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Einstein–Podolsky–Rosen paradox
 Albert Einstein
The Einstein–Podolsky–Rosen (EPR) paradox is a thought experiment proposed by physicists Albert Einstein, Boris Podolsky and Nathan Rosen which argues that the description of physical reality provided by quantum mechanics is incomplete.[1] In a 1935 paper titled "Can Quantum-Mechanical Description of Physical Reality be Considered Complete?", they argued for the existence of "elements of reality" that were not part of quantum theory, and speculated that it should be possible to construct a theory containing these hidden variables. Resolutions of the paradox have important implications for the interpretation of quantum mechanics.
The thought experiment involves a pair of particles prepared in what would later become known as an entangled state. Einstein, Podolsky, and Rosen pointed out that, in this state, if the position of the first particle were measured, the result of measuring the position of the second particle could be predicted. If instead the momentum of the first particle were measured, then the result of measuring the momentum of the second particle could be predicted. They argued that no action taken on the first particle could instantaneously affect the other, since this would involve information being transmitted faster than light, which is impossible according to the theory of relativity. They invoked a principle, later known as the "EPR criterion of reality", positing that: "If, without in any way disturbing a system, we can predict with certainty (i.e., with probability equal to unity) the value of a physical quantity, then there exists an element of reality corresponding to that quantity." From this, they inferred that the second particle must have a definite value of both position and of momentum prior to either quantity being measured. But quantum mechanics considers these two observables incompatible and thus does not associate simultaneous values for both to any system. Einstein, Podolsky, and Rosen therefore concluded that quantum theory does not provide a complete description of reality.[2]
The "Paradox" paper
[edit]
The term "Einstein–Podolsky–Rosen paradox" or "EPR" arose from a paper written in 1934 after Einstein joined the Institute for Advanced Study, having fled the rise of Nazi Germany.[3][4] The original paper[5] purports to describe what must happen to "two systems I and II, which we permit to interact", and after some time "we suppose that there is no longer any interaction between the two parts." The EPR description involves "two particles, A and B, [which] interact briefly and then move off in opposite directions."[6] According to Heisenberg's uncertainty principle, it is impossible to measure both the momentum and the position of particle B exactly; however, it is possible to measure the exact position of particle A. By calculation, therefore, with the exact position of particle A known, the exact position of particle B can be known. Alternatively, the exact momentum of particle A can be measured, so the exact momentum of particle B can be worked out. As Manjit Kumar writes, "EPR argued that they had proved that ... [particle] B can have simultaneously exact values of position and momentum. ... Particle B has a position that is real and a momentum that is real. EPR appeared to have contrived a means to establish the exact values of either the momentum or the position of B due to measurements made on particle A, without the slightest possibility of particle B being physically disturbed."[6]
EPR tried to set up a paradox to question the range of true application of quantum mechanics: Quantum theory predicts that both values cannot be known for a particle, and yet the EPR thought experiment purports to show that they must all have determinate values. The EPR paper says: "We are thus forced to conclude that the quantum-mechanical description of physical reality given by wave functions is not complete."[6] The EPR paper ends by saying: "While we have thus shown that the wave function does not provide a complete description of the physical reality, we left open the question of whether or not such a description exists. We believe, however, that such a theory is possible." The 1935 EPR paper condensed the philosophical discussion into a physical argument. The authors claim that given a specific experiment, in which the outcome of a measurement is known before the measurement takes place, there must exist something in the real world, an "element of reality", that determines the measurement outcome. They postulate that these elements of reality are, in modern terminology, local, in the sense that each belongs to a certain point in spacetime. Each element may, again in modern terminology, only be influenced by events which are located in the backward light cone of its point in spacetime (i.e. in the past). These claims are founded on assumptions about nature that constitute what is now known as local realism.[7]
 Article headline regarding the EPR paradox paper in the May 4, 1935, issue of The New York Times.
