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Most Scientific Theories Are Wrong

“There could be no fairer destiny for any physical theory than that it should point the way to a more comprehensive theory in which it lives on as a limiting case.” -Albert Einstein

Imagine: you’ve worked hard all your life, through your primary and secondary school education, where you worked hard to get into a good college, through your undergraduate degree, where you found something you were passionate enough about that you wanted to study it even further, and then through graduate school, where you spent half-a-decade or more immersing yourself, non-stop, in an area of research in a field that you love.

Image credit: Sean Milam, Anna Davis, and Denise Koessler at ETSU.

Image credit: Sean Milam, Anna Davis, and Denise Koessler at ETSU.

You become familiar with the deepest known theories about whatever it is you’ve studied, and you begin to see where our understanding in some part of the material world begins to break down. The great unsolved problems of your time look like missing puzzle pieces, while the tools, equations and current theories begin to look like misshapen pieces that don’t quite fit where they’re supposed to.

Image credit: Lawrence Berkeley Laboratory / Paul Preuss / Michael Crommie.

Image credit: Lawrence Berkeley Laboratory / Paul Preuss / Michael Crommie.

In other words, you’ve run up against the limits of our current knowledge; to make any further progress is going to take an innovation that’s not yet a part of our scientific lexicon.

Image credit: Sarah E. Ross / Current Opinion in Neurobiology.

Image credit: Sarah E. Ross / Current Opinion in Neurobiology.

Maybe you’re a biologist, trying to understand how the sensation of itch actually works. The three main types of sensory neuron in humans — pain, pressure and temperature — don’t quite seem to cover it.

Image credit: Debra Krohn, via http://pbworks.com/.

Image credit: Debra Krohn, via http://pbworks.com/.

Maybe you’re a geoscientist, trying to figure out how to predict when the entire mantle convects, and when only the upper mantle convects to transport heat and materials.

Image credit: Fermilab, via http://www.fnal.gov/.

Image credit: Fermilab, via http://www.fnal.gov/.

Maybe you’re a particle physicist, trying to decipher what accounts for neutrino mass, and why they’re so mind-bogglingly light compared to all the rest of the massive, standard model particles.

Image credit: 2dFGRS, SDSS, Millenium Simulation/MPA Garching, and Gerard Lemson & the Virgo Consortium.

Image credit: 2dFGRS, SDSS, Millenium Simulation/MPA Garching, and Gerard Lemson & the Virgo Consortium.

Or maybe — like me — you’re an astrophysicist, trying to solve some of the great cosmic mysteries of just how it is our Universe got here, and came to be the way it is today.

Image credit: P. Chodas (NASA / JPL), via C. Seligman of http://cseligman.com/.

Image credit: P. Chodas (NASA / JPL), via C. Seligman of http://cseligman.com/.

The thing is, no matter what your field is, there’s more to learn, there’s progress to be made, and there’s work to be done. If the current theories and laws can’t explain everything that’s observed — all the experimental and observational phenomena — then that theory cannot be the entire story.

And in that sense, given that even the best scientific theory only has a limited range of validityall scientific theories are wrong. (And before you quote me out-of-context on that, keep reading.)

Image credit: Christopher Crockett from http://christophercrockett.com/.

Image credit: Christopher Crockett from http://christophercrockett.com/.

But that’s not really fair. Scientific theories are only meant to have a certain range of validity! We know that the Big Bang doesn’t explain what came prior to the Big Bang; we know that evolution doesn’t explain the origin of life; we know that Airy’s theory of isostatic compensation doesn’t explain the motion of the Earth’s crust over geologic timescales; we know that General Relativity doesn’t explain the existence of antimatter.

But we want to know the answer to all of those questions. And that requires new ideas; it requires new scientific theories.

Image credit: Adaptive Landscapes, via http://adaptive-landscapes.org/.

Image credit: Adaptive Landscapes, via http://adaptive-landscapes.org/.

To explain what happens prior to the Big Bang, we have the theory of cosmic inflation. To explain the origin of life, we have the theory of abiogenesis. To explain the motion of Earth’s crust, we have plate tectonics. And to explain the existence of antimatter, we have quantum field theory. All of these theories are very likely valid, as far as we understand them, but none are necessarily the final, complete and fully comprehensive answer to these questions.

And moreover, these are just the most successful ones; along the way, there were plethoras of alternative scientific theories that didn’t quite pan out. Here are some of the more interesting ones from my field: astrophysics.

