The New Thermodynamic Understanding of Clocks (quantamagazine.org) 53
Studies of the simplest possible clocks have revealed their fundamental limitations -- as well as insights into the nature of time itself. Natalie Wolchover, writing for Quanta Magazine: [...] Over the past five years, through studies of the simplest conceivable clocks, the researchers have discovered the fundamental limits of timekeeping. They've mapped out new relationships between accuracy, information, complexity, energy and entropy -- the quantity whose incessant rise in the universe is closely associated with the arrow of time. These relationships were purely theoretical until this spring, when the experimental physicist Natalia Ares and her team at the University of Oxford reported measurements of a nanoscale clock that strongly support the new thermodynamic theory.
Nicole Yunger Halpern, a quantum thermodynamicist at Harvard University who was not involved in the recent clock work, called it "foundational." She thinks the findings could lead to the design of optimally efficient, autonomous quantum clocks for controlling operations in future quantum computers and nanorobots. The new perspective on clocks has already provided fresh fodder for discussions of time itself. "This line of work does grapple, in a fundamental way, with the role of time in quantum theory," Yunger Halpern said. Gerard Milburn, a quantum theorist at the University of Queensland in Australia who wrote a review paper last year about the research on clock thermodynamics, said, "I don't think people appreciate just how fundamental it is."
Nicole Yunger Halpern, a quantum thermodynamicist at Harvard University who was not involved in the recent clock work, called it "foundational." She thinks the findings could lead to the design of optimally efficient, autonomous quantum clocks for controlling operations in future quantum computers and nanorobots. The new perspective on clocks has already provided fresh fodder for discussions of time itself. "This line of work does grapple, in a fundamental way, with the role of time in quantum theory," Yunger Halpern said. Gerard Milburn, a quantum theorist at the University of Queensland in Australia who wrote a review paper last year about the research on clock thermodynamics, said, "I don't think people appreciate just how fundamental it is."
Quote of the Article... (Score:5, Informative)
Re:Quote of the Article... (Score:5, Informative)
Kinda blows my mind, but is probably the best explanation for the normal distribution that I've ever heard.
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Why should it. We know from the theory of relative that gravity warps space-time and that in a gravity well time moves faster than when not in this well. This even relates to speed as we approach the speed of light and thus it's common sci-fi to envision all the ways this can play out which if I am not mistaken there are even purposed methods for reverse time travel (though the construction of these apparatus are stupid and likely beyond any amount of energy we can put into such a system, much less the forc
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How about a Neutron star? Not massive enough to be a black hole, but so massive that all matter is collapsed into neutrons packed in a completely uniform material.
Should be pretty damn smooth I would say.
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Like most of /., I'm not a scientist, but I like to give it a go...
I wonder if they're looking at this with such minute accuracy that the rotation and wobble of the earth causes alterations in the "rate" of time? I mean, if you're on a bit of the earth that is rotating towards the direction of the earth around the Sun, you're travelling through space just a little faster than someone on the other side of the world who's moving away from the earth's direction of travel. Because I'm not a scientist, I know th
Re:Quote of the Article... Lunchtime doubly so. (Score:2)
I liked this one
though I'm pretty sure that Hawkings talked about these kinds of ideas in "A Brief History of Time"? Is this really that new?
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though I'm pretty sure that Hawkings talked about these kinds of ideas in "A Brief History of Time"? Is this really that new?
The other day I heard a postulation that while many people purchased that book, no one actually read it. Thanks for proving that wrong.
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I think the suspicion arose due to an unusually large discrepancy between the ratio of the number of books purchased vs the number of times the book was checked-out of libraries. The conclusion being that the book was being bought as a gift rather than as something the purchaser actually wanted to read.
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The book is rather amazing at bringing you up to speed in modern physics but I didn't finish it. It's certainly easier to read than Mandelbrot's work but I guess that's the difference between the orderly mind of a physicists and that of a mathematician.
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I read it.
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Proving it right you mean! Twice, with you! :)
Hawking never talked about non-smooth time in that book.
