Certain subsectors of the scientifically-oriented blogosphere are abuzz — abuzz, I say! — about this new presentation on Dark Energy at the Hubblesite. It’s slickly done, and worth checking out, although be warned that a deep voice redolent with mystery will commence speaking as soon as you open the page.
But Ryan Michney at Topography of Ignorance puts his finger on the important thing here, the opening teaser text:
Scientists have found an unexplained force that is changing our universe,
forcing galazies farther and farther apart,
stretching the very fabric of space faster and faster.
If unchecked, this mystery force could be the death of the universe,
tearing even its atoms apart.We call this force dark energy.
Scary! Also, wrong. Not the part about “tearing even its atoms apart,” an allusion to the Big Rip. That’s annoying, because a Big Rip is an extremely unlikely future for a universe even if it is dominated by dark energy, yet people can’t stop putting the idea front and center because it’s provocative. Annoying, but not wrong.
The wrong part is referring to dark energy as a “force,” which it’s not. At least since Isaac Newton, we’ve had a pretty clear idea about the distinction between “stuff” and the forces that act on that stuff. The usual story in physics is that our ideas become increasingly general and sophisticated, and distinctions that were once clear-cut might end up being altered or completely irrelevant. However, the stuff/force distinction has continued to be useful, even as relativity has broadened our definition of “stuff” to include all forms of matter and energy. Indeed, quantum field theory implies that the ingredients of a four-dimensional universe are divided neatly into two types: fermions, which cannot pile on top of each other due to the exclusion principle, and bosons, which can. That’s extremely close to the stuff/force distinction, and indeed we tend to associate the known bosonic fields — gravity, electromagnetism, gluons, and weak vector bosons — with the “forces of nature.” Personally I like to count the Higgs boson as a fifth force rather than a new matter particle, but that’s just because I’m especially fastidious. The well-defined fermion/boson distinction is not precisely equivalent to the more casual stuff/force distinction, because relativity teaches us that the bosonic “force fields” are also sources for the forces themselves. But we think we know the difference between a force and the stuff that is acting as its source.
Anyway, that last paragraph got a bit out of control, but the point remains: you have stuff, and you have forces. And dark energy is definitely “stuff.” It’s not a new force. (There might be a force associated with it, if the dark energy is a light scalar field, but that force is so weak that it’s not been detected, and certainly isn’t responsible for the acceleration of the universe.) In fact, the relevant force is a pretty old one — gravity! Cosmologists consider all kinds of crazy ideas in their efforts to account for dark energy, but in all the sensible theories I’ve heard of, it’s gravity that is the operative force. The dark energy is causing a gravitational field, and an interesting kind of field that causes distant objects to appear to accelerate away from us rather than toward us, but it’s definitely gravity that is doing the forcing here.
Is this a distinction worth making, or just something to kvetch about while we pat ourselves on the back for being smart scientists, misunderstood once again by those hacks in the PR department? I think it is worth making. One of the big obstacles to successfully explaining modern physics to a broad audience is that the English language wasn’t made with physics in mind. How could it have been, when many of the physical concepts weren’t yet invented? Sometimes we invent brand new words to describe new ideas in science, but often we re-purpose existing words to describe concepts for which they originally weren’t intended. It’s understandably confusing, and it’s the least we can do to be careful about how we use the words. One person says “there are four forces of nature…” and another says “we’ve discovered a new force, dark energy…”, and you could hardly blame someone who is paying attention for turning around and asking “Does that mean we have five forces now?” And you’d have to explain “No, we didn’t mean that…” Why not just get it right the first time?
Sometimes the re-purposed meanings are so deeply embedded that we forget they could mean anything different. Anyone who has spoken about “energy” or “dimensions” to a non-specialist audience has come across this language barrier. Just recently it was finally beaten into me how bad “dark” is for describing “dark matter” and “dark energy.” What we mean by “dark” in these cases is “completely transparent to light.” To your average non-physicist, it turns out, “dark” might mean “completely absorbs light.” Which is the opposite! Who knew? That’s why I prefer calling it “smooth tension,” which sounds more Barry White than Public Enemy.