Image credit: Ute Kraus, Physics education group Kraus, Universitat Hildesheim.

Image credit: Ute Kraus, Physics education group Kraus, Universitat Hildesheim.

We know that black holes come in a couple of different varieties, ranging from a handful of solar masses (from collapsed supermassive stars) all the way up to millions or billions of times the mass of our Sun: the supermassive black holes found mostly at the center of galaxies. But could the Universe have been filled with lower-mass black holes from the early stages of the Universe? That’s the theory of primordial black holes, or PBHs!

Now these have been of interest for a number of reasons — as a dark matter candidate, for example — for some time. But we’ve looked for them, we’ve investigated their physics, we’ve tested the theory for compatibility with our current knowledge of large-scale structure of the Universe, and it just doesn’t seem to fit with what we know. It’s still a possibility, but a remote-looking one, and it doesn’t solve the problems it was designed to solve. So, no PBHs; that’s a scientific theory that’s wrong (so far), but it’s still interesting to think about.

Image credit: slice from the 2dF Galaxy Redshift Survey.

Image credit: slice from the 2dF Galaxy Redshift Survey.

We know that structure, on the largest scales, forms into giant superclusters with a certain large-scale distribution. Clumps beyond a certain size don’t seem to exist; and the large-scale features we do see tell us what the Universe is (and isn’t) made out of. But one of the great ideas that came along was that large-scale structure could have been seeded by a network of cosmic strings, or giant one-dimensional defects in the fabric of spacetime!

But despite a reasonable theoretical motive behind them, we’ve performed exhaustive surveys of our Universe, and the evidence against cosmic strings is overwhelming. The nail-in-the-coffin that our Universe’s structure doesn’t follow from cosmic strings came with the measurement of the low-multipoles from the COBE satellite; the disagreement is too much. But cosmic strings are still interesting to thing about for a variety of reasons, and could rear their head in the future in some other form.

Image credit: wikimedia commons user Incnis Mrsi.

Image credit: wikimedia commons user Incnis Mrsi.

One of the most important parts of relativity is the idea that experimental results are independent of what direction your experiment is oriented in, and also is independent of what your linear velocity happens to be. This, generally, is known as Lorentz invariance, and is a symmetry that — as far as we know — is always respected by nature.

But if you break this invariance, a whole slew of interesting phenomena could happen. And so we look, and we build theories based on breaking it. So far, the only results are null, within our statistical limits. But that doesn’t mean, at some level, this couldn’t potentially be interesting.

Image credit: Screenshots via the Animaniacs cartoon.

Image credit: Screenshots via the Animaniacs cartoon.

I don’t bring any of these ideas up to try and convince you that they’re right; I don’t think any of them are!

But I bring this up so that the next time you hear about some theory, it’s totally reasonable to ask, “What overwhelming evidence do we have that this is correct?” But rather than simply dismiss it, if it sets off your internal BS-detector, I want to assure you of a number of things:

  • Your BS-detector is probably right (and honestly, it’s probably not sensitive enough), and this isn’t likely to be the next great revolution in our understanding of the Universe,
  • This research is still important, as it’s exploring a hitherto unexplored possibility, which could teach us something about the Universe,
  • and if there’s even a germ of a good idea in there, scientific inquiry is what will grow that into a full-fledged theory that means something.

Most scientists go through their entire career without coming up with even one original idea, and most of the ideas that they do come up with aren’t worth the weight of the paper they’re printed on. But you’ve got to try, or you’ll never move forward. The danger of putting yourself out there and finding out that you might not be right is far worse than not putting yourself out there at all.

Image credit: S. Beckwith & the HUDF Working Group (STScI), HST, ESA, NASA.

Image credit: S. Beckwith & the HUDF Working Group (STScI), HST, ESA, NASA.

It’s a great big Universe out there, and there’s still so much to be understood. I’m one of the leastinclined to be credulous about a new idea in my field, but even I recognize why it’s important. Trying new things, learning why they fail, and trying again is the only way progress has ever been made; let’s continue to encourage people to do just that. Be daring, be bold, and dare to be a success. If you fail, it shouldn’t cost you your career; if you succeed, all of humanity wins!

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He has fantastic posts full of new knowledge, interpretations and even more fantastic gifs

“The joy of life consists in the exercise of one’s energies, continual growth, constant change, the enjoyment of every new experience. To stop means simply to die. The eternal mistake of mankind is to set up an attainable ideal.” -Aleister Crowley

But the Universe itself experiences continual growth, constant change, and new experiences all the time, and it does so spontaneously.