Yes, I read it, and I still own it.
You had to read it multiple times, unless you had some previous knowledge, because some topics at the start only became clear after you got some stuff that came later (a common mistake that writers make), but I didn't like giving up, back then.
Got it handed down from my stupid dad, who clearly only read the first and last chapter, because he had marked every second damn se
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Humans < People who purchased (/borrowed) A Brief History of Time < People who read part of the book < People who understood part of the book < People who read all of the book < People who understood all of the book < People who knew more about the subject than the book < Stephen Hawking < God
(Scale is exponential.)
Read it.. all.
Understood.. a bit.
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I don't think it's really new, but it's also not what Hawking was talking about, IIRC.
Time is essentially defined as interactions. Photons experience no time until they bump into something. Since the interactions are random, so is the "passage" of time.
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Heisenberg time compensators.
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Prior to that, this is exactly what Feynman said early on with QED.
Quantum theory wouldn't work without it. You have to calculate all the probabilities, including time moving backwards. For a photon, it is going to go all directions, but anything larger events can only be assembled forwards.
The flow of time is the average speed of all the photons. For example, an electron orbits by exchanging photons. When you hold something in your hand, the pressure you feel is, fundamentally, the exchange of photons with
Re: Quote of the Article... (Score:2)
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Isn't the expanding universe just entropy?
Entropy is my niece's room [gocomics.com] ...
Re: Quote of the Article... (Score:2)
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Perhaps.
Time slows asymptotically to infinity (from the point of view of a remote viewer) as one approaches the event horizon of a black hole. What it does inside the black hole is a matter of conjecture. But it's possible that it might be running the other way (compared to observers outside). And the occupants of a black hole would perceive that as their universe expanding.
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Thus outside the universe...
Outside the universe, time may not exist. The Big Bang model used to have time as being created in the Big Bang itself along with space. More recently there seem to be some questions about that and models that suggest that time may have had to exist before the Big Bang although, as a non-cosmologist, it's not clear to me whether that really is a fundamental necessity or simply the inability of our human brains to conceive of how anything can work without time!
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They found that an ideal clock — one that ticks with perfect periodicity — would burn an infinite amount of energy and produce infinite entropy, which isn’t possible. Thus, the accuracy of clocks is fundamentally limited.
That's just one way of stating the Uncertainty Principle, so there must be more to it than that. (No; I haven't [yet] read the paper, although I am planning to do so.)
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That makes sense. delta E * delta t > h/4pi;
So if delta t is zero, that makes delta E infinite.
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The "which isn't possible" annoyed me the most it is what it is. Each tock of the perfect clock an entire Universe is replaced with a whole new one. It kind of happens on a CPU at a much smaller scale, each instruction processed chages the whole. So goes my old tag line...
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The Second Law of Thermodynamics proven again... (Score:3)
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Most people don't know it, but Galileo wasn't the first to do this! A medieval thinker named John Philoponus [wikipedia.org] performed such a test as early as the sixth century.
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The other thing that life does is gather information. Information is very strange too, like time. Neither weigh anything. They're hard to define without a circular definition (i.e. that references itself). But information is very real, though intangible: "Where does the sabre-toothed tiger hide on the path?" "Where are the mines in this field?" "How do I convert food into usab
Asymmetry of Time (Score:2)
They found that an ideal clock — one that ticks with perfect periodicity — would burn an infinite amount of energy
That's been highly obvious to everyone who ever learnt Heisenberg's uncertainty principle: to have zero uncertainty in the time of an event you need an infinite change in energy since time and energy are linked like position and momentum.
What's interesting though is that they focus entirely on entropy as defining the arrow of time when, in actual fact, the arrow of time is much more fundamental than that. Particle physicists have known for ~25 years that time is asymmetric i.e. if you could reverse the
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Wouldn't clock accuracy be fundamentally limited by the Heisenberg Uncertainty Principle? Time makes up both parts of the equation - either as velocity (velocity vs. position accuracy), or as, well, time (time and energy).