Though the EPR paper has often been taken as an exact expression of Einstein's views, it was primarily authored by Podolsky, based on discussions at the Institute for Advanced Study with Einstein and Rosen. Einstein later expressed to Erwin Schrödinger that, "it did not come out as well as I had originally wanted; rather, the essential thing was, so to speak, smothered by the formalism."[8] Einstein would later go on to present an individual account of his local realist ideas.[9] Shortly before the EPR paper appeared in the Physical Review, The New York Times ran a news story about it, under the headline "Einstein Attacks Quantum Theory".[10] The story, which quoted Podolsky, irritated Einstein, who wrote to the Times, "Any information upon which the article 'Einstein Attacks Quantum Theory' in your issue of May 4 is based was given to you without authority. It is my invariable practice to discuss scientific matters only in the appropriate forum and I deprecate advance publication of any announcement in regard to such matters in the secular press."[11]: 189
The Times story also sought out comment from physicist Edward Condon, who said, "Of course, a great deal of the argument hinges on just what meaning is to be attached to the word 'reality' in physics."[11]: 189 The physicist and historian Max Jammer later noted, "[I]t remains a historical fact that the earliest criticism of the EPR paper — moreover, a criticism which correctly saw in Einstein's conception of physical reality the key problem of the whole issue — appeared in a daily newspaper prior to the publication of the criticized paper itself."[11]: 190
The publication of the paper prompted a response by Niels Bohr, which he published in the same journal (Physical Review), in the same year, using the same title.[12] (This exchange was only one chapter in a prolonged debate between Bohr and Einstein about the nature of quantum reality.) He argued that EPR had reasoned fallaciously. Bohr said measurements of position and of momentum are complementary, meaning the choice to measure one excludes the possibility of measuring the other. Consequently, a fact deduced regarding one arrangement of laboratory apparatus could not be combined with a fact deduced by means of the other, and so, the inference of predetermined position and momentum values for the second particle was not valid. Bohr concluded that EPR's "arguments do not justify their conclusion that the quantum description turns out to be essentially incomplete."
Einstein's own argument
[edit]
In his own publications and correspondence, Einstein indicated that he was not satisfied with the EPR paper and that Rosen had authored most of it. He later used a different argument to insist that quantum mechanics is an incomplete theory.[13][14][15][16]: 83ff He explicitly de-emphasized EPR's attribution of "elements of reality" to the position and momentum of particle B, saying that "I couldn't care less" whether the resulting states of particle B allowed one to predict the position and momentum with certainty.[a]
For Einstein, the crucial part of the argument was the demonstration of nonlocality, that the choice of measurement done in particle A, either position or momentum, would lead to two different quantum states of particle B. He argued that, because of locality, the real state of particle B could not depend on which kind of measurement was done in A and that the quantum states therefore cannot be in one-to-one correspondence with the real states.[13] Einstein struggled unsuccessfully for the rest of his life to find a theory that could better comply with his idea of locality.
Later developments
[edit]
In 1951, David Bohm proposed a variant of the EPR thought experiment in which the measurements have discrete ranges of possible outcomes, unlike the position and momentum measurements considered by EPR.[17][18][19] The EPR–Bohm thought experiment can be explained using electron–positron pairs. Suppose we have a source that emits electron–positron pairs, with the electron sent to destination A, where there is an observer named Alice, and the positron sent to destination B, where there is an observer named Bob. According to quantum mechanics, we can arrange our source so that each emitted pair occupies a quantum state called a spin singlet. The particles are thus said to be entangled. This can be viewed as a quantum superposition of two states, which we call state I and state II. In state I, the electron has spin pointing upward along the z-axis (+z) and the positron has spin pointing downward along the z-axis (−z). In state II, the electron has spin −z and the positron has spin +z. Because it is in a superposition of states, it is impossible without measuring to know the definite state of spin of either particle in the spin singlet.[20]: 421–422
 The EPR thought experiment, performed with electron–positron pairs. A source (center) sends particles toward two observers, electrons to Alice (left) and positrons to Bob (right), who can perform spin measurements.
