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Energy, Matter, Inflation, Eternal Inflation and Multiverses

(Andrei Linde) eternal inflation and the multiverse.
https://darkmatterdarkenergy.com/2015/12/06/eternal-inflation-and-the-multiverse/

Multiverse Controversy Heats Up over Gravitational Waves – By Clara Moskowitz on March 31, 2014
http://www.scientificamerican.com/article/multiverse-controversy-inflation-gravitational-waves/

Some physicists think they can explain why the universe first formed. If they are right, our entire cosmos may have sprung out of nothing at all – By Robert Adler –
6 November 2014
http://www.bbc.com/earth/story/20141106-why-does-anything-exist-at-all

The Case for Parallel Universes –
Why the multiverse, crazy as it sounds, is a solid scientific idea
By Alexander Vilenkin, Max Tegmark on July 19, 2011
http://www.scientificamerican.com/article/multiverse-the-case-for-parallel-universe/

What Came Before the Big Bang?
Cosmologist Alexander Vilenkin believes the Big Bang wasn’t a one-off event, but merely one of a series of big bangs creating an endless number of bubble universes – By Steve Nadis – Thursday, October 10, 2013
http://discovermagazine.com/2013/september/13-starting-point

A BALLOON PRODUCING BALLOONS, PRODUCING BALLOONS: A BIG FRACTAL
A Conversation with Andrei Linde [8.24.12]
https://www.edge.org/conversation/andrei_linde-a-balloon-producing-balloons-producing-balloonsa-big-fractal

Scientists find first evidence that many universes exist
December 17, 2010 by Lisa Zyga
http://m.phys.org/news/2010-12-scientists-evidence-universes.html

Cause And Effect, The Perfect Vacuum & Absolute Nothing

In the Beginning before the Big Bang | Michio Kaku | Dr Param Singh
http://mymultiplesclerosis.co.uk/btbb/beginning-big-bang-nothing/

The Physics of Nothing, The Philosophy of Everything – Ethan Siegel (August 16th 2011)
http://scienceblogs.com/startswithabang/2011/08/16/the-physics-of-nothing-the-phi/

Something from Nothing? A Vacuum Can Yield Flashes of Light
http://www.scientificamerican.com/article/something-from-nothing-vacuum-can-yield-flashes-of-light/

Physicists Confirm Power of Nothing, Measuring Force of Universal Flux
By MALCOLM W. BROWNE
Published: January 21, 1997
http://www.nytimes.com/1997/01/21/science/physicists-confirm-power-of-nothing-measuring-force-of-universal-flux.html?pagewanted=all

The Bridge From Nowhere
How is it possible to get something from nothing?
BY AMANDA GEFTER
http://m.nautil.us/issue/16/nothingness/the-bridge-from-nowhere

EVERYTHING FROM NOTHING
Posted on January 4, 2013 by James Keen
http://www.isciencemag.co.uk/blog/everything-from-nothing/

“Gravity Doesn’t Exist” – Is This Fundamental Phenomenon Of The Universe An Illusion
http://www.dailygalaxy.com/my_weblog/2012/11/gravity-doesnt-exist-is-gravity-an-illusion.html

Saint Augustine, Albert Einstein & The Augustinian Era

New York Times – Dennis Overbye
“Before the Big Bang, There Was . . . What?”
http://www.nytimes.com/2001/05/22/science/before-the-big-bang-there-was-what.html?pagewanted=all

Scientific American – Gabriele Veneziano
“The Myth of the Beginning of Time”
http://www.scientificamerican.com/article/the-myth-of-the-beginning-of-time-2006-02/?print=true

Discover Magazine – Adam Frank
“3 Theories That Might Blow Up the Big Bang”
http://discovermagazine.com/2008/apr/25-3-theories-that-might-blow-up-the-big-bang

Arguing for the Existence of God in the Age of Quantum Indeterminacy
Author: Evan Cockshaw
Quodlibet Journal: Volume 3 Number 1, Winter 2001
http://www.quodlibet.net/articles/cockshaw-quantum.shtml

What Came Before The Big Bang?
By Paul Davies
http://boingboing.net/2014/05/20/what-came-before-the-big-bang.html

Wonder and Knowledge
http://static1.1.sqspcdn.com/static/f/297809/4445061/1255571558447/2009-09-30-Wonder.pdf?token=iRuSBqZY70tQX6lAMWFTLkxwSr0%3D

Has Physics Made Philosophy and Religion Obsolete?
http://www.theatlantic.com/technology/archive/2012/04/has-physics-made-philosophy-and-religion-obsolete/256203/
“A Universe From Nothing: Why There Is Something Rather Than Nothing” [Book]
http://www.amazon.com/Universe-Nothing-There-Something-Rather/dp/145162445X

String theory: From Newton to Einstein and beyond By David Berman December 1, 2007

This article is part of the Researching the unknown project, a collaboration with researchers from Queen Mary University of London, bringing you the latest research on the forefront of physics.

Unifying forces

To understand the ideas and aims of string theory, it’s useful to look back and see how physics has developed from Newton’s time to the present day. One crucial idea that has driven physics since Newton’s time is that of unification: the attempt to explain seemingly different phenomena by a single overarching concept. Perhaps the first example of this came from Newton himself, who in his 1687 work Principia Mathematicae explained that the motion of the planets in the solar system, the motion of the Moon around the Earth, and the force that holds us to the Earth are all part of the same thing: the force of gravity. We take this for granted today, but pre-Newton the connection between a falling apple and the orbit of the Moon would have been far from obvious and quite amazing.

