There are, in general, two ways in which scientific advancement occurs. There’s the slow, incremental change that represents most scientific advances: where the existing scientific foundation gets built upon in a small but meaningful way. Typically, we perform experiments or observations, acquire new data, better determine key parameters about whatever it is we’re investigating, but in a way that doesn’t invalidate our revolutionize our prior understanding. On the other hand, there are also scientific revolutions: where a new discovery, or sometimes even just a new theoretical framework, blows up our old scientific foundation, and demands that we replace it with an entirely new conception about how some phenomenon in the Universe actually works.
This latter class of advances — representing huge shifts in our scientific foundations — have happened many times before. Examples include:
Kepler’s development of a heliocentric solar system with elliptical planetary orbits,
the theory of continental drift and plate tectonics for describing Earth’s crust,
the Darwin’s theory of evolution, guided by the mechanism of natural selection and random mutations,
and Einstein’s overthrow of Newtonian gravity, replacing it with General Relativity.
These advances, in contrast to incremental improvements to knowledge, represent some of the grandest, most revolutionary shifts in our understanding of the natural world.
These shifts couldn’t have happened if scientists weren’t willing to challenge accepted wisdom, and to imagine new foundations beyond the limits of our current ones. Very clearly, there is a “right way” to be a scientific contrarian, otherwise such revolutions would never have been possible within a scientific framework.
One of the great puzzles of the 1500s was how planets moved in an apparently retrograde fashion. This could either be explained through Ptolemy’s geocentric model (left), or Copernicus’ heliocentric one (right). However, getting the details right to arbitrary precision was something neither one could do. It would not be until Kepler’s notion of heliocentric, elliptical orbits, and the subsequent mechanism of gravitation proposed by Newton, that heliocentrism would triumph by scientific standards.
Credit: E. Siegel/Beyond the Galaxy
But in order to initiate such a revolution, there are key motivators that need to be in place, accompanied by an idea that’s sturdy enough to not only explain what the prior theory cannot, but to also reproduce all of the prior theory’s successes. That’s an incredibly tall order.
Kepler had Copernicus’s earlier heliocentric work to build upon, but it was up to him to better fit the existing data of planetary orbits than Ptolemy’s prevailing geocentric theory could.
Alfred Wegener’s initial idea of continental drift, from 1912, required a physical mechanism (later, plate tectonics and the various layers of Earth) that could support it: an endeavor that took nearly 50 years.
Darwinian evolution required direct observational and experimental support to validate it over alternative evolutionary pathways (e.g. Lamarckian evolution), with Mendelian genetics and later DNA providing the necessary underlying mechanism.
And Einstein didn’t just need to explain the precession of Mercury’s perihelion, he also needed to reproduce all of Newtonian gravity’s copious earlier successes, and find a new prediction (the deflection of starlight during a total eclipse) that differed from Newton’s.
Only by reproducing all of the prior theory’s triumphs, successfully explaining a phenomenon that the prior theory could not, and making new predictions that differed from the old theory’s that can be observationally or experimentally validated, can such a scientific revolution occur.
Today, many contrarians are hard at work, attempting to do exactly this. But are they approaching the problem the right way? The answers to these key five questions showcase whether such researchers are being scrupulous, careful, and comprehensive, or whether they’re merely elevating a contrarian position — and potentially themselves — to prominence, despite what the evidence shows.
The results of Arthur Eddington’s 1919 expedition, which confirmed and validated the predictions of Einstein’s general relativity, while disagreeing significantly with the alternative (Newtonian) predictions, was the first observational confirmation of Einstein’s new theory of gravity. The amount that starlight was deflected by during a total solar eclipse was a key prediction that was unique to Einstein’s new theory.
Credit: London Illustrated News, 1919
1.) Are they accurately representing the consensus position?
This is the simplest, first, and most straightforward sanity check: are they accurately representing the current scientific consensus that they’re seeking to overthrow, or have they replaced the actual scientific consensus with a strawmanned version of it?
Scientists, quite notoriously, are not always the most agreeable of people. We’re often painted as insufferable: always questioning everything, wondering how strongly an assertion is supported by the evidence, and what the wiggle-room is for things to be different than our current conceptions admit. It’s for these reasons that “consensus” is not an easy thing to achieve, particularly among experts.
