13 ms·

At Multiverse Impasse, a New Theory of Scale

176 points by akrymski 12y ago

Natsu 12y ago
Things like this keep me wondering if eventually we will reach a point where we are unable to distinguish theories about our own past due to lacking the energy necessary to experiment with those conditions thanks to entropy.
- vecter 12y ago
  What does entropy have to do with anything?
  - lutusp 12y ago
    Entropy = the inverse of available energy to do anything at all. EDIT: Look -- if you don't understand physics, don't compound your ignorance by downvoting the posts of people who do. Instead, post a written objection, and I will explain why you're wrong.
    - vecter 12y ago
      I'm pretty sure entropy isn't what's stopping us from probing high energy levels.
      - lutusp 12y ago
        That's true -- we're a long way from being limited by entropy in experimental physics.
    - possibilistic 12y ago
      I don't like that definition. I like to consider ∆S the result of a smoothing operation over energy differentials. You can put work into a system to reestablish an energy differential. It just necessitates obtaining that other energy differential with which to do the work.
      - lutusp 12y ago
        >> Entropy = the inverse of available energy to do anything at all. > I don't like that definition. Physics isn't a popularity contest. http://en.wikipedia.org/wiki/Entropy http://en.wikipedia.org/wiki/Entropy > You can put work into a system to reestablish an energy differential. Yes, but that doesn't change the definition of entropy -- it just borrows energy from somewhere else.
        possibilistic 12y ago
        I feel like you're being that guy. Forgive me if I come across the same way. Why link me to the Wikipedia article or insinuate I'm pulling this out of--to put it more politely--ex culo? Given my use of notation, one might assume I am at least a little familiar with how the thermodynamic entropy functions are mathematically derived. To be pedantic for a bit, Entropy is an abstract mathematical state function useful for the prediction of thermodynamic systems. Much like the Gibbs and Helmholtz terms, entropy has no direct qualitative basis; there are many open-ended interpretations seeking to justify what it means, which is not unlike looking for God or faeries or what have you. Mathematically speaking, I think you got your equality / definition wrong. Which energy function do you refer to? If you are still convinced about an error on my part, you can demonstrate in classical thermodynamics that, S = "the inverse of available energy to do anything" Or stats thermo, if that's how you roll. (Mine isn't that great anymore, sadly.)
        lutusp 12y ago
        > I feel like you're being that guy. What's my incentive to continue a discussion with someone who has abandoned the topic? In a closed system, the amount of exploitable energy, and the quantity called entropy, move in opposite directions. > ... or insinuate I'm pulling this out of--to put it more politely--ex culo? Point to where I said this. If you can't, then you have abandoned the topic. > Much like the Gibbs and Helmholtz terms, entropy has no direct qualitative basis; there are many open-ended interpretations seeking to justify what it means, which is not unlike looking for God or faeries or what have you. Nonsense. Entropy is clearly understood, it's not a philosophical puzzle as you suggest. It's easily quantifiable. It's science, not philosophy. > Given my use of notation, one might assume I am at least a little familiar with how the thermodynamic entropy functions are mathematically derived. Anyone can adopt the notations used in science. This doesn't tell me anything about their knowledge of the topics under discussion. You simultaneously apply standard terminology, but you go on to say that explaining entropy is "not unlike looking for God or faeries or what have you", which means you don't understand the significance of the symbols you used. Entropy = k log(n) k = Boltzmann's constant. n = number of states the system can be in. How difficult is that? http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/temper2.html http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/temper2.ht... Quote: "Temperature is expressed as the inverse of the rate of change of entropy with internal energy, with volume V and number of particles N held constant. This is certainly not as intuitive as molecular kinetic energy, but in thermodynamic applications it is more reliable and more general."
    - lifeisstillgood 12y ago
      Well, I don't think I understand entropy - even after Wikipedia. So is there somewhere in universe some energy that is not available to do anything at all? How does that work? Is it too diffuse such that the energy needed to pull it together to perform a unit of work is greater than the energy available ? If so how did it get to that state?
      - lutusp 12y ago
        > Well, I don't think I understand entropy - even after Wikipedia. Okay, here's a commonly used explanation. Entropy and time are bound together -- as time passes, overall entropy increases (with local violations like us). This is one idea about why time "moves" in the direction it does -- if time were to reverse, we could tell because some classic entropy results would run in reverse, violating common sense. Imagine that there's a room, and in one corner of the room there's a perfume bottle. At time zero, the cork is removed from the perfume bottle. Because of entropy, the tendency of isolated systems to move from order to disorder, the perfume disperses through the room. Ask yourself what the probability is for the perfume to spontaneously recombine in the bottle, versus the probability that it will disperse through the room. That probability differential is a measure of entropy. > So is there somewhere in universe some energy that is not available to do anything at all? Sure -- any isolated system can eventually get to a point where no useful work can be performed. Imagine an engine without any temperature differentials anywhere, or any way to acquire a temperature differential from an external source. Such an engine cannot do useful work. A steam engine requires a heat source and a heat sink. Without a temperature differential, the engine cannot function. Same with a gas engine. > Is it too diffuse such that the energy needed to pull it together to perform a unit of work is greater than the energy available ? But without tapping an external energy source, the energy in an isolated system won't concentrate itself or spontaneously create a temperature differential suitable for exploitation. In an isolated system, the level of disorder always increases over time. > If so how did it get to that state? Simple physics. For two masses having a temperature difference, one with temperature "a", the other "b", and a temperature conductivity of "k", they will eventually reach the same temperature this way: Δ = (b-a) e^(-t k) Δ (delta) = temperature difference at time t a = temperature a b = temperature b t = time k = energy transfer coefficient The above refers to an isolated system with an initial temperature difference. As time passes, that difference declines.
