Disagreement and Philosophical Progress

In “Belief in the Face of Controversy,” Hilary Kornblith argues for a radical form of epistemic modesty: given that there has been no demonstrable cumulativeprogress in the history of philosophy – as there has been in formal logic, math, and science – Kornblith concludes that philosophers do not have the epistemic credibility to be trusted as authorities on the questions they attempt to answer. After reconstructing Kornblith's position, I will suggest that it requires us to adopt a different conception of philosophy's epistemic value. First, I will argue that ‘progress’ has a different meaning in logic, science and philosophy, and that to judge one of these disciplines by the standards appropriate to one of the others obscures the unique epistemic functions of all. Second, I will argue that philosophy is epistemically unique in that it is a non-relativistic but historically determined excavation of foundations. Finally, drawing on Frank Herbert's Dune, I will suggest that Kornblith leaves us with a choice between two epistemic ideals: the hyper-logical ‘Mentat,’ or the historically informed ‘pre-born.

Radio sources near the core of globular cluster 47 Tucanae

We present ATCA radio images of the globular cluster 47 Tucanae made at 1.4 and 1.7 GHz and provide an analysis of the radio sources detected within 5 arcmin of the cluster centre. 11 sources are detected, most of which are clustered about the core of 47 Tuc. Both of the pulsars in 47 Tuc whose positions are known can be identified with sources in the 1.4 GHz image. The source distribution has a characteristic radius of ~100 arcsec, larger than the 23 arcsec radius of the cluster core. We compare source positions with the positions of nine X-ray sources and find no correspondence.Comment: 6 pages, 4 postscript figures, LaTeX with MNRAS macro; Accepted by MNRA

A Computational Kinetics Model To Quantify Radiation Induced Chemical Products Of Atmospheric Gas Mixtures

This research is focused on the development of a computational model which will calculate the effects of radiation on the chemical composition of the atmosphere. The approach utilizes the open-source chemical kinetics toolkit Cantera to model the creation of radiation-induced reactant species within irradiated air mixtures. Chemical solutions are iteratively stepped toward chemical equilibrium within a ‘constantly stirred’ (homogeneous) reactor of fixed volume. Three different radiation chemistry models are implemented in several different pulsed and continuous radiation schemes. The first model includes the mechanisms and rates of a pulse radiation model from the literature to test the validity of the new approach by comparison. The second uses identical mechanisms with the latest accepted rates to explore the change in induced chemical product yields in both schemes. The third model implements an extensive list of reactions and rates found within atmospheric chemistry literature and is an attempt to posit an updated radiation chemistry model that fits both pulsed and continuous radiation models and experimental data from the literature. Measurements of radiation-induced ozone within continuously irradiated air mixtures demonstrated a need for a more accurate representation of the energy deposition distribution specific to the radioactive source. The volume in the space above the source is partitioned into a grid of independent voxels, and an energy deposition rate at each location is calculated. The average dose rate along the optical path of the spectroscopy-based model validation experiment is calculated from the voxel data. This method offers the flexibility necessary to easily correlate precomputed solutions with experimental measurements made through any part of the irradiated air mixture. Several computational solutions are computed for dry 80/20 nitrogen/oxygen gas mixtures at various pressures with a gaseous mix of reactants introduced at different rates corresponding to a range of dose rates. Yields produced by the new approach in the pulse radiation scheme are found to be in good agreement with experimental results within the literature. Spectroscopy measurements of radiation-induced ozone show a strong correlation with computational results of the posited model in the continuous radiation scheme at the average dose rate of the optical measurements

A System For Conducting Laser-Induced Fluorescence Measurements On Gas Mixtures Exposed To Alpha Radiation

This paper documents modifications to an existing vacuum system to allow laser-induced fluorescence spectroscopy measurements within simulated atmospheres under a variety of conditions. This added capability will expand the laboratory’s ability to experimentally validate a computational model that calculates the effects of radiation within the atmosphere. The computational model could reveal radiation-induced chemical products that can be used to develop an alternative detection method that can be implemented from a safe distance. The selection of molecules for experimental validation has been limited to those which can be detected utilizing cavity ringdown spectroscopy. The current model indicates nitric oxide and ozone to be the primary reactants that dictate production rates and concentrations for many of the resulting chemical products. Because strong absorption cross sections for nitric oxide are too deep in the ultraviolet to effectively use the cavity ringdown method, laser-induced fluorescence spectroscopy was seen as a viable alternative. Using a certified mix of NO2 and a second mix of NO, the system is validated by stepping a dye laser through wavelengths from 225.9 nm to 227.1 nm. The data collected was used to produce an excitation spectrum to compare with a simulated spectrum. These mixes were diluted with an ultra-high purity grade of N2 so that an experimental detection limit could be approximated. The excitation spectrum produced is in excellent agreement with that of the simulated spectrum and an experimental approximation of the detection limit for NO was found to be 3 ± 2 parts-per-billion in a background of N2