So You Think there is a Multiverse?

 

As appeared in New Scientist, 20 January 2015 by Lee Smolin

COSMOLOGY is in crisis. Recent experiments have given us an increasingly precise narrative of the history of our universe, but attempts to interpret the data have led to a picture of a “preposterous universe” that eludes explanation in the terms familiar to scientists.

Everything we know suggests that the universe is unusual. It is flatter, smoother, larger and emptier than a “typical” universe predicted by the known laws of physics. If we reached into a hat filled with pieces of paper, each with the specifications of a possible universe written on it, it is exceedingly unlikely that we would get a universe anything like ours in one pick – or even a billion.

The challenge that cosmologists face is to make sense of this specialness. One approach to this question is inflation – the hypothesis that the early universe went through a phase of exponentially fast expansion. At first, inflation seemed to do the trick. A simple version of the idea gave correct predictions for the spectrum of fluctuations in the cosmic microwave background.

But a closer look shows that we have just moved the problem further back in time. To make inflation happen at all requires us to fine-tune the initial conditions of the universe. And unless inflation is highly tuned and constrained, it leads to a runaway process of universe creation. As a result, some cosmologists suggest that there is not one universe, but an infinite number, with a huge variety of properties: the multiverse. There are an infinite number of universes in the collection that are like our universe and an infinite number that are not. But the ratio of infinity to infinity is undefined, and can be made into anything the theorist wants. Thus the multiverse theory has difficulty making any firm predictions and threatens to take us out of the realm of science.

These other universes are unobservable and because chance dictates the random distribution of properties across universes, positing the existence of a multiverse does not let us deduce anything about our universe beyond what we already know. As attractive as the idea may seem, it is basically a sleight of hand, which converts an explanatory failure into an apparent explanatory success. The success is empty because anything that might be observed about our universe could be explained as something that must, by chance, happen somewhere in the multiverse.

We started out trying to explain why the universe is so special, and we end up being asked to believe that our universe is one of an infinite number of universes with random properties. This makes me suspect that there is a basic but unexamined assumption about the laws of nature that must be overturned.

Cosmology has new questions to answer. Not just what are the laws, but why are these laws the laws? How were they chosen? We can’t just hypothesise what the initial conditions were at the big bang, we need to explain those initial conditions. Thus we are in the position of a computer program asked to explain its inputs. It is clear that if we are to get anywhere, we need to invent new methods, and perhaps new kinds of laws, to gain a scientific description of the universe as a whole.

Physicist James Hartle has talked about the “excess baggage” that has to be left on the platform before we can board the train to further progress in cosmology. In work together with philosopher Roberto Mangabeira Unger, we believe we have identified several of pieces of this baggage.

The first thing that must be discarded is the assumption that the same kind of laws that work on the scale of small subsystems of the world work, scaled up, at the level of the whole universe. We call this assumption the cosmological fallacy because it leads to a breakdown of predictability – as in the multiverse.

The second piece of excess baggage is the Newtonian paradigm, a method common to classical and quantum mechanics and general relativity. It is used to describe a subsystem of the universe, like a system studied in a laboratory, an atom or a star. This method depends on two elements: the set of possible initial configurations (or states) of the system and a law that specifies how the states change in time. Once we start the system off at an initial state, the law tells us what the state will be at later times. But if the laws and initial conditions are the inputs to the method, they cannot be its outputs too. If we want to understand why the laws hold and how the initial conditions of the universe are chosen, we need a new kind of law and methodology.

The Newtonian paradigm is ideal for describing systems in a laboratory but if we attempt to apply it to the universe, it explains both too little and too much. It fails to explain how the solution to the laws governing our universe is picked from the infinite number of solutions that don’t govern anything. But it also predicts an infinite number of facts about an infinite number of non-existent universes. This is one of the reasons why the Newtonian paradigm cannot be applied to the universe as a whole.

These concepts illuminate why the multiverse fails as a scientific hypothesis in spite of the fact that simple versions of inflation made some predictions that have been confirmed. The idea of inflation is plagued by the need to explain how the initial conditions were chosen. This was done in the context of a methodology that only makes sense when applied to a subsystem of a larger system. When applied to the universe, it forced us to treat the universe as a subsystem of a much larger system: hence we had to invent the multiverse. And thus with an infinite ensemble of unobservable entities we leave the domain of science behind. In some sense, the multiverse embodies the unreal ensemble of all possible solutions to the laws of physics, imagined as elements of an invented ensemble of bubble universes. But this just trades one imaginary, unreal ensemble for another.

