Time Is Out of Joint

By Sean Carroll | August 26, 2011 8:34 am

Greetings from Norway, where we’re about to embark on what is surely the most logistically elaborate conference I’ve ever attended. Setting Time Aright starts here in Norway, where we hop on a boat and cross the North Sea to Copenhagen. The get-together is sponsored by the Foundational Questions Institute, although it came together in an unusual way; I was part of a group that was organizing a conference, and we applied to FQXi for funding, at which point they mentioned they were planning almost exactly the same conference at the same time. So we joined forces, and here we are. Unity ’11!

The topic, if you haven’t guessed, is time. That’s a big subject, one that can hardly be done justice by sprawling books with hundreds of (admittedly quite charming) footnotes. You can see why the conference has to spread over two countries. We’re trying an experiment in interdisciplinarity: while the conference is a serious event meant for researchers, we have a wide variety of specialties represented, including biologists, computer scientists, philosophers, and neuroscientists, as well as the inevitable physicists and cosmologists. (There is also a public event, for those of you who find yourselves in Copenhagen next week.) I can’t wait to hear some of these talks, it should be a blast.

My job is to open the conference with an introductory talk that hits on some of the big questions. Here are the slides, at least as they are right now; last-minute editing is always a possibility. I think I put enough in there to provoke almost everyone at the conference one way or another.

CATEGORIZED UNDER: Science, Time, Top Posts, Travel
  • kirk

    Dissipative structures far from thermodynamic equilibrium. Accept no substitutes.

  • Thimker

    Time does not have a “direction”: This is a complex illusion created by the human mind’s propensity for linear perception. Time simply *is*, now and forever, much in the same way Vonnegut described it. To say that it has any sort of “direction” is erroneous, however. Rather, it is human perception that does, being made up out of matter that decays thermodynamically along a single “straight line”.

  • Gene

    Space is emergent but time isn’t. I’ve heard that before, and frankly I can’t imagine ‘no time’, but my guess is that nature doesn’t care. Also, this would imply a Lorentz violation and the possibilities of that seem unlikely.

  • FmsRse12

    1)”what is time?”
    For most practical purpose time is just an independent variable.
    2)”why does time have direction?”
    3)”how does complexity evolve?”

    question 3 is same as question 2 , I mean if time didn’t have direction how is it possible for anything to evolve…..or is it possible for time to flow but no evolution of complexity?? if yes then how can you tell them apart??

  • Alan

    This is very beautiful – The Symphony of Time – a kind of symphonic rap on time.

    http://www.youtube.com/watch?v=6AuQPqJPSKE

    from the upcoming Science and Nonduality conference.

    http://www.scienceandnonduality.com/

  • Naked Bunny with a Whip

    Time is, like, wow, man.

  • Alan

    In this idea of the future reaching back to affect the past (Paul Davies is at the FQXi conference):

    http://fqxi.org/community/articles/display/156

    Is this an alternative to a multiverse (I thought Paul Davies’ idea is that it is – don’t think he likes the multiverse) where this article implies a self-sustaining universe, just one universe – I don’t know. Or are universes within the multiverse self-sustaining (all of them), or just ours for some reason?

    Does the multiverse “select out” self-sustaining universes (and why)? Perhaps this way is there compatability between the two ideas?
    My impression is that the multiverse is really necessary but is Davies right as well?

    Just interested to known if anyone is thinking (with physics!) along these lines.
    Good to bring people together.

  • complexity

    Okay, how do you measure complexity of a system? Isn’t it a little arbitrary. You’re example shows two systems in equilibrium, which evolves into one system in equilibrium. So are you saying that complexity is a measure of distance from equilibrium?
    Macroscopically you might think its not complex, but microscopically its horribly complex, not to mention there is a loss of knowledge about how long ago the system was in its initial state.

  • Ray Gedaly

    Wow, small universe. Earlier in the summer I was scheduled to be in Bergen myself this very week. Priorities changed and I had to cancel, but were I there, I’d have invited you to a dinner of lutefisk.

