in King’s. The implement subsequently disappeared. (See here.)
“If you think this Universe is bad, you should see some of the others”*…
FIRST OF FOUR?: The first Copernican revolution moved the Earth out of the center of the solar system. The second recognized that there are many planets in our galaxy, and the third that there are many galaxies in the observable universe. Proving that our universe is one among many would represent a fourth Copernican revolution.
A challenge for 21st-century physics is to answer two questions. First, are there many “big bangs” rather than just one? Second—and this is even more interesting—if there are many, are they all governed by the same physics?
If we’re in a multiverse, it would imply a fourth and grandest Copernican revolution; we’ve had the Copernican revolution itself, then the realization that there are billions of planetary systems in our galaxy; then that there are billions of galaxies in our observable universe. But now that’s not all. The entire panorama that astronomers can observe could be a tiny part of the aftermath of “our” big bang, which is itself just one bang among a perhaps infinite ensemble.
At first sight, the concept of parallel universes might seem too arcane to have any practical impact. But it may (in one of its variants) actually offer the prospect of an entirely new kind of computer: the quantum computer, which can transcend the limits of even the fastest digital processor by, in effect, sharing the computational burden among a near infinity of parallel universes…
Cambridge physicist and Astronomer Royal Martin Rees suspects that our universe is one island in an archipelago: “The Fourth Copernican Revolution.”
* Philip K. Dick
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As we find our place, we might recall that it was on this date in 1884 that 41 delegates from 25 nations, meeting in Washington, DC for the International Meridian Conference, adopted Greenwich as the universal meridian. They also established that all longitude would be calculated both east and west from this meridian up to 180°.
“The truth is not always beautiful, nor beautiful words the truth.”*…
Does anyone who follows physics doubt it is in trouble? When I say physics, I don’t mean applied physics, material science or what Murray-Gell-Mann called “squalid-state physics.” I mean physics at its grandest, the effort to figure out reality. Where did the universe come from? What is it made of? What laws govern its behavior? And how probable is the universe? Are we here through sheer luck, or was our existence somehow inevitable?
In the 1980s Stephen Hawking and other big shots claimed that physics was on the verge of a “final theory,” or “theory of everything,” that could answer these big questions and solve the riddle of reality. I became a science writer in part because I believed their claims, but by the early 1990s I had become a skeptic. The leading contender for a theory of everything held that all of nature’s particles and forces, including gravity, stem from infinitesimal, stringy particles wriggling in nine or more dimensions.
The problem is that no conceivable experiment can detect the strings or extra dimensions…
John Horgan examines physicist Sabine Hossenfelder‘s claim that desire for beauty and other subjective biases have led physicists astray: “How Physics Lost Its Way.”
* Lao Tzu, Tao Te Ching
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As we contemplate certainty, we might recall that it was on this date in 1595 that Johann Kepler (and here) published Mysterium cosmographicum (Mystery of the Cosmos), in which he described an invisible underlying structure determining the six known planets in their orbits. Kepler thought as a mathematician, devising a structure based on only five convex regular solids; the path of each planet lay on a sphere separated from its neighbors by touching an inscribed polyhedron.
It was a beautiful, an elegant model– and one that fit the orbital data available at the time. It was, nonetheless, wrong.
Detailed view of Kepler’s inner sphere
“We cannot get behind consciousness. Everything that we talk about, everything that we regard as existing, postulates consciousness”*…
Ockham’s razor is the principle that, all things being equal, more parsimonious theories – that is to say, theories with relatively few postulations – are to be preferred. Is it not a great cost in terms of parsimony to ascribe fundamental consciousness to the Universe? Not at all. The physical world must have some nature, and physics leaves us completely in the dark as to what it is. It is no less parsimonious to suppose that the Universe has a consciousness-involving nature than that it has some non-consciousness-involving nature. If anything, the former proposal is more parsimonious insofar as it is continuous with the only thing we really know about the nature of matter: that brains have consciousness…
One of the thinkers quoted in (Roughly) Daily’s recent piece on panpsychism, Philip Goff, has elaborated on his argument that the Universe and everything in it is conscious. Cosmopsychism, as he now calls the notion, might seem crazy; but as he explains, it provides a robust explanatory model for how the Universe became fine-tuned for life: “Is the Universe a conscious mind?”
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As we ascribe some level of sentience to absolutely everything, we might send brave birthday greetings to Fang Lizhi; he was born on this date in 1936.
An astrophysicist, vice-president of the University of Science and Technology of China, who published published a paper (in 1972) on a topic central to the argument for cosmopsychism– the Big Bang theory, previously a forbidden topic in China (Marxists claimed that the universe was infinite)– which met condemnation from the Communist Party. He became an advocate of intellectual freedom and civic reform, whose liberal ideas helped inspire the pro-democracy student movement of 1986–87 and, finally, the Tiananmen Square protests of 1989– and for which he was expelled from the Communist Party and forced into exile.
“The missing link in cosmology is the nature of dark matter and dark energy”*…
Familiar visible matter can be thought of as the privileged percent—actually more like 15 percent—of matter. In business and politics, the interacting 1 percent dominates decision making and policy, while the remaining 99 percent of the population provides less widely acknowledged infrastructure and support—maintaining buildings, keeping cities operational, and getting food to people’s tables. Similarly, ordinary matter dominates almost everything we notice, whereas dark matter, in its abundance and ubiquity, helped create clusters and galaxies and facilitated star formation, but has only limited influence on our immediate surroundings today…
The common assumption is that dark matter is the “glue” that holds together galaxies and galaxy clusters, but resides only in amorphous clouds around them. But what if this assumption isn’t true and it is only our prejudice—and ignorance, which is after all the root of most prejudice—that led us down this potentially misleading path?…
Indeed, Harvard theoretical physicist and cosmologist Lisa Randall asks, “Does dark matter harbor life?”
* Stephen Hawking
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As we reach reflexively for a flashlight, we might send particular birthday greetings to Abraham Pais; he was born on this date in 1918. After earning his Ph.D. in physics in Holland five days before a Nazi deadline banning Jews from receiving degrees, he went into hiding– and worked out ideas in quantum electrodynamics (later shared with Niels Bohr) that became the building blocks of the theory of elemental particles. He was later a colleague of Robert Oppenheimer and Albert Einstein at the Institute for Advanced Studies at Princeton.
Pais was also an widely-respected historian of science. Among his many works were a biography of Bohr and (the work for which he’s best remembered as a historian) Subtle Is the Lord: The Science and Life of Albert Einstein, which is considered the definitive Einstein biography.
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