Science is taught like world history with special deference to the winners of major disputes independent of the retrospective merits of either side. Unlike history, however, science can and must eventually alter mistaken decisions made in the past. Science is different in that way – it should be different. Shouldn’t it? At what point should one cease to challenge an accepted but incomplete and inconsistent theoretical notion, a year, a decade, a century? What is the ‘use-by’ date for unanswered, even if unasked, questions?
Unanswered questions persist. What if one had taken another path based on other assumptions, leaving a different set of questions unanswered? What if one had persisted in considering the rejected assumptions even without accepting them. Might one in retrospect have come up with a better theory just by wondering why others had accepted them and addressing their rationale? If Einstein’s common-sense assumption of the “law of the transmission of light” with his “rays” of light had been questioned more persistently, the theory might have had a firmer physical basis rather than a strictly mathematical formulation to account for observations. There was no law of the transmission of light. In light of his discovery of the photo electric effect, quantum theory, and Lewis’s later considerations regarding the double-ended nature of what by then were considered ‘photons’ of light, the theory might have incorporated the observational indeterminacy of transaction geometry rather than a deterministic spacetime.
Students of a scientific discipline are sometimes confused about why the original investigators made this assumption rather than that one or accepted oneconstraint rather than another. ‘Validation’ by instrumental success causes their doubts to dissipate. By accepting legitimacy of decisions made at every juncture, the student eventually understands all the mechanisms and becomes adept at applying the resulting theory. He or she comes to believe that there was no other viable approach to solving related problems, eventually becoming the professor and mentor of a next generation. In world history genocide by ‘winners’ precludes a going back. Science should not preclude it. But graduate students who began publishing as members of long lists of contributors to technical papers, eventually became recognized professors in their own right and headlined publications.
Similar to Einstein’s acceptance of a commonsense notion carried forward into an innovative domain, the Doppler effect has long been accepted as the common-sense rationale for all spectral shifts of known sources of radiation. The spectra of similar galaxies seen to have shifted spectra therefore gave rise to the assumption of galaxy motions to account for their red shift. With Hubble’s observations, the assumption grew to an expanding universe. And that to acceptance of four dimensional ‘space’ with everything moving away from everything in ‘spacetime,’ assumptions reaffirming each other. A Big Bang became necessary.
With success, Hubble’s endeavor became much more significant. Surveys were made of galaxies plotted, in angle versus redshift space; the Sloan Digital Sky Survey-V (SDSS-V) was the first to provide spectroscopic plotting of galaxies across the entire sky. Suddenly, a new phenomenon appeared. Vast numbers of galaxies were seen to align along lines of sight out through the universe. Why? Why should they align like spokes in a wheel with us at the center? Had Copernicus been wrong all along? That possibility repelled scientific minds. These, sacrilegiously named, Fingers of God (FoG) needed a more scientific explanation. A commonsense explanation was immediate. These tightly grouped galaxies must be gravitationally bound clusters whose total mass propels orbital motions whose projected velocities along our line of sight must induce a cluster-unique Doppler redshift of the clustered galaxies over and above the ‘comoving’ expansion velocity of the universe itself. And just as Kepler determined masses of the planets, the virial theorem supports the determination of the mass of clusters based on motions of the galaxies. But there is a problem. A big problem. There isn’t enough mass.
‘Missing mass’ was an untenable problem; the explanation does not work without more mass, but the concept of what we call mass was tied up with the Periodic Table of the elements. Each element has its characteristic spectra that together make up the spectrum of the stars and galaxies. For all astronomical objects like our sun, other stars, and galaxies there is a total amount of luminosity of emitted radiation. There is in addition a ratio of mass-to-luminosity for these objects – galaxies in particular. This amount of luminosity in galaxy clusters collaborated that there isn’t enough of what we have long considered to be mass to account for the velocities of the orbiting galaxies.
Somewhere along the line, the missing matter was assumed to be present even if we couldn’t see it because it doesn’t emit or reflect light. It’s just like a pretend childhood friend. It got a name, ‘dark matter,’ and everyone assumes that it’s real because we need it, if our previous assumptions are valid. Introduced to satisfy the perceived need for additional mass to account for what were apparently gravitational effects, it is now ‘accepted’ to constitute between two and three times as much mass as categorized in the Periodic Table. And we still don’t know what it is. The hope has been that someday someone will determine exactly what it is, whether it is hot or cold, etc. A consensus is that it must be cold, since there is no radiation emission or absorption, i.e., it is thermodynamically inactive, so how could it be ‘hot.’ Here we are, well on in the twenty first century still wondering what ‘dark matter’ is – a century after its introduction and continued instrumental success.
What if, like adults who abandon their imaginary childhood friends, we address why we had them – what need they provided. What was the necessity and what were the assumptions? Maybe assuming that recessional motion is the only explanation of redshifted spectra was wrong. Then the galaxies may not be traveling that fast and there is no ‘missing’ mass, the mass we ‘see’ is all that is gravitationally required.
What if?
That question and an unbiased endeavor to answer it is what we call science. But is that an accurate description?
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