  • DMPalmer

    Why is this considered a mystery? The Universe starts out at maximum entropy, as you would expect; and then the entropy increases, as it must. this is possible because the Universe is expanding.

    In more detail, shortly after the Big Bang, the Universe was in a maximum entropy configuration, with massive and massless particles in a uniform equilibrium soup.

    As the Universe expanded, the maximum possible entropy increased (more volume means more possible states), and the actual entropy increases along with it, until the temperature drops to the point where the massive particles fall out of equilibrium with the radiation. (Stable massive particles like protons and electrons stick around even though the temperature is well below the particle mass because there aren’t anti-particles to annihilate with.)

    At that point, the actual entropy falls behind the maximum possible entropy. The actual entropy is the entropy of the cosmic background radiation, plus the entropy of the massive particles. The cosmic background radiation is at maximum entropy for its energy density (i.e. it is in a uniform thermal blackbody distribution).

    The particles are also in a uniform thermal distribution. However, massive particles in a uniform thermal distribution is not a maximum entropy or equilibrium state. Under the influence of gravity, any density fluctuations will start to collapse until the adiabatic compression heats it up until it is supported against gravity.

    A gravitating gas system like one of these clumps has a negative heat capacity. The more thermal energy it loses, the hotter it gets as it contracts adiabatically. So two such systems in thermal contact (e.g. by radiation) will diverge in temperature and you will get dense hot objects and diffuse cool gas.

    After a bit more evolution (dense hot objects starting to burn by fusion etc.) we get to the Universe we have today.

  • Ray Gedaly

    Alan (#7), thanks for the FQXi link. Just last week I asked in this forum if there were any experimental evidence for or against this interpretation of quantum phenomena.
    {Hmm … perhaps today’s blog influenced me to ask last week’s question? :) }

  • Fred

    Sean, how do you think the cosmological entropic claims of 1108.3080 fit into all this? Does it solve/address the fundamental issues?

  • http://terrybollinger.com Terry Bollinger

    Good set of slides, should provoke interesting discussions! Nice to see Boltzmann covered, too.

    (Hmm, it’s 2am with a hurricane coming this way?… Goodbye!)

  • roosh

    Time only exists as a concept; it is an abstraction; a manmade system of measurement much like the metric system; it is simply a method of comparison. We are conditioned to believe it exists because of incorrect deductions based on our experience of life/the universe – our ability to remember our experiences (“the past”) and our cognitive ability to project potential experiences (“the future”); both of which are only conceptual constructs.

    Time isn’t a property of the universe – well, no moreso than a unicorn is a property of the universe. That doesn’t mean however that we cannot retain it as what it actually is i.e. a system of measurement and comparison.

  • Giovanni

    How about time dilation of relativity roosh..

  • roosh

    Time dilation is based on the assumption that a clock measures the [non-conceptual] property called time. It doesn’t however, a clock is simply a standard unit of comparison against which change is compared.

    I’m not familiar with all of the time dilation experiments; but I’m not sure how the more famous ones – atomic clocks in the concords (was it concords used?) and the decaying process of muon that is accelerated to a certain speed – show anything other than the physical effects of either gravity or motion (or perhaps both) on the relevant particles – the assumption, that these physical processes are a measure of the [non-conceptual] property called time, violates occams razor.

  • roosh

    just to clarify though, that doesn’t mean that the results of the time dilation experiments are rendered inaccurate, simply that the assumption as to what they prove needs to be examined.

  • Giovanni

    Occam’s razor is not a law, it’s maybe just a guide when we have many explanations to the same result… and thats not the case. Those experiments as far as we know are very well established, and many other tests were made. Unless a new theory appears, it’s the best we have today to explain how time works. We already use relativity predictions in many real-life applications, such as GPS for example.

  • roosh

    I know Occams Razor is not a law, but that is just a way of expressing the fact that the assumption, that the aforementioned physical processes measure the [non-conceptual] property called time, is unjustified.