  - dspillett 12y ago
    If the available energy is dispersed and chaotic, we won't be able to concentrate enough to perform the experiments? Though I doubt that'll be the case at any time while the human race is in existence... (caveat: I know very little of real physics)
    - lutusp 12y ago
      > If the available energy is dispersed and chaotic, we won't be able to concentrate enough to perform the experiments? That's a layman's definition of entropy, but we're a long way from that state.
    - Drakim 12y ago
      If humanity lives to a point where entropy becomes a problem, I'm pretty sure our lives would be the first to go, not our "ability to perform experiments".
      - serf 12y ago
        that entirely depends on the magnitude of the experiment. If we were approaching any "universal energy" limitations, it'd stand to reason that our technology would be very much different than our technology now -- perhaps universe sized experiments would be feasible by that point, at which time we may hit a limit imposed on us not by anything other than the length of time since the last universe formation event, and our poor luck in meeting that point in technology at a time where the energy no longer exists to fuel it. Unlikely, and I think your idea of life being threatened before science is probably much more rational, but it's fun to think about. Plus, if we were using that much energy for a single experiment, one would wonder about that experiments' safety.
    - mwest 12y ago
      You might enjoy Isaac Asimov's short story: The Last Question http://www.multivax.com/last_question.html http://www.multivax.com/last_question.html I recommend you read the whole thing, but if you're looking for a plot summary: http://en.wikipedia.org/wiki/The_Last_Question#Plot_summary http://en.wikipedia.org/wiki/The_Last_Question#Plot_summary
itry 12y ago
"size differences are illusory" So two things standing next to each other are the same size as one thing alone? Damn hard to imagine. I would think "size" does not really "exist" but is a man made concept. And by its definition, two things next to each other form a "bigger" thing.
- coldtea 12y ago
  The article is badly written, but it doesn't really mean sizes are illusory (even if it says so at the beginning). It goes on to say that sizes and mass "spontaneously emerge" from lower interactions, which is to say, they become real for us. But, to address your example: "So two things standing next to each other are the same size as one thing alone? Damn hard to imagine". That might not hold for size, but a very similar thing does occur (and is proven) for speed. If you are in a car that goes at 0.8 miles per minute, and you throw a dart that goes at 0.3 miles/minute, its speed is 1.1 miles/minute (the sum). But if you travel at the 0.8x the speed of light and you throw something forward at 0.3x the speed of light, its speed is not 1.1x the speed of light, but c. That is, trying to add velocity doesn't get you faster than the speed of light. http://curious.astro.cornell.edu/question.php?number=145 http://curious.astro.cornell.edu/question.php?number=145
  - lutusp 12y ago
    > But if you travel at the 0.8x the speed of light and you throw something forward at 0.3x the speed of light, its speed is not 1.1x the speed of light, but c. Not really. Velocities near c don't sum that way. And your reference doesn't support your claim.
    - gus_massa 12y ago
      I agree. More details: http://en.wikipedia.org/wiki/Velocity-addition_formula http://en.wikipedia.org/wiki/Velocity-addition_formula If you add two velocities that are less than c, you can never get c, you always get something smaller. 0.8c + 0.3 c ~= 0.887 c (It's smaller than c) At low speeds the effect still exists, but it's negligible. There is an important difference between "it doesn't exist" and "it's so small that if we forget it we will be fine". It's so small that you must use floating point numbers with too many digits to calculate it. It's more useful to calculate the difference between the "relativistic" sum and the "classical" sum. Another way is to aproximate the formula with a Taylor expansion dif = (X+Y) / (1+(X * Y/c^2)) - (X+Y) ~= - (X + Y) (X * Y/c^2) 0.8mph + 0.3 mph = 11mph - 5.9 * 10^-39 mph The correction is veeeeery small.
mSparks 12y ago
I don't see why this kills the multi verse theory. Which is a basic conclusion of a 10 dimensional space-time environment that doesn't include mass anyway.
- lutusp 12y ago
  Well, it's just a hyperbolic headline that tries to call a speculation a theory (the latter meaning an idea with some supporting evidence). It certainly doesn't kill any other current speculation. It's journalism masquerading as science.
- calinet6 12y ago
  It "kills it" because it's only really appealing if the universe we're in appears extremely unlikely, like it's the "just right" goldilocks balance of cosmic variables that we can't explain, that happened to be the stable ones that resulted in life evolving eventually. If the universe is actually very likely to occur in the state that it's in, then we don't need to use this "vast multiverse where our universe was the one that produced an observer" explanation. It could be a single universe in all of existence, where everything makes sense mathematically and no further posturing is required in that silly unscientific field of cosmic philosophy. Or if it fails, and it remains that our universe is unexpectedly perfect, then we are forced to resort to statistical explanations within an impossible-to-observe external multiverse. Scientists don't very much like conclusions built on not being able to observe things. Though to me, the multiverse theory has a sort of fractal appeal to it. It is surely applicable to our planet, after all. Why not our entire universe?
  - tinco 12y ago
    A cool thing about the multiverse is that it makes a team out of us and the rest of our universe. 'We' are the universe that became stable and self aware, in contrast to many other universes. 'We' are a self aware universe. You, me, and the rest of the universe together, so we should act like it.
  - mSparks 12y ago
    But the whole point of the multi verse model is that universe also exists. Multi verse theory afaik is just a mathematical construct of the various dimensions we can observe in a space time framework. The whole http://en.m.wikipedia.org/wiki/Flatland http://en.m.wikipedia.org/wiki/Flatland Idea.
trhway 12y ago
