Earths' gravitational binding energy (shell model, not homogeneous average density) is -1.711×10^32 J. Earth mass is 5.97219×10^24 kg. 1kTon TNT/kg is 4.186×10^12 J/kg or net 2.5×10^37 J. Pauli exclusion collapse would Death Star the Earth with 147,000 J/kg excess kinetic energy.
I propose touching is c-axis graphene plane spacing in graphite or gecko adhesion proximity,
Define touching... depending on the definition, you can or can't touch your nose. Ok then, defining who you are is another matter ;-) Maybe healthy dose of L*D might help with that definition (just joking).
The above essay is an example of schematic deterministic thinking of contemporary theoretical physicists, who are thinking in deterministic, not emergent and as such physically realistic way. Such a thinking helps to derive formal models, but not to understand the physical reality. The realistic physical objects aren't flat but rough, so that their atoms overlap the touching plane to high degree even without actually touching anything. Furthermore, these atoms aren't sitting at rest, but they're in wild motion, which makes the overlapping region even more fuzzy. The chemical theory of mechanical friction considers the formation of temporal chemical bonds between touching objects: this model explains, why the friction of certain rough inert materials (Teflon) is much lower than this one of physically flat ones (glass).
BTW The concept of touching becomes even more composite, when the virtual forces following from negative space-time curvature and gravitational charge get involved. For example the massive object may get trapped into Lagrangian point of pair of objects, which wouldn't otherwise exist, if these objects would remain separated at distance. The system of multiple massive objects may create a gravitational shadow (dark matter galaxy) inside of their holes, which may trap another massive objects - in this situation you may not be even able to determine the actual source of interaction. The system of many gravitational shadows may behave like physically solid surface for some galaxies, enabling their touch and collision at distance (1, 2).
Our abstract notions like "touch" are constructed by analogy out of primitive sensations and notions, in this case the physiological sensation of touch. Like any analogy, some other information is required to apply it out of its proper domain - and different other information for different domains. Atoms touch each other when their mutual forces are strong compared to other forces in their environment. Open and closed sets touch when they share a portion of their respective boundaries.
The moon touches the sea when it reaches out to pull it closer.
I like the finger going directly to the brain comment. One can perhaps touch another's nose by touching your own but the reaction is half strength and is FM modulation. As in the Zeno infinite division scenario. Zephir, this could be demonstrated to you should someone give up and think you need a punch in the nose at a distance. Afterall, you may feel certain of the landscape while touching yourself but it is unclear if you can infer by touching s brick wall there is something outside yourself. How can the monkey's by thought alone direct their mechanical hands? How is it touching a mouse on a rough mouse pad we feel we are touching the screen but not the mouse? At what distance? As a matter of scale we exchange electron eating bacteria with our touch screens. I recall an article in Discover magazine saying we do not know the ultimate substance of the world, it may as well be "clown noses." This thousands of years problem is central to modern issues of physics. I call it Quasic as QM theory does not quite cover it. Perhaps gravity, like mass is that not some substance implied we cannot touch no matter if opened or closed or in some combination, or whenever, that seems like it emerges from all then positive against the Diracian nilpotent nothingness.
You can’t effectively answer such questions based on fundamental degrees of freedom; at each energy scale you must find the appropriate dof to describe the phenomena. That’s what Wilson taught to the world and that’s why we have effective theories.
Giotis: Sure, that's why I wrote normal atmospheric pressure, room temperature, and so on. But there's no definition of 'nose' (or 'you') and no notion of 'touch' in effective field theory, so that doesn't help much.
All the above comments read to me as if they touch on deeper connections, on the face of it, anyway.
How poetic that the moon touches the earth, its sea, even if the moon is not there unless we see it.
So we are back to a few years ago where we debate virtual particles inside Feynman diagrams, phases unto collaspe, hierarchies in scale degrees of freedom, particles stable in Lagrangian like nodes among and within nuclei.
Pre stringy theories in hopes of a unified physics and that this path leads to quantitave measure someday as such abstractions have done so before.
Giotis sums it all thus far, and uncle Al begins the geckos clinging on the microscale of walls. Which Wilson?
And should that touch break how is it that they fall? Here, like gender in language, we jettison the wide emerging inflated energy cost for life for systems replication evolving.
Yet, to initiate, to clone, the geckos have to find instinctual unrequited touch, as with uncertainty in reaching out half or both asleep to find the reality of a lover, different yet the same, albeit sideways.
The fact, that only the atom nuclei and stars are spherical and all larger and smaller objects are irregular brings the notion, that the human observers are actually very giant hyperdimensional objects projected with multiple stars and embedded into galaxies. We're not just touching, we are deeply overlapping mutually. In this moment it's just a working geometric hypothesis without predictions, but it has some observational support already.
Yes but in a much broader sense you have the effective theory of ‘Human physiology’ :-)
According to Wikipedia:
“Human physiology is the science of the mechanical, physical, bioelectrical, and biochemical functions of humans in good health.”
So these phenomena are best described for all intents and purposes within the realm of this effective theory.
Otherwise you run into paradoxes. Someone for example may punch you in the nose and then easily proclaim “I never touched the guy”. The court will have to rely on the effective theory of ‘Human physiology’ to resolve the paradox in order to persecute the culprit :-)
Yes, in principle I agree. You wouldn't get away in any court claiming you can't touch anything, but that is because we all share a notion of "touch" and use the word to express this shared idea rather than any deep philosophical definition. One can play the same game with pretty much every word, let me just give you some examples: alive, inside (outside), fall, difficult (simple), and so on and so forth. In each case you'd know what I'd mean would I use the word, but if you'd try to come up with a definition, it would be very difficult. The punchline is basically that our verbal language that evolved over hundreds of thousands of years is not a logical construct and shouldn't be used for scientific arguments.
As you probably guessed though, I just used the cartoon as a vehicle to convey some physics. Best,
Personally, I am not convinced that Zeno was not right. His argument as I understand it was that continuous motion must be an illusion, because to traverse a distance with continuous motion it is necessary to traverse to its end a sequence of points which has no end. (The sequence 1/2 the distance, 3/4 the distance, 7/8 the distance, etc.)
