Draft:Planck-scale physics
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Comment: There is already an article Planck units, so please do not resubmit this. Ldm1954 (talk) 09:18, 24 April 2025 (UTC)
- Comment: This is a essay, not an encyclopedia article. Physics is facts, not opinions such as this which is really WP:OR and synthesis WP:SYNTH. I was very tempted to completely reject this. I suggest asking for help at WT:Physics Ldm1954 (talk) 08:48, 24 April 2025 (UTC)
Planck-scale physics is the field of physics that studies the fundamental constituents of space and matter and their interactions. Like atomic physics it was long a topic of imagination before coming to be seen as fundamental.
The idea that matter might have a tiny structure may have originated with Leucippus and Democritus in ancient Greece in the 5th century BCE. The idea that space itself might have a granular structure was first documented in the mid-18th century by Bernhard Riemann. He said whether to regard space as continuous or granular was a choice to be made on the basis of experience.[1]
The Planck Constant
[edit]In 1901 Max Planck derived an equation to fit increasingly precise and extensive data for black-body infra-red radiation at various frequencies over a range of temperatures.[2] It required two constants to fit the data. One was the Boltzmann constant. The other, which came to be known as the Planck constant, had the dimensions of action or energy times time and a magnitude far smaller than any known physical event.
The Planck constant soon took on a pivotal role in equations of the emerging field of quantum theory but its physical meaning remained mysterious. Planck was convinced it was fundamental. He later recalled that, "[O]n the very day when I formulated this law, I began to devote myself to the task of investing it with a true physical meaning."[3] His son Erwin reported that he said "he had made the greatest discovery in physics since Newton."[4]
He combined his constant with two other fundamental constants (the gravitational constant and the speed of lightto derive soon-to-be-eponymous fundamental units of length, mass, time, and temperature, which he said, "retain their meaning for all times and for all cultures, including extraterrestrial and non-human ones, and which can therefore be described as 'natural units of measurement.'"[5]
The Planck constant provided the mathematical foundation for treating physical phenomena like energy or angular momentum as discontinuous entities in continuous space.
With few exceptions, physicists continued to use the infinitesimal calculus of Isaac Newton and Gottfried Wilhelm Leibniz, which is based upon continuous space and time that, following the works of Albert Einstein[6] and Hermann Minkowski[7], morphed into continuous spacetime.
Einstein's contributions
[edit]Einstein's theories of relativity were based on a continuum but he privately admitted to doubts that quantum physics could be compatible with continuous space, saying, "[P]erhaps the success of the Heisenberg method points to ... the elimination of continuous functions from physics. Then, however, we must also give up, on principle, the space-time continuum."[8]
His efforts to establish a mathematical foundation for granular space were unsuccessful: "But for this we unfortunately are still lacking the mathematical form. How much I have toiled in this direction already!"[9] But he foresaw that eventual success would displace his theories: "I consider it as entirely possible that physics cannot be based upon ... continuous structures. Then nothing will remain of my whole castle in the air including the theory of gravitation, but also nothing of the rest of contemporary physics."[10]
Einstein struggled to grasp the implications of the fundamental constant his mentor Planck had discovered, saying, "It was as if the ground had been pulled out from under one, with no firm foundation to be seen anywhere, upon which one could have built."[11]
Fundamental Physics
[edit]The meaning of Planck's units long remained obscure. In 1964 physical chemist Alden Mead inadvertently reinvented the Planck length and later said that "few [physicists] took seriously the idea of L as a possible fundamental length. The view was nearly unanimous ... that the Planck length could never play a fundamental role in physics."[12]
In the latter 20th century physicists sought to reconcile general relativity with quantum theory, devising several approaches under the broad title quantum gravity. Carlo Rovelli explained that "Quantum Gravity is ... the study of the structure of spacetime at the Planck scale."[13] One of the new approaches, string theory, depicts particles as tiny strings. Its mathematics feature a tiny six-dimensional space called a Calabi-Yau manifold or threefold. String theories do not require the manifold to be a real entity but its scale and that of strings are generally assumed to be the Planck length.[14] Loop quantum gravity is another approach to reconciling relativity with quantum theory. It depicts space and time as a network of tiny loops at Planck scale and any smaller scales as being meaningless. In a related development, Sundance Bilson-Thompson proposed a topological model in which the sixteen subatomic particles of the Standard Model were all composed of braided pairs of a single entity, a half twist (denoted a tweedle) in a two-dimensional "ribbon" with interactions at Planck scale.[15]
These approaches to fundamental physics confer physical meaning on Planck-scale entities and their interactions as Planck anticipated, saying in 1948: "I now knew for a fact that the elementary quantum of action played a far more significant part in physics than I had originally been inclined to suspect."[3]
The Post-empiricism Controversy
[edit]Physics at Planck-scale is far beyond the reach of direct experimental testing. Giovanni Amelino-Camelia wrote that, "Unfortunately it is not unlikely that experimenters might never give us any clear lead toward Quantum Gravity, especially if our intuition concerning the role of the tiny Planck length . . . turns out to be correct."[16] Some question whether Planck-scale physics is really physics.[17] George Ellis said, "The energy scales characterizing string theory are so high that it cannot be tested by any particle collider that we can ever hope to construct.... If we can’t ever hope to test the theory experimentally, is it really scientific?"[18] Others suggest a relaxation of the need for experimental testing of theories, a trend known as post-empiricism. Joseph Polchinski said, "The energy scales characterizing string theory are so high that it cannot be tested by any particle collider that we can ever hope to construct. . . . If we can’t ever hope to test the theory experimentally, is it really scientific? There is a danger of defining science too rigidly, so that one might decree that any discussion of the physics at 10-33 cm is unscientific because it is beyond reach of direct observation."[19]
Economic Potential
[edit]Former Greater London principal economist Alan Freeman estimated the potential economic impact of Planck-scale physics as "a quarter-century-long improvement in the well-being of the planet between 50 and 100% of its (presently $80 trillion per annum) economy."[20]
References
[edit]- ^ Riemann, Bernhard (1867). "On the Hypotheses Which Lie at the Foundation of Geometry". Nature. 8: 14.
