Hypothesis Article Signatures of a Shadow Biosphere

Abstract Astrobiologists are aware that extraterrestrial life might differ from known life, and considerable thought has been given to possible signatures associated with weird forms of life on other planets. So far, however, very little attention has been paid to the possibility that our own planet might also host communities of weird life. If life arises readily in Earth-like conditions, as many astrobiologists contend, then it may well have formed many times on Earth itself, which raises the question whether one or more shadow biospheres have existed in the past or still exist today. In this paper, we discuss possible signatures of weird life and outline some simple strategies for seeking evidence of a shadow biosphere

The variable functional effects of the pacing site in normal and scarred ventricles

The pacing site has been shown to influence functional improvement with cardiac resynchronization therapy. We evaluated the effects of the pacing site on left ventricular (LV) function in an animal model. Equilibrium radionuclide angiography was acquired in sinus rhythm (NSR) and with ventricular pacing, from three pacing sites in seven normal and eight infarcted dogs. QRS duration, electrical activation pattern, wall motion, LV ejection fraction (EF), synchrony of ventricular contraction, and mean arterial pressure (MAP), were related to the pacing site and infarct size, during each of 120 episodes. Little changed during pacing in normals. In infarcted dogs, LV wall motion, and synchrony worsened, LVEF and MAP often fell. These changes related to altered activation patterns which were influenced by the pacing site but were not related to infarct size. Hemodynamic and functional LV changes after infarction were found to vary with the pacing site and associated conduction and synchrony

The concept of computability

I explore the conceptual foundations of Alan Turing’s analysis of computability, which still dominates thinking about computability today. I argue that Turing’s account represents a last vestige of a famous but unsuccessful program in pure mathematics, viz., Hilbert’s formalist program. It is my contention that the plausibility of Turing’s account as an analysis of the computational capacities of physical machines rests upon a number of highly problematic assumptions whose plausibility in turn is grounded in the formalist stance towards mathematics. More specifically, the Turing account con ates concepts that are crucial for understanding the computational capacities of physical machines. These concepts include the idea of an “operation” or “action” that is “formal,” “mechanical,” “well-defined, ” and “precisely described,” and the idea of a “symbol” that is “formal,” “uninterpreted,” and “shaped”. When these concepts are disentangled, the intuitive appeal of Turing’s account is significantly undermined. This opens the way for exploring models of hypercomputability that are fundamentally different from those currently entertained in the literature

Historical Science, Experimental Science, and the Scientific Method

Wielu naukowców sądzi, że istnieje jedna, interdyscyplinarna metoda uprawiania dobrej nauki. Wzorcowe przykłady czerpane są jednak z obrębu klasycznych nauk eksperymentalnych. Czasem, kiedy hipotez o charakterze historycznym nie można testować w kontrolowanych warunkach laboratoryjnych, twierdzi się, że badania historyczne mają gorszą jakość niż badania eksperymentalne. Celem niniejszego artykułu jest wykazanie, na podstawie przykładów z różnych dyscyplin historycznych, że to przekonanie jest błędne. Po pierwsze, pogląd o rzekomej wyższości badań eksperymentalnych wynika z przyjęcia takich koncepcji metodologii naukowej (indukcjonizmu baconowskiego i falsyfikacjonizmu), które mają poważne mankamenty, zarówno na płaszczyźnie logicznej, jak też jako ujęcia rzeczywistych praktyk naukowców. Po drugie, chociaż między metodologiami nauk eksperymentalnych i nauk historycznych zachodzą zasadnicze różnice, związane są one z pewną wszechobecną właściwością świata przyrody - czasową asymetrią przyczynowości. Nie da się zatem utrzymać twierdzenia, że nauki historyczne są pod względem metodologicznym gorsze od nauk eksperymentalnych.Many scientists believe that there is a uniform, interdisciplinary method for the practice of good science. The paradigmatic examples, however, are drawn from classical experimental science. Insofar as historical hypotheses cannot be tested in controlled laboratory settings, historical research is sometimes said to be inferior to experimental research. Using examples from diverse historical disciplines, this paper demonstrates that such claims are misguided. First, the reputed superiority of experimental research is based upon accounts of scientific methodology (Baconian inductivism or falsificationism) that are deeply flawed, both logically and as accounts of the actual practices of scientists. Second, although there are fundamental differences in methodology between experimental scientists and historical scientists, they are keyed to a pervasive feature of nature, a time asymmetry of causation. As a consequence, the claim that historical science is methodologically inferior to experimental science cannot be sustained