The next key unifying discovery was made around 180 years after Newton by the Scottish mathematician James Clerk Maxwell. Maxwell showed that electrostatics and magnetism, by no means similar phenomena at first sight, are just different aspects of a single thing called electromagnetism. In the process Maxwell discovered electromagnetic waves, which are in fact light — Maxwell had inadvertently explained a further seemingly different aspect of nature.

Another two hundred years on, in 1984, the Pakistani Abdus Salam and the American Steven Weinberg showed that the electromagnetic force and the weak nuclear force, which causes radioactive decay, are both just different aspects of a single force called the electroweak force.

This leaves us with three fundamental forces of nature: gravity, the electroweak force and the strong nuclear force which holds protons together.

Unifying matter

That deals with the forces, but what about matter? Many ancient belief systems have postulated that matter — and reality itself — is made from a finite number of elements. Modern physics confirms this idea. Experiments performed with the particle accelerator at CERN in Geneva have shown that there are just twelve basic building blocks of matter. These are known as the elementary particles. Everything we’ve ever seen in any experiment, here or in distant stars, is made of just these twelve elementary particles.

All this is truly impressive: the entire Universe, its matter and dynamics explained by just three forces and twelve elementary objects. It’s good, but we’d like to do better, and this is where string theory first enters: it is an attempt to unify further. To understand this, we have to tell another story.

Quantum gravity

There have been two great breakthroughs in the 20th century physics. Perhaps the most famous is Einstein’s theory of general relativity. The other equally impressive theory is quantum mechanics.

Massive bodies warp spacetime. Image coutesy NASA.
General relativity is itself a unification. Einstein realised that space and time are just different aspects of a single object he called spacetime. Massive bodies like planets can warp and distort spacetime, and gravity, which we experience as an attractive force, is in fact a consequence of this warping. Just as a pool ball placed on a trampoline will create a dip that a nearby marble will roll into, so does a massive body like a planet distort space, causing nearby objects to be attracted to it.

The predictions made by general relativity are remarkably accurate. In fact, most of us will have inadvertently taken part in an experiment that tests general relativity: if it were false, then global positioning systems would be wrong by about 50 metres per day. The fact that GPSs work to within five metres in ten years shows just how accurate general relativity is.

The other great breakthrough of the 20th century was quantum mechanics. One of the key ideas here is that the smaller the scale at which you look at the world, the more random things become. Heisenberg’s uncertainty principle is perhaps the most famous example of this. The principle states that when you consider a moving particle, for example an electron orbiting the nucleus of an atom, you can never ever measure both its position and its momentum as accurately as you like. Looking at space at a minuscule scale may allow you to measure position with a lot of accuracy, but there won’t be much you can say about momentum. This isn’t because your measuring instruments are imprecise. There simply isn’t a “true” value of momentum, but a whole range of values that the momentum can take, each with a certain probability. In short, there is randomness. This randomness appears when we look at particles at a small enough scale. The smaller one looks, the more random things become!

The idea that randomness is part of the very fabric of nature was revolutionary: it had previously been taken for granted that the laws of physics didn’t depend on the size of things. But in quantum mechanics they do. The scale of things does matter, and the smaller the scale at which you look at nature, the more different from our everyday view of the world it becomes: randomness dominates the small scale world.

What happens to spacetime at small scales?

Again, this theory has performed very well in experiments. Technological gadgets that have emerged from quantum theory include the laser and the microchip that populate every computer, mobile phone and MP3 player.

But what happens if we combine quantum mechanics and relativity? According to relativity, spacetime is something that can stretch and bend. Quantum mechanics says that on small scales things get random. Putting these two ideas together implies that on very small scales spacetime itself becomes random, pulling and stretching, until it eventually pulls itself apart.

Evidently, since spacetime is here and this hasn’t happened, there must be something wrong with combining relativity and quantum mechanics. But what? Both these theories are well-tested and believed to be true.

Perhaps we have made a hidden assumption?

It turns out that indeed we have. The assumption is that it’s possible to consider smaller and smaller distances and get to the point where spacetime pulls itself apart. What has rested in the back of our minds is that the basic indivisible building blocks of nature are point-like — but this may not necessarily be true.

Strings to the rescue

This is where string theory comes to the rescue. It suggests that there is a smallest scale at which we can look at the world: we can go that small but no smaller. String theory asserts that the fundamental building blocks of nature are not like points, but like strings: they have extension, in other words they have length. And that length dictates the smallest scale at which we can see the world.

What possible advantage could this have? The answer is that strings can vibrate. In fact they can vibrate in an infinite number of different ways. This is a natural idea in music. We don’t think that every single sound in a piece of music is produced by a different instrument; we know that a rich and varied set of sounds can be produced by even just a single violin. String theory is based on the same idea. The different particles and forces are just the fundamental strings vibrating in a multitude of different ways.

The mathematics behind string theory is long and complicated, but it has been worked out in detail. But has anyone ever seen such strings? The honest answer is “no”. The current estimate of the size of these strings is about 10-34m, far smaller than we can see today, even at CERN. Still, string theory is so far the only known way to combine gravity and quantum mechanics, and its mathematical elegance is for many scientists sufficient reason to keep pursuing it.

