Saturday, September 29, 2012

Schrodinger's Cat


Whilst looking up something in the Bytes archives from the days when it was an email sent to a small number of persons, I came across an item that had not been later reposted on the blog. Here it is . . . 


Ever noticed that when you hear about something, see something, read something, you suddenly experience numerous examples. For instance, if I were to tell you a joke about a one-armed, Albanian dwarf, it’s guaranteed that in the next couple of days you will meet a one-armed Albanian dwarf, read about them, see one on the street… You may never again in your life meet another, but that joke will bring them to you like a magnet. 

Jung called it synchronicity, the experience of two or more events that are causally unrelated occurring together in a meaningful manner, more than just by chance. He said that there is no such thing as coincidence in our universe. Hamlet nailed it: “There are more things in Heaven and Earth, Horatio, than are dreamt of in your philosophy.” 

My synchronous item is not about Albanian dwarves but about a cat, Schrodinger’s cat, to be precise. 

I had come across Herr Schrodinger’s feline some time back but it was all too dull and complicated so I didn’t bother reading further or trying to understand what it was about. 

Recently my 15 year old asked, as we were driving to school, “What is Schrodinger’s Cat?” I asked why he had asked and he said that he had just seen someone wearing a T shirt with the message “Schrodinger’s cat is dead.” 

I looked it up that night and explained it to him. 

Then, a day later, Column 8 in the Sydney Morning Herald began a series of daily comments on Schrodinger’s cat eg: 

21 August: 
''As a PhD student in the field of neuroscience, I have a keen interest in experimental design, and your question about whether the 'Door close' buttons in lifts make any difference intrigued me,'' writes Deborah Apthorp, of Highbury, London (Column 8, yesterday). She suggests ''a simple experiment'' involving two researchers, in two identical lifts, with stopwatches, one pushing the button and the other not, with all manner of precautions to ensure accuracy. But would we really know, even then? Schroedinger's cat springs to mind. The very act of measurement may render the data meaningless in a sealed box. This is getting very deep - from quantum leap to quantum lift, we fear. 

25 August: 
''You need to stop misapplying random scientific terms in a feeble attempt to prolong discussion on a pointless topic,'' Joel Alexander, of Kensington advises us. We would normally ignore such advice, but we did confuse Schroedinger's Cat with Heisenberg's Uncertainty Principle on Friday, which is, we must admit, inexcusable. 

27 August: 
Ah, vindication! ''Having studied university physics, I am familiar with (though it's now a distant memory) Heisenberg's Uncertainty Principle,'' writes Greg Rutter of Mena Creek. ''Until Friday, however, I had not heard of Schroedinger's Cat. Thanks to Column 8, an inquisitive mind and the wonders of search engines, I am now familiar with this wondrous though slightly gruesome 'thought experiment'. Consider this a 'de-chastisement' to counter the serve delivered to you by Joel Alexander on Tuesday. Continue, to 'prolong discussion' as much as you please.'' 

So what is all this about Dr Schrodinger’s cat? 


Schrodinger and his feline: 

Schrodinger’s Cat is a thought experiment devised by Austrian physicist Erwin Schrodinger in 1935 to illustrate a problem with a then current interpretation (called the Copenhagen interpretation) of quantum mechanics applied to everyday objects. 

Quantum mechanics is a set of principles describing physical reality at the atomic level of matter (molecules and atoms) and the subatomic (electrons, protons and even smaller particles). 

In quantum mechanics there is a concept called quantum superposition, which is a combination of all the possible states of a system. The Copenhagen interpretation held that the superposition underwent collapse into a definite state only at the exact moment of quantum measurement. 

To counter such interpretation, Schrodinger proposed the following experiment: 

A cat, along with a flask containing a poison, is placed in a sealed box shielded against external environmental factors. If an internal Geiger counter detects radiation, the flask is shattered, releasing the poison that kills the cat. The Copenhagen interpretation of quantum mechanics implies that after a while, the cat is simultaneously alive and dead.. Yet, when we look in the box, we see the cat either alive or dead, not a mixture of alive and dead. 


Here's Schrödinger's (theoretical) experiment: We place a living cat into a steel chamber, along with a device containing a vial of hydrocyanic acid. There is, in the chamber, a very small amount of a radioactive substance. If even a single atom of the substance decays during the test period, a relay mechanism will trip a hammer, which will, in turn, break the vial and kill the cat. 

The observer cannot know whether or not an atom of the substance has decayed, and consequently, cannot know whether the vial has been broken, the hydrocyanic acid released, and the cat killed. Since we cannot know, the cat is both dead and alive according to quantum law, in a superposition of states. It is only when we break open the box and learn the condition of the cat that the superposition is lost, and the cat becomes one or the other (dead or alive). This situation is sometimes called quantum indeterminacy or the observer's paradox : the observation or measurement itself affects an outcome, so that the outcome as such does not exist unless the measurement is made. (That is, there is no single outcome unless it is observed.) 

A video commentary and explanation is at:


Geek Humour: 

You know that ad where a chap is in a room with boards from floor to ceiling on all the walls, covered with maths equations and calculations, and he changes one small figure on one of the boards. Another person comes in, sits down and starts work at the board, then sees the change and says in an annoyed tone “Oh, very funny”. 

Well, it’s true, geeks definitely do have senses of humour different from us normal people, as illustrated by their humour using Schrodinger’s Cat. Geek humour is much more subtle than Mrs Slocum’s cat, such as her calling out “Has anyone seen my pussy?” Witness the following: 



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