That sequence consists of the partial sums of the infinite series 1/2+1/4+1/8+... Calculus as we have defined it says that the sum of an infinite series is the limit of the sequence of partial sums, so that a mathematician does not need to add up all the terms to determine its value (or lack thereof). But how do we know that nature is a mathematician who uses our definitions and tricks and Handbooks of Mathematical Series, or whether nature must add up a series to its end to get a value?
It seems to me (perhaps wrongly) that Quantum Mechanics tells us that we live in a universe in which motion is a movie (consisting of billions of frames per nanosecond) and in fact continuous motion is an illusion, just as Zeno thought, over 2300 years ago. Whether his argument was correct or he just made a lucky guess, I think he deserves some credit for that.
The "prove you're not a robot" window immediately overwrites with a Photo Sphere advert, nulling the entry.
As you know, classical gravitational binding energy (homogeneous sphere) is quadratic with mass, (-3GM^2)/5r. A sufficiently massive and compact object would go fully degenerate and remain bound, and be hot (less a huge neutrino burst during compaction). If M is the ratio of a neutron star to the sun's mass and R its radius, relativisitc gravitational binding energy is 885.975M/(R - 738.313M),
http://www.ns-grb.com/PPT/Lattimer.pdf
By what mechanism would the hot compacted electronic- and nuclear-degenerate body radiate after the neutrino burst? With nothing pushing out but temperature (and possibly centripetal force), Schwarzschild radius is important.
Come to think of it, 147 KJ/kg excess thermal energy for fully degenerate Earth, less the neutrino burst, would still be in negative energy territory. Those pesky footnotes!
JimV Zeno made the point at least that there are two sides to the argument that things are in a state of change or are always fixed. The roundabout limits idea just avoids the issue.
Sabine's connecting the questions of touch with that of how we define "you" is both a paradox and useful example to show Descartes idea of what is real or not by the idea of dreams as an example. But are we responsible for our actions in our dreams? Are they only our own dreams? In the awakened world there is the intent to do the crime that counts a lot - or the cover up, that is we try to hide the crime like try by strange logic to stay in the dream state.
We "fall" asleep or are awakened like an explosion emerging from within our minds as perhaps a more useful than just the physiology of systems.
And falling is the beginning of intellectualization, says Jung. To understand gravity seems to a great extent to understand ourselves, the fall of man, the rabbit down the rabbit holes.
So I relate this to a long time current problem in my dreams and certainly arising due to my learning to type on a touch screen phone rather than the PC when all other connections were not available.
Having learned that one can read and write after all as if typing in a dream, yet not an everyday thing, I can type a perfect paper not needing say imperfect spell checkers, it fits the Parimendeian sphere to which we struggle with thoughts and projects in the Heraclitean changing awakened world. So I must recall it and type it on a computer to establish the collective memory of the social self, forgetting most of the form of it if not the essential ideas. But there is no button to say take a picture of the page or any picture of this dream photography. Why did I expect a button to touch if ultimately we cannot touch anything? Still, that leaves a local space and time that defines I - although what is truly my own and not proven a robot, Uncle Al, is the poetry... stuff like that lost and fallen into experience to incubate in my dreams even if hidden again like sweet nothings and pillow talk needing better than an encore or fading.
But if we are to talk about imaginary time and mass in the mix of the physics of all this - perhaps we should think again about where are the tachyons.
BTW Zephir, XeF4 was considered impossible and was quite surprise in my time but it is not really a no stick surface unless one things the surface itself does not stick.
For example the alkali metals adhere on Teflon, because they do react with it. It's sometimes utilized for teflone bonding. So that only zero friction can serve as an indicia, you're touching/overlapping the opposite surface not at least a bit.
Your view of surface fluorination is simplistic and smartless. After Neil Bartlett diddled "xenon hexafluoroplatinate" (which it wasn't), Xe + F_2 in sunlight rapidly gives crystalline XeF_2 at ambient temp and pressure. Tunnel through psychological barriers. Auto plastic oil jugs are surface fluorinated so that ink and labels will stick. Plexiglass surface fluorinated becomes water-wettable. I know that for a fact because I had it done, and contact angles were measured in-house.
I(CF_3)_7 has no static molecular structure (Bartell pseudorotation). It is the heaviest gas at ambient temperature, MW = 609.948 amu. Easy to make, too. SF_6 is a mere 146.05 amu, air 29 amu.
What is the "touch" operator in Quantum Mechanics? Without a notion of that, I don't think you can say very much.
One suggestion is that two things are not touching if you can slip something in between them.
So, in 3-D, if you can put a surface between the two objects, the surface providing an infinite (delta-function) potential, and not perturb the two objects significantly, then they are not touching.
Hmm, stare at this http://en.wikipedia.org/wiki/Delta_potential for a while, and perhaps conclude that with my proposal above, whether two solids are touching each other should be deduced by the behavior of their lowest energy modes (of phonons or electrons, take your pick).
Arun, Because of nonlocality we can only suggest a plane can fit between two solids. Conversely a solid between two planes. Things touch on the nano scale of separate through 5 layers of atoms thick. It is more like Velcro than adhesion. More like Newtonian fluid flow viscosity between two plates by pressure and temperature. So, it is more complicated than the idea that planes curved in space is a greater transfinte number than than line curves in a plane.
"One suggestion is that two things are not touching if you can slip something in between them."
Arun,
Damn Freud, it seems that in a group discussion our brain stem defaults into innuendo, otherwise why would a game based on spelling (crosswords) be as popular as it is?
But officer, I never touched her, I was only "falling" for her in my dreams.
I just looked up the delta function link. Thanks. So many deltas and triangle symbols! OK, not that it is string theory which at some zero becomes one as in the wiki article but that there are a few potential wells in duality ordered succession and these of two orders of five things mean the relations have to be squared for all the possibilities. So the idea of one singularity Dirac admits or graphs and antigraphs goes beyond the standard model up to a 25th particle, Higgs which as a unity is the beginning or carrier of all these concepts where logically superimposed or implied validity, or the merging of forces (a measure of entropy in a lattice as to what freedom merges or what vortices lose or gain degrees of freedom in dimensional models seen as half the positive picture). Already the 24 object defies modern syllogism validity so it there by deduction of 4 space and is not distinguishable from the 25th ultimately. In my day a half century ago XeonF was a big thing along with the ad saying "Lestoil makes water wetter" And now I happily jettison my teflon cookware for certamics as like with sunscreen this nano stuff is toxic to eat. Age or out generation has lost some of our sense of smell in this better living thru chemistry. But all this seems to me, or should be for anyone with a nose for physics, it is as plain as the nose on our face." :-)
Klein paradox: When the potential of a potential barrier becomes similar to the mass of the impinging particle, it becomes transparent.