The theory’s predictions

If string theory is indeed an accurate model of spacetime, then what else does it tell us about the world?

One of its more startling and most significant predictions is that spacetime is not four, but ten-dimensional. It is only in ten dimensions of spacetime that string theory works. So where are those six extra dimensions? The idea of hidden dimensions was in fact put forward many years before the advent of string theory by the German Theodor Kaluza and the Swede Oskar Klein.

Shortly after Einstein described the bending of space in general relativity, Kaluza and Klein considered what would happen if a spatial dimension would bend round and rejoin itself to form a circle. The size of that circle could be very small, perhaps so small that it couldn’t be seen. Those dimensions could then be hidden from view. Kaluza and Klein did show that in spite of this, these dimensions could still have an effect on the world we perceive. Electromagnetism becomes a consequence of the hidden circle with motion in the hidden dimension being electric charge. Hidden dimensions are possible and they in fact can give rise to forces in the dimensions that we can see.

String theory has embraced the Kaluza-Klein idea and currently various experiments are being devised to try and observe the hidden dimensions. One hope is that the extra dimensions may have left an imprint on the cosmic microwave background, the left-over radiation from the Big Bang, and that a detailed study of this radiation may reveal them. Other experiments are more direct. The force of gravity depends crucially on the number of dimensions, so by studying gravitational forces at short distances one can hope to detect deviations from Newton’s law and again see the presence of extra dimensions.

Mathematics and physics have always influenced each other, with new mathematics being invented to describe nature, and old mathematics turning out to lend perfect descriptions for newly-discovered physical phenomena. String theory is no different and many mathematicians work on ideas inspired by it. These include the possible geometries of the hidden dimensions, the basic ideas of geometry when there is a minimum distance, the ways in which strings can split and come together, and the question of how we can relate strings to the particles in the world that we see.

String theory gives us an exciting vision of nature as miniscule bits of vibrating string in a space with hidden curled-up dimensions. All the implications of these ideas are yet to be understood. String theory is an active area of research with hundreds of people working to see how the theory fits together and produces the world we see around us.

About the author

David Berman is a lecturer in theoretical physics at Queen Mary University of London. He previously spent time at the universities of Manchester, Brussels, Durham, Utrecht, Groningen, Jerusalem and Cambridge as well as a year at CERN in Geneva.

His interests outside of physics include football, music and theatre and the arts.

Physics Titan Still Thinks String Theory Is “On the Right Track” – By John Horgan on September 22, 2014

At a 1990 conference on cosmology, I asked attendees, who included folks like Stephen Hawking, Michael Turner, James Peebles, Alan Guth and Andrei Linde, to nominate the smartest living physicist.

Edward Witten got the most votes (with Steven Weinberg the runner-up). Some considered Witten to be in the same league as Einstein and Newton. Witten was and is famous for his work on string theory, which unifies quantum mechanics and relativity and holds that all of nature’s forces—including gravity–stem from infinitesimal particles wriggling in a hyperspace consisting of many extra dimensions.

Even then, string theory—which some enthusiasts (not including Witten) called a “theory of everything”–was extremely controversial, because there seemed to be no way to confirm experimentally the existence of strings or the extra dimensions they supposedly inhabit. I was thus thrilled a year later when Witten agreed, albeit reluctantly, to an interview at the Institute for Advanced Study in Princeton. After our encounter, I wrote a short profile of Witten, “The Pied Piper of Superstrings,” published in Scientific American in 1991; and a longer profile for my 1996 book The End of Science. Here is an excerpt from the latter:

I asked Witten how he responded to the claims of critics that superstring theory is not testable and therefore is not really physics at all. Witten replied that the theory had predicted gravity. “Even though it is, properly speaking, a post-prediction, in the sense that the experiment was made before the theory, the fact that gravity is a consequence of string theory, to me, is one of the greatest theoretical insights ever.”

He acknowledged, even emphasized, that no one has truly fathomed the theory, and that it might be decades before it yielded a precise description of nature. He would not predict, as others had, that string theory might bring about the end of physics. Nevertheless, he was serenely confident that it would eventually yield a profound new understanding of reality. “Good wrong ideas are extremely scarce,” he said, “and good wrong ideas that even remotely rival the majesty of string theory have never been seen.” When I continued to press Witten on the issue of testability, he grew exasperated. “I don’t think I’ve succeeded in conveying to you its wonder, its incredible consistency, remarkable elegance and beauty.” In other words, superstring theory is too beautiful to be wrong.

Recently, Witten won the prestigious Kyoto Prize, created by Japan’s Inamori Foundation to honor “those who have contributed significantly to the scientific, cultural and spiritual betterment of mankind.” Witten won 50 million yen, or about $500,000, in the category of basic sciences. The Kyoto Prize website states: “Dr. Witten has made significant contributions to theoretical physics for more than 30 years as a leader in the dramatic evolution of superstring theory. Moreover, by applying his physical intuition and mathematical skills, he has advanced mathematics, and prompted the cutting−edge research of many mathematicians.”

My profiles of Witten were pretty snarky. So when a publicist for the Kyoto Prize asked recently if I would like to interview Witten, I was pleasantly surprised. I submitted some questions, and Witten graciously answered them by email.