>With their field stuck at a nasty impasse of course. Natural thing when a field is dominated by orthodoxy that closes their eyes to everything that they don't want to see. Like yesterday "entangled photon imaging" where what really happens is that a beam modulated by an image heats/excites crystal (with that heating/excitement thus obviously modulated by the image) which generates another beam (thus that another beam is obviously also modulated by the image) which hits CCD - no miracle of entanglement here, yet Nature published it as such : https://news.ycombinator.com/item?id=8234221 https://news.ycombinator.com/item?id=8234221 as "entanglement" and "mutiverse" are very much in fashion this season and get you published. With Higgs as a "mass" boson it was also non-starter because the theory of it failed to address gravitational and inertial mass equivalence. I mean i don't doubt that CERN found new particle of course, yet nowhere it was shown that it is the boson "generating mass". The article seems to suggest that finally the mainstream physics starts to seriously ponder whether the mass is a result of dynamic interaction - that has been obvious for decades to the "fringe" physicists, who couldn't just dismiss the above mentioned gravitational and inertial mass connection, a pretty fundamental fact that has to be at the center of anything called physics :)
- l33tbro 12y ago
  I wouldn't say that the "field is dominated by orthodoxy that closes their eyes to everything that they don't want to see". I'll admit most physicists I've met are suspicious of wild-eyed theory. But I wouldn't say they're overly orthodox. I think it's more a healthy skepticism of anything which involves humans projecting science-ficiton wish-fulfilment into science. I'd go further and say that "entanglement" and "multiverse" are not at all en vogue. I think most seasoned physicists realize that these were trendy fields some years ago (for solipsistic reasons - ie, make us feel special). So I think the return to a fundamental assessment of phenomena is pretty natural thing. Calling out assumptions like scale. What's more, I think the more discerning will also be suspicious of the "post-multiverse" dialectic. It's just the process really.
  - trhway 12y ago
    >I'll admit most physicists I've met are suspicious of wild-eyed theory. ... >So I think the return to a fundamental assessment of phenomena is pretty natural thing. Calling out assumptions like scale. i see big difference between "Calling out assumptions like scale" as a "return to a fundamental assessment of phenomena" and "Calling out assumptions like scale" in order to fit it into a wild-eyed theory like superstrings (basically to salvage the theory).
notastartup 12y ago
Feels like I'm a kid and I've just been told Santa Claus is made up.
- coldtea 12y ago
  Actually it should feel more like a tall story from your uncle at a family dinner, that's not corroborated and doesn't even imply what he insists it implies. That is, half of the article is trash and the other doesn't represent the science correctly.
- walterbell 12y ago
  Depends on whether one considers Wired to be a high-quality filter.
givan 12y ago
I wonder if it's possible to ever find out what our reality is even if we will eventually reach the intellectual and technology necessary because we are part of it and it's probably impossible to have an objective view of the matter.
- collyw 12y ago
  Yes. Open minded comments like this, questioning the limits of science get down voted here on HN.
  - goblin89 12y ago
    I didn't downvote, but if you ask me I'd say others did it mainly because grandparent brought philosophy into scientific discussion. (And with reasoning or phrasing issues at that: “we can't do something even if we can”, for example, contradicts itself.)
    - halfcat 12y ago
      Ironic that science is a subset of philosophy.
      - goblin89 12y ago
        That's precisely why, IMHO, if you aren't prepared to make a complete well-thought-through argument, then you should think twice before venturing into a philosophical discussion. On the other hand, due to the nature of HN, one has to choose between either spending a few days researching the comment and posting it with a very slim chance of being read or answered, or blurting out something not very polished. In this case it's the latter. (How you define “objective”? “reality”? A rough example of how could the answer to the question “what reality is” roughly look like? Any links to existing research—people certainly attempted to ask a question of this nature before?) The resulting discussion may be worth it, though.
- unfunco 12y ago
  "There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable." – from The Restaurant at the end of the Universe.
teh_klev 12y ago
Original article with less visual crap around the sides: http://www.simonsfoundation.org/quanta/20140818-at-multiverse-impasse-a-new-theory-of-scale/ http://www.simonsfoundation.org/quanta/20140818-at-multivers...
- raldi 12y ago
  And, unlike the Wired article, it doesn't tell me I'm holding my phone wrong and cover up the content for no apparent reason.
- bellerocky 12y ago
  Better and it doesn't have a link bait title.
- dang 12y ago
  Thanks! Changed from http://www.wired.com/2014/08/multiverse http://www.wired.com/2014/08/multiverse.
3rd3 12y ago
Someone in the comment section claims plagiarism. What's that all about? http://www.wired.com/2014/08/multiverse#comment-1560643455 http://www.wired.com/2014/08/multiverse#comment-1560643455 Edit: Never mind, http://rationalwiki.org/wiki/Mensur_Omerbashich http://rationalwiki.org/wiki/Mensur_Omerbashich
pablisco 12y ago
"Radical New" and "Theory" doesn't make sense, surely this would be a hypothesis :)
JackC 12y ago
For a heroic attempt to explain this article to laypeople, check out physicsmatt's comments over at Metafilter: "First, for maximum sense-making, read my previous comments here, here, here, and here. I realize that's a lot, sorry. The Universe is complicated. Then, for what follows, recall that to a particle physicist such as myself, there is no difference between lengths and energies (or indeed, any other dimensional quantity). Length is inverse energy: very energetic phenomenon probe very small lengths ...." https://www.metafilter.com/142211/Multiverse-No-More-a-New-Theory-of-Scale#5703172 https://www.metafilter.com/142211/Multiverse-No-More-a-New-T...
- antimagic 12y ago
  Or don't - it's incredibly badly written, in the sense that it often descends into grammatical gibberish, even without worrying about the physics the gibberish is trying to describe.
  - calinet6 12y ago
    There's really not that much to understand, and the details aren't that important unless you're living them. The question boils down to this: are we one of an infinite number of universes that popped into existence that just happened to have the right variables to be stable and result in life? (The anthropic principle, a statistical conclusion, and a philosophical mind-bender...) Or are we in a single universe whose properties are mathematically aligned in such a way as to be very unlikely to result from chance, even if repeated an infinite number of times? The details of this are interesting, but extremely numerous and complex: basically, Physicists are trying everything. The latter does not require the hand-wavey wishy-washy existence of an infinite number of non-observable extremely large things, and therefore garners more enthusiasm. However, if observations conclude that the parameters of our universe are in fact paradoxically perfect, then the idea that we're an evolved observer of one chance universe out of many holds water. Hence the intense research on how this whole universe thing works. Fun.
