Read Frank Close on what happens when you can't test a theory
Experiment and observation lie at the heart of science. Ideas that are consistent with everything—positive and negative—that nature says about them, are empty; ideas that cannot be tested against nature lie under suspicion until some way of subjecting them to empirical interrogation is devised. That is the bottom line.
What, then, are we to say when enquiry in science has gone beyond the current limits of experiment, and is afloat in an ocean of possibilities too deep for such anchorage? In the article above, Frank Close identifies string theory and multiverse theory as examples of speculation in fundamental physics and cosmology respectively, where the ideas in play cannot be subjected to experimental test. Are they science at all?
A distinction is required between hypotheses for which, as a practical matter, experiment cannot (yet) be done because of cost or size constraints, and those speculations for which it is in principle impossible to devise a test. As a matter of scientific policy it is questionable whether we should ever say that experiment is “in principle impossible”; human ingenuity, discoveries elsewhere in science, empirical demolition of parts of currently accepted theory which underlie the speculations in question, and more, could change things.
The key to worthwhile speculation—using this word to denote the formulation of adventurous or seemingly-wild hypotheses that cannot be subjected to experimental test—is the nature of its connection to already-tested theory. Disciplined inference from current theory into the landscape of possibilities that it suggests is more than acceptable; it is necessary. That is how new lines of enquiry are found. When a field of enquiry has reached an experimental limit the number of possible ways forward increases, and with them the role of imagination—which is what is happening in the fields mentioned by Close. But if the speculation is to some degree constrained by keeping in sight current theory, if it “saves the appearances” as Aristotle long ago demanded of all hypothesis-formulation, and does not premise itself on notions that have no likelihood from current perspectives, then it merits the name of science.
New departures might end by revising current science, or arrive at a point very far from present theory, perhaps overthrowing it altogether. The idea that there should always be a plausibility-endowing link to current understanding is not intended to make any of this impossible. It is rather that the conceptual journey to a point beyond current theory has to be linked to the latter by explicable steps; we see (in the usual case) how theory evolves and adapts, or why new evidence and better reasons may require replacing an existing paradigm. If the experiments at Cern had not detected the Higgs boson, thus completing the current standard model, an exciting new quest to understand how elementary particles acquire mass would have begun. There were various speculations on this before empirical confirmation of the Higgs predictions was gained. But none of them involved ideas wholly disconnected from what experiment had so far revealed. No one was tempted to explain why electrons are far less massive than nuclear particles by speculating that (say) large gnomes sit on protons and neutrons and little gnomes sit on electrons.
The beautiful mathematics that suggest a vast landscape of ideas surrounding string theory is not mere fancy; the speculations have their roots (somewhat distantly, it is true) in the standard model. Likewise, puzzles about dark matter and dark energy, and why the constants of nature have the values they do, make multiverse theory intriguing. But in neither case is experiment and observation, even if indirect and requiring extremely subtle detective work, ruled out in principle. It is this all-important fact that makes not science fiction, but science proper.
AC Grayling is a philosopher
Experiment and observation lie at the heart of science. Ideas that are consistent with everything—positive and negative—that nature says about them, are empty; ideas that cannot be tested against nature lie under suspicion until some way of subjecting them to empirical interrogation is devised. That is the bottom line.
What, then, are we to say when enquiry in science has gone beyond the current limits of experiment, and is afloat in an ocean of possibilities too deep for such anchorage? In the article above, Frank Close identifies string theory and multiverse theory as examples of speculation in fundamental physics and cosmology respectively, where the ideas in play cannot be subjected to experimental test. Are they science at all?
A distinction is required between hypotheses for which, as a practical matter, experiment cannot (yet) be done because of cost or size constraints, and those speculations for which it is in principle impossible to devise a test. As a matter of scientific policy it is questionable whether we should ever say that experiment is “in principle impossible”; human ingenuity, discoveries elsewhere in science, empirical demolition of parts of currently accepted theory which underlie the speculations in question, and more, could change things.
The key to worthwhile speculation—using this word to denote the formulation of adventurous or seemingly-wild hypotheses that cannot be subjected to experimental test—is the nature of its connection to already-tested theory. Disciplined inference from current theory into the landscape of possibilities that it suggests is more than acceptable; it is necessary. That is how new lines of enquiry are found. When a field of enquiry has reached an experimental limit the number of possible ways forward increases, and with them the role of imagination—which is what is happening in the fields mentioned by Close. But if the speculation is to some degree constrained by keeping in sight current theory, if it “saves the appearances” as Aristotle long ago demanded of all hypothesis-formulation, and does not premise itself on notions that have no likelihood from current perspectives, then it merits the name of science.
New departures might end by revising current science, or arrive at a point very far from present theory, perhaps overthrowing it altogether. The idea that there should always be a plausibility-endowing link to current understanding is not intended to make any of this impossible. It is rather that the conceptual journey to a point beyond current theory has to be linked to the latter by explicable steps; we see (in the usual case) how theory evolves and adapts, or why new evidence and better reasons may require replacing an existing paradigm. If the experiments at Cern had not detected the Higgs boson, thus completing the current standard model, an exciting new quest to understand how elementary particles acquire mass would have begun. There were various speculations on this before empirical confirmation of the Higgs predictions was gained. But none of them involved ideas wholly disconnected from what experiment had so far revealed. No one was tempted to explain why electrons are far less massive than nuclear particles by speculating that (say) large gnomes sit on protons and neutrons and little gnomes sit on electrons.
The beautiful mathematics that suggest a vast landscape of ideas surrounding string theory is not mere fancy; the speculations have their roots (somewhat distantly, it is true) in the standard model. Likewise, puzzles about dark matter and dark energy, and why the constants of nature have the values they do, make multiverse theory intriguing. But in neither case is experiment and observation, even if indirect and requiring extremely subtle detective work, ruled out in principle. It is this all-important fact that makes not science fiction, but science proper.
AC Grayling is a philosopher