Ammonia and Phosphine in the Clouds of Venus as Potentially Biological Anomalies

We are of the opinion that several anomalies in the atmosphere of Venus provide evidence of yet-unknown processes and systems that are out of equilibrium. The investigation of these anomalies on Venus should be open to a wide range of explanations, including unknown biological activity. We provide an overview of two anomalies, the tentative detection of ammonia and phosphine in Venus’s atmosphere. These anomalies fly in the face of the tacit assumption that the atmosphere of Venus must be in chemical redox equilibrium, an assumption connected to the belief that Venus is lifeless. We then discuss several major past discoveries in astronomy, biology and geology, which lead to the abandonment of certain assumptions held by many scientists as though they were well-established principles. The anomalies of ammonia and phosphine in the atmosphere of Venus are placed in the context of these historical discoveries. This context supports our opinion that persistence by the community in the exploration of these anomalies with a skeptical eye towards tacit assumptions will increase the chances of making profound discoveries about the atmosphere of Venus and the diverse and often strange nature of planetary environments. To be submitted to Aerospace Special Issue “The Search for Signs of Life on Venus: Science Objectives and Mission Designs”

Ammonia and Phosphine in the Clouds of Venus as Potentially Biological Anomalies

We are of the opinion that several anomalies in the atmosphere of Venus provide evidence of yet-unknown processes and systems that are out of equilibrium. The investigation of these anomalies on Venus should be open to a wide range of explanations, including unknown biological activity. We provide an overview of two anomalies, the tentative detection of ammonia and phosphine in Venus’s atmosphere. These anomalies fly in the face of the tacit assumption that the atmosphere of Venus must be in chemical redox equilibrium, an assumption connected to the belief that Venus is lifeless. We then discuss several major past discoveries in astronomy, biology and geology, which lead to the abandonment of certain assumptions held by many scientists as though they were well-established principles. The anomalies of ammonia and phosphine in the atmosphere of Venus are placed in the context of these historical discoveries. This context supports our opinion that persistence by the community in the exploration of these anomalies with a skeptical eye towards tacit assumptions will increase the chances of making profound discoveries about the atmosphere of Venus and the diverse and often strange nature of planetary environments. To be submitted to Aerospace Special Issue “The Search for Signs of Life on Venus: Science Objectives and Mission Designs”

Ammonia and Phosphine in the Clouds of Venus as Potentially Biological Anomalies

Peer reviewed: TrueWe are of the opinion that several anomalies in the atmosphere of Venus provide evidence of yet-unknown processes and systems that are out of equilibrium. The investigation of these anomalies on Venus should be open to a wide range of explanations, including unknown biological activity. We provide an overview of two anomalies, the tentative detection of ammonia and phosphine in Venus’s atmosphere. These anomalies fly in the face of the tacit assumption that the atmosphere of Venus must be in chemical redox equilibrium, an assumption connected to the belief that Venus is lifeless. We then discuss several major past discoveries in astronomy, biology and geology, which lead to the abandonment of certain assumptions held by many scientists as though they were well-established principles. The anomalies of ammonia and phosphine in the atmosphere of Venus are placed in the context of these historical discoveries. This context supports our opinion that persistence by the community in the exploration of these anomalies with a skeptical eye towards tacit assumptions will increase the chances of making profound discoveries about the atmosphere of Venus and the diverse and often strange nature of planetary environments. To be submitted to Aerospace Special Issue “The Search for Signs of Life on Venus: Science Objectives and Mission Designs”