In the last few years, it has become apparent that there are two theories of cosmology that can claim to successfully explain the observations. The standard theory is called the LCDM (Lambda-cold dark matter) model; the competing theory is called MOND, for modified Newtonian dynamics. Unlike the standard model, MOND does not postulate the existence of dark matter — the mysterious substance that comprises (according to standard-model theorists) the bulk of the mass of the universe. Observations that are explained under the standard model by invoking dark matter, are explained under MOND by postulating a modification to Einstein’s theory of gravity.
According to the standard model, the dark particles are passing through every terrestrial laboratory. But every attempt to detect them has failed. Standard-model theorists explain this fact by suggesting that the dark particles are so weakly interacting with normal matter that we can not hope to observe them, even if they are present.
Of course, both of these cosmological theories could be wrong. But at most one of them can be right. How can we determine which one?
Philosophers of science suggest an answer: by comparing methodologies. There is something approaching a consensus among philosophers that there is a “good” way and a “bad” way for theories to evolve. The “bad” way is via post-hoc accommodation: the theory is adjusted, or reinterpreted, to bring its predictions in line with each new piece of data as it becomes available. The “good” way is via prior prediction: the theory predicts facts in advance of their discovery, without (and this is crucial) any adjustments to the theory.
In this respect, the two theories are strikingly different. MOND has repeatedly made successful, new predictions, while the standard model has rarely, if ever, achieved this, at least not since the addition of dark matter to the theory around 1980.
My book is a systematic exploration of how the alternate theory has evolved, paying close attention to whether its evolution has satisfied the criteria set forth by the philosophers.
Author: David Merritt