Once we accept that we need a new paradigm to do science at the level of the universe as a whole, the next question to ask is what principle that new paradigm should be founded on. This is a question we hope to provoke cosmologists to think about. Mangabeira Unger and I propose three principles, which we argue are necessary to underlie any theory capable of explaining big cosmological questions – like the selection of the laws and initial conditions of the universe – in a way that is open to experimental test.

The first is that there is just one universe. The second is that time is real and the laws of nature are not timeless but evolve. The third is that mathematics is not a description of some separate timeless, Platonic reality, but is a description of the properties of one universe.

These principles take us beyond the Newtonian paradigm and the cosmological fallacy, and are a starting point for exploring the science of the universe as a whole.

The Meaning of Time – another view

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(reprinted with thanks from Frank A. Well, Chairman, Abacus & Associates 11/27/2003)

We all have some sense of time, whether the agonies of waiting or amazingly fast moments of excitement. But, most of us rarely reflect much on where those senses and sensibilities come from.

Humans began measuring time so long ago that there is no clear beginning to when and how the concept emerged.

Obviously early humans observed the daily rituals of sun up and sun down and the rise and fall of the moon. Gradually, people began to calculate the intervals and attach what we call numbers to those events.

It was not as if anyone ever discovered a universal element of time that dictated those passages. If that had happened some of our concepts of time might well have evolved differently. But, as Einstein proved, time itself is relative.

For example, today we think that the time since Jesus was on earth was a LONG time ago. If you were told that that long period of time (about 2000 years) was only one tiny part in 2,000,000 years (quicker than an eye blink) since the beginnings of planet Earth, you would probably have a hard time grasping the meaning of that metric in human terms. Still, it does seem like a long time.

To many humans alive today, JFK’s death 50 years ago seems like ancient history. The 150 years since Lincoln’s Gettysburg address seems so long ago that few grasp its nearness and timeliness today.

People 80 years old today have been alive for more than one-third of the life of the United States. For someone that age, it’s hard to believe. (Younger readers will simply have to trust me.)

A light year is the distance light travels in a year (at a velocity of 186,282.4 miles per second, or some 461 million miles per hour).

One might say, “How on earth are we supposed to think about time and distances like that?” In human terms such scales are unfathomable- and a lot of our potential theoretical destinations are thousands or millions of light years away.

So, if we want to begin to think seriously about exoplanet exploration, will we have to go back to square one and rethink our basic concepts of time and distance and perhaps reengineer the human species -at least for some of us–for indefinite life?

Some of the fundamental measurements of time, distance and direction, such as 360 degrees in a circle could possibly have been other numbers, such as 3600. But the concepts of those fundamentals are fixed, and universal. (To get around this apparent limitation, some physicists are now positing the existence of maybe billions of additional universes!). And, up to now, these fundamentals, our system of time and distances as we need them here on mother earth, have served us pretty well.

In earlier times, different places and regions kept their own time schedules somewhat the way we have time zones today. Then Greenwich, England became the base marker of global time and chronometers (the forerunners of individual clocks) as recently as a couple of hundred years ago. And, now with the Internet, though it may be darker or lighter in different places every day, we really are in one time zone globally–which is NOW!

What all this adds up to is this: since time is basically a human construct to fit the needs of humans as we grow and evolve, it stands to reason that we can and should rethink and try to adapt our ideas and use of time into something that will be more useful in the coming age of the Universe.

What is time? An interview with Sean Carroll

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SAN DIEGO — One way to get noticed as a scientist is to tackle a really difficult problem. Physicist Sean Carroll has become a bit of a rock star in geek circles by attempting to answer an age-old question no scientist has been able to fully explain: What is time?

carroll_mug2Sean Carroll is a theoretical physicist at Caltech where he focuses on theories of cosmology, field theory and gravitation by studying the evolution of the universe. Carroll’s latest book, From Eternity to Here: The Quest for the Ultimate Theory of Timeis an attempt to bring his theory of time and the universe to physicists and nonphysicists alike.

Here at the annual meeting of the American Association for the Advancement of Science, where he gave a presentation on the arrow of time, scientists stopped him in the hallway to tell him what big fans they were of his work.

Carroll sat down with Wired.com on Feb. 19 at AAAS to explain his theories and why Marty McFly’s adventure could never exist in the real world, where time only goes forward and never back.

Wired.com: Can you explain your theory of time in layman’s terms?