What I would really like to get rid of is any discussion of “negative pressure.” The important thing about dark energy is that it’s persistent — the density (energy per cubic centimeter) remains roughly constant, even as the universe expands. Therefore, according to general relativity, it imparts a perpetual impulse to the expansion of the universe, not one that gradually dilutes away. A constant density leads to a constant expansion rate, which means that the time it takes the universe to double in size is a constant. But if the universe doubles in size every ten billion years or so, what we see is distant galaxies acceleratating away — first they are X parsecs away, then they are 2X parsecs away, then 4X parsecs away, then 8X, etc. The distance grows faster and faster, which we observe as acceleration.
That all makes a sort of sense, and never once did we mention “negative pressure.” But it’s nevertheless true that, in general relativity, there is a relationship between the pressure of a substance and the rate at which its density dilutes away as the universe expands: the more (positive) pressure, the faster it dilutes away. To indulge in a bit of equationry, imagine that the energy density dilutes away as a function of the scale factor as R-n. So for matter, whose density just goes down as the volume goes up, n=3. For a cosmological constant, which doesn’t dilute away at all, n=0. Now let’s call the ratio of the pressure to the density w, so that matter (which has no pressure) has w=0 and the cosmological constant (with pressure equal and opposite to its density) has w=-1. In fact, there is a perfectly lockstep relation between the two quantities:
n = 3(w + 1).
Measuring, or putting limits on, one quantity is precisely equivalent to the other; it’s just a matter of your own preferences how you might want to cast your results.
To me, the parameter n describing how the density evolves is easy to understand and has a straightforward relationship to how the universe expands, which is what we are actually measuring. The parameter w describing the relationship of pressure to energy density is a bit abstract. Certainly, if you haven’t studied general relativity, it’s not at all clear why the pressure should have anything to do with how the universe expands. (Although it does, of course; we’re not debating right and wrong, just how to most clearly translate the physics into English.) But talking about negative pressure is a quick and dirty way to convey the illusion of understanding. The usual legerdemain goes like this: “Gravity feels both energy density and pressure. So negative pressure is kind of like anti-gravity, pushing things apart rather than pulling them together.” Which is completely true, as far as it goes. But if you think about it just a little bit, you start asking what the effect of a “negative pressure” should really be. Doesn’t ordinary positive pressure, after all, tend to push things apart? So shouldn’t negative pressure pull them together? Then you have to apologize and explain that the actual force of this negative pressure can’t be felt at all, since it’s equal in magnitude in every direction, and it’s only the indirect gravitational effect of the negative pressure that is being measured. All true, but not nearly as enlightening as leaving the concept behind altogether.
But I fear we are stuck with it. Cosmologists talk about negative pressure and w all the time, even though it’s confusing and ultimately not what we are measuring anyway. Once I put into motion my nefarious scheme to overthrow the scientific establishment and have myself crowned Emperor of Cosmology, rest assured that instituting a sensible system of nomenclature will be one of my very first acts as sovereign.
Ned Wright noted this work on his site, with an implied disclaimer…COBE eliminated the possibility of topological defects in the CMB. However Ned remains open and speculated that perhaps there was one out there somewhere.
Topological defects have a place, an important place, I would think, but not in the realm of basic cosmological structure, which as Sean pointed out is a matter of stuff and gravity.
Solitons in a swimming pool are a visual (observed) phenomenon. The stuff in the swimming pool and the effects of wind and gravity are the structure which causes the topological defect…not the other way around.
The static universe is an interesting concept with a very long and interesting history. Just as the expanding universe, a static or quasi-static universe can be conceptualized in many different ways. If John wants to, he can Google the topic and just enter static or quasi-static universe. He will find enough on the subject to keep him occupied for quite some time.
Somebody pointed out that when Einstein first conceptualized his static universe, it was widely regarded that the milky Way Galaxy WAS the universe, and he had a peculiar, and not particularly modern way of visulaizing the concept anyway.