    Again, the issue isn’t that the well established experiments are inaccurate, simply that the interpretation of the results needs to be examined; the assumption that they prove the existence of time is incorrect, because it can be more accurately said that they demonstrate the effect of motion and/or gravity on the specific physical processes.

    No new theory is needed to challenge the assumptions upon which the current theory is based; indeed, a new theory may emerge or be developed if those in the field challenge the assumptions of the existing theory.

  • A Sean

    The only thing that’s “real” in the second slide (intuitive time) is the present hypersurface for the stick figure that maybe should be drawn as something much more microscopic, like an electron. The past is just as conjectural as the future – our memories are terribly unreliable and our records are highly incomplete. The local availability of information required to predict the generalized elsewhere diminishes with distance in all four dimensions, and the reliability of those predictions almost certainly decreases much faster.

    Suppose, arguendo, that we actually do remember the future almost exactly as well as we remember the past, but that for whatever reason that memory isn’t available to what we think of as our conscious self. The reason we can catch a ball, or the reason that a parrot can catch an insect is not because the brains involved are especially good calculators that learn an effective theory of ballistics through practice, but because they have access to unreliable memory of their respective bundles of worldlines, where memory retrieval improves with practice. Just because humans don’t admit to having reasonable memories of the future doesn’t necessarily mean they don’t actually have them; it might just be that we can’t “visualize” future memories as clearly as past ones.

    Perhaps an intelligent species which perceives little difference between prediction and retrodiction might think we’re a little odd in how we perceive time. Why did you catch the ball? Because you did. Why will you catch the ball? Because you did. Why can’t I remember both those events? Maybe because the parts of your brain that let you *realize* that you remember the future just as well as the past are vestigial because it consumed more food energy than it helped your ancestors acquire through hunting and gathering. (But don’t worry, your descendants may construct an analogue. :-)) Why do I give more weight to my memory of the past rather than my imagining of memory of the future? Again, perhaps something in the human brain shapes what one considers evidence independent of cultural influences (which again is probably related to something in the human brain).

    Most of us likely would rely more upon 20th century records than 20th century speculative fiction, but perhaps that’s just because of biases that emerge from the structure of our brains. We also probably rely more upon recent records than ancient ones, and probably would agree that recent hard science fiction describing the near future is more likely to be right than hard science fiction from fifty years ago describing the distant future. We also probably prefer authors writing in our languages and if we’re American, we might prefer an American writer speculating about a future America over a British one doing the same. In other words, do we rely more on data and arguments compiled and made nearer to us in all four dimensions? Do we also give extrapolations they made greater weight when they attempt to predict events nearer to the authors in all four dimensions?

    In other words, is there a relativity of knowledge?

    Slide 6: is it quantum harmonic oscillators that underlie the assumption that time is somehow more real than a coordinate? Otherwise, is there some mechanism that generates “holes” as in the hole argument?

  • Sili

    Pity. You’re a week early for the Skeptics in the Pub meeting. They’re even early due to football.

  • Dan

    DMPalmer #10,

    You wrote: “As the Universe expanded, the maximum possible entropy increased (more volume means more possible states), and the actual entropy increases along with it…”

    You should read Roger Penrose’s ‘The Road to Reality’ to better understand the true mystery. In particular, chapter 27 on page 701 which he writes:

    “There is a common view that the entropy increase in the second law is somehow just a necessary consequence of the expansion of the universe. This opinion seems to based on the misunderstanding that there are comparatively few degrees of freedom available to the universe when it is ‘small’, providing some kind of low ‘ceiling’ to the possible entropy values …”
    “This cannot be the correct explanation for the entropy increase; for the degrees of freedom that are available to the universe are described by the phase space P_U.”
    “This phase space is just ‘there’, and it does not in any sense ‘grow with time’, time not being a part of P_U.”

    IOW the phase space describes the totality of all possible universes, incorporating their evolution wrt the laws of dynamics. This phase space is independent of time. So the mystery is why is our universe a “Big Bang” universe rather than a vastly more likely universe in near equilibrium.