Alice now measures the spin along the z-axis. She can obtain one of two possible outcomes: +z or −z. Suppose she gets +z. Informally speaking, the quantum state of the system collapses into state I. The quantum state determines the probable outcomes of any measurement performed on the system. In this case, if Bob subsequently measures spin along the z-axis, there is 100% probability that he will obtain −z. Similarly, if Alice gets −z, Bob will get +z. There is nothing special about choosing the z-axis: according to quantum mechanics the spin singlet state may equally well be expressed as a superposition of spin states pointing in the x direction.[21]: 318
Whatever axis their spins are measured along, they are always found to be opposite. In quantum mechanics, the x-spin and z-spin are "incompatible observables", meaning the Heisenberg uncertainty principle applies to alternating measurements of them: a quantum state cannot possess a definite value for both of these variables. Suppose Alice measures the z-spin and obtains +z, so that the quantum state collapses into state I. Now, instead of measuring the z-spin as well, Bob measures the x-spin. According to quantum mechanics, when the system is in state I, Bob's x-spin measurement will have a 50% probability of producing +x and a 50% probability of -x. It is impossible to predict which outcome will appear until Bob actually performs the measurement. Therefore, Bob's positron will have a definite spin when measured along the same axis as Alice's electron, but when measured in the perpendicular axis its spin will be uniformly random. It seems as if information has propagated (faster than light) from Alice's apparatus to make Bob's positron assume a definite spin in the appropriate axis.
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In 1964, John Stewart Bell published a paper[22] investigating the puzzling situation at that time: on one hand, the EPR paradox purportedly showed that quantum mechanics was nonlocal, and suggested that a hidden-variable theory could heal this nonlocality. On the other hand, David Bohm had recently developed the first successful hidden-variable theory, but it had a grossly nonlocal character.[23][24] Bell set out to investigate whether it was indeed possible to solve the nonlocality problem with hidden variables, and found out that first, the correlations shown in both EPR's and Bohm's versions of the paradox could indeed be explained in a local way with hidden variables, and second, that the correlations shown in his own variant of the paradox couldn't be explained by any local hidden-variable theory. This second result became known as the Bell theorem.
To understand the first result, consider the following toy hidden-variable theory introduced later by J.J. Sakurai:[25]: 239–240 in it, quantum spin-singlet states emitted by the source are actually approximate descriptions for "true" physical states possessing definite values for the z-spin and x-spin. In these "true" states, the positron going to Bob always has spin values opposite to the electron going to Alice, but the values are otherwise completely random. For example, the first pair emitted by the source might be "(+z, −x) to Alice and (−z, +x) to Bob", the next pair "(−z, −x) to Alice and (+z, +x) to Bob", and so forth. Therefore, if Bob's measurement axis is aligned with Alice's, he will necessarily get the opposite of whatever Alice gets; otherwise, he will get "+" and "−" with equal probability.
Bell showed, however, that such models can only reproduce the singlet correlations when Alice and Bob make measurements on the same axis or on perpendicular axes. As soon as other angles between their axes are allowed, local hidden-variable theories become unable to reproduce the quantum mechanical correlations. This difference, expressed using inequalities known as "Bell's inequalities", is in principle experimentally testable. After the publication of Bell's paper, a variety of experiments to test Bell's inequalities were carried out, notably by the group of Alain Aspect in the 1980s;[26] all experiments conducted to date have found behavior in line with the predictions of quantum mechanics. The present view of the situation is that quantum mechanics flatly contradicts Einstein's philosophical postulate that any acceptable physical theory must fulfill "local realism". The fact that quantum mechanics violates Bell inequalities indicates that any hidden-variable theory underlying quantum mechanics must be non-local; whether this should be taken to imply that quantum mechanics itself is non-local is a matter of continuing debate.[27][28]
Inspired by Schrödinger's treatment of the EPR paradox back in 1935,[29][30] Howard M. Wiseman et al. formalised it in 2007 as the phenomenon of quantum steering.[31] They defined steering as the situation where Alice's measurements on a part of an entangled state steer Bob's part of the state. That is, Bob's observations cannot be explained by a local hidden state model, where Bob would have a fixed quantum state in his side, that is classically correlated but otherwise independent of Alice's.
