=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= EDline Vol. 8, no. 33 (25 March 2003) Editorial mailing list (digest version) Published by the Electric Editors =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Contents: Q & A [2xs] Schroedinger and cats [Offshoot of [4hu] Public liability insurance] =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= ---[2]-- Q & A -------------------------------------------------- Date: Mon, 24 March 2003 From: Susan Bramson, slbramson@aol.com Steve Rickaby writes: > On the subject of cats, I suspect that correlating domestic > accidents with the habit of cats of lurking at the tops of > stairs would reveal some interesting data. I have from time to > time considered fitting my two Burmese toms with tiny lights, > but this is as nothing to a friend whose large black-as- > Egypt's-night British Blue cross, Knopfler, lurks at the top of > a very dark Cornish cottage staircase. We have all now got into > the habit of gently kicking the cat out of the way before > descending the staircase, whether the cat is there or not. > Maybe he should be renamed Schroedinger. I'm pretty sure I get the reference to Knopfler (as in, Mark.) But- and I'm sure I'm showing my ignorance here, but just too curious to resist asking- who is Shrodinger? ------------------------ Date: Mon, 24 March 2003 From: Iwan Thomas, iwan@iwanthomas.plus.com Maybe he should be renamed Schroedinger. I'm uncertain! ------------------------ Date: Mon, 24 March 2003 From: Steve Rickaby, srickaby@wordmongers.demon.co.uk Susan Bramson wrote: > I get the reference to Knopfler (as in, Mark.) But ... who is > Shrodinger? You are right about the Blessed Mark... (As it's clearly a good idea to start with a disclaimer, I'm not an atomic physicist, nor do I have more than a meagre smattering of knowledge of the subject: 'everything is a lot smaller than you think and it goes round in rings' just about sums it up.) Erwin Schroedinger was an Austrian physicist who proposed a seminal experiment designed to illustrate a paradox of the Quantum Theory of Matter. It can be shown that in a radioactively decaying isotope, there is a fifty-fifty change of any atom decaying or not. In the imaginary experiment, a cat and a vial of poison are arranged in a closed box with a radioactive isotope and a detector in such a way that should such a decay be detected, the vial is broken, poisoning the cat. In the 'normal' non-quantum world, there is a fifty-fifty chance that when the box is opened, the cat is dead. So it is possible to say, without opening the box, that the cat is either alive or dead (leaving aside the shrieks of fury by now no doubt emanating from the box, should the cat not have snuffed it). However, according to Quantum Theory, neither decay or non-decay has any reality unless it is observed: the decay has therefore either happened or not happened at one and the same time. Therefore the cat, until the box is opened, is in a state of dead-or-not-deadness. Knopfler, back at the head of the dark stair-well, is correspondingly in a state of there-or-not-thereness, but it's safest to kick him out of the way anyway. And for my money, it's pretty clear that Erwin Schroedinger either never owned a cat, or if he did, never tried to stuff his mog into a closed box. (Refs. 'In Search of Schroedinger's Cat: Quantum Physics and Reality', by John Gribbin, Black Swan, 1984, ISBN 0 552 12555 5). ------------------------ Date: Mon, 24 March 2003 From: Iwan Thomas, iwan@iwanthomas.plus.com Having made a feeble scientific joke, I feel obliged to give the details. Erwin Schroedinger (1887-1991) was largely responsible for developing the mathematics of quantum mechanics. The main equation of quantum mechanics is referred to as Schroedinger's equation. The reference to the cat comes from a letter that he wrote to Einstein, expounding one of the most famous paradoxes in modern physics. A cat is placed in a box, together with a radioactive atom. If the atom decays, and a Geiger-counter also inside the box detects an alpha particle, it triggers a hammer that breaks a flask of cyanide gas, killing the cat. If the atom does not decay, the cat lives. The box is then observed for just enough time for there to be an even chance of the atom decaying. According to the Schroedinger wave equation, you cannot determine what will happen, only the probability of the event occurring. The event, in effect, does not actually happen until it has been observed. Because the waveform collapses (or the universe splits into parallel universes) when the system is observed, and not when the event occurs, you cannot tell whether the cat is alive or dead before you look in the box. Therefore, the cat is both alive and dead at the same time! ------------------------ Date: Mon, 24 March 2003 From: David Ibbetson, isserlis@rogers.com Susan Bramson wrote: > who is Shrodinger? 1. An equation is named after him. 2. In explaining the uncertainty principle he considered a cat and a box. You would have to open the box to find out whether the cat was there, but opening the box changes things. (There are other, better, explanations.) =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= END OF EDline 8.33 Admin page: < http://www.electriceditors.net/edline/admin.htm > ** The views expressed in this mailing list are strictly those of the individual contributors, and do not necessarily reflect the views of the moderators or of the Electric Editors. ** Articles (c) 2002--2003, by individual contributors Design (c) 1996--2003 Iain Brown Compilation (c) 2003 Iain Brown / The Electric Editors =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=