Year: 2022

THE WORLD OF PROBABILITIES. “Quantum theories are conceptually very different from classical theories: in particular, the state of a system does not assign real-number values to physical quantities but only probabilities for obtaining such values if appropriate measurements are made. And, though they share with general relativity the assumption that it is appropriate to coordinatise space and time with real numbers, they do not treat gravity as curvature of the corresponding spaces: they use either Newtonian spacetime (which corresponds to a degenerate spacetime metric), or the flat metric of special relativity.” https://lnkd.in/dMm_YkR View in LinkedIn

UNRESOLVED CONFLICT. “The fact that general relativity treats matter classically, and gravity as curvature, while our best theories of matter are quantum theories using a flat metric, is enough to show that some sort of reconciliation is needed.” https://lnkd.in/dMm_YkR View in LinkedIn

THE ASSUMPTION. “Gravity is, at least prima facie, a force like the others, and these have turned out to be quantum in nature.” https://lnkd.in/dMm_YkR View in LinkedIn

VALIDITY CEASES TO EXIST. “The idea that simple manifold concepts may not apply at small distances was anticipated by Riemann in his famously prophetic Habilitationschrift of 1854: “Now it seems that the empirical notions on which the metrical determinations of space are founded, the notion of a solid body and of a ray of light, cease to be valid for the infinitely small.” https://lnkd.in/dMm_YkR View in LinkedIn

THE KNOT. “Space and time are such crucial categories for thinking about, and describing, the empirical world, that it is bound to be ferociously difficult to understand their emerging, or even some aspects of them emerging, from ‘something else’.” https://lnkd.in/dMm_YkR View in LinkedIn

THE GREAT UNKNOWN. “The difficulties arise from the inaccessibility of the Planck scale (at least, in regard to terrestrial experiments), and the associated lack of any specific data to guide theoretical speculations.” https://lnkd.in/dMm_YkR View in LinkedIn

WHERE WORDS FAIL. “This inaccessibility not only implies a lack of data. It is so extreme that it suggests that those aspects of reality that require a theory of quantum gravity for their description hardly deserve such names as ‘appearance’, ‘phenomenon’, or even perhaps ‘empirical reality’.” https://lnkd.in/dMm_YkR View in LinkedIn

EXPECT THE UNEXPECTED. “Our predicament is aggravated by the continuum model of spacetime being so crucial to our normal physical description of the world. So we must be wary of assuming that the emergence of time will be like more familiar cases of emergence.” https://lnkd.in/dMm_YkR View in LinkedIn

SO ENDS this first of two weekends on a wonderful paper. Dr Jeremy Butterfield" "Senior Research Fellow, Trinity College, Cambridge, MA, PhD, FBA was interested in philosophical aspects of quantum theory. I incorrectly assigned the authorship of this paper to Professor Sir John Butterfield, the diabetologist in the introduction, and made an error. Professor Jeremy Butterfield’s research centers faround a variety of topics in the philosophy of physics and philosophy of science, and he has also made contributions to the philosophy of language and logic, particularly with regard to the treatment of time and tense. https://en.m.wikipedia.org/wiki/Jeremy_Butterfield View in LinkedIn

THE CENTRAL DOGMAP. “FIGURE 99. An analogy is established between two fundamental Tangled Hierarchies: that of molecular biology and that of mathematical logic. (Page 528). https://lnkd.in/dmfn9qW View in LinkedIn