    Penrose proposes a “solution” to this mystery in his Conformal Cyclic Cosmology by positing that the final state and the initial state of the universe are indistinguishable, therefore leading to a eternal series of big bangs, referred to by Penrose as “Eons”.

    Sean correctly concludes in his book “From Eternity to Here” that this doesn’t really solve the mystery, as he puts it :”Why our universe is so atypical is, of course, at the heart of the mystery.”

    IOW the CCC is just as atypical as a Big Bang universe.

    Dan

  • DMPalmer

    Dan said: “IOW the phase space describes the totality of all possible universes, incorporating their evolution wrt the laws of dynamics. This phase space is independent of time. So the mystery is why is our universe a “Big Bang” universe rather than a vastly more likely universe in near equilibrium.”

    The Universe does spend just about all its time in the vastly more likely universe in near equilibrium. It spends all but the first googol years or so in that state. It’s only the small fraction of time that it is out of equilibrium that is inhabited by people who look around and wonder why. Only when the Universe is small.

    So the ‘mystery’ is, why is there a time when the Universe is small? In other words, why did the Universe start with a Big Bang. To me the idea of a Universe starting at a point seems more likely than the Universe starting simultaneously over an extended volume googols of light-years across in a spatially uniform thermal state.

  • Dan

    DMPalmer,

    As Sean wrote in “From Eternity to Here” that the mystery is not that there are fluctuations away from equilibrium, but rather the enormity of the magnitude of the fluctuation in order to create a Big Bang is so immensely unlikely. He also writes that we could invoke the anthropic principle (AP), except that “Our actual universe seems to be an enormously more dramatic departure from emptiness than would be required by any anthropic criterion.” (FHtoE pg.312)

    It seems that you are invoking the AP without stating it explicitly when you wrote: “It’s only the small fraction of time that it is out of equilibrium that is inhabited by people who look around and wonder why.”

    I guess if you have a eternity of existence, a universe will eventually form that is immensely unlikely, even if the probability of its beginning state is on the order of one in 10^10^88. The problem arises as to why the entropy of the initial state was one in 10^10^88, when it could have been in any of the 10^10^120 possible states, which represents the max entropy of the observable universe.

    So Sean (and his contemporaries) doesn’t give much credence to this argument since he writes: “The conclusion is perfectly clear: The state of the early universe was not chosen randomly among all possible states. Everyone in the world who has thought about the problem agrees with that. What they don’t agree on is why the early universe was so special – what is the mechanism that put it in that state?” (see FHtoE pg. 301)

    Dan

  • AS

    Be careful, because another example of irreversible T-odd process is: crackpots never become good theorists, while some theorists go crackpot.

  • http://www.qwertyous.blogspot.com/ John R Ramsden

    @Alan (#7) : Does the multiverse “select out” self-sustaining universes? ..

    That’s an interesting idea, which might fit well with my notion of each universe (lowercase – meaning a causally connected chunk of the Universe AKA multiverse) comprising the constantly evolving combination of “neighbouring” parallel universes immensely speeded up, a sort of composite of ever-changing tangential possibilities.

    I’ll paste a post of mine in a recent a many-worlds discussion in another forum.

    > aren’t the scientific multiverse theories a bit less vague than that, in that they DO
    > posit some kind of relationship between universes as a way to explain how ours works? ..

    No, that’s the problem. Conventional parallel universe interpretations posit no influence of one on any others, which means the theory is impossible to test directly.

    I reckon the opposite is true, but each universe evolves to completion in the other in the shortest possible time (in fact defines a Planck time unit), where “completion” here means either expand to infinity or collapse.

    So we, and everything we experience, in other words all fields and particles, are nothing _but_ parallel universes constantly being created and destroyed, with each “split” representing a choice at the most fundamental level (individual energy quanta) between two possibilities.

    Evolving so fast, for all practical purposes the parallel universes are late stage ones, comprising nothing but vacuum, as ours will one day in something like 10^500 years once all the black holes have evaporated.