dlevine 12y ago
To be fair, this only kills one of the multiverse hypotheses. I'm reading Brian Greene's "The Hidden Reality" right now, and he describes about 8 independent (or semi-independent) multiverse hypotheses. From what I understand (and I'm no physicist), this just provides evidence against the anthropic principle, and the multiverse associated with that line of thinking...
MisterMashable 12y ago
There's a very subtle undertone of negativity in this article about physics. Before I get into, William Bardeen is not in the same league as 'Surfer Dude and his E8 Theory of Everything' which throws basic facts about representation theory out the window, coming up with 'todalay boogus' arguments which amazes auntie, mommie and magazine editors but a real physicist would instantly dismiss. Bardeen is the real deal. His papers are very interesting and feel a bit like reading Sidney Coleman's papers. If you're interested... http://arxiv.org/find/hep-th/1/au:+Bardeen_W/0/1/0/all/0/1 http://arxiv.org/find/hep-th/1/au:+Bardeen_W/0/1/0/all/0/1 Is nature scale invariant? So far the answer is absolutely NO but I strongly advise to wait and see. There are many topics that point to some breakdown in scale or reorganizing what we think of space and distance (dualities in string theory, conformal field theory). OK, now the important thing I want everyone here to realize. You are living through a GOLDEN AGE of physics. You wouldn't think that based on what all the popular magazines tell you. Here's why... 1. Higgs particle - discovered! 2. Inflation - discovered! Denying this one is like denying the Big Bang itself. The evidence is overwhelming and in fact I would list this as the single greatest scientific discovery of all time. The concurrent discovery of gravity waves, quantum gravity and a real life example of a Hawking process only sweetens the deal. 3. Supersymmetry has basically already been discovered IMHO. They aren't announcing anything at CERN and won't until they have so many sigmas under their belt but trust me, it's coming and truth be told, it isn't really so surprising. SUSY physics has always been rock solid from the beginning. The situation is very similar to that before offical Higgs announcement and before someone went knocking on Andre Linde's front door. Many were extremely confident in the Higgs particle a least a year before the official announcement. The BICEP 2 results were even more glaringly apparent than the Higgs results. Many people were walking around the Earth with 'secret knowledge' that inflation theory was correct even 2 to 3 years before the official announcement. So you are living through EXTREMELY interesting times but you wouldn't know it with all the big science bashing being thrown around.
- AtmaScout 12y ago
  Thanks for your post and link. I recently watched Particle Fever on Netflix and became extremely fascinated with the field. A lot of the information you posted is touched on in the documentary. It is mostly focused around CERN and the years leading up to the Higgs particle discovery. There are also great interviews with David Kaplan and Nima Arkani-Hamed. You've likely seen it but if not you might enjoy it.
playing_colours 12y ago
When I became interested in modern physics theories of both quantum and universe level, I found the following book [0] by Max Tegmark to have very good explanations regarding origin and nature of the universe, quantum mechanics, and just interesting stories / facts from the life of physicists. [0] http://www.amazon.com/Our-Mathematical-Universe-Ultimate-Reality-ebook/dp/B00DXKJ2DA/ref=sr_1_1?ie=UTF8&qid=1409321567&sr=8-1&keywords=our+mathematical+universe http://www.amazon.com/Our-Mathematical-Universe-Ultimate-Rea...
kazinator 12y ago
WOBAD! http://www.theonion.com/articles/worlds-top-scientists-ponder-what-if-the-whole-uni,712/ http://www.theonion.com/articles/worlds-top-scientists-ponde...
- kimdouglasmason 12y ago
  From the article: "That shit would be too much," Gupta said. "It'd be like that Dr. Seuss book Horton Hears A Who and shit. I read that when I was, like, six, and it totally weirded me out." Nailed it.
kazinator 12y ago
> "Multiverse ennui cannot last forever" says Graham Ross? That is naive. There is no way to prove or disprove it; it can be safely regarded as true without ever contradicting any possible observation we can ever make. I do not think physics will ever settle the questions in such a way that the "multiverse ennui" is not invoked to cover the loose ends; in fact, it will become more and more obvious as the inescapable conclusion. The deeper we dig into nature, either we keep finding more mathematics, or we encounter some absolute that can no longer be analyzed. Once we know every physical law, and are certain nothing more is to be discovered, how do we distinguish our universe from a set of mathematical axioms? We have two choices then: to suspect there is some outer universe which implements the rules and axioms of this one. Or else admit that axioms do not require an implementation: they just are, and that's what makes their system exist (which means that any other axioms and rules we can imagine also exist just as much). Either hypothesis is an unprovable "cop out"; but the latter of the two is more plausible. The first hypothesis still leads to an infinity of universes, and they have to be nested in each other in an infinitely regressing sequence. The second one has no such silly requirement; and it has the anthropic principle which plausibly explains everything that seems arbitrary or special.
hcarvalhoalves 12y ago
> Perhaps the fundamental description of the universe does not include the concepts of “mass” and “length,” implying that at its core, nature lacks a sense of scale. This little-explored idea, known as scale symmetry, (...) Isn't the word for that fractal?
- andrewflnr 12y ago
  Ah, no, that's a completely different sense of scale invariance. In a fractal you still have to measure the sizes of different similar structures, and generally pay attention to length. It seems that this article is discussing a much deeper abandonment of length.
ccvannorman 12y ago
I once read that "black holes orbiting each other follow the exact same mathematics as electrons orbiting protons", but I was unable to find the direct source. I did find another article comparing black holes to elementary particles: http://www.technologyreview.com/view/413483/could-all-particles-be-mini-black-holes/ http://www.technologyreview.com/view/413483/could-all-partic...
- Bognar 12y ago
  They would naturally follow the same mathematics, since the formula for gravitational attraction and the formula for electrical attraction are both following the inverse square law. http://en.wikipedia.org/wiki/Inverse-square_law http://en.wikipedia.org/wiki/Inverse-square_law