?????????
The analogy is a paradox listed in quantum mechanics. So, your saying......topology as an abstraction does not work when we look at the terrain, as if, of hills and valleys? This is a the topography of energy, right?
"It is" the ability of mind to explore those regions.
Visionaries may talk about the future, yet, some of those same visionary can see deeper into the very structure nature provides.
You just have to get past "it."
You understand three models of geometry having looked at the Friedman equation? What does this intuitive sense say when you are moving into the world of geometries?
IN their figure 2. Hyperbolic space, and their comparative relation to the M.C.Escher's Circle Limit woodcut, Klebanov and Maldacena write, " but we have replaced Escher's interlocking fish with cows to remind readers of the physics joke about the spherical cow as an idealization of a real one. In anti-de Sitter/conformal theory correspondence, theorists have really found a hyperbolic cow."
So if these thought experiments are properly grounded it can help one to formulate....most certainly.
“Whereas Plato envisioned common perceptions as revealing a mere shadow of reality, the holographic principle concurs, but turns the metaphor on it’s head. The Shadows-then things that are flattened out and hence live on a lower-dimensional surface-are real, while what seemed to be more richly structured, higher dimensional entities (us; the world around us) are evanescent projections of the shadows.” Brian Greene-The Fabric of the Cosmos, pg. 482
blog link within comment section seems to have some issues with leaving page as an option(?). I can work around if I wanted, so that is new.......any one else experiencing?
Well, if we want to do physics rather than philosophy, we need to ask "Is "touching" a physical property?" where in the Robert B. Griffiths' sense http://quantum.phys.cmu.edu/CQT/chaps/cqt04.pdf we have to ask - how do we identify the subspace of quantum states where two objects are touching?
If we can't do that, then "touching" turns into a matter of understanding human perception.
The idea to touch or not to touch something is strictly connected to our idea of space-time. We can say to touch something if and only if the distance between two points is zero but is a pure mathematical concept. From the other side we know that quantum mechanics can act whatever the distance between A and B The entanglement does not worry about distances or space-time. Why then should I say that energy and matter does not 'exists' ? Isn't more easy to think that is the space-time that does not exist? The light to travel does not need any aether. So why we need to put the light inside and 'empty box' called space-time? Space-time is a wonderful way to question the Nature with mathematics, but after that, we need to build models with real things. Space-time does not have any property that can be 'directly' measured. All what we know about space-time belongs from electromagnetism. Without space-time things become easier to understand.
That is true, still we can imagine things beyond our perception once we have a center or our thinking. This would explain what can be interpreted at least abstractly as intuition or faith as thought experiences the phenomenon.
The construction of a higher 4 dimensional solid is like each step digs thru a mountain and we do not know if the tunnels from both ends will meet while the digging but they exactly do, after long work that takes a guess or faith.
@Plato your posts and links were helpful in making matters clearer as to how we see or try to impose ideas on the landscape... or a bridge of understanding, a super topo sense so to speak. It also points out the inadequacy of QM thus string theory when we try to work within a limited theory. I am amazed how the lack, yet hint of a higher theory leads to reasonable conclusions as to what we think are total models, ones that moreover exclude others from the quest for a theory of everything until the next level comes together. This is not clearly a matter that separates science and philosophy, or for that matter, science and religion (in principle or as a mirror to our thoughts implied.) We can think of many newly discovered phenomena or data that seems perplexing by which from a higher sense of the landscape the issues appear as a trivial question. The origin of high energy cosmic rays unexplained within or outside the universe for example, or that particles quite freely experience different spacetimes or it an illusion they do. So Dirac imagines at least one single monopole, a singularity at pushes to the limits the idea of renormalization or even how singularities relate to established physics principles. I am reminded of a sci fi by Rudy Rucker where in successive renormalizations of such monopoles as they describe each generation of particles the hero eats them (they happen to be within his observable universes at the time) then goes on to describe the universe of what he sees. This is a step beyond the idea of a universe as quantum tunneling or wormholes or even that a particle may go off (your O. Klein link) to infinity not above or below a zero axis. At spacious singularity so to speak we can come back to a symmetry again before it is broken where that asymmetric is equivalent to that symmetrical. We can say that as we pass thru "transparent" singularity where forces cancel or can be created as physical each phase adds to the perceived energy say of a cosmic ray as a sort of multiple boost. The information then suggests in different phase eras, all present quantumly, there are new sources of energy to tap, just as simple hydrogen once organized to become stars or dark stars. Here where we cannot quite yet determine, if ever, the realm we call science or even pseudoscience the mirror exists as to say meaning, where does the meaning go. For example, it is quite reasonable to assume that if our minds once reaching a certain complexity has a spirit, this spirit can undergo such a boost or appear to do so that we stay awhile as ghosts before passing thru invisibly the black hole like structures and atmospheres to some still higher undetermined topology of our existence. It is not the map as such but the picture we put on a puzzle that helps us put all the pieces together. But as all physics is present if unified, stars still form only the process is rarer, ghosts and aliens and where they go is something a thinking creature may conclude- and something we need a better way to explore as physical data. Do we know if things loop or bounce back from singularities once we go beyond the scope of the known single or multiple universe?
I have always enjoyed you blog Plato, and yes there is some leave page problems which can result at least from the pc in multiple posts... programmers should eat the right singularities too as they merger the platforms and presentations.
The only assumption being everything (includes 'something' and 'nothing') is correlated.
Bob
My favorite is the Quantum Zeno Effect. Anything less than decay is static (life in suspension)
My least favorite is the quantum pigeonhole principle. http://arxiv.org/pdf/1407.3194v1.pdf
Probably because the experimentation is still out on this one.
p.s.
True. We never actually ever touch. The information used for whatever anyone labels 'touch' is information stored.
The same goes for 'you'. Storage (of information) is necessary and sufficient. Yes, of course, incomplete as well - that is the cost of being consistent and contradiction-free.
Electricity can be conducted across two blocks of copper (say that in a vacuum) that are touching each other and a tiny voltage is applied. There are probably some few intermediate states of conductivity when the blocks are a few microns apart, but the conductivity of the combination rapidly approaches zero as they are moved apart. Therefore the idea of "touching" does have some physical content.