Locality has several different meanings in physics. EPR describe the principle of locality as asserting that physical processes occurring at one place should have no immediate effect on the elements of reality at another location. At first sight, this appears to be a reasonable assumption to make, as it seems to be a consequence of special relativity, which states that energy can never be transmitted faster than the speed of light without violating causality;[20]: 427–428 [32] however, it turns out that the usual rules for combining quantum mechanical and classical descriptions violate EPR's principle of locality without violating special relativity or causality.[20]: 427–428 [32] Causality is preserved because there is no way for Alice to transmit messages (i.e., information) to Bob by manipulating her measurement axis. Whichever axis she uses, she has a 50% probability of obtaining "+" and 50% probability of obtaining "−", completely at random; according to quantum mechanics, it is fundamentally impossible for her to influence what result she gets. Furthermore, Bob is able to perform his measurement only once: there is a fundamental property of quantum mechanics, the no-cloning theorem, which makes it impossible for him to make an arbitrary number of copies of the electron he receives, perform a spin measurement on each, and look at the statistical distribution of the results. Therefore, in the one measurement he is allowed to make, there is a 50% probability of getting "+" and 50% of getting "−", regardless of whether or not his axis is aligned with Alice's.
As a summary, the results of the EPR thought experiment do not contradict the predictions of special relativity. Neither the EPR paradox nor any quantum experiment demonstrates that superluminal signaling is possible; however, the principle of locality appeals powerfully to physical intuition, and Einstein, Podolsky and Rosen were unwilling to abandon it. Einstein derided the quantum mechanical predictions as "spooky action at a distance".[b] The conclusion they drew was that quantum mechanics is not a complete theory.[34]
Bohm's variant of the EPR paradox can be expressed mathematically using the quantum mechanical formulation of spin. The spin degree of freedom for an electron is associated with a two-dimensional complex vector space V, with each quantum state corresponding to a vector in that space. The operators corresponding to the spin along the x, y, and z direction, denoted Sx, Sy, and Sz respectively, can be represented using the Pauli matrices:[25]: 9 ��=ℏ2[0110],��=ℏ2[0−��0],��=ℏ2[100−1], where ℏ is the reduced Planck constant (or the Planck constant divided by 2π).
The eigenstates of Sz are represented as|+�⟩↔[10],|−�⟩↔[01] and the eigenstates of Sx are represented as|+�⟩↔12[11],|−�⟩↔12[1−1].
The vector space of the electron-positron pair is �⊗� , the tensor product of the electron's and positron's vector spaces. The spin singlet state is|�⟩=12(|+�⟩⊗|−�⟩−|−�⟩⊗|+�⟩), where the two terms on the right hand side are what we have referred to as state I and state II above.
From the above equations, it can be shown that the spin singlet can also be written as|�⟩=−12(|+�⟩⊗|−�⟩−|−�⟩⊗|+�⟩), where the terms on the right hand side are what we have referred to as state Ia and state IIa.
To illustrate the paradox, we need to show that after Alice's measurement of Sz (or Sx), Bob's value of Sz (or Sx) is uniquely determined and Bob's value of Sx (or Sz) is uniformly random. This follows from the principles of measurement in quantum mechanics. When Sz is measured, the system state |�⟩ collapses into an eigenvector of Sz. If the measurement result is +z, this means that immediately after measurement the system state collapses to|+�⟩⊗|−�⟩=|+�⟩⊗|+�⟩−|−�⟩2.
Similarly, if Alice's measurement result is −z, the state collapses to|−�⟩⊗|+�⟩=|−�⟩⊗|+�⟩+|−�⟩2. The left hand side of both equations show that the measurement of Sz on Bob's positron is now determined, it will be −z in the first case or +z in the second case. The right hand side of the equations show that the measurement of Sx on Bob's positron will return, in both cases, +x or -x with probability 1/2 each.