Horgan: When I interviewed you in 1991, you said that “good wrong ideas that even remotely rival the majesty of string theory have never been seen.” Are you still confident that string theory (or its descendant, M theory) will turn out to be “right”?

Witten: I think I will stick with what I said in 1991. Since then, we have lived through the second superstring evolution and many surprising developments in which string theory has been used to get a better understanding of conventional theories in physics (and math). All this makes most sense if one assumes that what we are doing is on the right track. (My 2005 article “Unravelling string theory,” gives somewhat more detail.)

Horgan: Do you see any other rivals for a unified theory of physics?

Witten: There are not any interesting competing suggestions. One reason, as remarked in “Unravelling,” is that interesting competing ideas (twistor theory, noncommutative geometry, …) tend to be absorbed as part of a larger picture in string theory. The competing interesting ideas have been very fragmentary and have tended to gain power when absorbed in string theory.

Horgan: There are an estimated 10500 versions of string theory, each of which “predicts” a different universe. Leonard Susskind and others propose that these hypothetical universes actually exist, forming a multiverse “landscape.” But physicists such as Peter Woit, Paul Steinhardt and George Ellis complain that string and multiverse theories may be untestable and hence not truly scientific. How do you respond to these criticisms?

Witten: Personally, I hope the landscape interpretation of the universe would turn out to be wrong, as I would like to be able to eventually calculate from first principles the ratio of the masses of the electron and muon (among other things). However, the universe wasn’t made for our convenience. Plenty of leading physicists — prominent examples being Steve Weinberg and Martin Rees — have taken the acceleration of the cosmic expansion seriously as a hint that a landscape interpretation of the universe may be correct. This was a monumental discovery, which was announced in 1998 (two years after publication of your book The End of Science — unfortunate timing!). It was so shocking that it was several years, and a lot more data, before I personally was convinced of that finding.

If the landscape interpretation is correct, can we get additional clues that would make this more believable? One obvious possibility involves the outcome of Large Hadron Collider experiments. I explain why in my 2004 article, “When symmetry breaks down.” What I wrote there wasn’t original but provides a succinct explanation. The literature is filled with other suggestions about how we might conceivably get more clues about a landscape interpretation if that is correct (for example seeing a signature of a prior phase transition in the cosmic microwave radiation). It is hard to summarize these suggestions for you as it is hard to know which proposals are most worth describing.

Another possibility is that a theory that predicts a landscape would become well-established because of other predictions it made. The trouble with criticizing string theory because it plausibly predicts a landscape of vacua is that the landscape interpretation of the universe might be correct. 200 years from now, if more clues have emerged, possibly including some that are unforeseeable now, it might seem obvious that the landscape of string vacua was necessary to make string theory viable.

Horgan: Do you agree with Sean Carroll that falsifiability is overrated as a criterion for distinguishing science from pseudo-science?

Witten: Scientists aim to get as reliable and precise an understanding of nature as we can. The gold standard is a precise prediction that can be tested in a precise way in a laboratory experiment. Experiments that disprove theories are an important part of the scientific process.
With that said, it is a little too narrow to claim that science consists of trying to falsify theories because a lot of science consists of trying to discover things. (Chemists who attempt a new synthesis could say they are trying to falsify the hypothesis that this new synthesis won’t work. But that isn’t what they usually say. People who search for life on Mars could say they are trying to falsify the hypothesis that there is no life on Mars. Again, people don’t usually talk that way.)

Horgan: Are multiverse theories—whether inspired by string theory or other ideas—falsifiable? If not, should they be taken seriously?

Witten: If the landscape interpretation of the universe is correct, it certainly might be possible to get additional clues supporting this, as I indicated in an answer above.

Horgan: Some proponents of multiverse theories have promoted the anthropic principle as an answer to the question of why we live in this universe and not an entirely different one. Do you think the anthropic principle is a legitimate scientific proposition?

Witten: As I also wrote above, I would prefer an explanation of the universe from first principles, with no anthropic considerations. But once again, the universe wasn’t created for our convenience and it is useless to have preconceptions about what the answer is.

Horgan: Do you think science will ever explain exactly how the universe came into being? Why there is something rather than nothing?

Witten: Science has had an amazing amount of success in understanding the early universe, and for example, as you probably know, the evidence for cosmic “inflation” is vastly greater than when we last talked (or when your book appeared). However, when you ask if we will understand “exactly” how the universe came into being, that is a very high bar.

I think I would prefer to just say what I can see that might give a better understanding. Obviously, there are forthcoming observations that may help. The most immediate will be more data on the polarization of the cosmic microwave radiation. We should know more there within a few years. On a time scale of a few decades, fundamentally new insight might come from observations of the cosmic 21-centimeter background radiation and probably from other techniques.

However, as a theorist, I would like to also comment on theoretical loose ends that might offer hope of further progress. One involves cosmic inflation. As I’ve remarked, there is by now quite a lot of evidence for cosmic inflation. But there also isn’t a completely consistent, logically sound mathematical framework for the theory of cosmic inflation. If inflation is correct, then I think there is a good hope this problem might eventually be solved and that might lead to a better understanding of the early universe. Likewise, since we last talked, there has been tremendous progress in understanding the behavior of string theory when quantum effects are strong. But there has been very little progress in understanding the behavior when time-dependent effects are large (which would be important in the very early universe).
This is a relatively well-posed mathematical problem and I imagine there is a good chance for eventually getting insight, which again might lead to a better understanding about the early universe.