Seems like the accuracy of a clock will naturally be limited - if you know an object's position well, its velocity (change in position over time) is unknown, and we can't really say it's because we don't know its change in position or the change in time. Likewise, you can borrow energy for
Only two things to understand about time (Score:1)
Either: Big hand is the hour, little hand is the minute.
Or: The universe, and all the dimensions including time are all a giant computer simulation and we're trapped inside. No point in trying to understand, because the interrupt driver can edit reality in between clock cycles.
Stuff like TFA seems like someone trying to get a ROI from their PHD.
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well thick but short hand is hour, thin but long hand is minute
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Always remember (Score:4, Informative)
entropy -- the quantity whose incessant rise in the universe is closely associated with the arrow of time
Time flies like an arrow. Fruit flies like a banana.
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Definitions (Score:2)
"Could it be that time is an illusion and smooth time is an emergent consequence of us trying to put events into a smooth order.."
This sounds like someone trying to redefine something to sound profound. Like those annoying people who talk about how most of the mass in your body is taken up by space in between atoms and in between subatomic particles, and that from a certain perspective you barely exist. Then you slap them in the face and act stunned that your hand didn't go right their head.
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Ah, you were that kid on the playground who everyone knew as going to grow up to drink beer and yell at the television, yes?
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"Could it be that time is an illusion ..."
The problem being that the word "illusion" refers to a philosophical/psychological
concept that has nothing to do with physics.
I'm going to have proved this wrong 5 years ago... (Score:2)
...sometime next year.
so what is the limit? (Score:2)
The summary and also article didn't say what the limit is. I'm guessing that each tick is a quantum measurement, and the accuracy of quantum measurements is bounded by deltaSpace * deltaMomentum = Planck's constant. You do a measurement per tick, the mass is known, the measurement has to be in some bounded space, so that tells you the uncertainty of the time per measurement. Is that what this is, or is there more to it than that?
Heisenberg uncertainty principle (Score:2)
I always thought that time-energy is a complimentary pair for HUP, just like position-momentum. Is the novelty of the article in confirming it experimentally?
Re: Heisenberg uncertainty principle (Score:2)
I think that an absolute zero drift clock is impossible because the Heisenburg principle acts all the way down to the quantum level.
I am not a scientist, so I might just be talking out of my ass, but this limitation of. macrospace surely is present in tbe tiniest of levels?
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In short yes.
Long version.
A perfect ticking clock has only 1 oscillation frequency, thus each 'tick' take exactly the same time.
An imperfect clock(real world) clock always has fundamental freq + various overtones, thus there is uncertainty btw each tick.
Single oscillation frequency implies the clock ticks from -infinity to +infinity => forever. Even with limited operating power, it would take infinity energy to operate.
Since irl machines can't work with infinite energy, single oscillation frequency is im
Keep this in mind (Score:2)
That people are not machines and no super accurate clock will ever change this.
When people expect others to act as precision machines, you are going to have some real problems.
This is also why very few peoole could even make it through the door to train to be a Navy SEAL.
kinds of entropy (Score:1)
I have often heard it said that thermodynamic entropy and information entropy are to some extent apples and oranges (though I don't profess to fully understand why this is). Is there a conflation here though? Or does the research build a stronger relation between the two? This is a subject I love to think about but lack the technical vocabulary to describe my thoughts.
Grab a towel (Score:1)
Quantum Clockery (Score:2)
Terry Pratchett's novel, Thief of Time, entertainingly describes some chaotic side effects of building fancy Glass Clocks.
These clever new 'Auditors of Reality' buggers, tick, will build tick, another, tick, perfect clock, tick, again, tick.
Quantum tick, time tick, will become tick, even tick, more tick, confusing.
Till, tock, they, tick, stop, tick, time, again, tick, again, tick, ...
definition contradicted by time crystals? (Score:2)
If this is true I'd like to know where they fit in with a thermodynamic definition of a clock, if there's no contradiction.