Sean Carroll: I’m trying to understand how time works. And that’s a huge question that has lots of different aspects to it. A lot of them go back to Einstein and spacetime and how we measure time using clocks. But the particular aspect of time that I’m interested in is the arrow of time: the fact that the past is different from the future. We remember the past but we don’t remember the future. There are irreversible processes. There are things that happen, like you turn an egg into an omelet, but you can’t turn an omelet into an egg.

And we sort of understand that halfway. The arrow of time is based on ideas that go back to Ludwig Boltzmann, an Austrian physicist in the 1870s. He figured out this thing called entropy. Entropy is just a measure of how disorderly things are. And it tends to grow. That’s the second law of thermodynamics: Entropy goes up with time, things become more disorderly. So, if you neatly stack papers on your desk, and you walk away, you’re not surprised they turn into a mess. You’d be very surprised if a mess turned into neatly stacked papers. That’s entropy and the arrow of time. Entropy goes up as it becomes messier.

 

So, Boltzmann understood that and he explained how entropy is related to the arrow of time. But there’s a missing piece to his explanation, which is, why was the entropy ever low to begin with? Why were the papers neatly stacked in the universe? Basically, our observable universe begins around 13.7 billion years ago in a state of exquisite order, exquisitely low entropy. It’s like the universe is a wind-up toy that has been sort of puttering along for the last 13.7 billion years and will eventually wind down to nothing. But why was it ever wound up in the first place? Why was it in such a weird low-entropy unusual state?

That is what I’m trying to tackle. I’m trying to understand cosmology, why the Big Bang had the properties it did. And it’s interesting to think that connects directly to our kitchens and how we can make eggs, how we can remember one direction of time, why causes precede effects, why we are born young and grow older. It’s all because of entropy increasing. It’s all because of conditions of the Big Bang.

Wired.com: So the Big Bang starts it all. But you theorize that there’s something before the Big Bang. Something that makes it happen. What’s that?

Carroll: If you find an egg in your refrigerator, you’re not surprised. You don’t say, “Wow, that’s a low-entropy configuration. That’s unusual,” because you know that the egg is not alone in the universe. It came out of a chicken, which is part of a farm, which is part of the biosphere, etc., etc. But with the universe, we don’t have that appeal to make. We can’t say that the universe is part of something else. But that’s exactly what I’m saying. I’m fitting in with a line of thought in modern cosmology that says that the observable universe is not all there is. It’s part of a bigger multiverse. The Big Bang was not the beginning.

And if that’s true, it changes the question you’re trying to ask. It’s not, “Why did the universe begin with low entropy?” It’s, “Why did part of the universe go through a phase with low entropy?” And that might be easier to answer.

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Wired.com: In this multiverse theory, you have a static universe in the middle. From that, smaller universes pop off and travel in different directions, or arrows of time. So does that mean that the universe at the center has no time?

Carroll: So that’s a distinction that is worth drawing. There’s different moments in the history of the universe and time tells you which moment you’re talking about. And then there’s the arrow of time, which give us the feeling of progress, the feeling of flowing or moving through time. So that static universe in the middle has time as a coordinate but there’s no arrow of time. There’s no future versus past, everything is equal to each other.

Wired.com: So it’s a time that we don’t understand and can’t perceive?

Carroll: We can measure it, but you wouldn’t feel it. You wouldn’t experience it. Because objects like us wouldn’t exist in that environment. Because we depend on the arrow of time just for our existence.

Wired.com: So then, what is time in that universe?

Carroll: Even in empty space, time and space still exist. Physicists have no problem answering the question of “If a tree falls in the woods and no one’s there to hear it, does it make a sound?” They say, “Yes! Of course it makes a sound!” Likewise, if time flows without entropy and there’s no one there to experience it, is there still time? Yes. There’s still time. It’s still part of the fundamental laws of nature even in that part of the universe. It’s just that events that happen in that empty universe don’t have causality, don’t have memory, don’t have progress and don’t have aging or metabolism or anything like that. It’s just random fluctuations.

Wired.com: So if this universe in the middle is just sitting and nothing’s happening there, then how exactly are these universes with arrows of time popping off of it? Because that seems like a measurable event.

Carroll: Right. That’s an excellent point. And the answer is, almost nothing happens there. So the whole point of this idea that I’m trying to develop is that the answer to the question, “Why do we see the universe around us changing?” is that there is no way for the universe to truly be static once and for all. There is no state the universe could be in that would just stay put for ever and ever and ever. If there were, we should settle into that state and sit there forever.

It’s like a ball rolling down the hill, but there’s no bottom to the hill. The ball will always be rolling both in the future and in the past. So, that center part is locally static — that little region there where there seems to be nothing happening. But, according to quantum mechanics, things can happen occasionally. Things can fluctuate into existence. There’s a probability of change occurring.