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Subestación eléctrica de maniobras Magdalena I (Parque Solar Magdalena I)
NOVIEMBRE 17, 2021 PV MAGAZINE
Pirámide de la Espiral Xochitecatl, Tlaxcala
Fotografía: Gobierno del estado de Tlaxcala
La Dirección General de Impacto y Riesgo Ambiental de la Secretaría de Medio Ambiente y Recursos Naturales informa que ha recibido la documentación de la firma promovente Más Energía, para el proyecto de la Subestación eléctrica de maniobras Magdalena I (Parque Solar Magdalena I).
El proyecto consiste en la construcción, operación y mantenimiento de una subestación eléctrica de maniobras, dos accesos, y una línea eléctrica de entronque de 400 Kv que se interconectará a una línea de transmisión eléctrica existente de 400 Kv propiedad de la Comisión Federal de Electricidad para desahogar la energía eléctrica que se genera en la planta fotovoltaica parque solar Magdalena I al Sistema Eléctrico Nacional.
Este contenido está protegido por derechos de autor y no se puede reutilizar. Si desea cooperar con nosotros y desea reutilizar parte de nuestro contenido, contacte: editors@pv-magazine.com.
 
6 Schematic representation of a cyclotron. The distance between the pole pieces of the magnet is shown larger than reality to allow seeing what is inside
https://www.researchgate.net/figure/Schematic-representation-of-a-cyclotron-The-distance-between-the-pole-pieces-of-the_fig3_237993541
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Llama de la Libertad (París)
 La Llama de la Libertad, ofrecida al pueblo francés por donantes de todo el mundo como símbolo de la amistad franco-americana, en la plaza Diana (París).
La Llama de la Libertad (en francés, Flamme de la Liberté) de París es una réplica del mismo tamaño de la nueva llama situada en el extremo de la antorcha que lleva en la mano la Estatua de la Libertad de Nueva York desde 1986.1 El monumento, que tiene aproximadamente 3,5 metros de longitud, es una escultura de una llama de cobre dorado, apoyada en un pedestal de mármol gris y negro. Está situado cerca del extremo norte del puente del Alma, en la plaza Diana, en el distrito 8 de París, Francia.2
Fue ofrecida a la ciudad de París en 1989 por el International Herald Tribune en nombre de los donantes, que habían contribuido aproximadamente 400 000 dólares para su realización. Representaba la culminación de las celebraciones de 1987 del periódico por su cien aniversario de la publicación de un periódico en inglés en París. Más importante, la Llama era una muestra de agradecimiento por la restauración de la Estatua de la Libertad realizada tres años antes por dos empresas francesas que hicieron el trabajo artesanal del proyecto: Métalliers Champenois, que hizo el trabajo del bronce, y Gohard Studios, que aplicó el pan de oro. Aunque el regalo a Francia fue motivado por el centenario del periódico, la Llama de la Libertad es un símbolo más general de la amistad que une los dos países, igual que la Estatua de la Libertad cuando fue regalada a los Estados Unidos por Francia.
Este proyecto fue supervisado por el director de la unión de artesanos franceses en aquel momento, Jacques Graindorge. Propuso la instalación de la Llama de la Libertad en una plaza pública llamada Place des États-Unis en el distrito 16, pero el alcalde de París, Jacques Chirac, se opuso a esto. Tras un prolongado período de negociaciones, se decidió que la alama se situaría en una zona abierta cerca de la intersección de la Avenue de New-York y la Place de l'Alma. El monumento fue inaugurado el 10 de mayo de 1989 por Chirac.
En la base del monumento hay una placa conmemorativa que relata la siguiente historia:
"La Llama de la Libertad. Una réplica exacta de la llama de la Estatua de la Libertad ofrecida al pueblo de Francia por donantes de todo el mundo como símbolo de la amistad franco-americana. Con ocasión del centenario del International Herald Tribune, París 1887-1987."
La llama se convirtió en un monumento no oficial de Diana de Gales después de su muerte en 1997 en el túnel bajo el Pont de l'Alma.3 La llama es una atracción para turistas y seguidores de Diana, quiens pegan pósteres y folletos con material conmemorativo en la base. El antropólogo Guy Lesoeurs dijo que "la mayoría de las personas que vienen aquí piensan que se construyó para ella."2 La plaza del monumento se llama desde entonces Plaza Diana (París).
