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The Say of the Week July 28, 2008

Posted by dorigo in humor, physics, science.
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We are all agreed that your theory is crazy. The question which divides us is whether it is crazy enough to have a chance of being correct. My own feeling is that it is not crazy enough.

Niels Bohr


1. Ed Darrell - July 28, 2008

What a great statement! To whom did he say it? What was the theory?

2. dorigo - July 28, 2008

Hi Ed,

I dunno – hope some reader here will shed some light though (one of the benefits of owning a blog!)


3. Alexziller - July 29, 2008

about skepticism

“Yes”, I said. “I believe in evidence. I believe in observation, measurement, and reasoning, confirmed by independent observers. I’ll believe anything, no matter how wild and ridiculous, if there is evidence for it”


4. Markk - July 29, 2008

Vaguely, I think he was talking to Pauli about some theory of Pauli and Heisenberg. Was this in a Freeman Dyson book? This is my murky memory, but it may jog someone.

5. goffredo - July 29, 2008

Ah the myth of crazy theories…

I too believe in this myth and like Bohr’s saying. But I think it gives the wrong message and should be told to non-physicists only if equal time, possibly even more, is spent to tell and cherish the conjugate nitty gritty side of science. The other side of the story should point out that just as crazy theories need freedom, imagination and creativity, good data requires discipline but also imagination and creativity. Then one should say again and again, taking exmaple from many human activities, that creativity requires both freedom and discipline. Just think of music, art, literature,…. A myth that definitely should be abolished is that freedom and discipline are at odds.

If you do this (spend equal time in telling the other side of the scientific story) then it is easier to put things in the proper context: a theory is crazy when there is no data; a theory supported with a lot of data is no longer crazy.

Some sayings:

Cliff Swartz (Physics Today, 1999):
“To err is human, to describe the error properly is sublime.”

“The first princple is that you must not fool yourself – and you are the easiest pesron to fool.” And again:
“If you thought science was CERTAIN – well that’s just an ERROR on your part!”

But then there was Madam Curie:
“There are these sadistic scientists who hurry to hunt down errors instead of establishing the truth.”

On another level yet there is Mark Twain:
“Get your facts first, then you can distort them as much as you please.” And again:
“Facts are stubborn things, but statistics are more pliable.”

I feel Twain is very wise (“Everyone is a moon, and has a dark side…”). For that I know there are sadistic and fraudulent scientists! So I am sympathetic with Curie, but after moment of thought I distance myself from her and agree with Swartz and Feynman.

“If you cann’t take the heat then physics is not for you, or you could become a factless theorist.” Me

6. Luboš Motl - July 29, 2008

Ed and Tommaso,

the famous sentence was said to Wolfgang Pauli himself, addressing Pauli’s idea of the spin of the electron. The idea turned out to be exactly crazy enough to be correct.

Best wishes

7. dorigo - July 29, 2008

Jeff, thank you for the entertaining list of quotes. I like Twain’s duo too… It goes well beyond science in fact.

Hi Lubos,
so this is Bohr talking to Pauli. Good to know!

Thanks to both of you… And you confirm that a blog is a wonderful tool to enlarge one’s knowledge.


8. Ed Darrell - July 29, 2008

Bohr to Pauli, about spin? Was this in reference to non-locality? And wasn’t that the topic over which Bohr and Einstein had their famous row? This gets to be a better story the more we know — if I’m on the wrong track, somebody let me know!

9. dorigo - July 29, 2008

Hi Ed,

Hmmm, I will take a minute or two to browse a book by Tomonaga I have at home tonight. It is “The history of spin”. If the anecdote is not there, then either Tomonaga is not a entertaining writer, or the quote does not belong to the story!


10. goffredo - July 29, 2008

Regards Pauli and Bohr. If my memory does not fail Bohr was willing to sacrifice the conservation of energy to explain the continuous energy spectrum of beta rays, while Pauli chose to propose existence of neutrino. The crazy neutrino would have to have 1/2 spin else the conservation of angular momentum would have to be sacrificed too. But this became apparent a couple of years later when the neutron was discovered and betas were understood to be electrons from the neutron decay.

Which guy was was crazier? Bohr or Pauli? In once instance Pauli was crazy but from another perspective he was conservative.

11. Luboš Motl - July 29, 2008

The quotation appeared after a seminar about the spin in which Pauli was heavily criticized.

Bohr’s comment summarized this whole flamewar and reflected his (Bohr’s) own revolutionary contributions to science because with his complementarity principle, he had to change the criteria how a good scientific theory should look like. According to the previous criteria, it would be “not even wrong”, using Pauli’s words for a revenge.😉

Freeman Dyson adds:

“When the great innovation appears, it will almost certainly be in a muddled, incomplete and confusing form. To the discoverer himself it will be only half understood … to everybody else it be a mystery. For any speculation which does not at first glance look crazy, there is no hope.”

This is a great comment because too many people are currently proposing too many ideas that are too easily understandable at first glance, even to the laymen. They don’t look crazy enough and there is indeed no hope for them.