Einstein knew nothing of the true size of the universe, until near the end of his life. He didn’t even regard black holes as more than mathematical artifacts of his relativity theory. He only learned that anti-matter even existed late in his life, and knew nothing of course about acceleration outward.
Einstein conceived the universe in 4D and after Kalusa offered extra dimensions as a solutions to some of the cosmological problems, proved that particulation only occurs in 4D. For these reasons, and Hubble’s discovery of the expansion of the universe, Einstein disgarded his static universe. However, Einstein knew something was missing…and was searching for the solution of unification when he died in 1955.
One fact about Einstein which has been widely neglected, is that he was a pretty good engineer, and was very interested in the problem of the existence of information and high complexity in the universe.
He knew that an expanding universe starts in a low entropy state and proceeds to higher entropy states- and understood the difficulties of finding widespread high complexity in such a universe. He also knew that in any structure, the sum of the moments must be 0 if that stucture is to remain stable…and he tended to view the universe as a structure.
While the convention of his day was to construct static cosmological models, I suspect that Einstein also had engineering reasons for conceptualizing the universe the way he did. We all remember the famous debate between Einstein and Bohr, and Einsteins remark that “God does not play dice…etc.”
We may live in a quantum universe, but SR/GR describe the observed universe of information and complexity we live in. Einstein knew that his concepts were deterministic (the “static” universe) in the extreme and felt that QM and SR/GR were as incompatable as oil and water. To Bohrs credit, he saw the outlines of the possible relationship between QM and SR/GR, a relationship which is becoming more clear with the passing decades…
Sam,
One point to consider with the idea of a convective cycle is the interaction between these opposing and opposite elements of expanding microcosm and collapsing macrocosm, and the complexity it would create.
Hello,
I am a simple layman that would like very much just to postulate to you all that one of the most coveted laws of physics is the one that states “for every action there must be an equal and opposite reaction”. Why would there not be, at some point in the grand scheme of things, a cosmological reaction to the force that makes automobile-sized rock move 30 million tons of dirt in about 15 milliseconds because of the force of gravity? What would make us so aware of this law (not theory) during high school and once we start being able to write out three page equations, we forget all about the fundamentals that we know to be true, beyond a shadow of a doubt. All I am trying to say is that for every pound (for lack of a better term) of attraction there should be, and Einstein knew it to be true, a force of repulsion to make the cosmos balance. You can call it a cosmological constant or a spaghetti monster or whatever, I will tell you that I am of sound mind and I would be willing to bet even money that we will soon discover that the force of gravity will be offset with a repulsive force at presicely the ratio of 1 to 1. Just because we call it dark matter, does not necessarily mean it is either dark nor matter, the we’ll call it the repulsive force that MUST be present in the universe to acheive balance.
Thanks for your time.
Bren
Sam Cox on Dec 16th, 2007 at 8:45 pm
Ned Wright noted this work on his site, with an implied disclaimer…COBE eliminated the possibility of topological defects in the CMB. However Ned remains open and speculated that perhaps there was one out there somewhere.
——————
This depends upon what you mean by topological defect. There is no clear indication that the universe is multiply connected. Though that idea has popped up, with some saying the cosmos was a dodecahedron a few years back. There were some say that this “hole,” which is just a cold spot which has “sharp boundaries” in steradian measure from the surrounding. There is a kurtosis measure, a fourth moment as standard deviation is a second moment, for this variation. So there appears to be some sort of physics here, which might be a texture or the result of cosmic strings.
As a general comment to some of the posters here, I think that in order to understand these matters some familiarity with relativity and general relativity (gravitation) is in order. Some of the ideas expressed here are a bit on the odd side, and frankly just wrong. The resources are out there, in books or on the web.
Lawrence B. Crowell
Well, somehow sensing a great need and market niche, I have an idea to promote (not that it seems to need promotion, heh) amateur efforts to weigh in on the deepest questions of cosmology: How about us CPEs (cocktail-party Einstein’s or wannabees) collaborate on a how-to book, I am Einstein (and so can you!) It will of course be a “coffee table book” with plenty of neat diagrams and pictures of curved space and black holes, and just enough equations to give a sophomoric sense that the reader understands these topics even if he or she really doesn’t. It would make a great Xmas gift, so many we can quickly throw together our posts and edit them into a workable approximation thereof; just need some graphics and layout editing.