So, what I’m thinking of is the universe is kind of like an atomic nucleus. It’s not completely stable. It has a half-life. It will decay. If you look at it, it looks perfectly stable, there’s nothing happening … there’s nothing happening … and then, boom! Suddenly there’s an alpha particle coming out of it, except the alpha particle is another universe.

Wired.com: So inside those new universes, which move forward with the arrow of time, there are places where the laws of physics are different — anomalies in spacetime. Does the arrow of time still exist there?

Carroll: It could. The weird thing about the arrow of time is that it’s not to be found in the underlying laws of physics. It’s not there. So it’s a feature of the universe we see, but not a feature of the laws of the individual particles. So the arrow of time is built on top of whatever local laws of physics apply.

Wired.com: So if the arrow of time is based on our consciousness and our ability to perceive it, then do people like you who understand it more fully experience time differently then the rest of us?

Carroll: Not really. The way it works is that the perception comes first and then the understanding comes later. So the understanding doesn’t change the perception, it just helps you put that perception into a wider context. It’s a famous quote that’s in my book from St. Augustine, where he says something along the lines of, “I know what time is until you ask me for a definition about it, and then I can’t give it to you.” So I think we all perceive the passage of time in very similar ways. But then trying to understand it doesn’t change our perceptions.

Wired.com: So what happens to the arrow in places like a black hole or at high speeds where our perception of it changes?

Carroll: This goes back to relativity and Einstein. For anyone moving through spacetime, them and the clocks they bring along with them – including their biological clocks like their heart and their mental perceptions – no one ever feels time to be passing more quickly or more slowly. Or, at least, if you have accurate clocks with you, your clock always ticks one second per second. That’s true if you’re inside a black hole, here on Earth, in the middle of nowhere, it doesn’t matter. But what Einstein tells us is that path you take through space and time can dramatically affect the time that you feel elapsing.

The arrow of time is about a direction, but it’s not about a speed. The important thing is that there’s a consistent direction. That everywhere through space and time, this is the past and this is the future.

Wired.com: So you would tell Michael J. Fox that it’s impossible for him to go back to the past and save his family?

Carroll: The simplest way out of the puzzle of time travel is to say that it can’t be done. That’s very likely the right answer. However, we don’t know for sure. We’re not absolutely proving that it can’t be done.

Wired.com: At the very least, you can’t go back.

Carroll: Yeah, no. You can easily go to the future, that’s not a problem.

Wired.com: We’re going there right now!

Carroll: Yesterday, I went to the future and here I am!

One of things I point out in the book is that if we do imagine that it was possible, hypothetically, to go into the past, all the paradoxes that tend to arise are ultimately traced to the fact that you can’t define a consistent arrow of time if you can go into the past. Because what you think of as your future is in the universe’s past. So it can’t be one in the same everywhere. And that’s not incompatible with the laws of physics, but it’s very incompatible with our everyday experience, where we can make choices that affect the future, but we cannot make choices that affect the past.

Wired.com: So, one part of the multiverse theory is that eventually our own universe will become empty and static. Does that mean we’ll eventually pop out another universe of our own?

Carroll: The arrow of time doesn’t move forward forever. There’s a phase in the history of the universe where you go from low entropy to high entropy. But then once you reach the locally maximum entropy you can get to, there’s no more arrow of time. It’s just like this room. If you take all the air in this room and put it in the corner, that’s low entropy. And then you let it go and it eventually fills the room and then it stops. And then the air’s not doing anything. In that time when it’s changing, there’s an arrow of time, but once you reach equilibrium, then the arrow ceases to exist. And then, in theory, new universes pop off.

Wired.com: So there’s an infinite number of universes behind us and an infinite number of universes coming ahead of us. Does that mean we can go forward to visit those universes ahead of us?

Carroll: I suspect not, but I don’t know. In fact, I have a postdoc at Caltech who’s very interested in the possibility of universes bumping into each other. Now, we call them universes. But really, to be honest, they are regions of space with different local conditions. It’s not like they’re metaphysically distinct from each other. They’re just far away. It’s possible that you could imagine universes bumping into each other and leaving traces, observable effects. It’s also possible that that’s not going to happen. That if they’re there, there’s not going to be any sign of them there. If that’s true, the only way this picture makes sense is if you think of the multiverse not as a theory, but as a prediction of a theory.

