Archive: Physics

The BEHGHK particle

In advance of the big announcement from LHC, here are some links to information about the Higgs boson.
John Conway explains, in “Higgs 101” at Cosmic Variance, why physicists think there has to be a Higgs field and a corresponding particle
The so-called “Higgs mechanism”, by which massive particles receive their mass, consists in the force of the field being “felt” by those particles as resisting their motion (as a ping-pong ball immersed in water “feels” the resistance of the water, and—in good Aristotelian fashion—therefore moves at finite speed). The Higgs mechanism “breaks” an original symmetry among fundamental particles, so that some, like the proton and electron, have mass and some, like the photon, don’t. Only massless particles can travel at the speed of light; all others must move more slowly.
(the “carrier” of the field, as the photon is the carrier of electromagnetic fields, and the hypothetical graviton of gravitational fields). This is not for the totally naïve, but if you have a decent impressionistic grasp of high-energy physics, Conway’s piece will give you a good account of the importance of the Higgs particle to the so-called “Standard Model” in fundamental physics. Were it not to exist, that model would have to be radically revised.
See also the video at PhD Comics. The viXra.org blog has a nice list of papers on electroweak symmetry and symmetry breaking, from Heisenberg in 1928 to Ellis, Gaillard, and Nanopoulos in 1976, which initiated discussion of ways to detect the Higgs particle.
Skulls in the Stars notes that the hypothesis of the existence of the symmetry-breaking mechanism was put forward almost simultaneously by six physicists in three groups,
Peter Higgs. Source: APS.
all of whom published their work in Physical Review Letters in 1964. One of the six, Carl Richard Hagan, was among the teachers of the author of Skulls, whose account of the graduate students’ relative ignorance of their teachers’ eminence, and of their consuming interest in gossip about those same teachers, sounds very familiar.
All six co-discoverers of the Higgs mechanism were awarded the Sakurai Prize in 2010. But only Higgs’s name is used to designate the particle (on the controversy surrounding the naming of the Higgs, see Alasdair Wilkins’ piece at io9)—this even though the paper by Robert Brout and François Englert, which also put forward the hypothesis of a symmetry-breaking mechanism responsible for creating mass, was published several months earlier. It did not, however, explicitly mention the particle.
Guralnik & Hagan in 1961
Baron May of Oxford, Guralnik, Hagan (1961).
Source: Guralnik 2011.
Another group of three physicists, Tom Kibble, Gerald Guralnik and Carl Hagen, finished their paper on the symmetry-breaking mechanism just as the other papers were being published (see Guralnik’s history of his group’s contribution; also Guralnik 2009). In his detailed analysis of the three papers, Guralnik holds that only his group had a complete solution to the problem of explaining spontaneous symmetry-breaking; the earlier papers did not (2009:19–20). The moral, perhaps, is that the best presentation of a hypothesis need not be the best-known: celebrity, like grace, tracks works only imprecisely.

LinkJuly 4, 2012

Year of Physics — Quantum Diaries

Physics · Science ·· More from June 2005
Well, the year’s half over, but it’s never too late (until New Year’s) to start reading the Quantum Diaries, a collection of weblogs by physicists around the world. It’s refreshingly multilingual, though (I suppose because the lingua franca of physics is now English) many of the weblogs are in English.

LinkJune 28, 2005

Really Big Science (and really small minds)