El monumento está cerca de la estación del Metro de París llamada Alma-Marceau en la línea 9 y de la estación Pont de l’Alma Línea 'C' del RER, así como por los buses número 42, 63, 72, 80, 92, y los autobuses turísticos Balabus.
El 14 de junio de 2008 se inauguró una nueva Llama de la Libertad, una escultura de Jean Cardot, que también simboliza las relaciones cálidas y respetuosas entre Francia y los Estados Unidos. Fue instalada en los jardines de la Embajada de los Estados Unidos en Francia en la Place de la Concorde, y se inauguró en presencia del Presidente de la República Francesa, Nicolas Sarkozy, y el Presidente de los Estados Unidos, George W. Bush. Esta nueva llama es la realización de un impulso compartido por el empresario francés Marc Ladreit de Lacharrière, y el embajador estadounidense Craig Roberts Stapleton, y tiene dos inscripciones, una del francés Marqués de La Fayette y otra del estadista americano Benjamin Franklin.
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Metric Time
Aside from you chronically late people, we all know how time works:
This system is okay. But also, it’s kind of crazy.
Why 60 minutes per hour? Why 60 seconds per minute? It goes back to Babylon, with their base 60 number system—the same heritage that gives us 360 degrees in a circle. Now, that’s all well and good for Babylon 5 fans, but our society isn’t base-60. It’s base-10. Shouldn’t our system of measuring time reflect that?
So ring the bells, beat the drums, and summon the presidential candidates to “weigh in,” because I hereby give you… metric time.
Now, this represents a bit of a change. The new seconds are a bit shorter. The new minutes are a bit longer. And the new hours are quite different—nearly two and a half times as long.
So why do this? Because it’d be so much easier to talk about time!
Here’s one improvement: analog clocks are easier to read. At first glance, the improvement may not be so obvious—we’ve simply reshuffled the numbers a bit.
But notice, the minute hand makes more sense now. When it’s at the 2, we’re 20 minutes past the hour. When it’s at the 7, we’re 70 minutes after the hour. And so on.
Second, times are no longer duplicated. For example, instead of needing to distinguish between 6am and 6pm, we can simply say “2:50” and “7:50.” (This is, of course, how “military time” currently works.)
Third—this is a big one—the time tells you how far through the day you are. The time 2:00 is exactly 20% of the way through the day. At 8:76, we’re exactly 87.6% of the way through the day.
Fourth, consider the moment when we’re 99.9% of the way through the day. In the new metric system, we get to watch the clock roll from 9:99 back around to 0:00. Isn’t that nicer and more conclusive than 11:59pm rolling around to 12:00am?
Fifth, it’s so much easier to talk about longer times. Two and a half days? That’s 25 hours. Three days and 6 hours? That’s simply 3.6 days. Since an hour is now a nice decimal fraction of a day, these conversions become easy.
Will there be adjustments to make? Certainly! But the adjustments are half of the fun.
Let’s start, as all good things do, with television. Whether you enjoy half-hour sitcoms or hour-long dramas, the length of your favorite shows is probably going to change. Why? Because, under our new system, what we now call “half an hour” will be 20.83 minutes. What we now call “an hour” will be 41.67.
There’s nothing magical about these “half-hour” and “hour” lengths, obviously. They were chosen simply because they were nice round numbers. But under the new system, they aren’t! Since it’d be silly to divide the TV schedule into 21-minute intervals, presumably television networks would tweak the lengths to go more evenly into an hour.
If so, they’d have two choices: 5 blocks per hour (i.e., two dramas, plus a sitcom), or 4 blocks per hour (i.e., two dramas).
If you choose the former, shows will be 4% shorter than today, leading to accelerated storytelling. (It’s the same change that’s unfolded over the last 20 years, as increased ad time has squeezed the shows themselves to be shorter.)