Or does interacting via a field means they touch already?
Yes. Virtual photons are virtual. There are no actual photons flying back and forth. Hydrogen atoms don't twinkle. Magnets don't shine. The electron is not some billiard ball thing that has a field, field is what it is. It's like playing repulsion with a couple of magnets, but with just the field, and no magnets in the middle.Those virtual photons do "belong to any one of the objects". The reality that underlies virtual photons is the evanescent wave aka near field, which is just the electromagnetic field.
Robert I still think your general idea of wider scale, as others have said in one form or the other for a long time, is a good one. Simple questions can be confusing when we imagine concrete or virtual substance math forms... for examples here as some of the post comments. I mean could we not just imagine particles what may touch or not as little classical electron radii then claim the field is the thing virtual? I like to imagine a field as a chessboard and the pieces in it as the mass... rather simple, assumes many things like the grid is real and uniform. Do particles exchange virtual fields - there are several systems existing describing it either way in some form or the other. It amounts to what is virtual or what is physical interchangeable concepts...not just a virtual physics, and if these can be several systems like say multiple paths or times. Pushing qm things to ideas of some relation of scale and size between string tension may just bury the issues to some remote complexity to which we all can be embarrassed once we understood such simple foundational questions, perhaps.
I recall a Yeats poem where the priest like the incense because he liked the way his finger stinks. No one has mentioned the thought that some theories really stink. And I wonder why the cartoon characters in the illustration do not have noses, to drive the metaphor into the ground : ) : - ) for sense of completion.
Yeah, but can you? Believe it or not, it’s a question philosophers have plagued themselves with for thousands of years, and it keeps reappearing in my feeds!
[Image]
Best source I could find for this image: IFLS.
My first reaction was of course: It’s nonsense – a superficial play on the words “you” and “touch”. “You touch” whatever triggers the nerves in your skin. There, look, I’ve solved a thousand year’s old problem in a matter of 3 seconds.
Then it occurred to me that with this notion of “touch” my shoes never touch the ground. Maybe I’m not a genius after all. Let me get back to that cartoon then. Certainly deep thoughts went into it that I must unravel.
The average size of an atom is an Angstrom, 10-10 m. The typical interatomar distance in molecules is a nanometer, 10-9 meter, or let that be a few nanometers if you wish. At room temperature and normal atmospheric pressure, electrostatic repulsion prevents you from pushing atoms any closer together. So the 10-8 meter in the cartoon seem about correct.
But it’s not so simple...
To begin with it isn’t just electrostatic repulsion that prevents atoms from getting close, it is more importantly the Pauli exclusion principle which forces the electrons and quarks that make up the atom to arrange in shells rather than to sit on top of each other.
If you could turn off the Pauli exclusion principle, all electrons from the higher shells would drop into the ground state, releasing energy. The same would happen with the quarks in the nucleus which arrange in similar levels. Since nuclear energy scales are higher than atomic scales by several orders of magnitude, the nuclear collapse causes the bulk of the emitted energy. How much is it?
The typical nuclear level splitting is some 100 keV, that is a few 10-14 Joule. Most of the Earth is made up of silicon, iron and oxygen, ie atomic numbers of the order of 15 or so on the average. This gives about 10-12 Joule per atom, that is 1011 Joule per mol, or 1kTon TNT per kg.
This back-of-the envelope gives pretty much exactly the maximal yield of a nuclear weapon. The difference is though that turning off the Pauli exclusion principle would convert every kg of Earthly matter into a nuclear bomb. Since our home planet has a relatively small gravitational pull, I guess it would just blast apart. I saw everybody die, again, see that’s how it happens. But I digress; let me get back to the question of touch.
So it’s not just electrostatics but also the Pauli exclusion principle that prevents you from falling through the cracks. Not only do the electrons in your shoes don’t want to touch the ground, the electrons in your shoes don’t want to touch the other electrons in your shoes either. Electrons, or fermions generally, just don’t like each other.
The 10-8 meter actually seem quite optimistic because surfaces are not perfectly even, they have a roughness to them, which means that the average distance between two solids is typically much larger than the interatomic spacing that one has in crystals. Moreover, the human body is not a solid and the skin normally covered by a thin layer of fluids. So you never touch anything just because you’re separated by a layer of grease from the world.
To be fair, grease isn’t why the Greeks were scratching their heads back then, but a guy called Zeno. Zeno’s most famous paradox divides a distance into halves indefinitely to then conclude then that because it consists of an infinite number of steps, the full distance can never be crossed. You cannot, thus, touch your nose, spoke Zeno, or ram an arrow into it respectively. The paradox resolved once it was established that infinite series can converge to finite values; the nose was in the business again, but Zeno would come back to haunt the thinkers of the day centuries later.
The issue reappeared with the advance of the mathematical field of topology in the 19th century. Back then, math, physics, and philosophy had not yet split apart, and the bright minds of the times, Descarte, Euler, Bolzano and the like, they wanted to know, using their new methods, what does it mean for any two objects to touch? And their objects were as abstract as it gets. Any object was supposed to occupy space and cover a topological set in that space. So far so good, but what kind of set?
In the space of the real numbers, sets can be open or closed or a combination thereof. Roughly speaking, if the boundary of the set is part of the set, the set is closed. If the boundary is missing the set is open. Zeno constructed an infinite series of steps that converges to a finite value and we meet these series again in topology. Iff the limiting value (of any such series) is part of the set, the set is closed. (It’s the same as the open and closed intervals you’ve been dealing with in school, just generalized to more dimensions.) The topologists then went on to reason that objects can either occupy open sets or closed sets, and at any point in space there can be only one object.
Sounds simple enough, but here’s the conundrum. If you have two open sets that do not overlap, they will always be separated by the boundary that isn’t part of either of them. And if you have two closed sets that touch, the boundary is part of both, meaning they also overlap. In neither case can the objects touch without overlapping. Now what? This puzzle was so important to them that Bolzano went on to suggest that objects may occupy sets that are partially open and partially closed. While technically possible, it’s hard to see why they would, in more than 1 spatial dimension, always arrange so as to make sure one’s object closed surface touches the other’s open patches.