Physics · Science ·· More from June 2005
The universe is very flat and very smooth. By “flat” the physicist means that if you take regions whose dimensions are “small” (for a cosmologist, small is something like 108 lightyears, or 100 times the distance to the Andromeda galaxy)
Addendum 30 Jun: I just came across a page according to which “local” in discussions of dark energy, the cosmological constant, and so on means 10 billion (1010) light-years. See News of the Universe and search on “within about 10 billion”. The diameter of a proton is between
.8 and .9 femtometer (=10-15 meter).
One light-year is
9.5 · 1015 meters.
A light-year is proportionately about as much greater in length than a person as a person is greater than a proton. 10 billion is roughly the ratio between a person’s height and the diameter of a carbon atom (2.2 · 1010 meters).
, space looks like the Euclidean space of high-school geometry—the angles of a triangle add up to 180° and so forth. “Smooth” means that the distribution of matter is uniform except at very large scales; the universe near the beginning must be smooth enough to account for the distribution we now observe, but lumpy enough to allow for the formation of galaxies. The favored explanation for both flatness and smoothness is that at a very early period in its history the universe expanded enormously over a short period of time, and then slowed down to its present more sedate rate of expansion.
Present-day theories of inflation begin with a proposal by Alan Guth in 1979, and have since been incorporated into various Grand Unified Theories that attempt to give a single account of all the forces of nature (gravitational, strong, weak, electromagnetic). At first blush inflation looks like an ad hoc addition to the then standard history of the universe, beginning with the Big Bang. But its predictions concerning fluctuations in the omnipresent microwave background (the 3° K. “black-body” radiation, discovered in 1964–1965 by Arno Penzias and Robert Woodrow Wilson, that pervades the heavens) have been borne out by recent observations (see the Cosmic Background Explorer or the COBE page at NASA).
Fluctuations in the microwave background from four years of observations by the Differential Microwave Radiometers on COBE. Source: CMB Astrophysics Research Program.
μK = microkelvins (10-6 °C)
As Guth says of the fluctuations, "I really never thought that anybody would ever actually measure these things … now they're measuring them with such high precision—it really is just fantastic" (Castelvecchi, “Growth”). The density fluctuations show up at a scale of 10-5 (by comparison the smallest or “just noticeable” difference in the human perception of brightness is roughly 10-2).
The 45% of Americans who agree that “God created human beings pretty much in their present form at one time within the last 10,000 years or so” are effectively casting aside most of the last two centuries of physics, observational and theoretical astronomy, and cosmology. Not just particular claims about the age of the universe, but the science behind them. We have got the basic features of the micro- and macrocosm basically right at what might be called the “middle” scale: from galaxies, say, to the nucleus of the atom. From that we can infer with great confidence that our instruments are reliable, and thus that the theories which explain results obtained by the use of those instruments are well-confirmed. Conversely, to engage in the kind of radical doubt—for that is what is required—according to which an error of six orders of magnitude in the age of the universe is possible (1010 years, according to the scientists, 104 according to 45% of Americans) would require giving up an enormous mass of middle-level theory.
The question “What is the composition of the Sun?” and the question “Why is the composition of the Sun what it now is?” (where a genetic answer is expected) are indeed logically distinct. I noted earlier that in the evangelical Christian universities there is a tendency to isolate the synchronic from the diachronic in biology: molecular biology but not evolution. A science that had very little notion of what in the nineteenth century came to be called “development” (not only in biology, but in geology, cosmology, and the human sciences, including the study of religion) is certainly possible. Until the seventeenth century, natural philosophy hardly concerned itself with development. The difference now is that science has pervasively taken up notions of development; to do away with that would require an enormous forgetting, not to mention outright suppression of inquiry. There are indications that some Christian groups are not averse to curtailing the discussion of “origins” in public school teaching: would they go so far as to forbid it in science generally?
  • Inflationary Cosmology
    Charles J. Peterson. A basic outline of the problems and their solution in Grand Unified Theories. Less technical and less nuanced than Watson.
  • An exposition on inflationary cosmology
    Gary Scott Watson. A detailed account, intended to be accessible to undergraduates (meaning, I think, undergraduate physics majors). Even if equations are Greek to you (make that Cherokee for the Greek readers), the last line of the summary ought to give you something to think about.
  • The growth of inflation
    Davide Castelvecchi. From Symmetry, Dec 2004–Jan 2005. A survey, written at New Scientist level, of recent experimental results pertinent to inflation. Symmetry is published by Fermilab and SLAC. It covers developments in high-energy physics, especially experimental. See, for example, Kurt Riesselmann, “The elusive neutrino”, on “neutrino oscillations”—spontaneous transformations of neutrinos from one to another of the three kinds now thought to exist.
    When I was growing up there was just one neutrino, not three, and so of course no oscillations. The neutrino (or rather a neutral particle at first not well distinguished from the neutron) was proposed by Wolfgang Pauli in 1930 to account for the apparent violation of the law of conservation of energy in the β-decay of certain radioactive atoms. The first “direct” observations of neutrinos were made in 1956 by Reines and Cowan (Franklin Are there…? ch. 5.2). By the 1990s, neutrinos were being used to “observe” the interior of the Sun. See Alain de Bellefon, “Le neutrino, particule fantôme”, Didier Verkindt “History of the neutrinos”, and especially Allan Franklin, Are there really neutrinos? An evidential history (Perseus Book Group, 2001) · 0738202657 at Best Book Buys, isbn.nu, Powells, ABE.
  • The Big Questions
    Phillip Adams and Paul Davies. Davies, a physicist and cosmologist, discusses a variety of fundamental questions concerning the origin of the universe and its fate long hence.
  • “[One-]Third of Americans Say…
    “…Evidence Has Supported Darwin's Evolution Theory/Almost half of Americans believe God created humans 10,000 years ago”. Frank Newport. Gallup Report 19 Nov 2004. (Also at Canadian Content.) Newport notes that the numbers haven’t changed much over the last few years, or even over the last thirty.
  • Creationists.org
    What the name implies. The “position statement” referred to above takes as its second choice the abandonment of any reference to origins. See also the Back to Genesis page at the Institute for Creation Research. On ICR and the accreditation of its graduate school, The Panda’s Thumb.

LinkJune 25, 2005