176 points by akrymski 12y ago

Natsu 12y ago

Things like this keep me wondering if eventually we will reach a point where we are unable to distinguish theories about our own past due to lacking the energy necessary to experiment with those conditions thanks to entropy.

vecter 12y ago
What does entropy have to do with anything?
- lutusp 12y ago
  Entropy = the inverse of available energy to do anything at all. EDIT: Look -- if you don't understand physics, don't compound your ignorance by downvoting the posts of people who do. Instead, post a written objection, and I will explain why you're wrong.
  - vecter 12y ago
    I'm pretty sure entropy isn't what's stopping us from probing high energy levels.
    - lutusp 12y ago
      That's true -- we're a long way from being limited by entropy in experimental physics.
  - possibilistic 12y ago
    I don't like that definition. I like to consider ∆S the result of a smoothing operation over energy differentials. You can put work into a system to reestablish an energy differential. It just necessitates obtaining that other energy differential with which to do the work.
    - lutusp 12y ago
      >> Entropy = the inverse of available energy to do anything at all. > I don't like that definition. Physics isn't a popularity contest. http://en.wikipedia.org/wiki/Entropy http://en.wikipedia.org/wiki/Entropy > You can put work into a system to reestablish an energy differential. Yes, but that doesn't change the definition of entropy -- it just borrows energy from somewhere else.
      - possibilistic 12y ago
        I feel like you're being that guy. Forgive me if I come across the same way. Why link me to the Wikipedia article or insinuate I'm pulling this out of--to put it more politely--ex culo? Given my use of notation, one might assume I am at least a little familiar with how the thermodynamic entropy functions are mathematically derived. To be pedantic for a bit, Entropy is an abstract mathematical state function useful for the prediction of thermodynamic systems. Much like the Gibbs and Helmholtz terms, entropy has no direct qualitative basis; there are many open-ended interpretations seeking to justify what it means, which is not unlike looking for God or faeries or what have you. Mathematically speaking, I think you got your equality / definition wrong. Which energy function do you refer to? If you are still convinced about an error on my part, you can demonstrate in classical thermodynamics that, S = "the inverse of available energy to do anything" Or stats thermo, if that's how you roll. (Mine isn't that great anymore, sadly.)
        lutusp 12y ago
        > I feel like you're being that guy. What's my incentive to continue a discussion with someone who has abandoned the topic? In a closed system, the amount of exploitable energy, and the quantity called entropy, move in opposite directions. > ... or insinuate I'm pulling this out of--to put it more politely--ex culo? Point to where I said this. If you can't, then you have abandoned the topic. > Much like the Gibbs and Helmholtz terms, entropy has no direct qualitative basis; there are many open-ended interpretations seeking to justify what it means, which is not unlike looking for God or faeries or what have you. Nonsense. Entropy is clearly understood, it's not a philosophical puzzle as you suggest. It's easily quantifiable. It's science, not philosophy. > Given my use of notation, one might assume I am at least a little familiar with how the thermodynamic entropy functions are mathematically derived. Anyone can adopt the notations used in science. This doesn't tell me anything about their knowledge of the topics under discussion. You simultaneously apply standard terminology, but you go on to say that explaining entropy is "not unlike looking for God or faeries or what have you", which means you don't understand the significance of the symbols you used. Entropy = k log(n) k = Boltzmann's constant. n = number of states the system can be in. How difficult is that? http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/temper2.html http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/temper2.ht... Quote: "Temperature is expressed as the inverse of the rate of change of entropy with internal energy, with volume V and number of particles N held constant. This is certainly not as intuitive as molecular kinetic energy, but in thermodynamic applications it is more reliable and more general."
  - lifeisstillgood 12y ago
    Well, I don't think I understand entropy - even after Wikipedia. So is there somewhere in universe some energy that is not available to do anything at all? How does that work? Is it too diffuse such that the energy needed to pull it together to perform a unit of work is greater than the energy available ? If so how did it get to that state?
    - lutusp 12y ago
      > Well, I don't think I understand entropy - even after Wikipedia. Okay, here's a commonly used explanation. Entropy and time are bound together -- as time passes, overall entropy increases (with local violations like us). This is one idea about why time "moves" in the direction it does -- if time were to reverse, we could tell because some classic entropy results would run in reverse, violating common sense. Imagine that there's a room, and in one corner of the room there's a perfume bottle. At time zero, the cork is removed from the perfume bottle. Because of entropy, the tendency of isolated systems to move from order to disorder, the perfume disperses through the room. Ask yourself what the probability is for the perfume to spontaneously recombine in the bottle, versus the probability that it will disperse through the room. That probability differential is a measure of entropy. > So is there somewhere in universe some energy that is not available to do anything at all? Sure -- any isolated system can eventually get to a point where no useful work can be performed. Imagine an engine without any temperature differentials anywhere, or any way to acquire a temperature differential from an external source. Such an engine cannot do useful work. A steam engine requires a heat source and a heat sink. Without a temperature differential, the engine cannot function. Same with a gas engine. > Is it too diffuse such that the energy needed to pull it together to perform a unit of work is greater than the energy available ? But without tapping an external energy source, the energy in an isolated system won't concentrate itself or spontaneously create a temperature differential suitable for exploitation. In an isolated system, the level of disorder always increases over time. > If so how did it get to that state? Simple physics. For two masses having a temperature difference, one with temperature "a", the other "b", and a temperature conductivity of "k", they will eventually reach the same temperature this way: Δ = (b-a) e^(-t k) Δ (delta) = temperature difference at time t a = temperature a b = temperature b t = time k = energy transfer coefficient The above refers to an isolated system with an initial temperature difference. As time passes, that difference declines.
- dspillett 12y ago
  If the available energy is dispersed and chaotic, we won't be able to concentrate enough to perform the experiments? Though I doubt that'll be the case at any time while the human race is in existence... (caveat: I know very little of real physics)
  - lutusp 12y ago
    > If the available energy is dispersed and chaotic, we won't be able to concentrate enough to perform the experiments? That's a layman's definition of entropy, but we're a long way from that state.
  - Drakim 12y ago
    If humanity lives to a point where entropy becomes a problem, I'm pretty sure our lives would be the first to go, not our "ability to perform experiments".
    - serf 12y ago
      that entirely depends on the magnitude of the experiment. If we were approaching any "universal energy" limitations, it'd stand to reason that our technology would be very much different than our technology now -- perhaps universe sized experiments would be feasible by that point, at which time we may hit a limit imposed on us not by anything other than the length of time since the last universe formation event, and our poor luck in meeting that point in technology at a time where the energy no longer exists to fuel it. Unlikely, and I think your idea of life being threatened before science is probably much more rational, but it's fun to think about. Plus, if we were using that much energy for a single experiment, one would wonder about that experiments' safety.
  - mwest 12y ago
    You might enjoy Isaac Asimov's short story: The Last Question http://www.multivax.com/last_question.html http://www.multivax.com/last_question.html I recommend you read the whole thing, but if you're looking for a plot summary: http://en.wikipedia.org/wiki/The_Last_Question#Plot_summary http://en.wikipedia.org/wiki/The_Last_Question#Plot_summary