More time went by and on the stage of science appeared the notion of fields that mediate interactions between things. Now objects could interact without touching, awesome. But if they don’t repel what happens when they get closer? Do or don’t they touch eventually? Or does interacting via a field means they touch already? Before anybody started worrying about this, science moved on and we learned that the field is quantized and the interaction really just mediated by the particles that make up the field. So how do we even phrase now the question whether two objects touch?
We can approach this by specifying that we mean with an “object” a bound state of many atoms. The short distance interaction of these objects will (at room temperature, normal atmospheric pressure, non-relativistically, etc) take place primarily by exchanging (virtual) photons. The photons do in no sensible way belong to any one of the objects, so it seems fair to say that the objects don’t touch. They don’t touch, in one sentence, because there is no four-fermion interaction in the standard model of particle physics.
Alas, tying touch to photon exchange in general doesn’t make much sense when we think about the way we normally use the word. It does for example not have any qualifier about the distance. A more sensible definition would make use of the probability of an interaction. Two objects touch (in some region) if their probability of interaction (in that region) is large, whether or not it was mediated by a messenger particle. This neatly solves the topologists’ problem because in quantum mechanics two objects can indeed overlap.
What one means with “large probability” of interaction is somewhat arbitrary of course, but quantum mechanics being as awkward as it is there’s always the possibility that your finger tunnels through your brain when you try to hit your nose, so we need a quantifier because nothing is ever absolutely certain. And then, after all, you can touch your nose! You already knew that, right?
But if you think this settles it, let me add...
[Image]
Yes, no, maybe, wtf.
There is a non-vanishing probability that when you touch (attempt to touch?) something you actually exchange electrons with it. This opens a new can of worms because now we have to ask what is “you”? Are “you” the collection of fermions that you are made up of and do “you” change if I remove one electron and replace it with an identical electron? Or should we in that case better say that you just touched something else? Or are “you” instead the information contained in a certain arrangement of elementary particles, irrespective of the particles themselves? But in this case, “you” can never touch anything just because you are not material to begin with. I will leave that to you to ponder.
And so, after having spent an hour staring at that cartoon in my facebook feed, I came to the conclusion that the question isn’t whether we can touch something, but what we mean with “some thing”. I think I had been looking for some thing else though…
posted by Sabine Hossenfelder at 10:15 AM on Jul 29, 2014
"Can you touch your nose?"
41 Comments -
This comment has been removed by the author.
1:14 PM, July 29, 2014
http://typnet.net/Essays/EarthBind.htm
Earths' gravitational binding energy (shell model, not homogeneous average density) is -1.711×10^32 J. Earth mass is 5.97219×10^24 kg. 1kTon TNT/kg is 4.186×10^12 J/kg or net 2.5×10^37 J. Pauli exclusion collapse would Death Star the Earth with 147,000 J/kg excess kinetic energy.
I propose touching is c-axis graphene plane spacing in graphite or gecko adhesion proximity,
http://faculty.washington.edu/bergs/Simon_Sponberg/Gecko_Adhesion.html
2:48 PM, July 29, 2014
Define touching... depending on the definition, you can or can't touch your nose. Ok then, defining who you are is another matter ;-) Maybe healthy dose of L*D might help with that definition (just joking).
3:49 PM, July 29, 2014
The above essay is an example of schematic deterministic thinking of contemporary theoretical physicists, who are thinking in deterministic, not emergent and as such physically realistic way. Such a thinking helps to derive formal models, but not to understand the physical reality. The realistic physical objects aren't flat but rough, so that their atoms overlap the touching plane to high degree even without actually touching anything. Furthermore, these atoms aren't sitting at rest, but they're in wild motion, which makes the overlapping region even more fuzzy. The chemical theory of mechanical friction considers the formation of temporal chemical bonds between touching objects: this model explains, why the friction of certain rough inert materials (Teflon) is much lower than this one of physically flat ones (glass).
4:16 PM, July 29, 2014
BTW The concept of touching becomes even more composite, when the virtual forces following from negative space-time curvature and gravitational charge get involved. For example the massive object may get trapped into Lagrangian point of pair of objects, which wouldn't otherwise exist, if these objects would remain separated at distance. The system of multiple massive objects may create a gravitational shadow (dark matter galaxy) inside of their holes, which may trap another massive objects - in this situation you may not be even able to determine the actual source of interaction. The system of many gravitational shadows may behave like physically solid surface for some galaxies, enabling their touch and collision at distance (1, 2).
4:35 PM, July 29, 2014
Our abstract notions like "touch" are constructed by analogy out of primitive sensations and notions, in this case the physiological sensation of touch. Like any analogy, some other information is required to apply it out of its proper domain - and different other information for different domains. Atoms touch each other when their mutual forces are strong compared to other forces in their environment. Open and closed sets touch when they share a portion of their respective boundaries.
The moon touches the sea when it reaches out to pull it closer.
4:50 PM, July 29, 2014
I like the finger going directly to the brain comment. One can perhaps touch another's nose by touching your own but the reaction is half strength and is FM modulation. As in the Zeno infinite division scenario.
Zephir, this could be demonstrated to you should someone give up and think you need a punch in the nose at a distance. Afterall, you may feel certain of the landscape while touching yourself but it is unclear if you can infer by touching s brick wall there is something outside yourself.
How can the monkey's by thought alone direct their mechanical hands? How is it touching a mouse on a rough mouse pad we feel we are touching the screen but not the mouse? At what distance?
As a matter of scale we exchange electron eating bacteria with our touch screens.
I recall an article in Discover magazine saying we do not know the ultimate substance of the world, it may as well be "clown noses."
This thousands of years problem is central to modern issues of physics. I call it Quasic as QM theory does not quite cover it.
Perhaps gravity, like mass is that not some substance implied we cannot touch no matter if opened or closed or in some combination, or whenever, that seems like it emerges from all then positive against the Diracian nilpotent nothingness.
4:59 PM, July 29, 2014
Uncle,
Thanks for confirming my guess. It seems like heavier planets would collapse though?
1:02 AM, July 30, 2014
You can’t effectively answer such questions based on fundamental degrees of freedom; at each energy scale you must find the appropriate dof to describe the phenomena. That’s what Wilson taught to the world and that’s why we have effective theories.
2:37 AM, July 30, 2014
Giotis: Sure, that's why I wrote normal atmospheric pressure, room temperature, and so on. But there's no definition of 'nose' (or 'you') and no notion of 'touch' in effective field theory, so that doesn't help much.
