## Posts Tagged ‘**quantum**’

## “Time is the longest distance between two places”*…

In quantum mechanics, time is universal and absolute; its steady ticks dictate the evolving entanglements between particles. But in general relativity (Albert Einstein’s theory of gravity), time is relative and dynamical, a dimension that’s inextricably interwoven with directions

x,yandzinto a four-dimensional “space-time” fabric. The fabric warps under the weight of matter, causing nearby stuff to fall toward it (this is gravity), and slowing the passage of time relative to clocks far away. Or hop in a rocket and use fuel rather than gravity to accelerate through space, and time dilates; you age less than someone who stayed at home.Unifying quantum mechanics and general relativity requires reconciling their absolute and relative notions of time. Recently, a promising burst of research on quantum gravity has provided an outline of what the reconciliation might look like — as well as insights on the true nature of time…

The effort to unify quantum mechanics and general relativity means reconciling totally different notions of time; catch up on the state of play at “Quantum Gravity’s Time Problem.”

* Tennessee Williams, *The Glass Menagerie*

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**As we set our watches,** we might send carefully-calculated birthday greetings to Gabrielle-Émilie Le Tonnelier de Breteuil, Marquise du Châtelet, the French mathematician and physicist who is probably (if unfairly) better known as Voltaire’s mistress; she was born on this date in 1706. Fascinated by the work of Newton and Leibniz, she dressed as a man to frequent the cafes where the scientific discussions of the time were held. Her major work was a translation of Newton’s *Principia*, for which Voltaire wrote the preface; it was published a decade after her death, and was for many years the only translation of the *Principia* into French.

Judge me for my own merits, or lack of them, but do not look upon me as a mere appendage to this great general or that great scholar, this star that shines at the court of France or that famed author. I am in my own right a whole person, responsible to myself alone for all that I am, all that I say, all that I do. it may be that there are metaphysicians and philosophers whose learning is greater than mine, although I have not met them. Yet, they are but frail humans, too, and have their faults; so, when I add the sum total of my graces, I confess I am inferior to no one.

– Mme du Châtelet to Frederick the Great of Prussia

## “in this case there were three determinate states the cat could be in: these being Alive, Dead, and Bloody Furious”*…

Of all the bizarre facets of quantum theory, few seem stranger than those captured by Erwin Schrödinger’s famous fable about the cat that is neither alive nor dead. It describes a cat locked inside a windowless box, along with some radioactive material. If the radioactive material happens to decay, then a device releases a hammer, which smashes a vial of poison, which kills the cat. If no radioactivity is detected, the cat lives. Schrödinger dreamt up this gruesome scenario to mock what he considered a ludicrous feature of quantum theory. According to proponents of the theory, before anyone opened the box to check on the cat, the cat was neither alive nor dead; it existed in a strange, quintessentially quantum state of alive-and-dead.

Today, in our LOLcats-saturated world, Schrödinger’s strange little tale is often played for laughs, with a tone more zany than somber. It has also become the standard bearer for a host of quandaries in philosophy and physics. In Schrödinger’s own time, Niels Bohr and Werner Heisenberg proclaimed that hybrid states like the one the cat was supposed to be in were a fundamental feature of nature. Others, like Einstein, insisted that nature must choose: alive or dead, but not both.

Although Schrödinger’s cat flourishes as a meme to this day, discussions tend to overlook one key dimension of the fable: the environment in which Schrödinger conceived it in the first place. It’s no coincidence that, in the face of a looming World War, genocide, and the dismantling of German intellectual life, Schrödinger’s thoughts turned to poison, death, and destruction. Schrödinger’s cat, then, should remind us of more than the beguiling strangeness of quantum mechanics. It also reminds us that scientists are, like the rest of us, humans who feel—and fear…

More of this sad story at “How Einstein and Schrödinger Conspired to Kill a Cat.”

* Terry Patchett

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**As we refrain from lifting the box’s lid,** we might spare a thought for Charles Babbage; he died on this date in 1871. A mathematician, philosopher, inventor and mechanical engineer, Babbage is best remembered for originating the concept of a programmable computer. Anxious to eliminate inaccuracies in mathematical tables. By 1822, he built small calculating machine able to compute squares (1822). He then produced prototypes of portions of a larger Difference Engine. (Georg and Edvard Schuetz later constructed the first working devices to the same design which were successful in limited applications.) In 1833 he began his programmable Analytical Machine (AKA, the Analytical Engine), the forerunner of modern computers, with coding help from Ada Lovelace, who created an algorithm for the Analytical Machine to calculate a sequence of Bernoulli numbers— for which she is remembered as the first computer programmer.

Babbage’s other inventions include the cowcatcher, the dynamometer, the standard railroad gauge, uniform postal rates, occulting lights for lighthouses, Greenwich time signals, and the heliograph opthalmoscope. He was also passionate about cyphers and lock-picking.

## “The past is never dead. It’s not even past”*…

Science has a habit of asking stupid questions. Stupid, that is, by the standards of common sense. But time and time again we have found that common sense is a poor guide to what really goes on in the world.

So if your response to the question “Why does time always go forwards, not backwards?” is that this is a daft thing to ask, just be patient…

In our experience the past is the past and the future is the future, but sometimes the two can cross over; and while the past seems set in stone, some scientists believe that the future can change it: “The quantum origin of time.”

* William Faulkner, *Requiem for a Nun*

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**As we head down the rabbit hole,** we might spare a thought for Jules Henri Poincaré; he died on this date in 1912. A mathematician, theoretical physicist, engineer, and a philosopher of science, Poincaré is considered the “last Universalist” in math– the last mathematician to excel in all fields of the discipline as it existed during his lifetime.

Poincaré was a co-discoverer (with Einstein and Lorentz) of the special theory of relativity; he laid the foundations for the fields of topology and chaos theory; and he had a huge impact on cosmogony. His famous “Conjecture” held that if any loop in a given three-dimensional space can be shrunk to a point, the space is equivalent to a sphere; it remained unsolved until Grigori Perelman completed a proof in 2003.

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