    Note that in theory if you fell into a large rotating black hole then as you approach the inner horizon, the outside universe you had left behind would appear to evolve ever faster until it evolved to completion in a tremendous blue flash. So that illustrates in a crude way that universes can manifest themselves enormously speeded up in others!

    One can sort of see how this might conserve energy in normal circs, but at the same time allow for mysterious effects that apparently don’t, such as dark energy or the Big Bang.

    It also seems vaguely plausible that limiting splitting to an unambiguous situation, where say there are only two possibilities, might ultimately be what allows energy to collect in and preserve the resonant states we call particles (and determine their relative masses etc).

    But without being able to whump up some formal model consistent with conventional QM and GR, it’s just a lot of vague musing and most physicists would (rightly) not give the idea the time of day.

    End of paste

    The only snag with relating this idea with selection of long-lived universes is that as I have explained the parallel universes splitting from another must time-wise be very localized in the latter, as much so as can be. So it’s hard to see how collectively they could impart a long term property to the universe from which they split.

  • Thomas

    I’m only 4 hours from Bergen, I’d ran into you if I had known.

  • Chris

    As T->0 K, the entropy goes to zero.
    The universe started at zero entropy
    So was the temperature at the moment of the big bang absolute zero?

    I think that was my Boltzmann Brain popping into existence.

  • Suchy

    “while the conference is a serious event meant for researchers, we have a wide variety of specialties represented, including biologists, computer scientists, philosophers, and neuroscientists, as well as the inevitable physicists and cosmologists.”

    hahaha

  • Josh

    It seems to me that this medium entropy — high complexity connection is a similar conundrum to the fine-tuning problem associated with the matter-dominated universe. On a logarithmic scale, the universe is matter dominated for only a few orders of magnitude in scale factor while deSitter space is infinte in extent during lambda-domination or past-eternal inflation and even the radiation-domination phase spans far more decades in time than matter-domination. And yet we live within an order of magnitue of this particularly unique time in our universe’s history. What gives? And why is there so much medium entropy right now?

  • marcel

    I cannot find a video or recording of Severn Darden’s metaphysics lecture, so this transcript will have to do:

    http://groups.google.com/group/rec.music.dementia/browse_thread/thread/86f5c66980d81fa3

  • http://www.lowellprescott.com Lowell

    I am not a physicist (inevitable or otherwise), but it seems to me that the questions of time all amount wholly to perception issues given that the laws of physics have no requirement of running one direction or another — or in any sort of “direction” at all. Thus, changes in relative entropy, while certainly interesting, can’t really be used to address the time question at all because they are not necessarily synchronized with perceptions — even if they may seem to be.

    Simply said, there is no reason to believe that humans would perceive the arrow of time any differently if there were no correlation with changes in entropy (or any other external condition, for that matter). But there are clear indications that the problem has more to do with the design of the human (and the view of time provided by the senses, processed by a brain) than it does the design of the universe.

    I realize that this may sound like an application of the anthropic principle, but I don’t exactly intend it that way.

    In physical space we are limited to a certain point of view based on location. This is inherent in the design of our senses. We can conceive of different points of view (say the view of the universe from the Andromeda galaxy) but we have no way of actually experiencing it (though that could be theoretically overcome).

    Likewise, why could we not be limited to a certain point of view in time based on our design? We can conceive of different points of view in time (namely, remembering the future and predicting the past), but have no way of actually experiencing it (though perhaps that could be overcome).

    The direction we face in time, just like the point of view we’ve been given in physical space, could be completely arbitrary, requiring no further explanation.

    (I’ll admit that this is not wholly satisfying.)

  • http://terrybollinger.com Terry Bollinger

    A Predictive Interlude

    Hmm, lots of general discussion of highly unprovable things. So just for grins, here’s a specific prediction I’ve been making to friends for about three years now. I know it seems unrelated to time, yet there are connections.

