We consider the historic Harress-Sagnac experiment in the light of our absolute space-time theory, proposing two modifications, and we give an account of its recent practical performance. We show that the effect of the rotating disk experiment is a direct result of the light velocity's direction dependence and we point out that our recently performed coupled-mirrors experiment, with whose help for the first time we have measured the Earth's absolute velocity, can be considered as a logical result of the (...) rotating disk experiment. (shrink)

We have compared two different laser-induced optical light traps for their utility in moving organelles within living animal cells and walled fungal cells. The first trap employed a continuous wave neodymium-yttrium aluminum garnet laser at a wavelength of 1.06 micron. A second trap was constructed using a titanium-sapphire laser tunable from 700 to 1000 nm. With the latter trap we were able to achieve much stronger traps with less laser power and without damage to either mitochondria or spindles. Chromosomes and (...) nuclei were easily displaced, nucleoli were separated and moved far away from interphase nuclei, and Woronin bodies were removed from septa. In comparison, these manipulations were not possible with the Nd-YAG laser-induced trap. The optical force trap induced by the tunable titanium-sapphire laser should find wide application in experimental cell biology because the wavelength can be selected for maximization of force production and minimization of energy absorption which leads to unwanted cell damage. (shrink)

Bokanmeldelse av Katharina Bocks _Philosemitische Schwärmereien. Jüdische Figuren in der dänischen Erzählliteratur des 19. Jahrhunderts_ (Tübingen: Narr Francke Attempto Verlag, 2021).

Typically developing 3-day-old newborns take significantly more forward steps on a moving treadmill belt than on a static belt. The current experiment examined whether projecting optic flows that specified forward motion onto the moving treadmill surface would further enhance forward stepping. Twenty newborns were supported on a moving treadmill without optic flow, with optic flow matching the treadmill’s direction and speed, with optic flow in the same direction but at a faster speed, and in a control (...) condition with an incoherent optic flow moving at the same speed as in the Congruent condition but in random directions. The results revealed no significant differences in the number or coordination of forward treadmill steps taken in each condition. However, the Faster condition generated significantly fewer leg pumping movements than the Random control condition. When highly aroused, newborns made significantly fewer single steps and significantly more parallel steps and pumping movements. We speculate the null findings may be a function of the high friction material that covered the treadmill surface. (shrink)

Significantly, Berkeley, in his Essay Towards a New Theory of Vision, leveled a sustained attack on just this geometrical theory of distance perception. At first glance it may seem, as it did to Berkeley, that Descartes’ geometrical theory is produced by a simple error: namely, by the idea that a physiological optics provides an adequate description of the psychological processes of judging distances. In truth, this is the weakest of Berkeley’s objections to Descartes’ theory. Obviously we do not see the (...) angles and lines of convergence when we focus on a distant object, nor are we aware of having used any geometrical rules in judging distance. And Descartes never claimed this. (shrink)