Horgan: Are there any mysteries that you think science will never explain?

Witten: As in any endeavor, all we can do is to do our best, without knowing at the beginning of the journey how far we will be able to get. The modern scientific endeavor has been going on for hundreds of years by now, and we’ve gotten way farther than our predecessors probably imagined.

Horgan: Some physicists, such as Stephen Hawking and Lawrence Krauss, have denigrated philosophy as obsolete. Do you agree? Are there any philosophers, living or dead, whose work you find interesting or useful to your work?

Witten: Personally I am most influenced by some of the “natural philosophers” of the past, such as James Clerk Maxwell.
Horgan: Are you religious? Do you think science and religion are compatible?

Witten: I consider scientific explanations to be more interesting and illuminating.

Addendum: Like Witten, I was shocked by—and initially skeptical of–the discovery in the late 1990s that the universe is expanding at a growing rate. Now, I view it as “by far the most exciting advance in physics and cosmology in the last decade,” as I put it in 2006. If I wanted to criticize The End of Science, I’d lead with cosmic acceleration. But so far the discovery remains just an interesting twist in the big bang theory, which has not precipitated the kinds of revolutionary theoretical breakthroughs and paradigm shifts that took place in the early 20th century.

Clarification from Witten: I was not alluding to the BICEP findings when I said that the evidence for inflation today is vastly greater than it was when your book appeared. I was referring to the totality of data on cosmic microwave fluctuations which emerged in the decade after your book was published. The evidence for something like inflation in the early universe is indeed vastly stronger. Virtually any physicist or astronomer will tell you that, although there are exceptions. The only implicit allusion to BICEP in my remarks was actually when I wrote (later in the interview, in answer to the question about whether we would ever have a complete knowledge about the origin of the universe) that within a few years we would know more about the polarization of the CMB. What I meant (and I think my phrasing, which reflects questions that have been raised about BICEP, would be clear to colleagues) was that within a few years we will know whether the effect claimed by BICEP exists at a level that can be detected in the CMB.

A Theory of Everything? By Brian GreenePosted 10.28.03 NOVA

The fundamental particles of the universe that physicists have identified—electrons, neutrinos, quarks, and so on—are the “letters” of all matter. Just like their linguistic counterparts, they appear to have no further internal substructure. String theory proclaims otherwise. According to string theory, if we could examine these particles with even greater precision—a precision many orders of magnitude beyond our present technological capacity—we would find that each is not pointlike but instead consists of a tiny, one-dimensional loop. Like an infinitely thin rubber band, each particle contains a vibrating, oscillating, dancing filament that physicists have named a string.

Although it is by no means obvious, this simple replacement of point-particle material constituents with strings resolves the incompatibility between quantum mechanics and general relativity (which, as currently formulated, cannot both be right). String theory thereby unravels the central Gordian knot of contemporary theoretical physics. This is a tremendous achievement, but it is only part of the reason string theory has generated such excitement.

FIELD OF DREAMS

In Einstein’s day, the strong and weak forces had not yet been discovered, but he found the existence of even two distinct forces—gravity and electromagnetism—deeply troubling. Einstein did not accept that nature is founded on such an extravagant design. This launched his 30-year voyage in search of the so-called unified field theory that he hoped would show that these two forces are really manifestations of one grand underlying principle. This quixotic quest isolated Einstein from the mainstream of physics, which, understandably, was far more excited about delving into the newly emerging framework of quantum mechanics. He wrote to a friend in the early 1940s, “I have become a lonely old chap who is mainly known because he doesn’t wear socks and who is exhibited as a curiosity on special occasions.”

Einstein was simply ahead of his time. More than half a century later, his dream of a unified theory has become the Holy Grail of modern physics. And a sizeable part of the physics and mathematics community is becoming increasingly convinced that string theory may provide the answer. From one principle—that everything at its most microscopic level consists of combinations of vibrating strands—string theory provides a single explanatory framework capable of encompassing all forces and all matter.

String theory proclaims, for instance, that the observed particle properties—that is, the different masses and other properties of both the fundamental particles and the force particles associated with the four forces of nature (the strong and weak nuclear forces, electromagnetism, and gravity)—are a reflection of the various ways in which a string can vibrate. Just as the strings on a violin or on a piano have resonant frequencies at which they prefer to vibrate—patterns that our ears sense as various musical notes and their higher harmonics—the same holds true for the loops of string theory. But rather than producing musical notes, each of the preferred mass and force charges are determined by the string’s oscillatory pattern. The electron is a string vibrating one way, the up-quark is a string vibrating another way, and so on.

A THEORY TO END THEORIES

For the first time in the history of physics we therefore have a framework with the capacity to explain every fundamental feature upon which the universe is constructed. For this reason string theory is sometimes described as possibly being the “theory of everything” (T.O.E.) or the “ultimate” or “final” theory. These grandiose descriptive terms are meant to signify the deepest possible theory of physics—a theory that underlies all others, one that does not require or even allow for a deeper explanatory base.