😉
PS you won’t *need* weed to use or enjoy this proposed tome, but it will certainly help you enjoy it. Then please watch “What the Bleep do we Know?”, filled with ridiculous fancies I suppose like multiple worlds and the idea that the waves never really collapse. (I haven’t seen it yet, or I suppose I did – since one of my ostensible and unproven, “celestial teapot”-like other selves must have done so out there somewhere. BTW, just where *are* those other universes? “Just asking.”)
Re: “One fact about Einstein which has been widely neglected, is that he was a pretty good engineer…”
The “Einstein Refrigerator” is a type of refrigerator co-invented in 1926 by Albert Einstein and former student Leó Szilárd, who were awarded U.S. Patent 1,781,541 on November 11, 1930. The machine is a single-pressure absorption refrigerator, similar in design to the gas absorption refrigerator. The refrigeration cycle uses ammonia (pressure-equalizing fluid), butane (refrigerant), and water (absorbing fluid). It has been claimed that the Einstein refrigerator is portable, made of inexpensive, nonmoving parts, operates silently, and is very reliable. However, ammonia leaks caused problems among the earlier models, and whether it can cool things adequately is unknown.
Einstein undertook this invention as a way of helping along his former student. He used the knowledge he had acquired during his years at the Swiss Patent Office to get valid patents for the invention in several countries. The refrigerator was not immediately put into commercial production, but rights to use the patents were sold to companies such as Electrolux of Sweden, and the funds obtained supported Szilárd for several years….
There’s more on this at Wikipedia, from which I excerpted the above.
One may be assured that Einstein thus had a very practical (as well as theoretical) grasp of Thermodynamics. It is also clear that he was interested in the connections between Thermodynamics and Information Theory.
Whether he related that to Cosmology, I do not know. I would ask my teacher, Feynman, to whom Einstein and Oppenheimer and Wheeler were mentors, but, alas, all these men (excepting John Wheeler) are on the other side of a horizon from which, as Shakespeare noted: “No traveller returns.”
Bren,
I’m also of the opinion it went off the track aways back, but they are the bank and they are printing their own money, so it will take some time for this bubble to reach the popping point.
Neil,
Interesting idea, but for my part, I actually do this to decompress. That I feel I’m making some sense, but that no one is listening serves its own purpose. Out in the real world, there are plenty of situations where questioning the powers that be just gets you squashed like a bug. I think that when the history books record this epoch, future psychologists will find it far more interesting then future physicists. Of course, much useful geometry came out of epi-cycles, so we always learn from our mistakes, even those we try to forget. Life is one step back for every two forward and the trick is to make sure as few of them land on you as possible.
“Out in the real world, there are plenty of situations where questioning the powers that be just gets you squashed like a bug.”
That may be a little too melodramatic. Let’s just say I’ve learned to shut up and do what I’m told.
“That may be a little too melodramatic. Let’s just say I’ve learned to shut up and do what I’m told.”
That would be the macrocosmic contraction, as opposed to my microcosmic expressions.
Bren,
The problem with your analysis is that a single force in Newton’s terms is a force of one object upon another. The force of object A on object B, by newton’s third law, will always be equal to and opposite in direction of the force of object B on object A. This does, in no way, indicate that an attractive force between objects A and B should be offset by a repulsive force (if this were the case, then nothing could ever move with respect to anything else). An attractive force merely means that the force of object A on object B is towards object A, which means that the force of B on A will be towards B. A repulsive force will have the arrows pointing the other way. The forces are balanced by Newton’s third law, and there is no reason a priori to expect there to be any additional forces in there.
Jason,
It does appear that Bren is trying to raise a broader issue about gravity then just specific reaction.