_ Source: _Volume 29, Issue 1, pp 86 - 102 The aim of this paper is to give an overview of the place that Hobbes assigns to optics in the context of his classification of sciences and disciplinary boundaries. To do this, I will begin with an account of Hobbes’s conception of philosophy or science, and particularly his distinction between true and hypothetical knowledge. I will also show that in his demarcation between mathematics or geometry and natural philosophy Hobbes was (...) influenced by Galileo’s _Dialogue_. I then analyse the consequences of this distinction for optics, and conclude by clarifying its status among the scientific disciplines. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Diacritics 31.4 (2001) 85-102 [Access article in PDF] Culture in the Disk Drive Computationalism, Memetics, and the Rise of Posthumanism Stephen Dougherty Ever since Descartes argued that there are striking similarities between a man and a clock, humanism has been in a state of crisis. To put it more pointedly, humanism has always been in a state of crisis, ever since it emerged in the sixteenth and seventeenth (...) centuries as a constellation of beliefs that made man rather than God the measure of all things. Thus, since we are arguably witnesses now to the eclipse of the humanist tradition, we might take some comfort (if any is desired) in considering that if we have failed the ideal of humanism, it has also failed us. From the beginning its borders were too porous, its boundaries too ill defined. For even as man turned himself into a god, he increasingly began to resemble a machine.In terms of bodily representation, our machinic evolution through the last four centuries culminates in the figure of the cyborg; and if we have already become posthuman, as N. Katherine Hayles suggests, then the cyborg stands as the iconic pop culture figure of our epochal transformation. But you don't need electronic prosthetic devices attached to your body or silicon chips implanted in your head to be posthuman. As Hayles argues, "[w]hether or not interventions have been made on the body, new models of subjectivity emerging from such fields as cognitive science and artificial life imply that even a biologically unaltered Homo sapiens counts as posthuman" [4]. What counts especially, according to Hayles, is not the body/machine interface but how we conceptualize the workings of the mind/brain.In the humanist tradition signalled by Descartes, the subject is an I, an ego that is master of itself, a unified consciousness thinking itself. Before it is anything else, the Cartesian subject is a function of thought—ineffable and immaterial, and partaking in its nature of the divine and ineffable spirit that guarantees its communication with the material world. Thus, even though God has always been in the process of disappearing through the centuries since the Renaissance, spirit hasn't. Humanism never abandoned the concept of a spiritualized man, registering at the least a dissatisfaction with science's conventional claim to the possession of special and superior knowledge, and until quite recently dualism of one variety or another has been the normative philosophical attitude.But in posthumanism matters are different. To begin with, as Hayles puts it, "computation rather than possessive individualism is taken as the ground of being" [34]. Human consciousness is no longer that which thinks itself into its own unity, a mysterious phenomenon of infinite reflexivity that would become the central subject of, and the central problem for, modern philosophy. In fact, in the posthumanist regime human consciousness is no longer primarily a matter for philosophy, since questions regarding ontology and epistemology are displaced by the question of functionality. Cognitive processes are turned into syntactical operations similar to those that computers perform, 1 [End Page 85] and consciousness is reduced to mere epiphenomena of those machinic operations. 2Further, the cognitive functions of posthuman subjectivity are dispersed among a complex network of interrelated systems and subsystems (modules) responsible for receiving and interpreting data. 3 Consciousness thus loses the holistic unity it had possessed with a considerable degree of consensus from Descartes up to the behavioralists. Just as significantly, it loses its ineffability. The computationalists do not interrogate the mind as something beyond the grasp of scientific rationality because they do not approach thought as immaterial. Insofar as the brain has become a machine, mind is reduced to matter. In the new posthuman dispensation, then, philosophical dualism gives way to monism.Such an outcome would seem to suggest that the onset of posthumanism represents the ultimate victory for positivism and scientific rationalism in explaining human behavior. As Francis Crick explains in The Astonishing Hypothesis: The Scientific Search for the Soul, "the aim of science is to explain all aspects of the behavior of our brains, including... (shrink)

Minkowski geometry is axiomatized in terms of the asymmetric binary relation of optical connectibility, using ten first-order axioms and the second-order continuity axiom. An axiom system in terms of the symmetric binary optical connection relation is also presented. The present development is much simpler than the corresponding work of Robb, upon which it is modeled.

The screen is not a pre established object: it becomes a screen—and that screen—when it interacts with a group of elements and relates to a set of practices that produce it as a screen. In this process of becoming screen, a crucial step is played by the space in which the screen is located and where spectators gather. The confluence of screen and space changes our perception of both: the screen displays the situatedness of its action, and the space its (...) nature of medium. The landscape becomes a screenscape, in which individuals access images through which they negotiate with reality and others. Eventually, the insistence on becoming screen highlights the role of contingency and conjuncture in the process of mediation: screenscapes emerge according opportunities, conflicts, and potentialities. Hence a media archeology that, far from being linear and teleological, follows unpredicted paths and creates surprising links—a rhizomatic media archeology. (shrink)

Bokanmeldelse av Johan Schücks _Herman Friedländer. En svensk judisk historia_ (Stockholm: Medströms bokförlag, 2021).

The disk that rotates in an inertial frame in special relativity has long been analysed by assuming a Lorentz contraction of its peripheral elements in that frame, which has produced widely varying views in the literature. We show that this assumption is unnecessary for a disk that corresponds to the simplest form of rotation in special relativity. After constructing such a disk and showing that observers at rest on it do not constitute a true rotating frame, we (...) choose a “master” observer and calculate a set of disk coordinates and spacetime metric pertinent to that observer. We use this formalism to resolve the “circular twin paradox”, then calculate the speed of light sent around the periphery as measured by the master observer, to show that this speed is a function of sent-direction and disk angle traversed. This result is consistent with the Sagnac Effect, but constitutes a finer analysis of that effect, which is normally expressed using an average speed for a full trip of the periphery. We also use the formalism to give a resolution of “Selleri’s paradox”. (shrink)

Seventeenth-century optics naturalizes the eye while estranging the mind from objects. A mere screen, on which rests a blurry array of light stains, the eye no longer furnishes the observer with genuine re-presentations of visible objects. The intellect is thus compelled to decipher flat images of no inherent epistemic value, accidental effects of a purely causal process, as vague, reversed reflections of wholly independent objects. Reflecting on and trespassing the boundaries between natural and artificial, orderly and disorderly, this optical paradox (...) is a Baroque phenomenon; and it is the origin of Descartes’ celebrated doubt---whether we know anything at all. (shrink)