3:32 AM, July 30, 2014
All the above comments read to me as if they touch on deeper connections, on the face of it, anyway.
How poetic that the moon touches the earth, its sea, even if the moon is not there unless we see it.
So we are back to a few years ago where we debate virtual particles inside Feynman diagrams, phases unto collaspe, hierarchies in scale degrees of freedom, particles stable in Lagrangian like nodes among and within nuclei.
Pre stringy theories in hopes of a unified physics and that this path leads to quantitave measure someday as such abstractions have done so before.
Giotis sums it all thus far, and uncle Al begins the geckos clinging on the microscale of walls. Which Wilson?
And should that touch break how is it that they fall? Here, like gender in language, we jettison the wide emerging inflated energy cost for life for systems replication evolving.
Yet, to initiate, to clone, the geckos have to find instinctual unrequited touch, as with uncertainty in reaching out half or both asleep to find the reality of a lover, different yet the same, albeit sideways.
4:15 AM, July 30, 2014
The fact, that only the atom nuclei and stars are spherical and all larger and smaller objects are irregular brings the notion, that the human observers are actually very giant hyperdimensional objects projected with multiple stars and embedded into galaxies. We're not just touching, we are deeply overlapping mutually. In this moment it's just a working geometric hypothesis without predictions, but it has some observational support already.
4:31 AM, July 30, 2014
Fuzzy sets?
http://en.wikipedia.org/wiki/Fuzzy_set
4:50 AM, July 30, 2014
Yes but in a much broader sense you have the effective theory of ‘Human physiology’ :-)
According to Wikipedia:
“Human physiology is the science of the mechanical, physical, bioelectrical, and biochemical functions of humans in good health.”
So these phenomena are best described for all intents and purposes within the realm of this effective theory.
Otherwise you run into paradoxes. Someone for example may punch you in the nose and then easily proclaim “I never touched the guy”. The court will have to rely on the effective theory of ‘Human physiology’ to resolve the paradox in order to persecute the culprit :-)
5:57 AM, July 30, 2014
Hi Giotis,
Yes, in principle I agree. You wouldn't get away in any court claiming you can't touch anything, but that is because we all share a notion of "touch" and use the word to express this shared idea rather than any deep philosophical definition. One can play the same game with pretty much every word, let me just give you some examples: alive, inside (outside), fall, difficult (simple), and so on and so forth. In each case you'd know what I'd mean would I use the word, but if you'd try to come up with a definition, it would be very difficult. The punchline is basically that our verbal language that evolved over hundreds of thousands of years is not a logical construct and shouldn't be used for scientific arguments.
As you probably guessed though, I just used the cartoon as a vehicle to convey some physics. Best,
B.
6:18 AM, July 30, 2014
PS: I want to add though that human physiology doesn't get you anywhere if you want to know if your shoes touch the ground...
6:20 AM, July 30, 2014
Personally, I am not convinced that Zeno was not right. His argument as I understand it was that continuous motion must be an illusion, because to traverse a distance with continuous motion it is necessary to traverse to its end a sequence of points which has no end. (The sequence 1/2 the distance, 3/4 the distance, 7/8 the distance, etc.)
That sequence consists of the partial sums of the infinite series 1/2+1/4+1/8+... Calculus as we have defined it says that the sum of an infinite series is the limit of the sequence of partial sums, so that a mathematician does not need to add up all the terms to determine its value (or lack thereof). But how do we know that nature is a mathematician who uses our definitions and tricks and Handbooks of Mathematical Series, or whether nature must add up a series to its end to get a value?
It seems to me (perhaps wrongly) that Quantum Mechanics tells us that we live in a universe in which motion is a movie (consisting of billions of frames per nanosecond) and in fact continuous motion is an illusion, just as Zeno thought, over 2300 years ago. Whether his argument was correct or he just made a lucky guess, I think he deserves some credit for that.
10:41 AM, July 30, 2014
Bee,
The "prove you're not a robot" window immediately overwrites with a Photo Sphere advert, nulling the entry.
As you know, classical gravitational binding energy (homogeneous sphere) is quadratic with mass, (-3GM^2)/5r. A sufficiently massive and compact object would go fully degenerate and remain bound, and be hot (less a huge neutrino burst during compaction). If M is the ratio of a neutron star to the sun's mass and R its radius, relativisitc gravitational binding energy is 885.975M/(R - 738.313M),
http://www.ns-grb.com/PPT/Lattimer.pdf
By what mechanism would the hot compacted electronic- and nuclear-degenerate body radiate after the neutrino burst? With nothing pushing out but temperature (and possibly centripetal force), Schwarzschild radius is important.
Come to think of it, 147 KJ/kg excess thermal energy for fully degenerate Earth, less the neutrino burst, would still be in negative energy territory. Those pesky footnotes!
11:44 AM, July 30, 2014
JimV
Zeno made the point at least that there are two sides to the argument that things are in a state of change or are always fixed. The roundabout limits idea just avoids the issue.
Sabine's connecting the questions of touch with that of how we define "you" is both a paradox and useful example to show Descartes idea of what is real or not by the idea of dreams as an example.
But are we responsible for our actions in our dreams? Are they only our own dreams? In the awakened world there is the intent to do the crime that counts a lot - or the cover up, that is we try to hide the crime like try by strange logic to stay in the dream state.
We "fall" asleep or are awakened like an explosion emerging from within our minds as perhaps a more useful than just the physiology of systems.
And falling is the beginning of intellectualization, says Jung. To understand gravity seems to a great extent to understand ourselves, the fall of man, the rabbit down the rabbit holes.
So I relate this to a long time current problem in my dreams and certainly arising due to my learning to type on a touch screen phone rather than the PC when all other connections were not available.
Having learned that one can read and write after all as if typing in a dream, yet not an everyday thing, I can type a perfect paper not needing say imperfect spell checkers, it fits the Parimendeian sphere to which we struggle with thoughts and projects in the Heraclitean changing awakened world. So I must recall it and type it on a computer to establish the collective memory of the social self, forgetting most of the form of it if not the essential ideas. But there is no button to say take a picture of the page or any picture of this dream photography. Why did I expect a button to touch if ultimately we cannot touch anything? Still, that leaves a local space and time that defines I - although what is truly my own and not proven a robot, Uncle Al, is the poetry... stuff like that lost and fallen into experience to incubate in my dreams even if hidden again like sweet nothings and pillow talk needing better than an encore or fading.
