theoretical physicist

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Et cetera

This is the rest. Things I wanted to keep on this website but didn’t really fit in other tabs. Here you can find some quotations I like, links to websites I like, et cetera.


My old website already had a space for quotations in its Et cetera tab, but none of them had any sources. This time I’m gonna try to be more rigorous with these references, despite liking many quotations that are probably apocryphal. They are ordered according to the author’s last name, year, and title. For quotes from movies or TV series, I order them according to the actor’s last name.

  • Therefore, conclusions based on the renormalization group arguments concerning the behavior of the theory summed to all orders are dangerous and must be viewed with due caution.
    So is it with all conclusions from local relativistic field theories.

    James D. Bjorken and Sidney D. Drell, in Relativistic Quantum Fields (McGraw-Hill, New York, 1965).

  • When it comes to atoms, language can be used only as in poetry. The poet, too, is not nearly so concerned with describing facts as with creating images and establishing mental connections.

    Niels Bohr, as quoted by Werner Heisenberg in Physics and Beyond: Encounters and Conversations (Harper & Row, New York, 1972).

  • You have no idea how high I can fly.

    Michael G. Scott (Steve Carrell), in The Office, S05E20: “New Boss”.

  • “Have you guessed the riddle yet?” the Hatter said, turning to Alice again.
    “No, I give it up,” Alice replied. “What’s the answer?”
    “I haven’t the slightest idea,” said the Hatter.
    “Nor I,” said the March Hare.

    A piece of a conversation between Alice, the Mad Hatter and the March Hare, in Lewis Carroll’s Alice’s Adventures in Wonderland.

  • The set of transformations (50.22)–(50.24) is called the renormalization group. Rarely has there been a more pretentious name in the history of physics. It’s like calling classical dynamics “the study of the Hamiltonian group of time translations”. Nevertheless, that’s what it’s called.

    Sidney Coleman, in Quantum Field Theory: Lectures of Sidney Coleman, eds. Chen, B. G., Derbes, D., Griffiths, D., Hill, B., Sohn, R., Ting, Y.-S. (World Scientific, New Jersey, 2018).

  • Only questions about the results of experiments have a real significance and it is only such questions that theoretical physics has to consider.

    Paul A. M. Dirac, in The Principles of Quantum Mechanics (Oxford University Press, Oxford, 1967).

  • One can find thousands of statements in the literature to the effect that ‘general relativity and quantum mechanics are incompatible’. These are completely outdated and no longer relevant.

    John F. Donoghue, in The Effective Field Theory Treatment of Quantum Gravity. AIP Conference Proceedings 1483, 73–94 (2012). doi: 10.1063/1.4756964.

  • Toto, I have a feeling we’re not in Kansas anymore.

    Dorothy Gale (Judy Garland), in The Wizard of Oz. This is not a line from the book!

  • It should be clear that there is no real content to these proofs: all one has to do to obtain a proof is keep from getting confused.

    Robert Geroch, in Mathematical Physics (University of Chicago Press, Chicago, 1985).

  • Because you may be smart, but I’ve been smart longer.

    Dr. Hyde, in John Green’s Looking for Alaska (Penguin Books, New York, 2005).

  • Would Ovid still had been Ovid if he had lived in America? […] So did Ovid matter because he was Ovid or because he was born in Ancient Rome?

    Thought by Colin Singleton, in John Green’s An Abundance of Katherines (Penguin Books, New York, 2006).

  • Sometimes it seems the universe wants to be noticed.

    Mr. Lancaster quoting his college math teacher, in John Green’s The Fault in Our Stars (Penguin Books, New York, 2012).

  • It’s an energy field created by all living things. It surrounds us and penetrates us; it binds the galaxy together.

    Obi-Wan “Ben” Kenobi (Alec Guiness) on the Force, in Star Wars: Episode IV—A New Hope.

  • Although there has been a lot of work in the last fifteen years, I think it would be fair to say that we do not yet have a fully satisfactory and consistent quantum theory of gravity.

    Stephen W. Hawking, in Particle Creation by Black Holes. Communications in Mathematical Physics 43, 199–220 (1975). doi: 10.1007/BF02345020.

  • If you only do what you can do, you will never be more than you are now.

    Master Shifu (Dustin Hoffman), in Kung Fu Panda 3.

  • While I was in school I hated history, but since then I have come to recognize the usefulness of quoting dead people to support my convictions.

    Sabine Hossenfelder, in Lost in Math: How Beauty Leads Physics Astray (Basic Books, New York, 2018).

  • It’s a leap of faith. That’s all it is, Miles. A leap of faith.

    Peter B. Parker (Jake Johnson) to Miles, after he asks when he’ll know he is ready, in Spider-Man: Into the Spider-Verse.

  • One often meets his destiny on the road he takes to avoid it.

    Master Oogway (Randall Duk Kim), in Kung Fu Panda. (I eventually learned this phrase is originally due to Jean de La Fontaine, but I’ll keep Oogway’s name because I found this mistake of mine really funny).