If you think you understand the rules of gravity and quantum mechanics really, really well, you can say, “According to the rules, universes pop into existence. Even if I can’t observe them, that’s a prediction of my theory, and I’ve tested that theory using other methods.” We’re not even there yet. We don’t know how to have a good theory, and we don’t know how to test it. But the project that one envisions is coming up with a good theory in quantum gravity, testing it here in our universe, and then taking the predictions seriously for things we don’t observe elsewhere.

**** Interviewed by Wired magazine 2/26/10

In Search of Physics’ “Holy Grail”

“… for us physicists believe the separation between past, present, and future is only an illusion, although a convincing one.”
– Albert Einstein

This statement arises from Einstein’s Special Theory of Relativity, which conclusively denies the existence of any absolute and universal significance to the present moment. The same event viewed from to different reference points occurs at different time.

Stated differently, time is relative to the observer; therefore, it is impossible to divide it up into past, present and future in a way that is universally meaningful. In this sense, past, present and future are all there at once.

Einstein’s theory, which describes the macroscopic world with precision, does not work at the subatomic level. To describe the microscopic, physicists use quantum mechanics, a theory that’s fundamentally different from Einstein’s. Reconciling the Special Theory of Relativity and quantum mechanics requires a new theory of quantum gravity. And this is the holy grail of modern physics. The search continues . . .

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A Short Intro to String Theory

 The article below, originally appearing in Phys.org*, is one of the best overviews of string theory – clear, concise and precise.  While there are dozens of books published on the topic, this article provides the perspective necessary for the continued journey to formulate The Theory of Time.  

Enjoy.  

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This is an image of a two-dimensional hypersurface of the quintic Calabi-Yau three-fold. Credit: Jbourjai/Wikipedia.

(Phys.org) —Scientists at Towson University in Towson, Maryland, have identified a practical, yet overlooked, test of string theory based on the motions of planets, moons and asteroids, reminiscent of Galileo’s famed test of gravity by dropping balls from the Tower of Pisa.

String theory is infamous as an eloquent theoretical framework to understand all forces in the universe —- a so-called “theory of everything” —- that can’t be tested with current instrumentation because the energy level and size scale to see the effects of string theory are too extreme.

Yet inspired by Galileo Galilei and Isaac Newton, Towson University scientists say that precise measurements of the positions of solar-system bodies could reveal very slight discrepancies in what is predicted by the theory of  and the equivalence principle, or establish new upper limits for measuring the effects of string theory.

String theory hopes to provide a bridge between two well-tested yet incompatible theories that describe all known physics: Einstein’s general relativity, our reigning theory of gravity; and the standard model of particle physics, or , which explains all the forces other than gravity.

String theory posits that all matter and energy in the universe is composed of one-dimensional strings. These strings are thought to be a quintillion times smaller than the already infinitesimal hydrogen atom and thus too minute to detect indirectly. Similarly, finding signs of strings in a particle accelerator would require millions of times more energy than what has been needed to identify the famous Higgs boson.

“Scientists have joked about how string theory is promising…and always will be promising, for the lack of being able to test it,” said Dr. James Overduin of the Department of Physics, Astronomy and Geosciences at Towson University, first author on the paper. “What we have identified is a straightforward method to detect cracks in general relativity that could be explained by string theory, with almost no strings attached.”

Overduin and his group —- including Towson University undergraduate research students Jack Mitcham and Zoey Warecki —- expanded on a concept proposed by Galileo and Newton to explain gravity.

Fable has it that Galileo dropped two balls of different weights from the Tower of Pisa to demonstrate how they would hit the ground at the same time. Years later Newton realized that the same experiment is being performed by Mother Nature all the time in space, where the moons and planets of the solar system fall continuously toward each other as they orbit around their common centers of mass. Newton used telescope observations to conclude that Jupiter and its Galilean moons fall with the same acceleration toward the Sun.

The same test could be used for string theory, Overduin said. The gravitational field couples to all forms of matter and energy with precisely the same strength, an observation that led Einstein to his theory of general relativity and is now enshrined in physics as the equivalence principle. String theory predicts violations of the equivalence principle because it involves new fields which couple differently to objects of different composition, causing them to accelerate differently, even in the same gravitational field.

Building on work done by Kenneth Nordtvedt and others beginning in the 1970s, Overduin and his collaborators consider three possible signatures of equivalence principle violation in the solar system: departures from Kepler’s Third Law of planetary motion; drift of the stable Lagrange points; and orbital polarization (also known as the Nordtvedt effect), whereby the distance between two bodies like the Earth and Moon oscillates due to differences in acceleration toward a third body like the Sun.