In practice, many string theorists take a more down-to-earth approach and think of a T.O.E. in the more limited sense of a theory that can explain the properties of the fundamental particles and the properties of the forces by which they interact and influence one another. A staunch reductionist would claim that this is no limitation at all, and that in principle absolutely everything, from the Big Bang to daydreams, can be described in terms of underlying microscopic physical processes involving the fundamental constituents of matter. If you understand everything about the ingredients, the reductionist argues, you understand everything.

The reductionist philosophy easily ignites heated debate. Many find it fatuous and downright repugnant to claim that the wonders of life and the universe are mere reflections of microscopic particles engaged in a pointless dance fully choreographed by the laws of physics. Is it really the case that feelings of joy, sorrow, or boredom are nothing but chemical reactions in the brain—reactions between molecules and atoms that, even more microscopically, are reactions between some of the fundamental particles, which are really just vibrating strings?

In response to this line of criticism, Nobel laureate Steven Weinberg cautions in Dreams of a Final Theory:
At the other end of the spectrum are the opponents of reductionism who are appalled by what they feel to be the bleakness of modern science. To whatever extent they and their world can be reduced to a matter of particles or fields and their interactions, they feel diminished by that knowledge….I would not try to answer these critics with a pep talk about the beauties of modern science. The reductionist worldview is chilling and impersonal. It has to be accepted as it is, not because we like it, but because that is the way the world works.

Some agree with this stark view, some don’t.

Others have tried to argue that developments such as chaos theory tell us that new kinds of laws come into play when the level of complexity of a system increases. Understanding the behavior of an electron or quark is one thing; using this knowledge to understand the behavior of a tornado is quite another. On this point, most agree. But opinions diverge on whether the diverse and often unexpected phenomena that can occur in systems more complex than individual particles truly represent new physical principles at work, or whether the principles involved are derivative, relying, albeit in a terribly complicated way, on the physical principles governing the enormously large number of elementary constituents.

My own feeling is that they do not represent new and independent laws of physics. Although it would be hard to explain the properties of a tornado in terms of the physics of electrons and quarks, I see this as a matter of calculational impasse, not an indicator of the need for new physical laws. But again, there are some who disagree with this view.

A FRESH START FOR SCIENCE

What is largely beyond question, and is of primary importance to the journey described in my book The Elegant Universe, is that even if one accepts the debatable reasoning of the staunch reductionist, principle is one thing and practice quite another. Almost everyone agrees that finding the T.O.E. would in no way mean that psychology, biology, geology, chemistry, or even physics had been solved or in some sense subsumed. The universe is such a wonderfully rich and complex place that the discovery of the final theory, in the sense we are describing here, would not spell the end of science.

Quite the contrary: The discovery of the T.O.E.—the ultimate explanation of the universe at its most microscopic level, a theory that does not rely on any deeper explanation—would provide the firmest foundation on which to build our understanding of the world. Its discovery would mark a beginning, not an end. The ultimate theory would provide an unshakable pillar of coherence forever assuring us that the universe is a comprehensible place.

This feature originally appeared on the site for the NOVA program The Elegant Universe.

Brian Greene is a professor of physics and mathematics at Columbia University and a leading string theorist. He is author of The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory (Norton, 1999).

Watch: The best explanation of string theory we’ve seen We get it now. FIONA MACDONALD 5 NOV 2015

Brian Greene:
Making sense of string theory
TED2005 · 19:06 · Filmed Feb 2005https://www.ted.com/talks/brian_greene_on_string_theory

When it comes to physics, there are some pretty complicated ideas out there, but one of the most confusing is string theory, which involves the existence of extra dimensions, tiny strings within atoms and, well, a whole lot else we don’t really understand. But in this 2005 TED talk, theoretical physicist Brian Greene, author of New York Times bestsellers The Fabric of the Cosmos and The Hidden Reality, explains the basics. And to date it’s still the best explanation we’ve ever seen.

In addition to his work as a science communicator, Greene is also a researcher at Cornell University in the US, where he works on superstring theory, which is an attempt to come up with a theory for everything to explain how all the particles and forces in the Universe work. Importantly, superstring theory tries to explain why all the conditions in the Universe are finely tuned to support life.

So what does it all mean? As you might expect, Greene does a much better job of breaking it down than we can, so you should really watch the video above. But if you’re looking or the ELI5 version, we can help you out with that.

Basically, superstring theory is an attempt to figure out what the smallest, most indivisible, fundamental constituents of the Universe are. Take an object like a candle, for example. We all know that if you look closely enough, that candle is made up of atoms. And the atoms are made up of electrons, protons, and neutrons. If you get even further down, protons and neutrons are made up of quarks. And that’s where conventional ideas end.

But, according to string theory, there’s actually something even smaller inside the quarks, and these are dancing filaments of energy that look a lot like beautiful vibrating strings – hence the name string theory. According to the idea of string theory, these cosmic strings vibrate in different patterns to make up all the different types of particles that form the world around us.

And that’s where the theory of everything comes into it, because if string theory is correct, then everything in the Universe is controlled and composed of these tiny cosmic strings, and if we can understand them, then we could understand the fundamental rules that govern nature.

Unfortunately it’s not that simple, because for this theory to pan out mathematically, we can’t just have three dimensions of space in the Universe. We actually need 10 dimensions of space, and one dimension of time.

