The Universe Revealed by Science

The Universe Revealed by Science
Its Tentative Character
And the Status of Older Theories

Response to a Quora Question

12/31/2019

Anil Mitra

Link https://www.quora.com/In-every-century-scientists-think-they-have-worked-out-the-universe-and-are-always-wrong-what-I-want-to-know-is-how-wrong-are-they-Are-they-always-wrong-to-the-same-degree

The Question—In every century scientists think they have worked out the universe. What is the truth of the current view given that the view changes?

Disclaimer—the answer below first appeared on Quora. Their policy, which I presume is an agreement, is that they retain non-exclusive rights to answers by members. Changes made here but not made in the Quora answer are marked in differently colored font.

The plan of this answer is to look at the history of physics to conclude that (a) scientific theories are models of the empirical universe and so they are not wrong as far as they go (and remain useful in their domain of validity), (b) theories may need revision as the empirical edge moves out, and (d) physics has a history of such revisions.

The conclusions will be (i) viewed as models theories have a domain of validity within which they are predictive and useful, (ii) above the level of the individual theories of science, the process of science (so far) has quite universal validity, but (iii) if we think of the theories so far as valid we are mistaken (definitely for older theories and very likely for the most modern theories).

Let’s first look at—

A brief history of physics as the science of the universe and its elementary entities—

· Aristotle’s ideas were not predictive because the Greeks seemed not to have appreciated the relevance of experiment. They did not realize that thought alone was not sufficient.

· Later Arabic, Indian, and European appreciated experiment and quantitative measurement in mechanics and astronomy. Galileo and Kepler (and others) got some concepts and quantitative results. For example, Kepler’s laws of planetary motion, Galileo’s law of inertia (which is Newton’s first law of motion). Galileo determined that the distance in the uniform acceleration of free fall is proportional to the square of the time.

That is, these thinkers were not just doing science—they were forging the dual experimental-conceptual nature of science.

· Newton formulates the first great synthesis in science in the late 17th century—the laws of motion and of universal gravitation. He presupposed ‘absolute’ space and time, essentially Euclidean. The strengths of his system—(i) based in the idea of continuous change (i.e. calculus, even though his work was presented as geometry, calculus is implicit) (ii) he understands that motion and force are (what we came to call) vector in character.

His system stands for about 250 years and, in his work and the work of those who followed him, subsumes motion of the solar system, motion on Earth, solid - fluid - and statistical mechanics.

His work, together with Maxwell’s electrodynamics, is so successful that it is thought of as necessarily true (Immanuel Kant thought of Euclidean Geometry and Newton’s mechanics this way) and the completion of physics (by some).

But then, famously, toward the end of the 19th century, discrepancies began to arise. I’ll not go into that bit of history here except to say that the outcome was—

· The theories of relativity and quantum theory. Because relativity shows that space-time-matter are one dynamic entity (space-time-matter interact and space-time is not Euclidean and even if it is finite it need not have an edge), they give us a theory, not just of how the universe behaves, but also of its origins (the big bang). Quantum theory begins as a theory of particles but then extends to fields, subsuming the electromagnetic, the weak, and the strong as one. We begin to think we understand the universe.

But not all is well. What is the difficulty in unifying gravity with the other three forces (it is theoretical—the methods that work for the other fields do not work for gravity… and experimental—we don’t have experiments that are sufficiently incisive to tell us in which direction theory might go)? And there are other open questions, e.g. whether the empirical cosmos is all there is. Stephen Hawking argued that because the theoretical model of the universe has an origin in time, therefore there is no origin; and some physicists agree. However, that is conceptually mistaken because it uses a conceptual model of the empirical universe to predict beyond the edge of the empirical universe. It might extrapolate beyond but we don’t know that; and history and the possibility of limitless variety suggest that it is unlikely to extrapolate beyond.

So we may now confirm the anticipated conclusions—I’ll repeat them here in italics so you don’t have to go back to the beginning to review them (i) theories are viewed as models theories and have a domain of validity within which they are predictive and useful: Newtonian mechanics and Maxwell’s electrodynamics remain useful, especially in engineering, because they are still predictive and where this is so they are simpler than relativity and quantum theory, (ii) above the level of the individual theories of science, the process of science (so far) has quite universal validity—the history revealed not only that the theories advance from one to the next but so do method and concept of what science is, but (iii) if we think of the theories so far as valid we are mistaken (definitely for older theories and very likely for the most modern theories)—as pointed out even though we know Newtonian Mechanics is inadequate for the very small and very large and high energy (quantum, relativistic) scales, it was thought of as absolute at one time. But still Newtonian Mechanics, as noted, has a domain in which it is ‘right’.

Another observation—certainly it is not “every century” that scientists think they have worked out the universe, however there is a tendency to think that way in a ‘mature’ phase of a theory or system.

Two further thoughts—(i) So (at least I hold) that it is very wrong to think our modern theories are final, either quantitatively (i.e. for prediction) or qualitatively (the nature of space, time, matter). I’ve explained why above. What is interesting to me is that we—some scientists, some philosophers, some lay persons—seem to be repeating the kind of error committed when in the 19th century people had a feeling that physics is near the end of its conceptual development. (ii) Given the possible impasse in physics, perhaps what is needed is a new approach in science—a supplement more than a replacement—for even if we are not at the end of sufficiently incisive experiment that is likely to come at some future point. What addition to the scientific toolbox might we consider without moving into mere speculation? I think that there is room for development of rational thought—in mathematics, computation and mathematics for physics, and perhaps in analytical metaphysics. The latter—analytical metaphysics—is in fact one of my interests; I anticipate sharing—publishing—it in the future.