  • Yesterday is history, tomorrow is a mystery, but today is a gift. That is why it is called the present.

    Master Oogway (Randall Duk Kim), in Kung Fu Panda.

  • The fix is to learn quantum field theory.

    knzhou, in an answer to Does collapse of wave function to a momentum eigenstate violate speed of light restriction?.

  • Dedicated to the memory of L. D. Landau, who understood the importance of pedagogy.

    Thanu Padmanabhan, in Theoretical Astrophysics Vol. I: Astrophysical Processes (Cambridge University Press, Cambridge, 2000).

  • This life in the stars is all I’ve ever known
    Stars and stardust in infinite space is my only home

    Greg Universe (Tom Scharpling), in Steven Universe, S01E49: “Story for Steven”.

  • There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy.

    Prince Hamlet, in William Shakespeare’s The Tragedy of Hamlet, Prince of Denmark, Act I, Scene V.

  • The topic with which I regularly conclude my six-term series of lectures in Munich is the partial differential equations of physics. We do not really deal with mathematical physics, but with physical mathematics; not with the mathematical formulation of physical facts, but with the physical motivation of mathematical methods. The oft-mentioned “prestabilized harmony” between what is mathematically interesting and what is physically important is met at each step and lends an esthetic — I should like to say metaphysical — attraction to our subject.

    Arnold Sommerfeld, in Partial Differential Equations in Physics (Academic Press, New York, 1949).

  • Stoke’s theorem shares three important attributes with many fully evolved major theorems:
    1. It is trivial.
    2. It is trivial because the terms appearing in it have been properly defined.
    3. It has significant consequences.

    Michael Spivak, in Calculus on Manifolds: A Modern Approach to Classical Theorems of Advanced Calculus (CRC Press, Boca Raton, 2018).

  • Far from an isolated gravitational source one might expect an idealized simple description of spacetime—asymptotic Utopia. However the remark of the British Prime Minister Chamberlain in 1939 on Czechoslovakia is relevant here: “This is a far far away country about which we know very little”.

    John Stewart, in Advanced General Relativity (Cambridge University Press, Cambridge, 1991).

  • As usual, all roads lead to black holes.

    Andrew Strominger, in Lectures on the Infrared Structure of Gravity and Gauge Theory (Princeton University Press, Princeton, 2018).

  • Isn’t it surprising that we can do physics at all?

    Kurt Sundermeyer, in Symmetries in Fundamental Physics (Springer, Cham, 2014).

  • Being myself a remarkably stupid fellow, I have had to unteach myself the difficulties, and now beg to present to my fellow fools the parts that are not hard. Master these thoroughly, and the rest will follow. What one fool can do, another can.

    Silvanus P. Thompson, in Calculus Made Easy: Being a very-simplest introduction to those beautiful methods of reckoning which are generally called by the terrifying names of the Differential Calculus and the Integral Calculus (Macmillan, London, 1914).

  • It is well known that the exercise of logic never adds to our knowledge: its role is to make a certain aspect of that knowledge clearer or more explicit, while keeping all the rest conveniently out of our sight.

    Tommaso Toffoli, in “Entropy? Honest!”. Entropy 18, 247 (2016). doi: 10.3390/e18070247.

  • The fundamental issue addressed by weak cosmic censorship can be expressed in graphic terms by posing the following question: Could a mad scientist—with arbitrarily large, but finite, resources—destroy the universe?

    Robert M. Wald, in “Weak” Cosmic Censorship. PSA: Proceedings of the Biennial Meeting of the Philosophy of Science Association 1992, 181–190 (1992). doi: 10.1086/psaprocbienmeetp.1992.2.192834.

  • [S]emiclassically, an initial pure state will evolve to a mixed state. For reasons I have not been able to understand during the course of the past 40 years, this is widely viewed as being highly problematic. The conflict between this view and the semiclassical analysis is referred to as the black hole information loss paradox.

    Robert M. Wald, in Particle and energy cost of entanglement of Hawking radiation with the final vacuum state. Physical Review D 100, 065019 (2019). doi: 10.1103/PhysRevD.100.065019. arXiv: 1908.06363 [gr-qc].

  • Quantum field theory is—as its name suggests—the quantum theory of fields. “Particles” do not play any fundamental role in the formulation of quantum field theory.

    Robert M. Wald, in Particle and energy cost of entanglement of Hawking radiation with the final vacuum state. Physical Review D 100, 065019 (2019). doi: 10.1103/PhysRevD.100.065019. arXiv: 1908.06363 [gr-qc].

  • The above considerations allow us to answer the following question that has been asked for many centuries: What are electricity and magnetism? Electricity and magnetism are the phenomena arising from the electromagnetic field and its coupling to charged fields. The electromagnetic field itself is a connection on a principal fiber bundle over spacetime with structure group U(1).

    Robert M. Wald, in Advanced Classical Electromagnetism (Princeton University Press, Princeton, 2022).

  • [O]ur purpose in theoretical physics is not just to describe the world as we find it, but to explain—in terms of a few fundamental principles — why the world is the way it is.