Image credit: ESA and the Planck collaboration.

Image credit: ESA and the Planck collaboration.

And yet, the better we understand our Universe — what the laws are that govern it, what particles inhabit it, and what it looked/behaved like farther and farther back in the distant past — the moreinevitable it appears that it would look just as it appears today.

Image credit: 2dFGRS, SDSS, Millenium Simulation Team / MPA Garching, and Gerard Lemson & the Virgo Consortium.

Image credit: 2dFGRS, SDSS, Millenium Simulation/MPA Garching, and Gerard Lemson & the Virgo Consortium.

On the largest scales in our observable Universe, matter clumps and clusters together in a filamentary, web-like structure, while the densest parts form galaxies, stars and planets in isolation, in groups, and in clusters as appropriate.

Although different regions of space and different simulation runs will have slightly different details, the pattern of clustering is always the same; if we were to go as far back to the beginning as our physical understanding allows, we would get a Universe indistinguishable from ours in all but the most minute details 100 times out of 100.

Image credit: ESO's wide field imager (WFI)/Chandra Deep Field South (CDF-S).

Image credit: ESO’s wide field imager (WFI)/Chandra Deep Field South (CDF-S).

By time the Universe is as old as ours is — 13.8 billion years — it will look exactly the same every time in so many important ways:

  • It will have the same number of galaxies, of the same mass, clustered together in the same ways,
  • The ratios of the elements in the Universe will be identical, overall, to the elemental abundance today,
  • It will have the same number of stars and planets with the same mass distribution as our Universe,
  • It will have the same ratio of dark energy, dark matter, normal matter, neutrinos, and radiation as our Universe,
  • and, perhaps most importantly, all of the fundamental constants will have the same value.

This last one is so important, because starting with the same rough initial conditions is what guarantees our Universe will look the way it does. But what are these constants?

Image credit: Fundamental Constants as of 1986, via http://hannah2.be/optische_communicatie/CODATA/elect.html.

Image credit: Fundamental Constants as of 1986, via http://hannah2.be/optische_communicatie/CODATA/elect.html.

You might be used to constants like c, the speed of light, h (or ħ), Planck’s constant, and G, Newton’s gravitational constant. But these constants are dimension-ful, meaning that they depend on the units (e.g., meters, seconds, kilograms, etc.) you use to measure them.

But the Universe, very clearly, doesn’t care what units-of-measurement you use! So we can create dimensionless constants, or combinations of these physical constants that are simply just numbers, numbers that describe how different parts of the Universe relate to one another.

Image credit: Fermilab Visual Media Services, 1980.

Image credit: Fermilab Visual Media Services, 1980.

We’d like to describe our Universe as simply as possible; one of the goals of science is to describe nature in the simplest terms possible, but no simpler. How many does of these does it take, as far as we understand our Universe today, to completely describe the particles, interactions, and laws of our Universe?

Quite a few, surprisingly: 26, at the very least. Let’s take a look at what these are.

Image credit: Dr. W. John McDonald, of the Roy. Astron. Soc. of Canada.

Image credit: Dr. W. John McDonald, of the Roy. Astron. Soc. of Canada.

1.) The fine-structure constant, or the strength of the electromagnetic interaction. In terms of some of the physical constants we’re more familiar with, this is a ratio of the elementary charge (of, say, an electron) squared to Planck’s constant times the speed-of-light. At the energies of our Universe, this number comes out to ≈ 1/137.036, although the strength of this interaction increases as the energy of the interacting particle rises. This is thought to be due to a relative increase in how elementary charges behave at higher energies, although this is not yet a certainty.

Image credit: Wikimedia Commons user Manishearth.

Image credit: Wikimedia Commons user Manishearth.

2.) The strong coupling constant, or the strength of the strong nuclear force. Although the way the strong force works is very different and counterintuitive compared with either the electromagnetic force or gravity, the strength of this interaction can be parametrized by a single coupling constant. This constant of our Universe, too, like the electromagnetic one, changes strength with energy.

Image credit: Matt Strassler, 2011, via http://profmattstrassler.com/.

Image credit: Matt Strassler, 2011, via http://profmattstrassler.com/.