Watch the video above to find out why that makes more sense than you might think and how physicists are now actively seeking out these extra dimensions. We promise that by the end of it you’ll actually be able to explain string theory to your friends at your next dinner party.

But there is one quick update we need to make – obviously this was filmed while the Large Hadron Collider was still being built at CERN in Switzerland, and as yet, the machine hasn’t been able to confirm the existence of these extra dimensions.

However, now that it’s running at record-breaking new energy levels, and with China announcing they’re going to be buliding a particle accelerator twice the size in the coming years, we’re closer than ever to being able to actually test string theory. And that’s really, really exciting.

Behemoth Black Hole Found in an Unlikely Place

Astronomers have uncovered a near-record breaking supermassive black hole, weighing 17 billion suns, in an unlikely place: in the center of a galaxy in a sparsely populated area of the universe. The observations, made by NASA’s Hubble Space Telescope and the Gemini Telescope in Hawaii, may indicate that these monster objects may be more common than once thought.

Until now, the biggest supermassive black holes – those roughly 10 billion times the mass of our sun – have been found at the cores of very large galaxies in regions of the universe packed with other large galaxies. In fact, the current record holder tips the scale at 21 billion suns and resides in the crowded Coma galaxy cluster that consists of over 1,000 galaxies.

“The newly discovered supersized black hole resides in the center of a massive elliptical galaxy, NGC 1600, located in a cosmic backwater, a small grouping of 20 or so galaxies,” said lead discoverer Chung-Pei Ma, a University of California-Berkeley astronomer and head of the MASSIVE Survey, a study of the most massive galaxies and supermassive black holes in the local universe. While finding a gigantic black hole in a massive galaxy in a crowded area of the universe is to be expected – like running across a skyscraper in Manhattan – it seemed less likely they could be found in the universe’s small towns.

“There are quite a few galaxies the size of NGC 1600 that reside in average-size galaxy groups,” Ma said. “We estimate that these smaller groups are about 50 times more abundant than spectacular galaxy clusters like the Coma cluster. So the question now is, ‘Is this the tip of an iceberg?’ Maybe there are more monster black holes out there that don’t live in a skyscraper in Manhattan, but in a tall building somewhere in the Midwestern plains.”

The researchers also were surprised to discover that the black hole is 10 times more massive than they had predicted for a galaxy of this mass. Based on previous Hubble surveys of black holes, astronomers had developed a correlation between a black hole’s mass and the mass of its host galaxy’s central bulge of stars – the larger the galaxy bulge, the proportionally more massive the black hole. But for galaxy NGC 1600, the giant black hole’s mass far overshadows the mass of its relatively sparse bulge. “It appears that that relation does not work very well with extremely massive black holes; they are a larger fraction of the host galaxy’s mass,” Ma said.

Ma and her colleagues are reporting the discovery of the black hole, which is located about 200 million light years from Earth in the direction of the constellation Eridanus, in the April 6 issue of the journal Nature. Jens Thomas of the Max Planck-Institute for Extraterrestrial Physics, Garching, Germany is the paper’s lead author.

One idea to explain the black hole’s monster size is that it merged with another black hole long ago when galaxy interactions were more frequent. When two galaxies merge, their central black holes settle into the core of the new galaxy and orbit each other. Stars falling near the binary black hole, depending on their speed and trajectory, can actually rob momentum from the whirling pair and pick up enough velocity to escape from the galaxy’s core. This gravitational interaction causes the black holes to slowly move closer together, eventually merging to form an even larger black hole. The supermassive black hole then continues to grow by gobbling up gas funneled to the core by galaxy collisions. “To become this massive, the black hole would have had a very voracious phase during which it devoured lots of gas,” Ma said.

The frequent meals consumed by NGC 1600 may also be the reason why the galaxy resides in a small town, with few galactic neighbors. NGC 1600 is the most dominant galaxy in its galactic group, at least three times brighter than its neighbors. “Other groups like this rarely have such a large luminosity gap between the brightest and the second brightest galaxies,” Ma said.

Most of the galaxy’s gas was consumed long ago when the black hole blazed as a brilliant quasar from material streaming into it that was heated into a glowing plasma. “Now, the black hole is a sleeping giant,” Ma said. “The only way we found it was by measuring the velocities of stars near it, which are strongly influenced by the gravity of the black hole. The velocity measurements give us an estimate of the black hole’s mass.”

The velocity measurements were made by the Gemini Multi-Object Spectrograph (GMOS) on the Gemini North 8-meter telescope on Mauna Kea in Hawaii. GMOS spectroscopically dissected the light from the galaxy’s center, revealing stars within 3,000 light-years of the core. Some of these stars are circling around the black hole and avoiding close encounters. However, stars moving on a straighter path away from the core suggest that they had ventured closer to the center and had been slung away, most likely by the twin black holes.

Archival Hubble images, taken by the Near Infrared Camera and Multi-Object Spectrometer (NICMOS), supports the idea of twin black holes pushing stars away. The NICMOS images revealed that the galaxy’s core was unusually faint, indicating a lack of stars close to the galactic center. A star-depleted core distinguishes massive galaxies from standard elliptical galaxies, which are much brighter in their centers. Ma and her colleagues estimated that the amount of stars tossed out of the central region equals 40 billion suns, comparable to ejecting the entire disk of our Milky Way galaxy.