itry 12y ago

"size differences are illusory" So two things standing next to each other are the same size as one thing alone? Damn hard to imagine. I would think "size" does not really "exist" but is a man made concept. And by its definition, two things next to each other form a "bigger" thing.

coldtea 12y ago
The article is badly written, but it doesn't really mean sizes are illusory (even if it says so at the beginning). It goes on to say that sizes and mass "spontaneously emerge" from lower interactions, which is to say, they become real for us. But, to address your example: "So two things standing next to each other are the same size as one thing alone? Damn hard to imagine". That might not hold for size, but a very similar thing does occur (and is proven) for speed. If you are in a car that goes at 0.8 miles per minute, and you throw a dart that goes at 0.3 miles/minute, its speed is 1.1 miles/minute (the sum). But if you travel at the 0.8x the speed of light and you throw something forward at 0.3x the speed of light, its speed is not 1.1x the speed of light, but c. That is, trying to add velocity doesn't get you faster than the speed of light. http://curious.astro.cornell.edu/question.php?number=145 http://curious.astro.cornell.edu/question.php?number=145
- lutusp 12y ago
  > But if you travel at the 0.8x the speed of light and you throw something forward at 0.3x the speed of light, its speed is not 1.1x the speed of light, but c. Not really. Velocities near c don't sum that way. And your reference doesn't support your claim.
  - gus_massa 12y ago
    I agree. More details: http://en.wikipedia.org/wiki/Velocity-addition_formula http://en.wikipedia.org/wiki/Velocity-addition_formula If you add two velocities that are less than c, you can never get c, you always get something smaller. 0.8c + 0.3 c ~= 0.887 c (It's smaller than c) At low speeds the effect still exists, but it's negligible. There is an important difference between "it doesn't exist" and "it's so small that if we forget it we will be fine". It's so small that you must use floating point numbers with too many digits to calculate it. It's more useful to calculate the difference between the "relativistic" sum and the "classical" sum. Another way is to aproximate the formula with a Taylor expansion dif = (X+Y) / (1+(X * Y/c^2)) - (X+Y) ~= - (X + Y) (X * Y/c^2) 0.8mph + 0.3 mph = 11mph - 5.9 * 10^-39 mph The correction is veeeeery small.

mSparks 12y ago

I don't see why this kills the multi verse theory. Which is a basic conclusion of a 10 dimensional space-time environment that doesn't include mass anyway.

lutusp 12y ago
Well, it's just a hyperbolic headline that tries to call a speculation a theory (the latter meaning an idea with some supporting evidence). It certainly doesn't kill any other current speculation. It's journalism masquerading as science.
calinet6 12y ago
It "kills it" because it's only really appealing if the universe we're in appears extremely unlikely, like it's the "just right" goldilocks balance of cosmic variables that we can't explain, that happened to be the stable ones that resulted in life evolving eventually. If the universe is actually very likely to occur in the state that it's in, then we don't need to use this "vast multiverse where our universe was the one that produced an observer" explanation. It could be a single universe in all of existence, where everything makes sense mathematically and no further posturing is required in that silly unscientific field of cosmic philosophy. Or if it fails, and it remains that our universe is unexpectedly perfect, then we are forced to resort to statistical explanations within an impossible-to-observe external multiverse. Scientists don't very much like conclusions built on not being able to observe things. Though to me, the multiverse theory has a sort of fractal appeal to it. It is surely applicable to our planet, after all. Why not our entire universe?
- tinco 12y ago
  A cool thing about the multiverse is that it makes a team out of us and the rest of our universe. 'We' are the universe that became stable and self aware, in contrast to many other universes. 'We' are a self aware universe. You, me, and the rest of the universe together, so we should act like it.
- mSparks 12y ago
  But the whole point of the multi verse model is that universe also exists. Multi verse theory afaik is just a mathematical construct of the various dimensions we can observe in a space time framework. The whole http://en.m.wikipedia.org/wiki/Flatland http://en.m.wikipedia.org/wiki/Flatland Idea.