Bren,
Try these;
http://www.plasmacosmology.net/
http://discovermagazine.com/2005/nov/two-against-the-big-bang/article_view?b_start:int=0&-C=
http://www.sciencedaily.com/releases/2005/01/050111115201.htm
http://www.astroleague.org/al/obsclubs/arppec/arphalt.html
http://www.cosmology.info/
LC:
“This depends upon what you mean by topological defect. There is no clear indication that the universe is multiply connected.”
I agree…the universe seems, from the field evidence so far, simply connected, which is not evidence consistent with an infinite universe or a possibly infinite series of universes.
Every indication from Ned’s reaction on his site is that he is skeptical, and he gives the circumstances under which he thinks this idea could be taken more seriously by the scientific community.
Simply connected…completely entangled with no “holes” to anywhere else…
The widely accepted notion that space in the universe is Euclidean, flat, even globally flat is, I think, a cause for wonderment. Every scientist who speaks about space is careful to use words like almost, or locally flat. The Omega total of 1.02 has been determined to such high precision that no objective person can reasonably assert that space in the universe is globally flat…it is almost flat and certainly marginally closed.
Ned suggests that the “cosmological constant” if taken with the Omega total might yield globally flat space, but he and everyone else I have questioned on this doubt that figuring a “cosmological constant” into the Omega really changes the inherent geometry of the universe. Neds question comes to mind: “Is space really flat?”.
The Standard Model requires that the universe had a very specific density at the big bang in order for the cosmos to have developed as it has. The density formula does not accept infinities; for that matter, neither does the grand proportion. Photons are observed to do work. Massless photons would not be expected to do work…as waves-or particles.
Space in GR is cosmologically curved and closed, Einstein himself visualized it that way. I realize hyperspherical space can be closed and understand that if space is assumed to be hypersperical, proof that space is multiply connected could be considered proof that space is either closed or open- but hyperspherical.
If space is shown conclusively to be simply connected, it is most likely also spheroid- globally marginally closed, as we already are led to conclude. Overall, space certainly is almost flat…I put emphasis on the word “almost” and remember at the same time the high precision of the experimentally determined Omega total, 1.02.
It will be interesting to watch and see how things develop! Crazier discoveries have been made in the history of science than (the possibility) that the universe might be multiply connected! Special and General Relativity themselves are so counterintuitive many still refuse to accept them.
Even folks who use SR and GR every day in their work usually spend little time following the functions and postulates logically. Those who do discover that SR/GR are not really counterintuitive at all. The functions, proportions and geometry explain particulation, space, time and existence in the most precise manner imaginable.
However, just when we feel the scientific community has a pretty good picture of what is going on, the world can be expected to be broadsided by new discoveries.
I have enjoyed following your posts, and those of the others as well. The scientific community as well as the general public should be forgiven, I think, their brainstorming.
As a well trained and informed person, you must smile at a lot of the ideas you see. We all have a tendancy to over generalize and come short in our concepts…missing many possibilites, and focusing on untenable ideas. However it is nice that even the general public senses that SR/GR and QM are astounding, and are interested in the subjects.
I have taught physics at the high school level, and my students could not wait to get to page 75 in our text…the introduction to Special Relativity!
Errata…
“Space in GR is cosmologically curved and closed, Einstein himself visualized it that way. I realize hyperbolic space can be closed and understand that if space is assumed to be hyperbolic, proof that space is multiply connected could be considered proof that space is either closed or open- but hyperbolic.”
The hole or texture which has been discovered in the CMB might be the first indication of experimental quantum gravity or quantum cosmology. I suspect this has much to do with the AdS/CFT. The Anti-deSitter spacetime has some quirky features, such as a periodic time for closed timelike curves, and its conformal infinity is a Minkowki spacetime. That means it is not possible to evolve a Cauchy data set (ie. initial conditions) to conformal infinity without additional boundary conditions on a Poincare 1/2-space. I suspect that this hole, and others doubtless exist as well, may be due to string or d-brane charges that give conformal completeness on the AdS space.