In fact, consensus is only ever achieved if one particular explanation, framework, theory, or model is so superior to all the others, in terms of quantitatively descriptive/predictive power, that denying its conclusions would be the unscientific thing to do. The Big Bang didn’t become the consensus picture because of groupthink; it became so because its quantitative predictions for the formation of cosmic structure, the abundances of the lightest elements, and the remnant radiation from the Big Bang matched what we observed. Sure, you can always find scientists that are actively challenging the picture of the Big Bang — such challenges are always important — but they almost always misrepresent one or more of its major successes.
This image shows a blackbody spectrum at 2.998 K (blue line) and how that spectrum shifts if the Universe expands: to eventually yield a cooler blackbody of 2.725 K (black line), which is what the COBE data from the 1990s indicated. (As shown with 400-sigma error bars.) The red line corresponds to how the 2.998 K CMB would have changed under a tired light scenario: losing energy but failing to maintain its blackbody character. We can therefore determine that no more than 0.001% of the CMB can be composed of “tired light” photons.
Credit: Ned Wright’s cosmology tutoria
Every few years, someone brings back the old, discredited idea of tired light cosmology: where the redshifts we observe for distant objects aren’t due to the expanding Universe, but are instead due to the light “getting tired” and losing energy as it travels. Even more stories, and papers, arise that contend that dark matter and dark energy aren’t real, and that if more scientists shifted their perspective the way these imaginative, brilliant contrarians have done, they’d see the light, too. Or perhaps we’ve got the age of the Universe all wrong, or the nature of supernovae, or some other well-accepted component of the consensus picture.
But all of these assertions don’t hold up under even a cursory examination. Tired light would result in a different spectrum for traveling light as opposed to the emitted light: a conflict with direct observations. Dark matter makes a wide series of predictions on a variety of cosmic scales, and the full suite of those predictions remains compatible with observations, while all alternatives need to include something that behaves equivalently to dark matter in order to be consistent. (And if you still need dark matter, what bonus does your alternative even offer?) Dark energy cannot be explained away by appealing to a lumpy, inhomogeneous Universe, despite contrarian contentions that it can be.
If someone only elevates an alternative to the consensus (especially if it’s their alternative to the consensus) to prominence by misrepresenting the consensus position itself, there’s a good chance that they’re fooling themselves. Don’t let yourself be fooled as well.
This four-panel animation shows the individual galaxies present within Abell 2744, Pandora’s Cluster, alongside the X-ray data from Chandra (red) and the lensing map constructed from gravitational lensing data (blue). The mismatch between the X-rays and the lensing map, as shown across a wide variety of X-ray emitting galaxy clusters, is one of the strongest indicators favoring the presence of dark matter. The Bullet Cluster, as well as other galaxy clusters, exhibit similar features.
Credit: X-ray: NASA/CXC/ITA/INAF/J.Merten et al, Lensing: NASA/STScI; NAOJ/Subaru; ESO/VLT, Optical: NASA/STScI/R.Dupke; Animation by E. Siegel
2.) Are you reckoning with the full suite of evidence, or only with a selection of it?
This is another classic move made by those who wish to promote an alternative that simply doesn’t measure up to the consensus position: to narrow their focus to a particular area where the alternative compares favorably with the consensus position. It’s easy to find an alternative theory to the hot Big Bang if all you wanted to do was explain the abundance of the light element lithium: it’s the one element predicted by the hot Big Bang where direct observations slightly deviate from the standard nucleosynthesis predictions. However, only if you ignore the other elements (hydrogen and helium) or the other lines of evidence for the Big Bang (cosmic structure and the CMB), can alternatives compete with the hot Big Bang.
Similarly, you can concoct lots of explanations for galaxies that don’t require dark matter, so long as you ignore the larger picture: galaxy clusters, colliding galaxy clusters, and the grand cosmic web. You can concoct many superior explanations for most physical phenomena if you add additional parameters or degrees-of-freedom: parameters that are not necessary for the consensus picture. The key to any good scientific theory is to explain the full suite of data with as few variables or parameters as is absolutely necessary. If someone ignores lines of evidence that the consensus theory explains (and that it explains better than their proposed alternative), they’re not just peddling contrarianism; they’re peddling a version of it that’s pure baloney.