- ^ Kuhn, Thomas (1978). Black-Body Theory and the Quantum Discontinuity, 1894–1912, (Oxford: Oxford University Press), repr. with new Afterword (Chicago: University of Chicago Press, 1987).
- ^ a b Planck, Max (1948). “A Scientific Autobiography,” in F. Gaynor, transl., M. von Laue, ed., Scientific Autobiography and Other Papers, (New York: Philosophical Library, 1949), p. 13.
- ^ Hermann, Armin (1973). Max Planck in Selbstzeugnissen und Bilddokumenten, (Hamburg: Rowohit), p. 29.
- ^ Planck, Max (1899). "Über irreversible Strahlungsvorgänge," Sitzungsberichte der Königlich Preussischen Akademie der Wissenschaften zu Berlin, (Sessional Reports of the Royal Prussian Academy of Science), Part 1, p. 440.
- ^ Gutfreund, Hannoch (2011). Notes in Einstein’s Masterpiece: The Foundation of General Relativity, (Jerusalem: Israel Academy of Sciences and Humanities), p. 83.
- ^ Minkowski, Hermann (1908). Address to the Gesellschaft Deutscher Naturforscher und Ärtze, 21 September; repr. as "Raum und Zeit," Jahresbericht der Deutschen Mathematiker-Vereinigung, (1909) 18: 75.
- ^ Einstein, Albert (1936). "Physics and Reality". J. Franklin Inst. 221 (March): 349. Bibcode:1936FrInJ.221..349E. doi:10.1016/S0016-0032(36)91047-5.
- ^ Einstein, Albert (1917). Letter to Walter Dällenbach, in A. M. Hentschel, transl., The Collected Papers of Albert Einstein, Vol. 8, The Berlin Years: Correspondence, 1914–1918, (Princeton: Princeton University Press, 1995), p. 285.
- ^ Einstein, Albert (1954). Letter to Michele Besso, quoted and transl. in J. Stachel, "Einstein and the Quantum," in R. G. Colodny, ed., From Quarks to Quasars: Philosophical Problems in Modern Physics, (Pittsburgh: University of Pittsburgh Press, 1986), p. 380.
- ^ Einstein, Albert (1949). "Autobiographical Notes," in P. A. Schilpp, trans. and ed., Albert Einstein: Philosopher-Scientist, (London: Cambridge University Press), p. 3; repr. in S. W. Hawking, ed., A Stubborn and Persistent Illusion: The Essential Scientific Works of Albert Einstein, (London: Running Press, 2007), p. 339.
- ^ Mead, C. Alden (2001), “Walking the Planck Length Through History,” Phys. Today, 54: 15.
- ^ Rovelli, Carlo (2000). “Unfinished Revolution.” in D. Oriti, ed., Approaches to Quantum Gravity: Toward a New Understanding of Space, Time and Matter (Cambridge: Cambridge University Press), p. 5.
- ^ Becker, Katrin; Becker, Melanie; Schwarz, John (2006). String Theory and M-Theory: A Modern Introduction, (New York: Cambridge University Press).
- ^ Bilson-Thompson, Sundance; Markopoulou, Fotini; Smolin, Lee (2007). "Quantum Gravity and the Standard Model," Class. Quantum Gravity, 24: 3975.
- ^ Amelino-Camelia, Giovanni (2009). “Quantum Gravity Phenomenology,” in Oriti, Daniele (ed.) (2009). Approaches to Quantum Gravity: Toward a New Understanding of Space, Time and Matter, Cambridge: Cambridge University Press, p. 427.
- ^ Smolin, Lee (2007). The Trouble with Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next, New York: Mariner Books.
- ^ Ellis, George (2013). “Theories Beyond Testability?,” Science, (2013) 342: 934
- ^ Polchinski, Joseph (2015). “Why Trust a Theory? Reconsidering Scientific Methodology in Light of Modern Physics,” meeting on String Theory to the Rescue, Ludwig Maximilians University, Munich, 7-9 December; https://arxiv.org/abs/1512.02477; https://videoonline.edu.lmu.de/de/node/7491; accessed 18 April 2025
- ^ Freeman, Alan (2016). "A Penny for Your Thoughts: A Note on the Impact of Ideas", Academia, https://www.academia.edu/30225601/A_Penny_for_Your_Thoughts_a_Note_on_the_Impact_of_Ideas; accessed 18 April 2025.