Ever since Big Data became a mot du jour across social fields, optical metaphors such as the microscope began to surface in popular discourse to describe and qualify its epistemological impact. While the persistence of optics seems to be at odds with the datafication of vision, this article suggests that the optical metaphor offers an opportunity to reflect about the material consequences of the modes of seeing and knowing that currently shape datafied worlds. Drawing on feminist new materialism, the article (...) investigates the optical metaphor as a material-discursive practice that actively constitutes the world, as metaphors imply modes of thinking, knowing and doing that have material enactions. Expanding visual culture theories, the notion of ‘optical unconscious’ is taken up to discuss the tensions between displacement and persistence of optics within datafied worlds, that is, how optical vision is displaced but also mobilised and repurposed by data-driven knowledge. In dialogue with feminist science and technology studies and speculative ethics, I suggest that the datafication of vision offers a chance to reconceptualize the sense of sight towards a sensorial engagement with Big Data premised on responsibility, care, and an ethics of unknowability. Within this framework, vision may be conceived differently, perhaps not only as enhancement and control, but as generator of new possibilities. Ultimately, the article proposes that the visual theories after which Big Data is being imagined matter not only for our understanding of Big Data's epistemic potential, but also for the possibility of shaping emerging data worlds. (shrink)

A major intellectual shift between Copernicus and the mid-17th century was the rejection of Aristotelian assertions concerning the relationship of mathematics to physical nature. Aristotle asserted that “The minute accuracy of mathematics is not to be demanded in all cases, but only in the case of things which have no matter. Therefore its method is not that of natural science; for presumably all nature has matter.” Thus, he pulled out the rug from under the feet of the aspiration to a (...) mathematically based natural sciences, asserting that: “And at the same time not even this is true, that mensuration deals with perceptible and perishable magnitudes; for then it would have perished, when they perished. And astronomy also cannot be dealing with perceptible magnitudes nor with this heaven above us. For neither are perceptible lines such lines as the geometer speaks of, nor are the movement and complex orbits in the heaven like those which astronomy treats, nor have geometrical points the same nature as the actual stars.”. (shrink)

This book is a long-term history of optics, from early Greek theories of vision to the nineteenth-century victory of the wave theory of light. It is a clear and richly illustrated synthesis of a large amount of literature, and a reliable and efficient guide for anyone who wishes to enter this domain.

The relativistic optics of the nondispersive media endowed with the metric gij(x) [Eq. (1.6)] and with a nonlinear connection [Eq. (1.2)] is studied. The d-connection [Eqs. (3.3)– (3.4)] relates the conformal and projective properties of the space- time. A post-Newtonian estimation for the metric gij(x) is also given. It is shown that the solar system tests impose a constraint [Eq. (4.20)] on a combination of the post- Newtonian parameters describing the model.

Socrates, in the Republic , uses the symbol of a divided line to illustrate the distinction between the Visible and Intelligible Worlds, and between the kinds of perception appropriate to each. This paper will present a new hypothesis: that the proportions of the line are derived from optical theory. The construction of the Divided Line is described as follows: Socrates asks his interlocutors to represent the Visible and Intelligible Worlds by a line divided into two unequal segments. The ratio in (...) which the division is to be made is not specified, and it seems that any ratio is acceptable provided that one segment is longer than the other. Socrates then tells them to cut each part again according to the same ratio as the original division. After describing the division of the line thus into four parts, Socrates goes on to explain the philosophical significance of each part. For the purposes of this paper the following brief identification of each segment of the line will suffice. (shrink)

Socrates, in the Republic, uses the symbol of a divided line to illustrate the distinction between the Visible and Intelligible Worlds, and between the kinds of perception appropriate to each. This paper will present a new hypothesis: that the proportions of the line are derived from optical theory. The construction of the Divided Line is described as follows: Socrates asks his interlocutors to represent the Visible and Intelligible Worlds by a line divided into two unequal segments. The ratio in which (...) the division is to be made is not specified, and it seems that any ratio is acceptable provided that one segment is longer than the other. Socrates then tells them to cut each part again according to the same ratio as the original division. After describing the division of the line thus into four parts, Socrates goes on to explain the philosophical significance of each part. For the purposes of this paper the following brief identification of each segment of the line will suffice. (shrink)