For more information, visit:

http://www.nasa.gov/hubble
http://hubblesite.org/newscenter/archive/releases/2016/12/

Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4488 / 410-338-4514
villard@stsci.edu

Last Updated: April 6, 2016

GM=tc^3 Adventures in Space/Time Monday, September 03, 2007 Not Dark Energy

The speculation called “dark energy” is subject of more questions in NEW SCIENTIST, Swiss cheese universe challenges dark energy.

“Dark energy may not be needed to explain why the expansion of space appears to be speeding up. If our universe is like Swiss cheese on large scales – with dense regions of matter and holes with little or no matter – it could at least partly mimic the effects of dark energy, suggests a controversial new model of the universe.”

As nige has noted, if the Universe is not homogeneous different regions will appear to expand at different rates. If your telescope looked in a direction of lower expansion, the Universe would appear to be accelerating. This adds to many anisotropies seen in the Cosmic Microwave Background. Though this model is very preliminary, physicists Sabino Matarrese and Rocky Kolb have published online On cosmological observables in a swiss cheese universe.

Back in March (2007), NEW SCIENTIST published Is dark energy an illusion?

“The quickening pace of our universe’s expansion may not be driven by a mysterious force called dark energy after all, but paradoxically, by the collapse of matter in small regions of space.”

Just last week A Hole In the Universe indicated that the Universe is not quite homogeneous, and a cosmology including “dark energy” may be all wrong. The proposed Supernova Acceleration Probe would survey only 15 square degrees of sky before ending its service life. The whole sky has an area of 41,253 square degrees! If SNAP looked at the wrong part of an inhomogeneous sky, it could give researchers the wrong value of cosmic acceleration. Then again, disciples of “dark energy” may already have the wrong idea.

Lawrence Krauss said that supernova data “naively implied that the Universe is accelerating.” The inferrence of cosmic acceleration relies on a daisy chain of assumptions, including homogeneity. It especially relies on assumption of a constant speed of light. SNAP/JDEM is subject to a review whose results will be announced Wednesday. With all the outstanding questions about its basic science, it is hard to see how SNAP can supersede projects like Constellation-X.
L. Riofrio at 5:50 PM

DAILY NEWS 31 August 2007 ‘Swiss cheese’ universe challenges dark energy By Anil Ananthaswamy

Dark energy may not be needed to explain why the expansion of space appears to be speeding up. If our universe is like Swiss cheese on large scales – with dense regions of matter and holes with little or no matter – it could at least partly mimic the effects of dark energy, suggests a controversial new model of the universe.

In 1998, astronomers found that distant supernovae were dimmer, and thus farther away, than expected. This suggested the expansion of the universe was accelerating as a result of a mysterious entity dubbed dark energy, which appears to make up 73% of the universe.

But trying to pin down the nature of dark energy has proven extremely difficult. Theories of particle physics suggest that space does have an inherent energy, but this energy is about 10120 times greater than what is actually observed.

This has caused some cosmologists to look for alternative explanations. “I don’t have anything against dark energy, but we ought to make all possible efforts to see whether we can avoid this exotic component in the universe,” says Sabino Matarrese of the University of Padova in Italy.

So he and colleagues, including Edward Kolb of the Fermi National Accelerator Laboratory in Batavia, Illinois, US, decided to model the universe as having large-scale variations in density.

That contradicts the standard model of cosmology, which assumes that the universe is homogeneous on large scales. In the homogeneous model, known as the Friedmann-Robertson-Walker (FRW) universe, the effect of dark energy is to stretch space, thus increasing the wavelength of photons from the supernovae.

Testing assumptions

A similar effect was seen when the researchers added large-scale spherical holes to the FRW universe. They allowed the density of matter within each hole to vary with radius and found that in certain cases, photons travelling through under-dense voids had their wavelengths stretched, mimicking dark energy.

The extent of the effect depends on the exact location of the supernovae and how many under-dense regions the photons have to cross before reaching Earth. And Matarrese cautions that the deviations are not enough to explain away all of the observed dark energy. He says their model is still very preliminary: “We are very far away from getting the full solution.”

Cosmologist Sean Carroll at Caltech in Pasadena, US, says the Swiss-cheese model is interesting and useful as a test of more mainstream theories. “The overwhelming majority of cosmologists think that the completely smooth approximation is a very good one,” Carroll told New Scientist. “But if you want to have confidence that you are on the right track, you better not just make assumptions and cross your fingers, you better test it.”

Up for debate

Astrophysicist Niayesh Afshordi of Harvard University in Cambridge, Massachusetts, US, is less impressed. Astronomical observations suggest that the density of matter in the universe is relatively smooth – and not like Swiss cheese – at scales of about 100 million light years or larger, he says. The new research, however, suggests that space is holey on scales of 500 million light years.

“The model is very inhomogeneous on scales that we observe as homogeneous,” Afshordi told New Scientist. “What we can learn from the toy model is not really applicable to this universe, because the properties of this model are very different what we see in our universe.”

However, team member Antonio Riotto of the University of Geneva in Switzerland argues that their Swiss-cheese model is realistic in the sense “that the universe is characterised by under-dense regions”.

“We know that the universe has voids, you can debate about their size,” he says. In fact, recent observations suggest that voids can extend across nearly a billion light years. Riotto says their model was worked out independently of that discovery, but “this observation is welcome by us”.