And if you choose the latter, shows will be 20% longer. They’ll perhaps unfold at a slower, more cinematic speed. Either way, expect the pacing and rhythm of TV shows to change.
Sports run into the same issue. Football will probably opt for four quarters of 10 minutes each, which shortens the game by 4%. Expect slightly diminished scoring as a result. (And, if we’re lucky, diminished concussions.)
Hockey, meanwhile, might go for three periods of 15 minutes each, which actually makes the game 8% longer. It might give someone a chance to tackle Wayne Gretzky’s scoring records (but then again, probably not—he’s way out of reach right now).
I’d expect soccer to select two halves of 30 minutes each, which (as with American football) shortens games by 4%. If you thought soccer was too high-scoring already, you’re in luck (and also in a very small minority, I suspect).
When it comes to sports, the lengths of games won’t be the only thing changing. We also need to reconsider record running times.
Usain Bolt’s world-record for the 100-meter dash (currently 9.58 seconds) would be, under the new system, 11.09 metric seconds. Doing the 100m in 11 metric seconds might be achievable in the future, but 10 seconds? Perhaps never. (That’s the equivalent of 8.64 of our seconds!)
What about the mile? Well, it’s a little funny to imagine a world with metric time still worrying about that strange unit of distance (5280 feet? Really?), but the famed 4-minute mile would correspond to a 2.78-minute mile.
This is weird because, for top runners in the 1940s and 1950s, the barrier to running a 4-minute mile may have been less physiological than psychological. Would the 2.8-minute mile have felt as intimidating? Would the 3-minute mile? Perhaps it’d be the 2.5-minute mile, seeing as the current world record (3:43 in our old system) is 2.58 metric minutes?
And we might as well mention the marathon, where the world record time (currently 2:02:57) is now under an hour: 85 minutes, 38 seconds. I suspect that the 1-hour marathon would be a real badge of honor, something that every distance runner aspires to.
Leaving sports aside, what about food?
Restaurants would open for breakfast at perhaps 3:00 or 3:50. (Of course, coffee shops like Starbucks might open as early as 2:50.)
You’d get lunch around 5:00—that is to say, noon. Under our current system, I feel silly eating before 11:30, which is 4:80 under the new system. But I wonder—would I feel comfortable grabbing lunch at 4:75? Perhaps even 4:60 (even though that’s earlier than 11am under our current scheme)?
Eating is psychological, and how we number our hours might steer our behavior.
As for dinner, I suspect 7:50 to 8:00 would be the preferred time (although the famously late-eating Spaniards might hold off until 8:75 or 9:00).
Other numbers change, too. Take speed limits: the typical 65mph limit on many highways translates to 156 mph under the new system; I suspect we’d see that bumped up to 160 mph or down to 150 mph for the sake of roundness (which translates to 66.7mph or 62.5mph under our current system).
The speed of sound? Not 340 meters per second any longer; it’s now just 294 meters per second. Meters haven’t changed, of course, but seconds have gotten shorter!
And the speed of light? Unfortunately, we lose the lovely number 300 million meters per second; instead, it becomes roughly 260 million meters per second.
Speaking of light, on the equinox, you get 5 hours of light and 5 hours of dark.
The winter solstice is pretty grim: in London, you’d see just 3 hours, 25 minutes, and 25 seconds of daylight.
The summer solstice is nice, though: London would get 6 hours, 93 minutes of sun.
Okay, time to come clean: I propose this without a single iota of seriousness. It’d be insane to ditch our current system. We’re used to it. We’ve agreed upon it. We’ve built our lives around it. The hassle of a change far outweighs the gains.
But I still love the thought experiment. It asks you, in some small way, to reimagine your life. How do you spend your time? How do you measure the success of a day? When you plan your hours, are you conceding to the arbitrary dictates of a quirky clock, or are you truly giving your tasks the time that they deserve? If I scrambled your sense of time, relabeling all your moments, would it change the way you feel about them? Do the numbers we assign to times matter? Or are we just scratching lines on the shifting dunes of eternity?
https://mathwithbaddrawings.com/2015/04/16/metric-time/
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