The global topology of the universe is as yet unknown. If it is a flat space, a spatial R^3 times a real line R, then this means in the inflationary process a three sphere is topologically changed and the boundary as seen by all observers was inflated “to infinity.” We might instead see a tiny piece of the universe, maybe one part in 10^{50} of the whole thing, and it inflated into a huge sphere — but not a flat space. Inflation may have pushed a tiny sphere, where our local region was a trillionth the size of a nucleus into a larger sphere where our local region was expaneded to around a meter across.
To think about these things does require an open mind. I also think people should not become partisan with either string theory or loop space quantum gravity (LQG). I suspect the two hypotheses are different keyhole views of the quantum gravity problem.
Lawrence B. Crowell
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I wrote the pingback above. I have exactly zero to add to the discussion of physics above; I just want to reinforce what I read to be Sean’s complaint about why imprecision in popular science writing matters. I don’t want people to get the message that they should not worry about what a given argument or story actually means. I cannot tell you how many times as a cub reporter at the then Time Inc. magazine Discover I argued with my boss over some variation on the phrase “Fusion: the force that powers the sun….”
See inversesquare.wordpress.com for my longer screed, taking off of Dennis Overbye’s use of the word “weird” to modify quantum mechanics.
Quantum mechanics involves a set of relationships between particles. These relationships don’t conform to our usual sense of things. That is why we call them “weird.” It has to be mentioned that space and spacetime involves another set of relationships, which in our low energy world at large is what we ordinarily perceive.
Two metrics at the same point p will have g_{ab}(p) = g’_{ab}(p), but if that point p is extended to another point in the two metrics the result will not be the same. This means that general relativity does not give an absolute definition of points and their distances, but rather can only determine the location of physical bodies with respect to each other. General relativity does not determine the position of bodies with respect to a manifold. This is the fundamental meaning of general covariance. It should be noted that with a bimetric theory the coordinate identification of points between two metrics completely violates this principle. This is a major criticism of string theory, which imposes a metric curvature on top of a background metric. Technically this runs into some trouble with general covariance in relativity theory. This is the triumph Smolin, Rovelli and others state for Loop Quantum Gravity (LQG). This was realized early on and caused Einstein to write, “That this requirement of general covariance, which takes away from space and time the last remnant of physical objectivity, is a natural one, …” Einstein, Albert; H. A. Lorentz, H. Weyl, and H. Minkowski (1916). The Principle of Relativity, 117.)
Quantum mechanics is another relationship system between particles. Two particles in an entangled state can exhibit nonlocal properties. For instance let two charged spin particles in an entangled state be separated by any distance. Then we let one of the particles enter a region with a magnetic field. This particle will in a certain basis of states exhibit a precession, just as a gyroscope does due to gravity — the wobbling top. Now assume you submit the other spinning charged particle, far removed from the region with a magnetic field, to a radio frequency (FR) detector. You will then find an RF blip indicating the particle is precessing as one would predict from the magnetic field the other particle is subject to. This will happen so long as the entanglement state is preserved — even if the two particles are light years apart! Without the entanglement issue this is how Magnetic Resonance Imaging works. This entanglement of states, violation of Bell’s equalities, and so forth has been tested positive in literally thousands of experimental tests. Most often it involves entangled photon states, such as squeezed states and parametrically amplitified states of photons and so forth. This is the other relationship system which exists in our universe.
Quantum gravity involves a unification of these two relationship systems. Most theorists are trying to quantize gravity — given the gravity field as described by general relativity most people try to write put the variables in general relativity in a quantum form, or to get quantum forms of gravity from quantization of strings (a sort of third quantization) and so forth. But I think that ultimately quantum gravity is a general system of relationships where quantum mechanics and relativity are specific examples of this.
As for writing popularization of science, that is very hard to do. To be honest I think Martin Gardner did the best job it, though his writings are not up to date. Aczel does a pretty good job. But I know from personal experience that I read popularizations as a teenager, where I got maybe 70% of it right, but I had to be disabused of the other 30% which were erroneous ideas I got. I also have talked to many people who have gotten bad ideas from popularizations. In particular my brother, who is a molecular biologist, ended up with all sorts of goofy ideas about things after reading Hawking’s “A Brief History of Time.”
