In scientific terms, the difference is very clear - until you have evidence that supports your hypothesis, you have a question not an answer. When you have enough evidence, your hypothesis becomes a full fat theory. It's an answer, and it may or may not be completely correct 🙂.
This is what annoys me about the great Dark Matter debate. Dark Matter ( nature unknown, evidence zero ) is commonly presented as if it were the answer, merely requiring some minor detail to be filled in in order to be complete.
In actual fact, Dark Matter is very much still a hypothesis. Decades of effort, and many expensive experiments, have failed to produce any positive evidence whatsoever for it's existence. Nothing. Nada. Zilch.
It's worth considering what the question for which Dark Matter is hypothesised to be the answer actually is. The question is :
'Why do large ( galactic and cosmological ) scale structures behave in ways which are not accurately described by current gravitational theories ?'.
It should be immediately apparent that there are in fact two paths towards an answer -
There is, in fact, a well developed example of the second approach, called MOND - 'Modified Newtonian Dynamics'. In this approach, Newton's equation for gravitational force is modified by the inclusion of a term which becomes significant only at very large distances/low forces. Observational evidence for MOND waxes and wanes, but observations supporting it are still occurring . [ 2021-05-27 - large scale distribution of Dark Matter not explained by General Relativity ] [ 2022-02-04 - Galaxy types better explained by MOND]
Sure, this approach is empirical - we're changing the math to match what is observed, rather than deriving the math from something more 'fundamental'. In this sense, we have a description, not an explanation.
However, it's critical to understand that the Gravitational Constant 'G', which is used by both Newtonian math and Einstein's field equations for general relativity, is a physical constant derived from observation - i.e. we don't escape a dependency on observation and measurement by sticking to existing theory, it's empirical too.
There are even ideas that, although they depend on 'unseen' mass ( i.e. 'Dark' matter ), do not require the invention of a whole new type of particle and also do not require changes to our gravitational theories.
In the meantime, rather than sucking it up, accepting the observational evidence, and admitting that maybe a precious equation or two is missing something ( or just maybe, needs to be torn up and remade using a new paradigm for space and time ), science - and in particular the particle guys, the cosmos are a little more balanced - seems intent on finding the fairy particles at the bottom of the cosmic garden that will allow it to claim that the existing formulae were right all along.
The question is, how deep into the undergrowth is it prepared to go ? And, of course, how much will be spent on the way ?.
© Mark de Roussier 2021, all rights reserved.