A Momentary Flow

Updating Worldviews one World at a time

Is our universe a bubble in the multiverse?
-
Researchers at the Perimeter Institute for Theoretical Physics are working to bring the multiverse hypothesis — we are living in one universe of many — into the realm of testable science. Perimeter Associate Faculty member Matthew Johnson and his team are looking for clues for the existence of multiverses (a.ka. parallel universes) in the cosmic microwave background data, assumed to be left over from the Big Bang. To do that, “we simulate the whole universe,” he says. “We start with a multiverse that has two bubbles in it, we collide the bubbles on a computer to figure out what happens, and then we stick a virtual observer in various places and ask what that observer would see from there.” For example, if another universe had collided with ours n the early universe, it would have left evidence in the form of a “a disk on the sky,” creating a “bruise” in the pattern, he says. That the search for such a disk has so far come up empty makes certain collision-filled models less likely.

Meanwhile, the team is at work figuring out what other kinds of evidence a bubble collision might leave behind. It’s the first time, the team writes in their paper, that anyone has produced a direct quantitative set of predictions for the observable signatures of bubble collisions. And though none of those signatures has so far been found, some of them are possible to look for.

The real significance of this work is as a proof of principle: it shows that the multiverse can be testable. In other words, if we are living in a bubble universe, we might actually be able to tell.

Abstract of Journal of Cosmology and Astroparticle Physics paper

The theory of eternal inflation in an inflaton potential with multiple vacua predicts that our universe is one of many bubble universes nucleating and growing inside an ever-expanding false vacuum. The collision of our bubble with another could provide an important observational signature to test this scenario. We develop and implement an algorithm for accurately computing the cosmological observables arising from bubble collisions directly from the Lagrangian of a single scalar field. We first simulate the collision spacetime by solving Einstein’s equations, starting from nucleation and ending at reheating. Taking advantage of the collision’s hyperbolic symmetry, the simulations are performed with a 1+1-dimensional fully relativistic code that uses adaptive mesh refinement. We then calculate the comoving curvature perturbation in an open Friedmann-Robertson-Walker universe, which is used to determine the temperature anisotropies of the cosmic microwave background radiation. For a fiducial Lagrangian, the anisotropies are well described by a power law in the cosine of the angular distance from the center of the collision signature. For a given form of the Lagrangian, the resulting observational predictions are inherently statistical due to stochastic elements of the bubble nucleation process. Further uncertainties arise due to our imperfect knowledge about inflationary and pre-recombination physics. We characterize observational predictions by computing the probability distributions over four phenomenological parameters which capture these intrinsic and model uncertainties. This represents the first fully-relativistic set of predictions from an ensemble of scalar field models giving rise to eternal inflation, yielding significant differences from previous non-relativistic approximations. Thus, our results provide a basis for a rigorous confrontation of these theories with cosmological data.

(via Is our universe a bubble in the multiverse? | KurzweilAI)

The Universe Is Programmable. We Need an API for Everything - Think about it like this: In the Book of Genesis, God is the ultimate programmer, creating all of existence in a monster six-day hackathon. Or, if you don’t like Biblical metaphors, you can think about it in simpler terms. Robert Moses was a programmer, shaping and re-shaping the layout of New York City for more than 50 years. Drug developers are programmers, twiddling enzymes to cure what ails us. Even pickup artists and conmen are programmers, running social scripts on people to elicit certain emotional results. The point is that, much like the computer on your desk or the iPhone in your hand, the entire Universe is programmable. Just as you can build apps for your smartphones and new services for the internet, so can you shape and re-shape almost anything in this world, from landscapes and buildings to medicines and surgeries to, well, ideas — as long as you know the code. That may sound like little more than an exercise in semantics. But it’s actually a meaningful shift in thinking. If we look at the Universe as programmable, we can start treating it like software. In short, we can improve almost everything we do with the same simple techniques that have remade the creation of software in recent years, things like APIs, open source code, and the massively popular code-sharing service GitHub. (via The Universe Is Programmable. We Need an API for Everything | Enterprise | WIRED)

The Universe Is Programmable. We Need an API for Everything
-
Think about it like this: In the Book of Genesis, God is the ultimate programmer, creating all of existence in a monster six-day hackathon. Or, if you don’t like Biblical metaphors, you can think about it in simpler terms. Robert Moses was a programmer, shaping and re-shaping the layout of New York City for more than 50 years. Drug developers are programmers, twiddling enzymes to cure what ails us. Even pickup artists and conmen are programmers, running social scripts on people to elicit certain emotional results. The point is that, much like the computer on your desk or the iPhone in your hand, the entire Universe is programmable. Just as you can build apps for your smartphones and new services for the internet, so can you shape and re-shape almost anything in this world, from landscapes and buildings to medicines and surgeries to, well, ideas — as long as you know the code. That may sound like little more than an exercise in semantics. But it’s actually a meaningful shift in thinking. If we look at the Universe as programmable, we can start treating it like software. In short, we can improve almost everything we do with the same simple techniques that have remade the creation of software in recent years, things like APIs, open source code, and the massively popular code-sharing service GitHub. (via The Universe Is Programmable. We Need an API for Everything | Enterprise | WIRED)

Source Wired

The problem of human consciousness looms large, not just in the quantum problem. In thinking about thinking we have to use thought. Our brains are computational machines like any other, and so presumably subject to the same fundamental limits on their ability to reason. So what allows the human mind to establish that there are limits beyond which it cannot think?

