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Friday, August 12, 2016

Today is Erwin Schrödinger's (he of the famous half-dead cat) birthday: explanation, quotes, jokes, video

A brief explanation of Schrödinger's cat (wiki): A cat, a flask of poison, and a radioactive source are placed in a sealed box. If an internal monitor detects radioactivity (i.e. a single atom decaying), 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. When one looks in the box, however, he sees the cat either alive or dead, not both alive and dead. This poses the question of when exactly quantum superposition ends and reality collapses into one possibility or the other. The Einstein quotation below refers to an earlier version of the experiment that replaced poison with an explosive charge to kill the cat.

If I am to have an interest in something, others must also have one. My word is seldom the first, but often the second, and may be inspired by a desire to contradict or to correct, but the consequent extension may turn out to be more important than the correction, which served only as a connection.

Erwin Schrödinger (Nobel Prize address, 1933)

I insist upon the view that "all is waves."

~ Schrödinger (letter to John Lighton Synge, 9 November 1959)

If we were bees, ants, or Lacedaemonian warriors, to whom personal fear does not exist, and cowardice is the most shameful thing in the world, warring would go on forever. But luckily we are only men - and cowards.

~ Schrödinger (Mind and Matter, 1958)

You are the only contemporary physicist, besides Laue,* who sees that one cannot get around the assumption of reality - if only one is honest. Most of them simply do not see what sort of risky game they are playing with reality - reality as something independent of what is experimentally established. Their interpretation is, however, refuted most elegantly by your system of radioactive atom + amplifier + charge of gun powder + cat in a box, in which the psi-function of the system contains both the cat alive and blown to bits. Nobody really doubts that the presence or absence of the cat is something independent of the act of observation.

Albert Einstein (1879-1955) (letter to Schrödinger, 1950)

Today is the anniversary of the birth of Austrian physicist Erwin (Rudolf Josef Alexander) Schrödinger (wiki) (1887-1961), one of the most important figures in the development of quantum theory. After early study at the University of Vienna and service in the Austrian fortress artillery during World War I, Schrödinger steadily advanced up the scientific/academic ladder in a series of positions at the universities of Stuttgart, Breslau, and Zurich before becoming a professor at the Friedrich Wilhelm University in Berlin in 1927.

He left Germany with the rise of Nazism in 1933 and taught briefly at Oxford, but then returned to the University of Graz (Austria) in 1936. After Austria was absorbed into the Third Reich, Schrödinger fled to Italy, then to England and Belgium, eventually settling in Ireland for most of the rest of his life. Schrödinger's greatest contribution to quantum theory was in his challenge to the "Copenhagen interpretation" of quantum behavior, which described aspects of fundamental particles only in terms of their probabilities of observation. He dramatized the resulting contradictions with common sense by devising the "thought experiment" known as Schrödinger's cat (wiki) and substituted a quantum interpretation based on the idea of "wave mechanics," in which the position of a particle is described in terms of probability functions, , satisfying the Schrödinger wave equation,

where E is the energy of a particle's state. The philosophical issues raised by Schrödinger's cat are still debated today, and it remains his most enduring legacy in popular science. His wave equation represents his most important finding at a more technical level and has been applied to the understanding of a long series of quantum phenomena and applications.

At an early age, Schrödinger became a student of eastern religions, and in addition to his prolific scientific writings, produced a number of philosophical studies on the relation of science to ethics and religion, as well as theoretical biology. He received the Nobel Prize for physics in 1933 for the derivation of his quantum wave equation. 

* N.B. Max von Laue (1879-1960) was a German physicist who won the Nobel Prize in 1914 for his work on the diffraction of X-rays by crystals.

Anyone remember the Heisenberg joke about being stopped for speeding?

Heisenberg was driving down the Jersey Turnpike when a policeman pulled him over.

The policeman asked Heisenberg, "Do you know how fast you were going?"

And Heisenberg said, "No, but I can tell you exactly where I was."

So there's a variation where Schrödinger is the driver, and the cop searches his car: 
The cop insists on searching the car (4th amendment doesn't apply in New Jersey) and then asks Schrödinger, "Do you know you have a dead cat in the trunk?",

Schrödinger replies, "Well, now I do."

And my personal favorite:

Schrödinger's cat walks into a bar... and doesn't.

Here's a brief (less than 2 minutes) explanation:

And here's a Big Bang Theory discussion of the concept:

Here are a couple of Dr. Seuss-esque explanations - the first is from Straight Dope, one of my favorite websites:

Schroedinger, Erwin! Professor of physics!
Wrote daring equations! Confounded his critics!
(Not bad, eh? Don't worry. This part of the verse
Starts off pretty good, but it gets a lot worse.)
Win saw that the theory that Newton'd invented
By Einstein's discov'ries had been badly dented.
What now? wailed his colleagues. Said Erwin, "Don't panic,
No grease monkey I, but a quantum mechanic.
Consider electrons. Now, these teeny articles
Are sometimes like waves, and then sometimes like particles.
If that's not confusing, the nuclear dance
Of electrons and suchlike is governed by chance!
No sweat, though — my theory permits us to judge
Where some of 'em is and the rest of 'em was."
Not everyone bought this. It threatened to wreck
The comforting linkage of cause and effect.
E'en Einstein had doubts, and so Schroedinger tried
To tell him what quantum mechanics implied.
Said Win to Al, "Brother, suppose we've a cat,
And inside a tube we have put that cat at —
Along with a solitaire deck and some Fritos,
A bottle of Night Train, a couple mosquitoes
(Or something else rhyming) and, oh, if you got 'em,
One vial prussic acid, one decaying ottom
Or atom — whatever — but when it emits,
A trigger device blasts the vial into bits
Which snuffs our poor kitty. The odds of this crime
Are 50 to 50 per hour each time.
The cylinder's sealed. The hour's passed away. Is
Our pussy still purring — or pushing up daisies?
Now, you'd say the cat either lives or it don't
But quantum mechanics is stubborn and won't.
Statistically speaking, the cat (goes the joke),
Is half a cat breathing and half a cat croaked.
To some this may seem a ridiculous split,
But quantum mechanics must answer, "Tough shit.
We may not know much, but one thing's fo' sho':
There's things in the cosmos that we cannot know.
Shine light on electrons — you'll cause them to swerve.
The act of observing disturbs the observed —
Which ruins your test. But then if there's no testing
To see if a particle's moving or resting
Why try to conjecture? Pure useless endeavor!
We know probability — certainty, never.'
The effect of this notion? I very much fear
'Twill make doubtful all things that were formerly clear.
Till soon the cat doctors will say in reports,
"We've just flipped a coin and we've learned he's a corpse."'
So saith Herr Erwin. Quoth Albert, "You're nuts.
God doesn't play dice with the universe, putz.
I'll prove it!" he said, and the Lord knows he tried —
In vain — until fin'ly he more or less died.
Win spoke at the funeral: "Listen, dear friends,
Sweet Al was my buddy. I must make amends.
Though he doubted my theory, I'll say of this saint:
Ten-to-one he's in heaven — but five bucks says he ain't."

Cecil Adams

This was sent by a friend, and the description and book cover design are by Nathan W. Pyle

I do not see him here or there.
I do not see him anywhere.
I think he may be in that box,
introducing me to paradox.

I think that cat,
he may be dead,
lying in his cardboard bed.
In the box he would not thrive,
but chances are he’s still alive.

There's lots of Schrödinger's cat merchandise out there - try Amazon and/or Cafepress.

The above was based on Ed's Quotation of the Day, available only via email. If interested in being added to his list, leave your information in the comments


  1. And this is why veterinarians seldom study quantum physics...