    Steven Weinberg, in The Quantum Theory of Fields Vol. 1: Foundations (Cambridge University Press, Cambridge, 1995).

  • To the wonderful teachers, students, and colleagues who have inspired and guided me over the years; and to the still unknown person(s) who will further illuminate the magic of this strange and beautiful world of ours by discovering How come the quantum? How come existence?
    We will first understand how simple the universe is when we recognize how strange it is.

    John Archibald Wheeler (with Kenneth Ford), in Geons, Black Holes, and Quantum Foam: A Life in Physics (W. W. Norton & Company, New York, 2000).

  • Quantum field theory arose out of our need to describe the ephemeral nature of life.

    Antony Zee, in Quantum Field Theory in a Nutshell (Princeton University Press, Princeton, 2010).

  • It is also possible that the function is non-analytic and does not admit a perturbative expansion. But these are merely words.

    Antony Zee, in Fly by Night Physics: How Physicists Use the Backs of Envelopes (Princeton University Press, Princeton, 2020).

Star Trek Quotations

I started watching Star Trek: The Next Generation a while ago and I’ve been taking notes of way too many quotes to keep them alongside the other ones. All of the following come from ST:TNG and I organize them by season and episode, instead of following the alphabetical patterns of the previous section.

  • Things are only impossible until they’re not!

    Captain Jean-Luc Picard. S01E16: “When the Bough Breaks”.

  • There is still much to do. Still so much to learn.

    Captain Jean-Luc Picard. S01E25: “The Neutral Zone”.

  • Captain, the most elementary and valuable statement in science, the beginning of wisdom is “I do not know”. I do not know what that is, sir.

    Lt. Commander Data. S02E02: “Where Silence Has Lease”.

  • Well, perhaps what we most needed was a kick in our complacency, to prepare us for what lies ahead.

    Captain Jean-Luc Picard. S02E16: “Q Who”.

  • Captain Jean-Luc Picard: Did you read that book I gave you?
    Ensign Wesley Crusher: Some of it.
    Picard: That’s reassuring.
    Crusher: I just don’t have much time.
    P: There’s no greater challenge than the study of philosophy.
    C: But William James won’t be on my Starfleet exams.
    P: The important things never will be. Anyone can be trained in the mechanics of piloting a starship.
    C: But Starfleet Academy…
    P: It takes more. Open your mind to the past—art, history, philosophy—and all this may mean something.

    S02E17: “Samaritan Snare”.

  • And Commander, it is possible to commit no mistakes and still lose. That is not a weakness. That is life.

    Captain Jean-Luc Picard. S02E21 “Peak Performance”.

  • Counselor Deanna Troi: One cannot deny human nature. What kind of a man is Commander Riker?
    Lt. Commander Data: A fighter?
    Troi: Yes.
    Data: The weaker his position, the more aggressive will be his posture.
    T: And he won’t give up.
    D: Then, despite whatever options he is given, he must be…
    T: The man that he is. Exactly.
    D: Is that a failing in humans?
    T: You’ll have to decide that for yourself.

    S02E21 “Peak Performance”.

  • It is at the heart of our nature to feel pain and joy. It is an essential part of what makes us who we are.

    Captain Jean-Luc Picard. S03E05 “The Bonding”.

  • To survive is not enough. To simply exist is not enough.

    Roga Danar. S03E11 “The Hunting”.

  • Q: What are you looking at?
    Lt. Commander Data: I was considering the possibility that you are telling the truth—that you really are human.
    Q: It’s the ghastly truth, Mr. Data. I can now stub my toe with the best of them.
    Data: An irony. It means you have achieved in disgrace what I have always aspired to be.

    S03E13 “Deja Q”.

  • Q: You’re very smart, Jean-Luc. But I know human beings. They’re all sopping over with compassion and forgiveness. They can’t wait to absolve almost any offense. It’s an inherent weakness of the breed.
    Captain Jean-Luc Picard: On the contrary, it is a strength.

    S03E13 “Deja Q”.

  • There are creatures in the universe who would consider you the ultimate achievement, android. No feelings, no emotions, no pain—and yet you covet those qualities of humanity. Believe me, you’re missing nothing. But if it means anything to you, you’re a better human than I.

    Q. S03E13 “Deja Q”.

Questionable Quotations

Who am I fooling? Apocryphal quotations can be fun as well. Just be aware that I might have no clue whether any of these were actually said.

  • Les papillons sont le seule chose importante…

    Attributed to Laurent Schwartz. I came across it while reading these notes on Green’s functions written by Prof. Henrique Fleming. Legend tells Schwartz enjoyed catching butterflies and, when he was in Rio de Janeiro, a reporter surprised with how much time he spent on this would have asked him whether the butterflies were as important as Mathematics. Schwartz’s answer? ‘‘The butterflies are the only important thing…’’

  • I can’t stay up that late.

    Attributed to Sidney Coleman, refusing to teach a 9 a.m. class. As quoted in his obituary at The Harvard Gazette.

Here are a few links that the readers of this website might find interesting.