But if we are to talk about imaginary time and mass in the mix of the physics of all this - perhaps we should think again about where are the tachyons.
BTW Zephir, XeF4 was considered impossible and was quite surprise in my time but it is not really a no stick surface unless one things the surface itself does not stick.
12:26 PM, July 30, 2014
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12:26 PM, July 30, 2014
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12:27 PM, July 30, 2014
/* Zephir, XeF4 was considered impossible */
For example the alkali metals adhere on Teflon, because they do react with it. It's sometimes utilized for teflone bonding. So that only zero friction can serve as an indicia, you're touching/overlapping the opposite surface not at least a bit.
1:41 PM, July 30, 2014
@L. Edgar Otto,
Your view of surface fluorination is simplistic and smartless. After Neil Bartlett diddled "xenon hexafluoroplatinate" (which it wasn't), Xe + F_2 in sunlight rapidly gives crystalline XeF_2 at ambient temp and pressure. Tunnel through psychological barriers. Auto plastic oil jugs are surface fluorinated so that ink and labels will stick. Plexiglass surface fluorinated becomes water-wettable. I know that for a fact because I had it done, and contact angles were measured in-house.
I(CF_3)_7 has no static molecular structure (Bartell pseudorotation). It is the heaviest gas at ambient temperature, MW = 609.948 amu. Easy to make, too. SF_6 is a mere 146.05 amu, air 29 amu.
3:23 PM, July 30, 2014
What is the "touch" operator in Quantum Mechanics? Without a notion of that, I don't think you can say very much.
One suggestion is that two things are not touching if you can slip something in between them.
So, in 3-D, if you can put a surface between the two objects, the surface providing an infinite (delta-function) potential, and not perturb the two objects significantly, then they are not touching.
4:59 PM, July 30, 2014
Hmm, stare at this http://en.wikipedia.org/wiki/Delta_potential for a while, and perhaps conclude that with my proposal above, whether two solids are touching each other should be deduced by the behavior of their lowest energy modes (of phonons or electrons, take your pick).
5:23 PM, July 30, 2014
Arun,
Because of nonlocality we can only suggest a plane can fit between two solids. Conversely a solid between two planes. Things touch on the nano scale of separate through 5 layers of atoms thick. It is more like Velcro than adhesion. More like Newtonian fluid flow viscosity between two plates by pressure and temperature.
So, it is more complicated than the idea that planes curved in space is a greater transfinte number than than line curves in a plane.
7:47 PM, July 30, 2014
"One suggestion is that two things are not touching if you can slip something in between them."
Arun,
Damn Freud, it seems that in a group discussion our brain stem defaults into innuendo, otherwise why would a game based on spelling (crosswords) be as popular as it is?
But officer, I never touched her, I was only "falling" for her in my dreams.
I just looked up the delta function link. Thanks. So many deltas and triangle symbols! OK, not that it is string theory which at some zero becomes one as in the wiki article but that there are a few potential wells in duality ordered succession and these of two orders of five things mean the relations have to be squared for all the possibilities. So the idea of one singularity Dirac admits or graphs and antigraphs goes beyond the standard model up to a 25th particle, Higgs which as a unity is the beginning or carrier of all these concepts where logically superimposed or implied validity, or the merging of forces (a measure of entropy in a lattice as to what freedom merges or what vortices lose or gain degrees of freedom in dimensional models seen as half the positive picture). Already the 24 object defies modern syllogism validity so it there by deduction of 4 space and is not distinguishable from the 25th ultimately.
In my day a half century ago XeonF was a big thing along with the ad saying "Lestoil makes water wetter" And now I happily jettison my teflon cookware for certamics as like with sunscreen this nano stuff is toxic to eat.
Age or out generation has lost some of our sense of smell in this better living thru chemistry. But all this seems to me, or should be for anyone with a nose for physics, it is as plain as the nose on our face." :-)
11:52 PM, July 30, 2014
Klein paradox: When the potential of a potential barrier becomes similar to the mass of the impinging particle, it becomes transparent.
?????????
The analogy is a paradox listed in quantum mechanics. So, your saying......topology as an abstraction does not work when we look at the terrain, as if, of hills and valleys? This is a the topography of energy, right?
9:42 AM, July 31, 2014
Effectively, you need examples to get you grounded:)
A Phase Space Formulation?
To touch something, you need Toposense:)
"It is" the ability of mind to explore those regions.
Visionaries may talk about the future, yet, some of those same visionary can see deeper into the very structure nature provides.
You just have to get past "it."
You understand three models of geometry having looked at the Friedman equation? What does this intuitive sense say when you are moving into the world of geometries?
IN their figure 2. Hyperbolic space, and their comparative relation to the M.C.Escher's Circle Limit woodcut, Klebanov and Maldacena write, " but we have replaced Escher's interlocking fish with cows to remind readers of the physics joke about the spherical cow as an idealization of a real one. In anti-de Sitter/conformal theory correspondence, theorists have really found a hyperbolic cow."
So if these thought experiments are properly grounded it can help one to formulate....most certainly.
10:24 AM, July 31, 2014
“Whereas Plato envisioned common perceptions as revealing a mere shadow of reality, the holographic principle concurs, but turns the metaphor on it’s head. The Shadows-then things that are flattened out and hence live on a lower-dimensional surface-are real, while what seemed to be more richly structured, higher dimensional entities (us; the world around us) are evanescent projections of the shadows.” Brian Greene-The Fabric of the Cosmos, pg. 482
Take the leap:)
10:31 AM, July 31, 2014
blog link within comment section seems to have some issues with leaving page as an option(?). I can work around if I wanted, so that is new.......any one else experiencing?
10:39 AM, July 31, 2014
Well, if we want to do physics rather than philosophy, we need to ask "Is "touching" a physical property?" where in the Robert B. Griffiths' sense
http://quantum.phys.cmu.edu/CQT/chaps/cqt04.pdf
we have to ask - how do we identify the subspace of quantum states where two objects are touching?
If we can't do that, then "touching" turns into a matter of understanding human perception.
4:22 PM, July 31, 2014
The idea to touch or not to touch something is strictly connected to our idea of space-time. We can say to touch something if and only if the distance between two points is zero but is a pure mathematical concept.