Lawrence B. Crowell
JVP:
An interesting post!
“One may be assured that Einstein thus had a very practical (as well as theoretical) grasp of Thermodynamics. It is also clear that he was interested in the connections between Thermodynamics and Information Theory.
Whether he related that to Cosmology, I do not know. I would ask my teacher, Feynman, to whom Einstein and Oppenheimer and Wheeler were mentors, but, alas, all these men (excepting John Wheeler) are on the other side of a horizon from which, as Shakespeare noted: “No traveller returns.”
Richard Feynman was an incredible person, and I envy you for having had the opportunity to be his student.
I like your mentioning “horizons”. I can’t imagine your studying under Feynman without having had that matter fully discussed!
I’m inclined, given Einstein’s biography, to believe Relativity theory started as a (static) philosophical world-life point of view he first was briefly exposed to in Hebrew School. Much later, he studied the work of Lorentz and realized its implications. He then integated ideas from Mach and others. Einstein intuitively realized even in 1905 that the universe was locally flat. He was also smart enough not to bite off more than he could chew, so he concentrated on his Special Theory first…but immediately continued with the development of General Relativity. I remember when I was a teenager in the 50’s that the General Theory was still very much being questioned.
Please note that Shakesphere, NOT Richard Feynman, asserted that death was a horizon “from which no traveler returns”!
LBC:
Two really interesting summaries! I want to check a few things, and ask a few questions a bit later…
Tom, Lawrence, other readers:
I suggest not being so hard on popularizers who loosely use words like “force.” Many words have a broader meaning than for example just in the narrow context of the specific physical parameter with units M*L*T^-2. It’s about extended usage by convention in English (and I’d like to hear from users of other languages of similar issues). “Force” can mean, a source of energy in general without being what moves over distance to give energy. Yet I still think using “the energy source” would have been better. BTW, is the “string tension” of string theory really a “tension” exactly? Maybe, I’m just asking. What examples if any can be found from *professional* usage that aren’t really apt or consistent, not just from popular writing?
John,
Sorry, I’m not in the mood for stupidity today. Call back when you’ve got something that has the remotest hint of validity to it.
A few comments here. First about Feynman, I believe he wrote a note to an associate or his wife something to the effect, “Remind me to not go to any more of those gravity conferences.”
Force is an interesting concept, and it is something that involves categorically different objects or concepts. Newton’s second law is
F = ma.
Now acceleration is a geometric object. It is a purely kinematical concept involving must distance and time. It is also something which can only be measured in an inertial frame, which Newton’s first law implicitely tells us. Mass is something which we have a physical sense of, but that usually involves a measurement on a scale. So then we take F = -kx for the scale (Hooke’s law) and let a = g (0ne gravity or 1-gee) and we measure the displacement x of the spring or scale and we get the mass. But wait a minute! We are defining mass according to a force, which Newton’s second law is supposed to define. The “force” is something which exists independently — it has no meaning outside of Newton’s law. Also notice that to define the “mass” we used Hooke’s law to measure a distance which with a constant gave the force.
Newton’s second law “compresses” categorically different concepts into a single rule. One must also do an Admiral Nelson “blind eye” approach to use this equation. And this equation is used to put robots on Mars, build passenger planes, automobiles and heart=lung machines. It works awfully darn well. But with some thought it is apparent that it is a rather funny rule.
Lawrence B. Crowell
I took a brief look at thise websites:
http://www.plasmacosmology.net/
http://discovermagazine.com/2005/nov/two-against-the-big-bang/article_view?b_start:int=0&-C=
http://www.sciencedaily.com/releases/2005/01/050111115201.htm
http://www.astroleague.org/al/obsclubs/arppec/arphalt.html
http://www.cosmology.info/
There do seem to be these strange “cults” in physics, such as people who think Tesla was some visionary of vacuum energy or these websites or threads based on Arp. These things really don’t measure up very well, and frankly are a physics analogue of what biologists have with Creationism. And in fact some biblical creationists have put their cross hairs on big bang and cosmology and I have seen references to these plasma cosmology ideas as “evidence” of God’s recent creation of the universe.