    Firstly though: I am poor, simple computer person, and emphatically not a trained physicist. So folks, this really is just for fun, an example of using heuristics and complexity reduction techniques to search for interesting postulates within intentionally minimized mathematical and topological frameworks. With that said, here’s my postulate:

    There is no Higgs boson — not at any energy, not at any level of data analysis. The particle simply does not exist. While the real mass mechanism has certain similarities to the Higgs premise, it is not created by the Higgs field for the simple reason that no such field exists. Mass derives instead from a different and rather simpler form of stickiness.

    My no-Higgs postulate can be generalized in the following way: There exist no fundamental (i.e. point-like and non-composite) spin-zero particles of any type. Such particles simply cannot can exist within the spacetime of our universe.

    Given the recent spate of anti-findings of Higgs analysis coming out of the LHC, this likely doesn’t count as much of a prediction, at least not now. Still, a lot of people have not quite given up on Higgs yet, so perhaps it’s still timely. And in any case, my prediction that there are no fundamental zero-spin particles is a bit broader than just saying “no Higgs.”

  • http://jbg.f2s.com/quantum2.txt James Gallagher

    That’s a pretty brave opening talk, but seems mostly reasonable, I hope you got some useful feedback.

  • http://ratioc1nat0r.blogspot.com/ Jochen

    As #8, I’m also somewhat confused as to the notion of ‘complexity’ employed. Generally, if we’re looking at the microscopics, the Kolmogorov complexity of the last shot glass should be highest — since it’s essentially a random string of ‘molecule of white liquid, molecule of black liquid’, etc. True, on the macroscopic level, a short description, and hence, low Kolmogorov complexity appears possible — something like ‘all brown’, for instance.

    But then, entropy is consistently measured against the microscopic level (as it must be). If we do the same thing wrt Kolmogorov complexity, it exhibits the same kind of behaviour: the shot glass with white and black substances separated will admit a heavily compressed description (writing 0 for ‘molecule of black liquid’ and 1 for ‘molecule of white liquid’, we get something like 111111…00000…, which is evidently highly compressible), the middle phase of partial mixing is still somewhat compressible, while the final, mixed state, equivalent to a random bitstring, will be almost totally incompressible, and thus, of maximum complexity.

    Otherwise, just looking at the macroscopic level, one could argue that there is one state for ‘black and white separated, white above black’, a number of states for ‘black and white partially mixed’, and just one state again for ‘all mixed’, or ‘all brown’, giving the impression that entropy decreases!

  • http://jbg.f2s.com/quantum2.txt James Gallagher

    complexity isn’t the same as randomness at microscopic level, the mandlebrot set has a very simple description mathematically but you couldn’t so well compress samples of the set at high resolutions.

    Similarly the heat death of the universe or the completely mixed liquids have a simple description (start from unmixed and mix until no further change (on some coarse scale) (ignore poincare recurrence)), but the intermediate stages have no such simple description, they are highly “complex”

  • http://universalrule.info Shahidur Rahman Sikder

    “An individual respective very location is the present and rest all locations are of the deep of the past”. That is to say- Our home planet is present before us, likewise just at this time it is again submerged into the depth or the past from another place of space. In the universe, there has been no incidence of present and future at all at any site of space, all are submerged into their respective depths of the past. In or under the circumstances: See into- Amazing facts about the Universe at http://t.co/a8LHwAY

  • Brett

    I have a couple of questions about Sean’s birthday photo example in ch. 9 of From Eternity to Here (granted this isn’t exactly on point with this thread, but I missed the interactive book club and I couldn’t think of a better place to possibly get a useful response). I teach physics at a school for gifted children and thought it would be fun to go over some of these ideas with my students when we get to thermodynamics, but I would like a better understanding of a few things first.

    The entropy increasing in both directions of time from a point of low entropy makes perfect sense to me, but the fact that the random apparition of a photo of you in a red shirt is a higher entropy state than the string of events that we would normally think of as leading to such a photo does not seem so evident. The fact that the photo would have to corroborate with so many things (possibly other people in the photo, other objects in your house, as well as your memories of the party) makes it seem even less probable than the universe producing an actual party. Maybe a photo of a stranger in an unfamiliar location would avoid these problems, or is there something I’m missing?