trhway 12y ago

>With their field stuck at a nasty impasse of course. Natural thing when a field is dominated by orthodoxy that closes their eyes to everything that they don't want to see. Like yesterday "entangled photon imaging" where what really happens is that a beam modulated by an image heats/excites crystal (with that heating/excitement thus obviously modulated by the image) which generates another beam (thus that another beam is obviously also modulated by the image) which hits CCD - no miracle of entanglement here, yet Nature published it as such : https://news.ycombinator.com/item?id=8234221 https://news.ycombinator.com/item?id=8234221 as "entanglement" and "mutiverse" are very much in fashion this season and get you published. With Higgs as a "mass" boson it was also non-starter because the theory of it failed to address gravitational and inertial mass equivalence. I mean i don't doubt that CERN found new particle of course, yet nowhere it was shown that it is the boson "generating mass". The article seems to suggest that finally the mainstream physics starts to seriously ponder whether the mass is a result of dynamic interaction - that has been obvious for decades to the "fringe" physicists, who couldn't just dismiss the above mentioned gravitational and inertial mass connection, a pretty fundamental fact that has to be at the center of anything called physics :)

l33tbro 12y ago
I wouldn't say that the "field is dominated by orthodoxy that closes their eyes to everything that they don't want to see". I'll admit most physicists I've met are suspicious of wild-eyed theory. But I wouldn't say they're overly orthodox. I think it's more a healthy skepticism of anything which involves humans projecting science-ficiton wish-fulfilment into science. I'd go further and say that "entanglement" and "multiverse" are not at all en vogue. I think most seasoned physicists realize that these were trendy fields some years ago (for solipsistic reasons - ie, make us feel special). So I think the return to a fundamental assessment of phenomena is pretty natural thing. Calling out assumptions like scale. What's more, I think the more discerning will also be suspicious of the "post-multiverse" dialectic. It's just the process really.
- trhway 12y ago
  >I'll admit most physicists I've met are suspicious of wild-eyed theory. ... >So I think the return to a fundamental assessment of phenomena is pretty natural thing. Calling out assumptions like scale. i see big difference between "Calling out assumptions like scale" as a "return to a fundamental assessment of phenomena" and "Calling out assumptions like scale" in order to fit it into a wild-eyed theory like superstrings (basically to salvage the theory).

notastartup 12y ago

Feels like I'm a kid and I've just been told Santa Claus is made up.

coldtea 12y ago
Actually it should feel more like a tall story from your uncle at a family dinner, that's not corroborated and doesn't even imply what he insists it implies. That is, half of the article is trash and the other doesn't represent the science correctly.
walterbell 12y ago
Depends on whether one considers Wired to be a high-quality filter.

givan 12y ago

I wonder if it's possible to ever find out what our reality is even if we will eventually reach the intellectual and technology necessary because we are part of it and it's probably impossible to have an objective view of the matter.

collyw 12y ago
Yes. Open minded comments like this, questioning the limits of science get down voted here on HN.
- goblin89 12y ago
  I didn't downvote, but if you ask me I'd say others did it mainly because grandparent brought philosophy into scientific discussion. (And with reasoning or phrasing issues at that: “we can't do something even if we can”, for example, contradicts itself.)
  - halfcat 12y ago
    Ironic that science is a subset of philosophy.
    - goblin89 12y ago
      That's precisely why, IMHO, if you aren't prepared to make a complete well-thought-through argument, then you should think twice before venturing into a philosophical discussion. On the other hand, due to the nature of HN, one has to choose between either spending a few days researching the comment and posting it with a very slim chance of being read or answered, or blurting out something not very polished. In this case it's the latter. (How you define “objective”? “reality”? A rough example of how could the answer to the question “what reality is” roughly look like? Any links to existing research—people certainly attempted to ask a question of this nature before?) The resulting discussion may be worth it, though.
unfunco 12y ago
"There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable." – from The Restaurant at the end of the Universe.

teh_klev 12y ago

Original article with less visual crap around the sides: http://www.simonsfoundation.org/quanta/20140818-at-multiverse-impasse-a-new-theory-of-scale/ http://www.simonsfoundation.org/quanta/20140818-at-multivers...

raldi 12y ago
And, unlike the Wired article, it doesn't tell me I'm holding my phone wrong and cover up the content for no apparent reason.
bellerocky 12y ago
Better and it doesn't have a link bait title.
dang 12y ago
Thanks! Changed from http://www.wired.com/2014/08/multiverse http://www.wired.com/2014/08/multiverse.

3rd3 12y ago

Someone in the comment section claims plagiarism. What's that all about? http://www.wired.com/2014/08/multiverse#comment-1560643455 http://www.wired.com/2014/08/multiverse#comment-1560643455 Edit: Never mind, http://rationalwiki.org/wiki/Mensur_Omerbashich http://rationalwiki.org/wiki/Mensur_Omerbashich

pablisco 12y ago

"Radical New" and "Theory" doesn't make sense, surely this would be a hypothesis :)

JackC 12y ago

For a heroic attempt to explain this article to laypeople, check out physicsmatt's comments over at Metafilter: "First, for maximum sense-making, read my previous comments here, here, here, and here. I realize that's a lot, sorry. The Universe is complicated. Then, for what follows, recall that to a particle physicist such as myself, there is no difference between lengths and energies (or indeed, any other dimensional quantity). Length is inverse energy: very energetic phenomenon probe very small lengths ...." https://www.metafilter.com/142211/Multiverse-No-More-a-New-Theory-of-Scale#5703172 https://www.metafilter.com/142211/Multiverse-No-More-a-New-T...

antimagic 12y ago
Or don't - it's incredibly badly written, in the sense that it often descends into grammatical gibberish, even without worrying about the physics the gibberish is trying to describe.
- calinet6 12y ago
  There's really not that much to understand, and the details aren't that important unless you're living them. The question boils down to this: are we one of an infinite number of universes that popped into existence that just happened to have the right variables to be stable and result in life? (The anthropic principle, a statistical conclusion, and a philosophical mind-bender...) Or are we in a single universe whose properties are mathematically aligned in such a way as to be very unlikely to result from chance, even if repeated an infinite number of times? The details of this are interesting, but extremely numerous and complex: basically, Physicists are trying everything. The latter does not require the hand-wavey wishy-washy existence of an infinite number of non-observable extremely large things, and therefore garners more enthusiasm. However, if observations conclude that the parameters of our universe are in fact paradoxically perfect, then the idea that we're an evolved observer of one chance universe out of many holds water. Hence the intense research on how this whole universe thing works. Fun.

dlevine 12y ago

To be fair, this only kills one of the multiverse hypotheses. I'm reading Brian Greene's "The Hidden Reality" right now, and he describes about 8 independent (or semi-independent) multiverse hypotheses. From what I understand (and I'm no physicist), this just provides evidence against the anthropic principle, and the multiverse associated with that line of thinking...