To date, there is no evidence for any of these effects. Indeed, the standard astronomical ephemeris assumes the validity of Kepler’s Third Law in deriving such fundamental quantities as the length of the Astronomical Unit. But all observations in science involve some degree of experimental uncertainty. The approach of Overduin’s team is to use these experimental uncertainties themselves to obtain upper limits on possible violations of the  by the planets, moons and Trojan asteroids in the solar system.

“The Saturnian satellites Tethys and Dione make a particularly fascinating test case,” said Warecki, who is presenting this work at Session 109 at the AAS meeting today. “Tethys is made almost entirely of ice, while Dione possesses a significantly rocky core. And both have Trojan companions.”

“The limits obtained in this way are not as sensitive as those from dedicated torsion-balance or laser-ranging tests,” said Mitcham. “But they are uniquely valuable as potential tests of  nonetheless because they cover a much wider range of test-body materials.”

Moreover, in an era of increasingly big-budget science, they come at comparatively little cost, said Overduin.

The Towson-based team presents its finding today, January 6, 2014, between 10 a.m. and 11:30 a.m., at the 223rd meeting of the American Astronomical Society, in Washington, D.C. The work also appears in the journal Classical and Quantum Gravity”

Read more at: http://phys.org/news/2014-01-scientists-theory.html#jCp

* Reprinted from the January 6, 2014 online issue of Phys.org

**The image is of a two-dimensional hypersurface of the quintic Calabi-Yau three-fold. Credit: Jbourjai/Wikipedia.

More to follow . . . 

Dark Matter Update post-LUX

As of November 1, 2013 many news outlets had reported that the Large Underground Xenon experiment, LUX, had “failed” to detect indicators of dark matter. It is true that the first 90 day run of LUX did not find the elusive WIMPS, a possible indicator of dark matter. However, far from bing a failure, this is what we call science. The search continues and LUX will start its’ 300 day run in January 2014. See http://www.nbcnews.com/science/dark-matter-eludes-scientists-first-results-lux-detector-8C11498659

Below is a lucid and well documented status report on dark matter by theoretical physicist Matt Strassler from his October 31, 2013 posting.

http://profmattstrassler.com/2013/10/31/questions-and-answers-about-dark-matter-post-lux/

▪   Do we know dark matter exists?

Scientists are, collectively, pretty darn sure, though not 100% certain. Certainly something is out there that acts a lot like a dark form of matter (i.e. something that gravitates and clumps, but doesn’t shine, either in visible light or in any other form of electromagnetic waves). There have been some proposals that try to get around dark matter, by modifying gravity, but these haven’t worked that well. Meanwhile the evidence that there really is dark stuff out there that really behaves like matter continues to grow year by year, and every claim that it actually isn’t there(such as this one I wrote about – see the second half of the article) has turned out to be wrong.  Dark matter is needed to explain features of the cosmic microwave background, to explain how galaxies form, to explain why we see certain types of gravitational lensing, etc. etc.  No one alternative can explain all of these things.  And dark matter easily arises in many particle physics theories, so it’s not hard to imagine it might be created in the early universe and be a dominant player today.

▪   Do we know dark matter is made from particles (i.e. ultra-microscopic objects with uniform properties)?

No, that’s not certain. Particles would do the job, but that’s not a proof it is made from particles.

▪   If dark matter is made from particles, do we know these are Weakly Interacting Massive Particles (WIMPs) — to be precise, particles that interact with the Standard Model via the weak nuclear force or the Higgs force or something else we already know about?

No. Dark matter could be WIMPs. Or dark matter could be made from a very different type of particle called “axions”. Or dark matter could be made from particles that aren’t of either of these types.  This could include particles that only interact with ordinary matter through the force of gravity, which could make them very, very hard to detect.

▪   Do most scientists believe dark matter is made from WIMPs? (This was claimed to be true in several news articles.)

As far as I can tell, most experts do not know what to think; some have a bias toward one idea or another, but when pressed admit there’s no way to know. Many scientists think WIMPs are a good candidate, but I’ve never heard anyone say they are the only one.

▪   So why are so many experiments (there’s a partial list here) looking for WIMPs?

Partly because they can. Sometimes science involves looking under the lamppost for your keys. You look where you can because you can look there, and you may get lucky — it has happened many times before in history.   That’s fine as long as you remember that’s what you are doing.