    A second question is actually of more interest to me. Granting that the spontaneous photo is indeed higher entropy than the event actually having taken place, I’m still having a hard time seeing how the Past Hypothesis gives a preference for lower entropy events in the past. Where I get caught up is when switching from looking at the entropy of the universe to looking at the likelihood of entropy states within a portion of the universe. Surely the PH excludes past higher entropy states for the entire universe, but does that make lower entropy states of a given sub-system of the universe more likely than high entropy states (i.e. the actual event over the random photo)? Would this depend on how far from equilibrium a low entropy state of the universe was (e.g. extremely low entropy states of the universe might make high entropy states of a sub-system unlikely, but entropy states of the universe near yet still below equilibrium would have sub-systems that favor high entropy states)?

    Any thoughts would be appreciated.

  • roosh

    Came across this:http://www.youtube.com/watch?v=Lvx945SP-RM&feature=player_embedded
    when someone posted the standard time dilation and simultaneity objection to the questioning of the existence of time. Unfortunately I am only coming at it from a lay-persons perspective so cannot really critique it, or challenge it, but it makes some interesting points which appear to be quite logical and are allegedly backed up with reproducible experiments.

    It attempts to highlight flaws in the thought experiment Einstein used, suggesting that there are flaws in the models which, when accounted for, would lead both the observer on the train and on the platform to conclude that the flashes of lighning occured simultaneously.

    Here is the website: http://absolute-relativity.be/node/7

    This potentially addresses the issue of simultaneity and time dilation as mentioned above, although I am not in a position to say whether it definitively does or not. It is, however, incidental to the argument that time does not exist.

  • roosh

    just on the above, the standard time dilation and simultaneity objection was not the one posted here, but in a message board – it was accompanied by a video explaining time dilation and simultaneity

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  • Jayendra Ganguli

    Time does not exist. It only exists to entities that are born in one “moment” and dead in another “moment”. Take away birth and death from the scene…and there is nothing called Time. Humans never measure anything that they have an infinite supply of (again infinity defined by what they perceive to be not finite per their senses). Anything they find finite ..as perceived by their senses…..will be measured…be it Time(bound by the finiteness of mans birth and death..) or Temperature ( bound by the finiteness of what s/he percieves to be “hot” or “cold”)

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  • jl@sf.us

    > “A Lifespan is a Billion Heartbeats”

    Only partly correct, according to an ancient essay by Issac Asimov.

    Briefly, he observed that for all mammals except humans, their lifespan is around 1 billion heartbeats. He analysis relied on a table of metabolic rates (expressed as pulse rate) multiplied by maximum lifespan for each species. Shrews have a pulse of about 3000 beats per minute, but only live about 3 years. He discovered that body mass is proportional to life span, and body mass is inversely proportional to pulse rate.

    Except for humans.

    Taking 60 bpm as a typical pulse rate, and 115 years as maximum known life span, we live up to 4.5 billion heartbeats.

    (Ignore the bleatings from religiouis types, shrieking, “Abraham lived to 900 years!” Piffle. Twaddle. Horse-feathers. Bicycling fish.)

    At age 50, I’m already past 1.5 billion heartbeats: 1,576,800,000 (according to MS Calc).

    My maternal grandmother lived to 102 years, 3.2 billion heartbeats.

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  • Anon

    Hold on, why do you assume a metaphysically libertarian model of free will?

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  • Niki Stashuk

    If you all are not physicists and “just laymen” I must be prostrate in a hole. But I followed most of what was said here and I found some of the ideas mind opening (for my limited brain). Thanks.
    Niki aka labellaflora

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Cosmic Variance

Random samplings from a universe of ideas.

About Sean Carroll

Sean Carroll is a Senior Research Associate in the Department of Physics at the California Institute of Technology. His research interests include theoretical aspects of cosmology, field theory, and gravitation. His most recent book is The Particle at the End of the Universe, about the Large Hadron Collider and the search for the Higgs boson. Here are some of his favorite blog posts, home page, and email: carroll [at] cosmicvariance.com .

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