From the other side we know that quantum mechanics can act whatever the distance between A and B
The entanglement does not worry about distances or space-time. Why then should I say that energy and matter does not 'exists' ? Isn't more easy to think that is the space-time that does not exist? The light to travel does not need any aether. So why we need to put the light inside and 'empty box' called space-time? Space-time is a wonderful way to question the Nature with mathematics, but after that, we need to build models with real things. Space-time does not have any property that can be 'directly' measured. All what we know about space-time belongs from electromagnetism. Without space-time things become easier to understand.
4:57 PM, July 31, 2014
Arun.
That is true, still we can imagine things beyond our perception once we have a center or our thinking. This would explain what can be interpreted at least abstractly as intuition or faith as thought experiences the phenomenon.
The construction of a higher 4 dimensional solid is like each step digs thru a mountain and we do not know if the tunnels from both ends will meet while the digging but they exactly do, after long work that takes a guess or faith.
@Plato your posts and links were helpful in making matters clearer as to how we see or try to impose ideas on the landscape... or a bridge of understanding, a super topo sense so to speak. It also points out the inadequacy of QM thus string theory when we try to work within a limited theory. I am amazed how the lack, yet hint of a higher theory leads to reasonable conclusions as to what we think are total models, ones that moreover exclude others from the quest for a theory of everything until the next level comes together. This is not clearly a matter that separates science and philosophy, or for that matter, science and religion (in principle or as a mirror to our thoughts implied.)
We can think of many newly discovered phenomena or data that seems perplexing by which from a higher sense of the landscape the issues appear as a trivial question. The origin of high energy cosmic rays unexplained within or outside the universe for example, or that particles quite freely experience different spacetimes or it an illusion they do.
So Dirac imagines at least one single monopole, a singularity at pushes to the limits the idea of renormalization or even how singularities relate to established physics principles. I am reminded of a sci fi by Rudy Rucker where in successive renormalizations of such monopoles as they describe each generation of particles the hero eats them (they happen to be within his observable universes at the time) then goes on to describe the universe of what he sees. This is a step beyond the idea of a universe as quantum tunneling or wormholes or even that a particle may go off (your O. Klein link) to infinity not above or below a zero axis.
At spacious singularity so to speak we can come back to a symmetry again before it is broken where that asymmetric is equivalent to that symmetrical. We can say that as we pass thru "transparent" singularity where forces cancel or can be created as physical each phase adds to the perceived energy say of a cosmic ray as a sort of multiple boost. The information then suggests in different phase eras, all present quantumly, there are new sources of energy to tap, just as simple hydrogen once organized to become stars or dark stars.
Here where we cannot quite yet determine, if ever, the realm we call science or even pseudoscience the mirror exists as to say meaning, where does the meaning go. For example, it is quite reasonable to assume that if our minds once reaching a certain complexity has a spirit, this spirit can undergo such a boost or appear to do so that we stay awhile as ghosts before passing thru invisibly the black hole like structures and atmospheres to some still higher undetermined topology of our existence. It is not the map as such but the picture we put on a puzzle that helps us put all the pieces together. But as all physics is present if unified, stars still form only the process is rarer, ghosts and aliens and where they go is something a thinking creature may conclude- and something we need a better way to explore as physical data. Do we know if things loop or bounce back from singularities once we go beyond the scope of the known single or multiple universe?
I have always enjoyed you blog Plato, and yes there is some leave page problems which can result at least from the pc in multiple posts... programmers should eat the right singularities too as they merger the platforms and presentations.
4:59 PM, July 31, 2014
Dear Alice,
Can you agree that we are correlated?
The only assumption being everything (includes 'something' and 'nothing') is correlated.
Bob
My favorite is the Quantum Zeno Effect. Anything less than decay is static (life in suspension)
My least favorite is the quantum pigeonhole principle.
http://arxiv.org/pdf/1407.3194v1.pdf
Probably because the experimentation is still out on this one.
p.s.
True. We never actually ever touch. The information used for whatever anyone labels 'touch' is information stored.
The same goes for 'you'.
Storage (of information) is necessary and sufficient.
Yes, of course, incomplete as well - that is the cost of being consistent and contradiction-free.
Anything 'Vollkommen'is romanhaft.
7:07 PM, July 31, 2014
Electricity can be conducted across two blocks of copper (say that in a vacuum) that are touching each other and a tiny voltage is applied. There are probably some few intermediate states of conductivity when the blocks are a few microns apart, but the conductivity of the combination rapidly approaches zero as they are moved apart. Therefore the idea of "touching" does have some physical content.
The challenge is to make the notion precise.
9:13 PM, July 31, 2014
Or does interacting via a field means they touch already?
Yes. Virtual photons are virtual. There are no actual photons flying back and forth. Hydrogen atoms don't twinkle. Magnets don't shine. The electron is not some billiard ball thing that has a field, field is what it is. It's like playing repulsion with a couple of magnets, but with just the field, and no magnets in the middle.Those virtual photons do "belong to any one of the objects". The reality that underlies virtual photons is the evanescent wave aka near field, which is just the electromagnetic field.
12:12 PM, August 01, 2014
Virtual photons and longitudinal photons, Oh My!
Virtual physics is the new reality?
10:32 PM, August 01, 2014
Robert
I still think your general idea of wider scale, as others have said in one form or the other for a long time, is a good one.
Simple questions can be confusing when we imagine concrete or virtual substance math forms... for examples here as some of the post comments. I mean could we not just imagine particles what may touch or not as little classical electron radii then claim the field is the thing virtual?
I like to imagine a field as a chessboard and the pieces in it as the mass... rather simple, assumes many things like the grid is real and uniform. Do particles exchange virtual fields - there are several systems existing describing it either way in some form or the other.
It amounts to what is virtual or what is physical interchangeable concepts...not just a virtual physics, and if these can be several systems like say multiple paths or times.
Pushing qm things to ideas of some relation of scale and size between string tension may just bury the issues to some remote complexity to which we all can be embarrassed once we understood such simple foundational questions, perhaps.
12:37 AM, August 02, 2014
I recall a Yeats poem where the priest like the incense because he liked the way his finger stinks. No one has mentioned the thought that some theories really stink. And I wonder why the cartoon characters in the illustration do not have noses, to drive the metaphor into the ground : ) : - ) for sense of completion.
12:43 AM, August 02, 2014
This is a really fun post! Thanks
7:51 PM, August 02, 2014