Not that WIMPs are the only things that people are looking for. They can also look for axions, and there are experiments doing that search too. Looking for other types of dark matter particles directly is sometimes very difficult. Some of these other types of particles could be found by the experiments at the Large Hadron Collider [LHC] (and people are looking.) Others could be found by experiments such as FERMI and AMS, through the effect of dark matter annihilation to known particles (and people are looking; there’s even a hint, not yet shown to be wrong). Still other possible types of dark matter particles are completely inaccessible to modern experiments, and may remain so for a long time to come.

▪   If we don’t know dark matter is particles, or that those particles are WIMPs, then why do the headlines say “dark matter search in final phase” in reference to the new result from LUX, even though LUX is mainly only looking for WIMPs?

Don’t ask me. Ask the editors at CBS and the BBC why their headlines about science are so often inaccurate.

The search for dark matter will end when some type of dark matter is found (or somehowshown convincingly not to exist), not before. The former could happen any day; the latter will not happen anytime soon.  The only thing that is currently approaching its end is the search forWIMPs as the dark matter (and even that search will not, unfortunately, end as soon or as conclusively as we would like.) If WIMPs aren’t found, that just probably means that dark matter is something else on the list I gave you above: some other type of particle, or some other type of thing that isn’t a particle. Or it could mean that dark matter forms clumps, rather than being smoothly distributed through our galaxy, and that we’re unlucky enough to be in an empty zone.  Certainly, if LUX and XENON1T and the other current experiments don’t find anything, we will not be able conclude that dark matter doesn’t exist. Only those who don’t understand the science will attempt to draw that conclusion.

▪   So why is the LUX experiment’s result so important?

Well, it’s important, but not amazingly important, because indeed, (a) they didn’t find anything, and (b) it’s not like they ruled out a whole class of possibilities (e.g. WIMPs) all at once. But still, (i) they did rule out a possibility that several other experiments were hinting at, and that’s important, because it settles an outstanding scientific issue,  and (ii) their experiment works very, very well, which is also important, because it means they have a better chance at a discovery in their next round of measurements than they would have otherwise. In short: they deserve and will get a lot of praise and admiration for their work… but their result, unlike the discover of the Higgs particle by the LHC experiments, isn’t Nobel Prize-worthy. And indeed, it’s not getting a front-page spread in the New York Times, for good reason.

The Foundations For Understanding Time, Part 2 – The Theory of Relativity

In 1905 Albert Einstein published his groundbreaking theory of special relativity. In order to come to an understanding of time, it is necessary to grasp the basic conclusions of the theory of relativity; as it created a fundamental link between space and time.

For our purposes, the two primary conclusions are:

1)   The universe can be viewed as having three space dimensions — up/down, left/right, forward/backward — and one time dimension. This 4-dimensional space is referred to as the space-time continuum, or space-time.

2)   Motion, and time, are relative to the observer. The theory of relativity explains how to interpret motion/time between reference frames; that is, places that are moving relative to each other.

For Einstein, the importance of reference frames was that there is no such thing as an absolute frame of reference – meaning that there is no place in the universe that is completely stationary. You may think that sitting on the couch in front the TV is stationary. Sorry – you are standing on a planet that is spinning at 1,000 miles per hour; moving around the sun at the rate of 66,600 miles per hour; in a solar system moving at 420,000 miles per hour around our galactic core. So, while we don’t really notice, our reference point in always changing in relation to other celestial bodies.

The relativity of motion and time become evident between two different reference frames.

Back on earth, there is a simple example:  ( see youtube http://www.youtube.com/watch?v=wteiuxyqtoM )

As shown below at the top, imagine that you are traveling in a spaceship at one-half the speed of light. You are holding a laser so it shoots a beam of light straight up, striking a mirror you’ve placed on the ceiling. In your reference from, the light beam will then come straight back down and strikes a detector. In your reference frame, no matter what speed you are traveling, you observe the laser beam as absolutely vertical.

shipimage0

At the the top of the image, you see a beam of light go up, bounce off the mirror, and come straight down. Below, astronaut Sharon sees the beam travel along a diagonal path.

However, if astronaut Sharon were spying on you, as in the image, she observes a very different result.

Since you are traveling past Sharon, she sees your beam of light travel upward along a diagonal path, strike the mirror, and then travel downward along a diagonal path before striking the detector. In other words, you and Sharon have different reference frames and would see different paths for the light.

More importantly, according to Einstein, those paths aren’t even the same length. This means that the time the beam takes to go from the laser to the mirror to the detector must also be different for you and Sharon. (the speed of light is always constant)

This phenomenon is known as time dilation, but the critical point here is that two observers can witness the same event, yet perceive different durations of time. The conclusion is that time is not absolute and can vary from one observation to another.