The edge of reason: When logic fails us - physics-math - 04 November 2013 - New Scientist

Keep in mind that life on Earth isn’t going to be getting easier throughout all that future time—it will be getting harder, as the planet becomes less and less conducive for complex life. So we may have—we may be—the only chance available for life on Earth to somehow escape a final, ultimate planetary and stellar death. If we don’t do that, then the book’s title would become a prophecy: After fading into oblivion, the sum total of life’s history on Earth will only be billions of years of solitude.

Are We Alone? - Ross Andersen - The Atlantic

Q: Wait a minute. What do you mean, the universe is a mathematical structure?

M.T.: So right now, I’m eating an orange, which is made of cells. Why do they have the properties they do? Well, because they’re made of molecules. Why do the molecules have their properties? Because they’re made of atoms put together in a certain way. Why do the atoms have those properties? Because they’re made of quarks and electrons. What about the electron? What properties does it have? And the cool thing is, all the properties that electrons have are purely mathematical. It’s just a list of numbers. So in that sense, an electron is a purely mathematical object. In fact, there’s no evidence right now that there’s anything at all in our universe that is not mathematical.

Do We Live Inside a Mathematical Equation? - ScienceNOW
What is the purpose of the Universe? Here is one possible answer.
-
The more we learn about the universe, the more we discover just how diverse all its planets, stars, nebulae and unexplained chunks of matter really are. So what is all this matter doing in our universe, other than just floating in space? Well, it just so happens that there is a theory that gives a kind of raison d’etre to our universe and all the objects flying through it. If true, it would mean that our universe is nothing more than a black hole generator, or a means to produce as many baby universes as possible. To learn more, we spoke to the man who came up with the idea. It’s called the theory of Cosmological Natural Selection and it was conjured by Lee Smolin, a researcher at the Perimeter Institute for Theoretical Physics and and an adjunct professor of physics at the University of Waterloo. (via What is the purpose of the Universe? Here is one possible answer.)

What is the purpose of the Universe? Here is one possible answer.

-

The more we learn about the universe, the more we discover just how diverse all its planets, stars, nebulae and unexplained chunks of matter really are. So what is all this matter doing in our universe, other than just floating in space? Well, it just so happens that there is a theory that gives a kind of raison d’etre to our universe and all the objects flying through it. If true, it would mean that our universe is nothing more than a black hole generator, or a means to produce as many baby universes as possible. To learn more, we spoke to the man who came up with the idea. It’s called the theory of Cosmological Natural Selection and it was conjured by Lee Smolin, a researcher at the Perimeter Institute for Theoretical Physics and and an adjunct professor of physics at the University of Waterloo. (via What is the purpose of the Universe? Here is one possible answer.)

The universe may grow like a giant brain, according to a new computer simulation. The results, published Nov. 16 in the journal Nature’s Scientific Reports, suggest that some undiscovered, fundamental laws may govern the growth of systems large and small, from the electrical firing between brain cells and growth of social networks to the expansion of galaxies. “Natural growth dynamics are the same for different real networks, like the Internet or the brain or social networks,” said study co-author Dmitri Krioukov, a physicist at the University of California San Diego. The new study suggests a single fundamental law of nature may govern these networks, said physicist Kevin Bassler of the University of Houston, who was not involved in the study. [ What’s That? Your Physics Questions Answered ] “At first blush they seem to be quite different systems, the question is, is there some kind of controlling laws can describe them?” he told LiveScience. By raising this question, “their work really makes a pretty important contribution,” he said. (via Universe may grow like a giant brain - Technology & science - Science - LiveScience | NBC News)

The universe may grow like a giant brain, according to a new computer simulation. The results, published Nov. 16 in the journal Nature’s Scientific Reports, suggest that some undiscovered, fundamental laws may govern the growth of systems large and small, from the electrical firing between brain cells and growth of social networks to the expansion of galaxies. “Natural growth dynamics are the same for different real networks, like the Internet or the brain or social networks,” said study co-author Dmitri Krioukov, a physicist at the University of California San Diego. The new study suggests a single fundamental law of nature may govern these networks, said physicist Kevin Bassler of the University of Houston, who was not involved in the study. [ What’s That? Your Physics Questions Answered ] “At first blush they seem to be quite different systems, the question is, is there some kind of controlling laws can describe them?” he told LiveScience. By raising this question, “their work really makes a pretty important contribution,” he said. (via Universe may grow like a giant brain - Technology & science - Science - LiveScience | NBC News)