The spin of the electron was crazy enough. Almost certainly, some participants protested that with such a large angular momentum, such a small particle would have to be spinning with superluminal speeds. This criticism was wrong, as we know today, but it had to be raised many times, I guess.

People were also too inertial concerning the very idea of a non-integer spin. Wave functions allow integral (orbital) angular momenta only.

These are exactly the things that Pauli wisely ignored because mathematically, the new spin degree of freedom was completely analogous to other quantum numbers that were already known in quantum mechanics. If representations were allowed, one should allow all representations, including spinors, and so forth. Of course, his intuition was precious.

No, there was no non-locality or EPR entanglement yet in this talk. It was started by Einstein many years later.

When you look at it from today’s perspective, the spin sounds pretty simple, so they could have also worried that it wasn’t crazy enough. But it was.

12. Luboš Motl - July 29, 2008

Dear goffredo,

I think that in all cases, Pauli was manifestly more conservative than Bohr. In this quote by Bohr, Bohr was completely serious. He actually did plan to reject Pauli’s theory of spin in case when the theory turns out to be too ordinary.

Bohr’s desire to get new crazy theories was perhaps shown to be excessive by the subsequent developments but it is surely true that new important ideas have to be crazier than a certain lower bound, otherwise they have no hope.


13. Chris Oakley - July 29, 2008

This flippant remark of Bohr’s has caused no end of harm. No – electron spin was not “crazy”, it was just not what people expected. Similarly, quantum mechanics was not “crazy” – it was just an unexpected, better explanation for spectral lines, and one which turned out to explain a lot more besides. These were rational, non-crazy ideas that turned out to be revolutionary. Bohr’s remark, though, seems to have convinced some that promulgating revolutionary ideas that don’t explain anything is acceptable. It is not. It was not then, and is not now.

14. Ed Darrell - July 30, 2008

Here’s the Wikiquote entry — I have none of these books on my historian/lawyer/teacher bookshelves:

* We are all agreed that your theory is crazy. The question that divides us is whether it is crazy enough to have a chance of being correct.
o Said to Wolfgang Pauli after his presentation of Heisenberg’s and Pauli’s nonlinear field theory of elementary particles, at Columbia University (1958), as quoted in Symposium on Basic Research (1959) by Dael Lee Wolfle, p. 66
o Your theory is crazy, but it’s not crazy enough to be true.
+ As quoted in First Philosophy: The Theory of Everything (2007) by Spencer Scoular, p. 89
o There are many slight variants on this remark:
o We are all agreed that your theory is crazy. The question which divides us is whether it is crazy enough.
o We are all agreed that your theory is crazy. The question is whether it is crazy enough enough to be have a chance of being correct.
o We in the back are convinced your theory is crazy. But what divides us is whether it is crazy enough.
o Your theory is crazy, the question is whether it’s crazy enough to be true.
o Yes, I think that your theory is crazy. Sadly, it’s not crazy enough to be believed.

15. Luboš Motl - July 30, 2008

Concerning the comment #13:

As long as we only talk about self-consistent theories and propositions, “crazy” and “totally unexpected” is pretty much the same thing in physics, and “mildly crazy” and “unexpected” are two equivalent softer expressions of the same thing.

Quantum mechanics indisputably *was* crazy. Using another quotation by Bohr, “Anyone who is not shocked by quantum theory has not understood it.” That obviously includes the author of the comment #13.

Finally, it was never important and it is still unimportant whether a theory can be explained to someone else. What matters is whether it is self-consistent and compatible with the actual empirical data, and one person who understands why it is suffices for the theory to be doing fine. Nothing has ever changed about these basic, obvious principles.

The author of the comment #13 will probably never understand any theory above a certain level but that certainly doesn’t imply that there is a problem with all theories.

16. Chris Oakley - July 30, 2008

Hi Lubos,

If you can spare the time from your blog or advising the Czech government about global warming (did you get that gig, BTW?), have a look at the dictionary definitions of “crazy” and “unexpected”. I think that you will find that they have little to do with each other.

17. Luboš Motl - July 30, 2008

Dear #16, I am surely no official adviser concerning global warming and if you think otherwise, it is probably because you use untrustworthy sources. I guess it’s the same sources where you contribute yourself which should make it clear that they’re untrustworthy.

You also use wrong dictionaries to understand physicists because in quotes like the famous sentence by Bohr, “crazy” means “unexpected”.

With your wrong dictionaries, neither of the definitions makes any sense. For example, in


it either means things that can only be applied to people; or it means foolish or impractical. Bohr was certainly not thinking about theories of spin as being unpractical – that was the last thing he meant.

More generally, please stop trying to teach people whose IQ is 35 above yours.

18. dorigo - July 31, 2008

Sorry to pitch in folks, but just a point: teaching people with a higher IQ (whatever that number means) is perfectly legal, and completely sound. A bigger IQ certainly does not imply a bigger knowledge by force. For instance, I am sure I know a couple of folks who could teack me and Lubos some chess ending techniques. Or how to pilot a F-16. Or how to prepare a good bread pudding.


19. dorigo - July 31, 2008

Ed, thank you so much for digging that out! It appears that there’s been several versions in the literature. Fortunately, the meaning did not change much.


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