What Is Your Dangerous Idea?

John Brockman’s Edge web-site has an annual feature where he asks a wide array of scientists and others how they would answer a hopefully thought-provoking question. Last year the question was What Do You Believe Is True Even Though You Cannot Prove It? This year it’s What Is Your Dangerous Idea?

There are responses to this question from 117 different people, a large fraction of them psychologists or cognitive scientists. Among the responses from physicists, several deal with the Landscape as a dangerous idea. Susskind takes credit for it, noting “I have been accused of advocating an extremely dangerous idea”, and that some of his colleagues believe it will lead to the end of science, leaving no way to defend physics as a truer path to knowledge than religion. He proudly describes the anthropic Landscape idea as “spreading like a cancer.”

On the opposite side of the issue, Brian Greene emphasizes the dangers of the Landscape philosophy:

When faced with seemingly inexplicable observations, researchers may invoke the framework of the multiverse prematurely — proclaiming some or other phenomenon to merely reflect conditions in our bubble universe — thereby failing to discover the deeper understanding that awaits us.

Paul Steinhardt is more emphatic about these dangers:

I think it leads inevitably to a depressing end to science. What is the point of exploring further the randomly chosen physical properties in our tiny corner of the multiverse if most of the multiverse is so different. I think it is far too early to be so desperate. This is a dangerous idea that I am simply unwilling to contemplate.

He also has his own “dangerous idea”, about a cyclic model of the universe explaining the small size of the cosmological constant. Lawrence Krauss gives his own version of an explanation of the danger that the Landscape will lead to an end-point for theoretical physics:

… all so-called fundamental theories that might describe nature would be purely “phenomenological”, that is, they would be derivable from observational phenomena, but would not reflect any underlying grand mathematical structure of the universe that would allow a basic understanding of why the universe is the way it is.

Some other interesting contributions from physicists come from Philip Anderson, who has some speculative comments about dark matter and dark energy, Lee Smolin, who discusses the possibility of natural selection having something to do with fundamental laws, and Carlo Rovelli, who remarks that we have still not completely absorbed the revolutionary ideas of 20th century physics:

I think that seen from 200 years in the future, the dangerous scientific idea that was around at the beginning of the 20th century, and that everybody was afraid to accept, will simply be that the world is completely different from our simple minded picture of it. As the physics of the 20th century had already shown.

What makes me smile is that even many of todays “audacious scientific speculations” about things like extra-dimensions, multi-universes, and the likely, are not only completely unsupported experimentally, but are even always formulated within world view that, at a close look, has not yet digested quantum mechanics and relativity!

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53 Responses to What Is Your Dangerous Idea?

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  3. Juan R. says:

    Rovelli exactly says:

    We still haven’t digested that the world is quantum mechanical, and the immense conceptual revolution needed to make sense of this basic factual discovery about nature.

    That is not true and perhaps it is the basis of the typical “we do not understand quantum mechanics”. Maybe people who claim to be doing fundamental physics would revise their knowledge of basic stuff.

    As brilliantly highlighted by Bohr -a century ago- there is two visions of the world. At the one hand, the quantum vision, mainly applicable to atomic scale. At the other, the classical vision, mainly applicable to macroscopic scale. Both are complementary between them and none view can be reduced to the other.

    Precisely, that is the reason that Schrödinger equation is totally inefficient when dealing with macroscopic phenomena, and that the old quantum measurement problem is not solved still. This is reason that Gell-Mann/Hartle ‘histories formalism’ [1] has not predictive power. It is the reason of great failure of the decoherence approach to solve measurement problem (far from P. W. Anderson unjustified claims [2]), this is reason that multiple-worlds Weinberg ‘interpretation’ sounds (see for example Penrose’s criticism on why multiple-worlds is wrong in both philosophical and technical details in one of his last books [3]) to joke for people doing serious stuff (i.e. people who is doing top-research in quantum measurement), etc.

    All realistic models of quantum measurement published in specialized literature are based in generalizations of the quantum: axiomatic generalizations of QM (e.g. Martingale models based in Lindblad semigroups that permit us derive Born rules), nonlinear equations violating superposition principle at large scales (e.g. ‘Caldeira-Leggett’ ones), LPS systems outside of Hilbert space (Austin-Brussels School Rigged-QM), etc.

    Simple equations of the kind Rovelly loves (H phi = 0 or ADM or similar ones) are rough approximations valid just in certain specific situations.

    Probably, the general misunderstanding about quantum mechanics is the explanation for the four decades futile effort about geometrodynamics, LQG, and so. I agree that superstring theory does rather poor our approach to quantum gravity, but LQG is not better. One can agree that both are complementary approaches. LQG does mistakes A, B, and C, whereas superstrings incorrectly deals with D, E, and F points.

    Unfortunately, Rovelly (as many others LQG theorists) does not understand time and this is the reason of his last decade unfounded claims on a pure relational structure for the universe.

    Of course, the superstring perturbative series around a fixed classical spacetime background is wrong and really trivial (one can use elementary R-QFT techniques); I agree with the LQG philosophy here. However, sorry to say this Lee Smolin, the principles of GR are not fundamental.

    Lee Smolin said:

    Yes, GR satisfies a weak form of BI (background independence) in which several things are kept fixed including dimensions, topology and asymptotics. So hence does any direct quantization of GR. We might posit a deeper theory that dispenced with these background structures, which takes us beyond the strict quantization of GR.

    I do not agree. We might posit a deeper theory explaining available (present and future) experimental data. Only that!

    There are no single experimental data suggesting us that topology of spacetime may change at Planck scales even if anyone in quantum gravity community think so. Therefore, you (as Rovelli) are expressing how you want universe was…

    [1] M. Gell-Mann and J. B. Hartle, Quantum Mechanics in the Light of Quantum Cosmology, in Complexity, Entropy, and the Physics of Information, W. Zurek, ed., Addison-Wesley, Reading (1990), p. 425; also in Proceedings of the 3rd International Symposium on Quantum Mechanics in the Light of New Technology, S. Kobayashi, H. Ezawa, Y. Murayama, and S. Nomura, eds., Physical Society of Japan (1990); Phys. Rev. D 47, 3345 (1993).

    [2] http://arxiv.org/abs/quant-ph/0112095

    [3] The Large, the Small and the Human Mind


    Juan R.

    Center for CANONICAL |SCIENCE)

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