Another example demonstrates the relativity of time: If you and Sharon synchronize your watches and she stays on the ground while you fly around the world a few times; upon landing, your watch and Sharon will no longer reflect the same time. Your watch will reflect a time earlier that Sharon (granted, in this example your watch will be a slower by a billionth of a billionth of a second). Times slows the faster you accelerate.

We will come back to this next time.

The Foundations of Understanding Time, Part 1

Time shapes our perceptions of the world and of our own identity. We have a memory of the past, a feeling of free will in the present, and hopes for the future. However, our perceptions are directly at odds with mainstream physics. The concept maybe difficult to grasp, but it is important to understand as a foundation for the meaning of time.

Time is a dimension, the 4th dimension along with the three dimensions of space. While it may feel like a leap of faith, we will see that yesterday, today, and tomorrow are equally concrete events existing together. The future exists as much as the past. It is just a place that we have yet to visit. Moreover, this paradigm does not defeat free will and choice because all futures simultaneously exist. Nothing in physics corresponds or recognizes our feelings of the passage of time. The flow of time is a human construct; a necessary one that forms the boundaries of how we experience life. Nevertheless, our division of past, present and future has no place in understanding the foundations of time.

Albert Einstein once said, “The past, present and future are only illusions, even if stubborn ones.” This statement arises for the Special Theory of Relativity, which conclusively denies the existence of any absolute and universal significance to the present moment. The same event viewed from to different reference points occurs at different times.

Stay with me – we will get there.

Life at the Speed of 140 Characters

It has been too long since my last post and I have a number of physics based observations about the theory of time to post. However this post is both personal and practical.

From one perspective, we look for life squeezed into 140 characters or six seconds of video. Technological advancements are undeniably positive, but the use of them not without negative impacts.  Simpler pleasures at a slower pace are a shared desire by millions. A short vacation from the technological onslaught of compulsive interactions with social media texting should be on everyone’s list. My generation saw the first PC at age 24 and the first car phone at 30. We now wonder how we every existed without them.
 We text compulsively at home, work and in the car. The 20 and 30 year olds have it worse and with gaming consoles kids don’t play outside anymore. Lost is the art of conversation and family or communal interactions. Going “off the grid” is not practical or necessary. Personally, I epitomize the tech addict of my age group. Minimally, I need to stay in touch with 4 kids 21 to 32 and I enjoy the access and freedom that comes with consumer technology. However, there is indeed a need to moderate and find simple pleasures at a slower pace that are not online.
 While I didn’t mention the word “time”, this is very much an issue about my time – and possibly yours.

Another Approach To Understanding Time

Time, simple enough from the everyday aspect, yet so allusive to define scientifically, metaphysically or otherwise, in sufficient terms. It should be difficult – men far smarter than I have pondered time for hundreds if not tens of thousands of years.

In physics, spacetime (or space–time continuum) is a model that combines space and time into a single continuum. Spacetime is usually interpreted with space as existing in three dimensions and time playing the role of a fourth dimension that is of a different sort from the spatial dimensions.  In the past physicists have significantly simplified a large number of physical theories, as well as described in a more uniform way the workings of the universe at both the supergalactic and subatomic levels.

Prior to 1900 non-relativistic classical mechanics, the use of Euclidean space instead of spacetime is appropriate, as time is treated as universal and constant. In spacetime, a coordinate grid that spans the 3+1 dimensions locates events.  These restrictions correspond roughly to a particular mathematical model that importantly manifest symmetry.

At the beginning of the 20th century, many experiments have confirmed time dilation, such as the relativistic decay of muons from cosmic ray showers and the slowing of atomic clocks aboard a Space Shuttle relative to synchronized Earth-bound inertial clocks. The duration of time can therefore vary according to events and reference frames.

When dimensions are understood as mere components of the grid system, rather than physical attributes of space, it is easier to understand the alternate dimensional views as being simply the result of coordinate transformations.

The term spacetime has taken on a generalized meaning beyond treating spacetime events with the normal 3+1 dimensions. It is really the combination of space and time. Other proposed spacetime theories include additional dimensions—normally spatial but there exist some speculative theories that include additional temporal dimensions and even some that include dimensions that are neither temporal nor spatial (e.g. superspace). How many dimensions are needed to describe the universe is still an open question. Speculative theories such as string theory predict 10 or 26 dimensions (with M-theory predicting 11 dimensions: 10 spatial and 1 temporal), but the existence of more than four dimensions would only appear to make a difference at the subatomic level.

Much of this is rehashed, but presented in a a different light. We need these building blocks to define a path to greater enlightenment, as a Buddhist may say.