The central idea of the lab leak hypothesis, that the virus spilled over from the Wuhan Institute of Virology, is only possible if the virus from which SARS-CoV-2 originated was actually ever inside the institute itself. If the virus originated naturally, with parts of it found in animals that were located in a wild population in Laos, which genetic sequencing uncovered in 2021 indicates, the lab leak hypothesis is ruled out as a possibility. You cannot create something through gain-of-function research that will have an identical genetic code to something that came about in the wild through natural processes such as recombination.
Credit: S. Temmam et al., Nature, 2022
3.) Is your proposed alternative able to explain everything that the current consensus successfully explains?
Assuming someone is willing to reckon with the full suite of evidence, this is the next follow-up question that must be asked: out of all of the successful predictions that the existing consensus theory can make, does the new alternative also make successful predictions for each and every one?
This is actually a hugely informative thing to consider when it comes to one of the most hotly debated topics — not among experts, but among laypersons and politicians — here in the 2020s: the origin of SARS-CoV-2, the virus that causes COVID-19 in humans. It might seem like there are two very reasonable possible explanations for how this virus originated:
It could have come about due to natural, zoonotic spillover, where human and wild animal populations came into contact, a disease was transmitted from that animal into a human, and then human-to-human transmission occurred, kicking off what would become the largest pandemic of the 21st century so far.
Or it could have come about due to a lab leak: where a virus was brought into a lab, was possibly genetically altered while in the lab, and then a lab worker was infected through an unreported accident, infecting the first human. Then, after that, human-to-human transmission occurred, kicking off that same pandemic.
For some time, it appeared to many that both explanations were admissible. But for several years, that’s no longer been the case.
This color-coded diagram represents 15 recombinant fragments of various SARS-related beta coronaviruses compared to the original genome of SARS-CoV-2 that first infected humans. Several different strains show a “best match” for a variety of these 15 fragments, indicating a recombination-based origin for SARS-CoV-2, and refuting the feasibility of a lab creation through gain-of-function research.
Credit: S. Temmam et al., Nature, 2022
That’s because, back in 2021 and 2022, there were a series of papers that revealed the genetic sequences of the SARS-CoV-2 samples that affected humans, and also that discovered those same genetic sequences — some of which had never been seen previously — in animal populations found in the wild. Additionally, even the earliest SARS-CoV-2 sequences indicated two independent lineages for the disease that were found in humans: ⅓ of all cases belonged lineage A, while the other ⅔ belonged to lineage B. If there were one unique introduction event, as would be the case in a lab leak scenario, you would not have this diversity. Only the natural, zoonotic spillover scenario admits it.
But unless you’ve gone very deep into the weeds of the science behind the origins of COVID-19, you’ve probably never heard of either of these lines of evidence, and you probably don’t know that gain of function research has absolutely nothing to do with the pandemic’s origins. It’s only by considering all of the relevant information, and comparing the actual data we have with the scenarios offered by both the consensus and contrarian positions, that we can draw meaningful conclusions about what does and doesn’t persist as a potentially valid explanation. On scientific grounds, the lab leak origin scenario for SARS-CoV-2 fell completely apart years ago, something you’d never know from viewing the US government’s website.
For approximately a decade, Roger Penrose has been touting extremely dubious claims that the Universe displays evidence of a variety of features such as low-temperature-variance concentric circles, which arise from dynamics imprinted prior to the Big Bang. These features are not robust and are insufficient to provide support for Penrose’s assertions.
Credit: V.G. Gurzadyan & R. Penrose, Eur. J. Phys. Plus, 2013
4.) Is there a fair head-to-head test that can compare the mainstream idea with the alternative directly?
Let’s assume you have (or your favorite contrarian has) been fair up until this point. They’ve considered the full suite of evidence, they’ve been able to reproduce all of the consensus picture’s successes, and everything has accurately been represented. Now, is there some way to tell the mainstream, consensus picture apart from your own?
If the answer is no, you have a problem: the problem of untestability. This criticism has been fairly leveled at a number of popular ideas: string theory, cyclic cosmology models, different interpretations of quantum mechanics, etc. If there isn’t a fair head-to-head test to conduct, then you cannot hope to have a revolution. Unless the data comes in and favors an alternative model over the consensus model, the current consensus cannot be overturned.
