# Accidental, unplanned breakthroughs in physics

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There is possibly some idioms or saying like this, If you try too hard for something, you will never get it. If you do not aim for something, it may fall on you accidentally, not as you originally planned.''

In physics, or generally in science, there are many moments where the success and the triumph come from the accidental, unplanned attempts. Moreover, there are some cases that originally having attempts for one specific question or a goal, but solve another seemly unrelated problems, or reach seemly the opposite goals. There are these kinds of moments leading to breakthrough of physics or science.

For example,

(1) Yang-Mills theory original paper has attempt to explain a theory of nucleon, such as neutron and proton interactions with isospin symmetry, but it turns out that Yang-Mills theory as a non-Abelian gauge theory suitable to describe a more fundamental subject, the gauge fields coupled to quarks and leptons in the standard model (EM, and especially the weak interaction and the strong interaction.)

(2) $Z_2$ topological insulator in 2+1D: the original paper of quantum spin hall effect from Kane and Mele is set for graphene. But it turns out the phenomena is not in graphene(C Kane jokes on this accident himself.), but the physics is profound and correct, and later realized in CdTe/HgTe/CdTe quantum wells with a 2D film HgTe sandwiched.

[Question]: Can any of the readers here list more? Both in theories or in experiments. Making an inspiring list for eager-mind scientists at Phys.SE here. To give us some inspiration and high motivations to be subconsciously aware of those random accidental moments.

This post imported from StackExchange Physics at 2014-06-24 19:47 (UCT), posted by SE-user Idear
recategorized Jan 11, 2016

This post imported from StackExchange Physics at 2014-06-24 19:47 (UCT), posted by SE-user Deer Hunter
Is listing CdTe twice in "CdTe/HgTe/CdTe" a typo?

This post imported from StackExchange Physics at 2014-06-24 19:47 (UCT), posted by SE-user Dan Neely
Don't forget the discovery of the heating effect of microwaves.

This post imported from StackExchange Physics at 2014-06-24 19:47 (UCT), posted by SE-user called2voyage
@Dan Neely. No, CdTe/HgTe/CdTe is not a typo. It is correct. CdTe/HgTe/CdTe is a sandwich decice with a HgTe in the middle.

This post imported from StackExchange Physics at 2014-06-24 19:47 (UCT), posted by SE-user Idear
There is also that string theory was first supposed to be a theory for scattering of hadrons but then some nasty gravitons popped up that could not have gotten rid off ... ;-)

This post imported from StackExchange Physics at 2014-06-24 19:47 (UCT), posted by SE-user Dilaton
A few of the most important ones are still missing: The magnetic effect of electric currents by Oersted (or better by Gian Domenico Romagnosi), radioactivity, quantum mechanics (Planck's constant playing a role in the photoelectric effect and in atomic physics) the laser, pulsars, holography, high-temperature superconductivity. Nassim Taleb called these events in his same-named bestseller "black swans".

This post imported from StackExchange Physics at 2014-06-24 19:47 (UCT), posted by SE-user ClassicalPhysicist

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A few more here:

Fractional quantum hall effects: had heard that the large magnetic field is originally aimed to see the Wigner crystal effect, instead of testing quantum hall physics.

Asymptotic freedom (QCD running couplings to small at high energy): from Wilczek's book Longing for the Harmonies,'' at that time David Gross originally aimed to prove that QFT cannot explain the Bjorken scaling, i.e. prove that (non-Abelian) QFT always lead to large coupling at high energy, simply that QFT cannot explain the couplings run to small at high energy. But the final result is the opposite. And they won the Nobel Prize.

String theory: originally aimed for explaining strong interaction, but not as successful as QCD. String had then been abandoned for a long while. Later string theory turned out to be a candidate for a theory of everything.

Inflation(cosmology): Alan Guth firstly studied particle physics and magnetic monopole in grand unified theory(GUT). He encountered the magnetic monopole problem (the sparsity of magnetic monopoles in the universe). Initially there is no significant progress. But he and colleagues turned out to detour to use a theory of supercooling to understand the phase transition of the early universe, which produces a false vacuum then decay to produces Inflation. This new idea discovery of Inflation goes backward solving the magnetic monopole problem.

The non-existence of luminiferous ether: Michelson and Morley had initially hypothesised that luminiferous ether exists, but they ended up showing otherwise.

This post imported from StackExchange Physics at 2014-06-24 19:47 (UCT), posted by SE-user Idear
answered Aug 22, 2013 by (1,455 points)
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The Stern-Gerlach Experiment: originally setting out to corroborate the Bohr-Sommerfield hypothesis that the direction of the angular momentum of an atom is quantized, it was eventually realized that the proper interpretation of the observations was as the first evidence of particle spin and that the electron is a spin-1/2 particle.

The Spin-Statistics Theorem: I can't imagine anyone expected this jewel to pop out of the union of quantum mechanics with special relativity.

This post imported from StackExchange Physics at 2014-06-24 19:47 (UCT), posted by SE-user David H
answered Aug 22, 2013 by (90 points)
actually Spin-Statistics Theorem may not need to have special relativity. What you implied may be is the CPT theorem derived in QFT. For Spin-Statistics, Quantum mechanics alone is good enough to derive. ps. In 2+1D, using fermions as the string ends, doing the trick of Feynman's plate also can show Spin-Statistics Theorem. Levin-Wen String-net also does the job to show Spin-Statistics Theorem. It will also be better to say what this is accidental and unplanned from a historical viewpoint.

This post imported from StackExchange Physics at 2014-06-24 19:47 (UCT), posted by SE-user Idear

Idear: you are completely wrong. The theory of spinless fermions is consistent nonrelativistically, as is the theory of spin 1/2 bosons. These theories are easy to formulate--- just consider a spinless fermion or a spin 1/2 boson! There's nothing wrong with it until you add relativity. The only thing you can conclude nonrelativistically is that if you start with constituents obeying spin-statistics, you build up composite particles that obey spin-statistics. But it is not true for effective excitations, you can make a spinless fermion at low-energy by considering neutrons in a strong magnetic field. There is no truth to these claims of nonrelativistic spin-statistics, they are wrong, and ridiculously so, and they should not be made.

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Discovery of X-rays: it happened when Röngten discovered that some photographic plates received radiation even if they were unexposed.

This post imported from StackExchange Physics at 2014-06-24 19:47 (UCT), posted by SE-user chuse
answered Aug 22, 2013 by (40 points)
Pls check this: I'm pretty sure you're confusing Röntgen with Becquerel

This post imported from StackExchange Physics at 2014-06-24 19:47 (UCT), posted by SE-user WetSavannaAnimal aka Rod Vance
@WetSavannaAnimalakaRodVance Becquerel discovered radioactivity, Röngten X-rays

This post imported from StackExchange Physics at 2014-06-24 19:47 (UCT), posted by SE-user chuse
Agreed, but I seem to recall the photographic plates were Bequerel's detector, whereas Röntgen I think used something different.

This post imported from StackExchange Physics at 2014-06-24 19:47 (UCT), posted by SE-user WetSavannaAnimal aka Rod Vance
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Plank's law of the black body radiation. Written first as an approximate formula bridging two opposite experimental asymptotes, it turned out to be an exact formula, thus it needed a "derivation". This is how the hypothesis of light quanta was advanced.

answered Jun 24, 2014 by (92 points)
reshown Jan 11, 2016
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Discovery of the Cosmic Microwave Background Radiation:  Penzais and Wilson first thought the background noise was due to pigeon poop in their antenna.  Another Nobel Prize discovery.

answered Jan 11, 2016 by Lewis Miller

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