3-17.) The (non-zero) masses of the fifteen fundamental standard model particles with a rest-mass, relative to a fundamental scale set by Einstein’s gravitational constant. (This way, no separate constant is needed for gravitation.) In the standard model, this typically manifests itself via fifteen coupling constants (to the Higgs field) for the electron, muon and tau, the three neutrino species, the six quarks, the W and Z bosons, and the Higgs boson. (If you preferred a different parametrization, you could replace the W-and-Z masses with the weak coupling constant and the Higgs field’s expectation value; your choice.) The photon and the eight gluons don’t get one, being intrinsically massless particles.

This is, I’ll note, a source of much distress for theorists, who hoped that these constants — the fundamental masses of the elementary particles — would either be part of some pattern (they’re not), calculable from first principles (they’re not), or would emerge dynamically from some larger framework, like a GUT or string theory (they don’t).

Image credit: Wikimedia Commons user Grandiose.

Image credit: Wikimedia Commons user Grandiose.

18-21.) The quark mixing parameters. These four parameters dictate how all of the weak nuclear decays happen, and allow us to calculate the probability amplitudes of different radioactive decay products. Because the up, charm and top quarks (as well as the bottom, strange and down quarks on the other hand) all have the same quantum numbers as one another, they can mix together. The details of the mixing is normally parametrized by the Cabibbo-Kobayashi-Maskawa (CKM) Matrix, which gives three quark mixing angles, as well as one CP-violatingcomplex phase.

These four parameters, again, cannot be predicted from any other principle, and must simply be measured at this point in time.

Image credit: © Amol S Dighe, via http://www.tifr.res.in/.

Image credit: © Amol S Dighe, via http://www.tifr.res.in/.

22-25.) The neutrino mixing parameters. Similar to the quark sector, there are four parameters that detail how neutrinos mix with one another, given that the three types of neutrino species all have the same quantum number. As of today, the three angles have been measured with some reasonable precision, although the CP-violating phase has not been. The mixing is parametrized by (what I know as) the Maki-Nakagawa-Sakata (MNS) Matrix, although it’s worth pointing out that the mixing angles are all huge compared to what they are for the quarks, so much so that the electron, muon and tau neutrinos are each superpositions of the three “fundamental” neutrino species that mix together significantly. This is because the mass differences between the different quark species is tremendous, ranging from maybe 6-to-300,000 times the mass of an electron, while the mass differences between neutrino species is at most 0.000016% an electron’s mass.

And finally…

Image credit: A.V. Vikhlinin, R.A. Burenin, A.A. Voevodkin, M.N. Pavlinsky.

Image credit: A.V. Vikhlinin, R.A. Burenin, A.A. Voevodkin, M.N. Pavlinsky.

26.) The cosmological constant, or the dimensionless constant driving the accelerated expansion of the Universe. This is another constant whose value cannot be derived, and is simply a measured fact, at least at this point in time.

If you rewind the Universe to a time just maybe a few picoseconds after the Big Bang, and start it off with roughly the same initial conditions and these 26 fundamental constants, you’ll get roughly the same Universe each and every time. The only differences will be encoded in quantum mechanical probabilities and the extent that the initial conditions varied.

But even this can’t explain everything about the Universe! For example:

  • The amount of CP-violation encoded by our constants, regardless of what the complex phase from the MNS-Matrix is, cannot explain the observed matter-antimatter asymmetry in our Universe. That requires some sort of new physics, which means there’s got to be a new fundamental parameter in there, too.
  • If there is CP-violation in the strong interactions, that would be a new parameter as well, and if not, the physics (or symmetry) that prevents it may well carry a new constant (or multiple constants) along with it.
  • Did cosmic inflation happen, and if so, what parameter(s) is/are associated with that?
  • What is the dark matter? Given the (reasonable) assumption that it’s a massive particle, it almost certainly requires at least one (and probably more than one) new fundamental parameter to describe it.

And so that’s where we are today.

Image credit: NASA / CXC / M.Weiss.

Image credit: NASA / CXC / M.Weiss.

We don’t yet know where the values of these constants come from, or whether that’s something that will ever be known with the information available in our Universe. Some people chalk them up to anthropics or appeal to the multiverse; I haven’t given up on our Universe just yet, though!

Our journey through the cosmos continues, and there’s so much more still to learn.

Some people also attribute these constants to their god-of-the-gaps.

Science is more than allowed to be wrong, it has to to begin with. How can it be constantly challenged if not assumed to be wrong?

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