When cosmic inflation was first introduced, this novel picture of our cosmic origins successfully provides explanations for three major unexplained problems of the hot Big Bang: the horizon problem (why the Universe was the same temperature in all directions), the flatness problem (why the expansion rate and the total energy density of the Universe matched so exquisitely), and the monopole problem (why there are no leftover high-energy relics if we had a very hot, dense, early cosmic state).
In the top panel, our modern Universe has the same properties (including temperature) everywhere because they originated from a region possessing the same properties. In the middle panel, the space that could have had any arbitrary curvature is inflated to the point where we cannot observe any curvature today, solving the flatness problem. And in the bottom panel, pre-existing high-energy relics are inflated away, providing a solution to the high-energy relic problem. This is how inflation solves the three great puzzles that the Big Bang cannot account for on its own.
Credit: E. Siegel/Beyond the Galaxy
However, noticing that unexplained puzzles in the consensus scenario are solved and explained in the alternative scenario is not enough. Nor is it enough to add in a successful reproduction of the consensus theory’s other predictions. Instead, it was also mandatory for new predictions to be teased out, and for those predictions to differ from the predictions of the prevailing theory. In the non-inflationary hot Big Bang versus a Big Bang set up by cosmic inflation, four key differences were identified in the 1980s and 1990s.
Whether the spectrum of seed fluctuations was scale-invariant (as predicted by the Big Bang) or with a slight departure from scale-invariance (as predicted by inflation).
Whether the fluctuations present were all adiabatic in nature (as predicted by inflation) or whether they were a mix of adiabatic and isocurvature (as predicted by the non-inflationary Big Bang).
Whether there are fluctuations on scales greater than a light signal could have traversed since the start of the hot Big Bang: super-horizon fluctuations. (Predicted by inflation, forbidden by a non-inflationary Big Bang.)
And whether the Universe achieved temperature in its past that rose up all the way to Planck energies (predicted by a non-inflationary past) or were limited to a temperature well below it (predicted by inflation).
Through direct observations and measurements, including of the Universe’s large-scale structure and the temperature and polarization measurements of the CMB, we found that inflation goes 4-for-4 on these fronts, while the inflation-free Big Bang is 0-for-4. As a result, science has definitively moved on from the hot Big Bang as our ultimate origin story to an earlier time period that preceded and set it up: cosmic inflation. Devising at least one such test is key for a fair comparison.
If one wants to investigate the signals within the observable Universe for unambiguous evidence of super-horizon fluctuations, one needs to look at super-horizon scales at the TE cross-correlation spectrum of the CMB. With the final (2018) Planck data now in hand, the evidence is overwhelmingly in favor of their existence, validating an extraordinary prediction of inflation and flying in the face of a prediction that, without inflation, such fluctuations shouldn’t exist.
Credit: ESA and the Planck collaboration; annotations by E. Siegel
5.) Are you being honest about the successes and failures of your alternative? Would those who support the consensus position agree?
If you ask this first sentence to practically anyone who’s taken up a contrarian position, you’re likely to get a vociferous “yes” answer to the first question. But that’s not going to convince others; it requires a “yes” to the second question as well. Not everyone needs to agree with the conclusions drawn by the one staking out the contrarian position, but everyone should be in agreement that:
their methods and analysis were sound,
they didn’t selectively ignore the pieces of data that undermined their position,
they considered the consensus fairly and represented it accurately,
and if someone who adhered to the consensus position discussed the successes and failures of the alternative, their take would have a lot in common with the alternative/contrarian take.
Of course, there are only a few instances in science where this actually occurs. Consensus is very difficult to achieve, and normally only arrives if there’s an overwhelming amount of evidence to support one particular theory, model, or interpretation of the data being superior to all others. Challenging that consensus is always important, but only if those challenges occur on legitimate grounds, rather than on invented ones. Passing peer review doesn’t necessarily mean that a contrarian viewpoint is legitimate; it only means that an idea has reached the threshold where at least one person has deemed it is worthy of consideration by the greater scientific community.
In this world, it’s vital that we approach scientific matters carefully: with all appropriate scrutiny and ruthless skepticism, where only the most robust ideas can survive. If an idea disagrees with reality, it’s discarded. After all, no amount of argumentation can change what reality is; it is up to us to accept and understand things exactly as they are, no matter how disagreeable it is to our intuition.