Even without these agendas it must be pointed out that plasma physics is the most difficult area of physics. At least this is my opinion. It is based on the Navier-Stokes (NS) equation, which has no known formal solution set. There is a million dollar Claymath award to find this set Magnetohydrodynamics (MHD) couples the fluid flow in the NS equation to the electromagnetic field, where of course the fluid is a bi-fluid of light negative charges and heavier positive charges. These give rise to the Boltzmann-Vlasov equations and related differential equations. Outside of a few artificial cases these equations have no general solutions, and make the pure NS equation look trivial by comparison. People then write and run MHD computer programs to solve problems. If the universe operated primarily by plasma physics then we are really faced with an almost unknowable universe.
It is worth mentioning that David Bohm wrote down a version of the Schrodinger equation split into its real and imaginary parts. The real part is a modified Hamilton-Jacobi equation and the imaginary part is an NS equation. The NS equation describes what Bohmians call the pilot wave. I am not a “Bohm-mystic” type who thinks this overthrows the “weirdness” of quantum mechanics, but there is something to Bohm’s ideas.
To imagine the universe as governed by plasma physics suffers from another problem. Gravity is very weak, but there is one “charge” or algebraic root to the field, which is its source called mass, or mass-energy. There is no negative mass. I will leave that bit as I just stated, for there are some controversies over this. This means that while gravity is a very weak interaction it can accumulate arbitrarily with mass-energy density. Electromagnetism has its source as + and – charges, which means the electromagnetic field “saturates.” So while the EM field is much stronger than gravity it cancels itself out on larger scales. For instance, while the sun is largely a very complex plasma its electromagnetic force on the world outside its atmsophere or heliosphere is negligable or zero.
BTW, the latest issue of science has a feature on the Hinode measurements on solar physics
Lawrence B. Crowell
Jason,
http://www.technologyreview.com/read_article.aspx?id=13755&ch=infotech&a=f
“The quantum world is a world of waves, not particles. So we have to think of electron waves and proton waves and so on. Matter is ‘incoherent’ when all its waves have a different wavelength, implying a different momentum. On the other hand, if you take a pure quantum system – the electrons in a superconducting magnet, or the atoms in a laser – they are all in phase with one another, and they demonstrate the wave nature of matter on a large scale. Then you can see quite visibly what matter is down at its heart.” (Carver Mead Interview, American Spectator, Sep/Oct2001, Vol. 34 Issue 7, p68)
http://en.wikipedia.org/wiki/Carver_Mead
http://www.amazon.com/Collective-Electrodynamics-Quantum-Foundations-Electromagnetism/dp/0262133784
Quotes from this book;
Quoting Feynman in the preface;
“If there is something slightly wrong in our definition of the theories, then the full mathematical rigor may convert these errors into ridiculous conclusions.”
“Einstein was a giant. His head was in the clouds, but his feet were on the ground. But those of us who are not that tall have to chose.”
The first line of the Introduction;
“It is my firm belief that the last seven decades of the twentieth century will be characterized in history as the dark ages of theoretical physics.”
Quoting Einstein in the Epilogue;
“Assuming the success of efforts to accomplish a complete physical description, the statistical quantum theory would, within the framework of future physics, take an approximately analogous position to the statistical mechanics within the framework of classical mechanics. I am rather firmly convinced that the development of theoretical physics will be of this type, but the path will be lenghty and difficult.”
Lawrence,
Light/radiation as negative mass? It would seem to be the opposite in many ways. Gravity contracts/light expands. Also when gravity reaches critical density, it ignites and releases energy as light. As Mead describes light as primarily as waves, possibly when it grounds out/detected as a particle/photon, that it is the first stage of it gravitationally collapsing. Resulting in a larger cycle.
I think the balance to gravity was what Bren was trying to describe.