MisterMashable 12y ago

There's a very subtle undertone of negativity in this article about physics. Before I get into, William Bardeen is not in the same league as 'Surfer Dude and his E8 Theory of Everything' which throws basic facts about representation theory out the window, coming up with 'todalay boogus' arguments which amazes auntie, mommie and magazine editors but a real physicist would instantly dismiss. Bardeen is the real deal. His papers are very interesting and feel a bit like reading Sidney Coleman's papers. If you're interested... http://arxiv.org/find/hep-th/1/au:+Bardeen_W/0/1/0/all/0/1 http://arxiv.org/find/hep-th/1/au:+Bardeen_W/0/1/0/all/0/1 Is nature scale invariant? So far the answer is absolutely NO but I strongly advise to wait and see. There are many topics that point to some breakdown in scale or reorganizing what we think of space and distance (dualities in string theory, conformal field theory). OK, now the important thing I want everyone here to realize. You are living through a GOLDEN AGE of physics. You wouldn't think that based on what all the popular magazines tell you. Here's why... 1. Higgs particle - discovered! 2. Inflation - discovered! Denying this one is like denying the Big Bang itself. The evidence is overwhelming and in fact I would list this as the single greatest scientific discovery of all time. The concurrent discovery of gravity waves, quantum gravity and a real life example of a Hawking process only sweetens the deal. 3. Supersymmetry has basically already been discovered IMHO. They aren't announcing anything at CERN and won't until they have so many sigmas under their belt but trust me, it's coming and truth be told, it isn't really so surprising. SUSY physics has always been rock solid from the beginning. The situation is very similar to that before offical Higgs announcement and before someone went knocking on Andre Linde's front door. Many were extremely confident in the Higgs particle a least a year before the official announcement. The BICEP 2 results were even more glaringly apparent than the Higgs results. Many people were walking around the Earth with 'secret knowledge' that inflation theory was correct even 2 to 3 years before the official announcement. So you are living through EXTREMELY interesting times but you wouldn't know it with all the big science bashing being thrown around.

AtmaScout 12y ago
Thanks for your post and link. I recently watched Particle Fever on Netflix and became extremely fascinated with the field. A lot of the information you posted is touched on in the documentary. It is mostly focused around CERN and the years leading up to the Higgs particle discovery. There are also great interviews with David Kaplan and Nima Arkani-Hamed. You've likely seen it but if not you might enjoy it.

playing_colours 12y ago

When I became interested in modern physics theories of both quantum and universe level, I found the following book [0] by Max Tegmark to have very good explanations regarding origin and nature of the universe, quantum mechanics, and just interesting stories / facts from the life of physicists. [0] http://www.amazon.com/Our-Mathematical-Universe-Ultimate-Reality-ebook/dp/B00DXKJ2DA/ref=sr_1_1?ie=UTF8&qid=1409321567&sr=8-1&keywords=our+mathematical+universe http://www.amazon.com/Our-Mathematical-Universe-Ultimate-Rea...

kazinator 12y ago

WOBAD! http://www.theonion.com/articles/worlds-top-scientists-ponder-what-if-the-whole-uni,712/ http://www.theonion.com/articles/worlds-top-scientists-ponde...

kimdouglasmason 12y ago
From the article: "That shit would be too much," Gupta said. "It'd be like that Dr. Seuss book Horton Hears A Who and shit. I read that when I was, like, six, and it totally weirded me out." Nailed it.

kazinator 12y ago

> "Multiverse ennui cannot last forever" says Graham Ross? That is naive. There is no way to prove or disprove it; it can be safely regarded as true without ever contradicting any possible observation we can ever make. I do not think physics will ever settle the questions in such a way that the "multiverse ennui" is not invoked to cover the loose ends; in fact, it will become more and more obvious as the inescapable conclusion. The deeper we dig into nature, either we keep finding more mathematics, or we encounter some absolute that can no longer be analyzed. Once we know every physical law, and are certain nothing more is to be discovered, how do we distinguish our universe from a set of mathematical axioms? We have two choices then: to suspect there is some outer universe which implements the rules and axioms of this one. Or else admit that axioms do not require an implementation: they just are, and that's what makes their system exist (which means that any other axioms and rules we can imagine also exist just as much). Either hypothesis is an unprovable "cop out"; but the latter of the two is more plausible. The first hypothesis still leads to an infinity of universes, and they have to be nested in each other in an infinitely regressing sequence. The second one has no such silly requirement; and it has the anthropic principle which plausibly explains everything that seems arbitrary or special.

hcarvalhoalves 12y ago

> Perhaps the fundamental description of the universe does not include the concepts of “mass” and “length,” implying that at its core, nature lacks a sense of scale. This little-explored idea, known as scale symmetry, (...) Isn't the word for that fractal?

andrewflnr 12y ago
Ah, no, that's a completely different sense of scale invariance. In a fractal you still have to measure the sizes of different similar structures, and generally pay attention to length. It seems that this article is discussing a much deeper abandonment of length.

ccvannorman 12y ago

I once read that "black holes orbiting each other follow the exact same mathematics as electrons orbiting protons", but I was unable to find the direct source. I did find another article comparing black holes to elementary particles: http://www.technologyreview.com/view/413483/could-all-particles-be-mini-black-holes/ http://www.technologyreview.com/view/413483/could-all-partic...

Bognar 12y ago
They would naturally follow the same mathematics, since the formula for gravitational attraction and the formula for electrical attraction are both following the inverse square law. http://en.wikipedia.org/wiki/Inverse-square_law http://en.wikipedia.org/wiki/Inverse-square_law