A Philosophical Approach to MOND: Assessing the Milgromian Research Program in Cosmology

285 Pages·2020·2.524 MB·English

by  David Merritt

A PHILOSOPHICAL APPROACH TO MOND
Dark matter is a fundamental component of the standard cosmological model, but
inspiteoffourdecadesofincreasinglysensitivesearches,no-onehasyetdetecteda
singledarkmatterparticleinthelaboratory.Analternativecosmologicalparadigm
exists: MOND (MOdified Newtonian Dynamics). Observations explained in the
standard model by postulating dark matter are explained in MOND by proposing
a modification of Newton’s laws of motion. Both MOND and the standard model
have had successes and failures – but only MOND has repeatedly predicted
observational facts in advance of their discovery. In this volume, David Merritt
outlines why such predictions are considered by many philosophers of science to
be the ‘gold standard’ when it comes to judging a theory’s validity. In a world
where the standard model receives most attention, the author applies criteria from
the philosophy of science to assess, in a systematic way, the viability of this
alternativecosmologicalparadigm.
david merritt was a professor at the Rochester Institute of Technology, and
beforethatatRutgersUniversity,whoseresearchinterestsincludegalaxydynamics
and evolution, supermassive black holes, and computational astrophysics. He
is a former Chair of the Division on Dynamical Astronomy of the American
Astronomical Society and is a founding member of the Center for Computational
RelativityandGravitationatRIT.HeisauthorofthegraduatetextbookDynamics
andEvolutionofGalacticNuclei.

A PHILOSOPHICAL APPROACH
TO MOND
Assessing the Milgromian Research Program in Cosmology
DAVID MERRITT
RochesterInstituteofTechnology,NewYork
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There are different sorts of conflicts between theories. One familiar kind
of conflict is that in which two or more theorists offer rival solutions of
thesameproblem.... often,naturally,theissueisafairlyconfusedone,in
whicheachofthesolutionsprofferedisinpartright,inpartwrongandin
partjustincompleteornebulous.Thereisnothingtoregretintheexistence
of disagreements of this sort. Even if, in the end, all the rival theories but
onearetotallydemolished,stilltheircontesthashelpedtotestanddevelop
thepoweroftheargumentsinfavourofthesurvivor.
(Ryle(1954))
Horatio:Odayandnight,butthisiswondrousstrange!
Hamlet:Andthereforeasastrangergiveitwelcome.
Therearemorethingsinheavenandearth,Horatio,
Thanaredreamtofinyourphilosophy.
(Hamlet,ActI,scenev)

Contents
Preface pageix
1 TheEpistemologyofScience 1
2 TheMethodologyofScientificResearchPrograms 20
3 TheMilgromianResearchProgram 43
4 TheoryVariantT :TheFoundationalPostulates 54
0
5 TheoryVariantT :ANon-relativisticLagrangian 82
1
6 TheoryVariantT :ARelativisticTheory 117
2
7 TheoryVariantT :AModifiedHardCore 181
3
8 Convergence 204
9 Summary/FinalThoughts 223
References 237
Index 265
vii

Preface
Some species of ant, bee and termite are ‘eusocial’: they live in colonies of
overlapping generations in which all the offspring are produced from one or a
few individuals (the queen bee, for instance) while the other, non-reproducing
membersofthecolonydevotetheirlivestoselflessbehavior,protectingthecolony
andcollectivelyrearingtheyoung.Explanationsfortheoriginofeusocialbehavior
start from the observation that eusocial insects share a large fraction of their DNA
with the other members of the colony – in the case of honeybees, the degree of
relatedness is 75%. Worker bees can pass on more of their genetic material by
helping their ‘sisters’ than by having offspring of their own, and natural selection
responds to this state of affairs by endowing them with the motivation to act
altruisticallytowardtheotherbeesinthecolony.
InMay1976,thebiologistRichardAlexandergavealectureatNorthernArizona
University on eusociality in which he tried to explain why it had never evolved in
vertebrates. As a thought experiment, he speculated on what a eusocial mammal
might be like. The need to accommodate a large and growing colony would favor
subterranean rodents. He predicted that the ideal niche would be tropical and that
the burrowing rodents would prefer to live in heavy clay soil that is inaccessible
to most predators, and to feed on large tubers. And of course there would be one
‘queen’ rodent that gave birth to all of the offspring, who would behave altruisti-
cally toward each other. After the lecture, Alexander was surprised to be told by a
member of the audience that he had just given a perfect description of the naked
mole-rat,aspeciesnativetoEastAfricaandwhichhadjustbeguntobestudiedby
biologists(Shermanetal.,1991,p.vii–viii).
Scientists tend to be very impressed by episodes like this. It is hard to believe
thatthetheoryonwhichAlexander’spredictionwasbased–inthiscase,Darwin’s
theoryofevolutionbynaturalselection–couldbeverywrongifitcorrectlypredicts
somethingasaprioriunlikelyasanakedmole-rat.
There is a research tradition in cosmology that has been repeatedly successful
in just this way, correctly predicting facts and relations – some quite surprising –
in advance of their discovery. I am not referring here to the standard model of
ix