This volume contains essays that examine the optical works of Giambattista Della Porta, an Italian natural philosopher during the Scientific Revolution. Coverage also explores the science and technology of early modern optics. Della Porta's groundbreaking book, Magia Naturalis, includes a prototype of the camera. Yet, because of his obsession with magic, Della Porta's scientific achievements are often forgotten. As the contributors argue, his work inspired such great minds as Johanes Kepler and Francis Bacon. After reading this book, researchers, historians, and (...) students will have a better appreciation of this influential scientist. They will also gain a greater understanding of an important period in the history of optics. Readers will learn about Della Porta's experimental method, a process governed by the protocols, aims, and theoretical assumptions of natural magic. Coverage also discusses the material properties and limitations of optical technology in the early 17th century, based on a recently discovered Dutch spyglass. It also demonstrates how diagrams were instrumental in the discovery of the sine law of refraction. In addition, the book includes an in-depth analysis of previously untranslated Latin sources. This makes the material useful to historians of optics unfamiliar with the language. More than 70 illustrations complement the text. (shrink)

This chapter discusses Thomas Hobbes's statements about the structure of philosophy and suggests that a focus on these reflections has led some scholars to understand Hobbes as an armchair speculative philosopher, both in his own natural‐philosophy endeavors and his well‐known criticisms of Robert Boyle and other experimental philosophers. Beyond Hobbes's statements about natural philosophy, it argues that a more complete understanding of his natural philosophy must also consider his practice of explaining in natural philosophy and optics. Hobbes divides all human (...) knowledge into two parts: scientia, and cognition. These two parts provide different levels of certainty to knowers. The chapter shows that explanations in optics and natural philosophy are ideally a mixture of appeals to everyday sense experience and Hobbes's own a priori geometry by providing two case studies: a case study from Hobbes's optics in De homine II and a case study of Hobbes's explanation of sense in De corpora XXV. (shrink)

The historical antecedents of Frege's treatment of binocular vision in "The thought" were the physiological writings of Johannes Mueller, Hermann von Helmholtz, and Emil du Bois-Reymond. In their research on human vision, logic was assigned an unexpected role: it was to be the means by which knowledge of a world extended in three dimensions arises from stimuli that are at best two-dimensional. An examination of this literature yields a richer understanding of Frege's insistence that a proper epistemology requires us to (...) recognize the existence and importance of nonsensible sources of knowledge. (shrink)

In the previous article (Found. Phys. Lett. 16:325–341, 2003), we showed that a reciprocity of the Gauss sums is connected with the wave and particle complementary. In this article, we revise the previous investigation by considering a relation between the Gauss optics and the Gauss sum based upon the recent studies of the Weil representation for a finite group.

Descartes's Dioptrics is more than a mere technical treatise on optics; it is an essay in the "practical philosophy" that he claimed could render us "masters and possessors of nature." Descartes's practical intent is indicated first by the instrumentalist character of his derivation of the sine law of refraction, which is based on a heuristic and readily mathematizable model that requires no consideration of light's "true nature." Descartes's subsequent discussion of human vision is an extended critique of nature's workmanship that (...) grounds the possibility of improving vision by artificial means. I suggest that this critique is the source of Descartes's doctrine that the purpose of sensory perception is to preserve the mind-body composite, not to provide knowledge of the essential nature of things. Accordingly, the ultimate goal of the Dioptrics is to "master" human vision by raising it from a mere means of self-preservation to an instrument of scientific knowledge. -/- . (shrink)

Leonardo's drawings of optical machinery have been used as evidence for the claim that Leonardo built machines to make concave mirrors with which he could project images. This paper argues that Leonardo's drawings cannot be used as evidence for this claim. It will be shown that Leonardo used the drawings to communicate with his patrons and craftsmen, to experiment on paper, to record trials with models, and to think about 'theoretical' problems in optics. At both the theoretical and the practical (...) level, Leonardo was only concerned with the burning properties of concave mirrors, not with their imaging properties. The paper will conclude that the drawings of optical machinery allowed Leonardo to differentiate himself from the ordinary mirror-makers in his workshop. The same drawings, however, also forced him to remain within the conceptual framework of perspectivist optics. (shrink)

In Mohist philosophy, the gnomon is a metaphor for the standard of valid arguments. This metaphor comes from the method of establishing due east and west by observing gnomon shadows at dusk and dawn. I argue that there is also an overlooked, implicit aspect of the gnomon metaphor that comes from its function of measuring the height of heaven indirectly through proportional calculation. The function of indirect measurement inspires a strategy of argumentation in Mohist ethics, which I call “analogical upscaling.” (...) Such an argument draws a parallel between small-scale and large-scale actions for the purpose of determining the Will of Heaven in a particular circumstance, just as the gnomon measures heaven’s physical height analogically. In the conclusion, I compare the epistemological status of light and shadow in the Mozi and Plato’s Republic. (shrink)