109,283 research outputs found
Searching for comets on the World Wide Web: The orbit of 17P/Holmes from the behavior of photographers
We performed an image search for "Comet Holmes," using the Yahoo Web search
engine, on 2010 April 1. Thousands of images were returned. We astrometrically
calibrated---and therefore vetted---the images using the Astrometry.net system.
The calibrated image pointings form a set of data points to which we can fit a
test-particle orbit in the Solar System, marginalizing over image dates and
detecting outliers. The approach is Bayesian and the model is, in essence, a
model of how comet astrophotographers point their instruments. In this work, we
do not measure the position of the comet within each image, but rather use the
celestial position of the whole image to infer the orbit. We find very strong
probabilistic constraints on the orbit, although slightly off the JPL
ephemeris, probably due to limitations of our model. Hyperparameters of the
model constrain the reliability of date meta-data and where in the image
astrophotographers place the comet; we find that ~70 percent of the meta-data
are correct and that the comet typically appears in the central third of the
image footprint. This project demonstrates that discoveries and measurements
can be made using data of extreme heterogeneity and unknown provenance. As the
size and diversity of astronomical data sets continues to grow, approaches like
ours will become more essential. This project also demonstrates that the Web is
an enormous repository of astronomical information; and that if an object has
been given a name and photographed thousands of times by observers who post
their images on the Web, we can (re-)discover it and infer its dynamical
properties.Comment: As published. Changes in v2: data-driven initialization rather than
JPL; added figures; clarified tex
The Doomsday Simulation Argument. Or why isn't the end nigh, and you're not living in a simulation.
According to the Carter-Leslie Doomsday Argument, we should assign a high probability to the hypothesis that the human species will go extinct very soon. The argument is based on the application of Bayes’s theo-rem and a certain indifference principle with respect to the temporal location of our observed birth rank within the totality of birth ranks of all humans who will ever have lived.
According to Bostrom’s Simulation Argument, which appeals to a weaker indifference principle than the Doomsday Argument, at least one of the following three propositions must be true: (1) the human species is very likely to go extinct before reaching a posthuman stage, (2) it is very unlikely that some posthuman civili-zation will run a significant number of ancestor simula-tions, (3) it is almost sure that we are living in a com-puter simulation.
According to my Doomsday Simulation Argument, both of the following propositions must be true: (1) it is almost sure that the human species will not go extinct before reaching a posthuman stage, (2) it is almost sure that we are not living in a computer simulation
Detect the unexpected: a science for surveillance
Purpose – The purpose of this paper is to outline a strategy for research development focused on addressing the neglected role of visual perception in real life tasks such as policing surveillance and command and control settings. Approach – The scale of surveillance task in modern control room is expanding as technology increases input capacity at an accelerating rate. The authors review recent literature highlighting the difficulties that apply to modern surveillance and give examples of how poor detection of the unexpected can be, and how surprising this deficit can be. Perceptual phenomena such as change blindness are linked to the perceptual processes undertaken by law-enforcement personnel. Findings – A scientific programme is outlined for how detection deficits can best be addressed in the context of a multidisciplinary collaborative agenda between researchers and practitioners. The development of a cognitive research field specifically examining the occurrence of perceptual “failures” provides an opportunity for policing agencies to relate laboratory findings in psychology to their own fields of day-to-day enquiry. Originality/value – The paper shows, with examples, where interdisciplinary research may best be focussed on evaluating practical solutions and on generating useable guidelines on procedure and practice. It also argues that these processes should be investigated in real and simulated context-specific studies to confirm the validity of the findings in these new applied scenarios
Evolution of circular, non-equatorial orbits of Kerr black holes due to gravitational-wave emission: II. Inspiral trajectories and gravitational waveforms
The inspiral of a ``small'' () compact body into a
``large'' () black hole is a key source of
gravitational radiation for the space-based gravitational-wave observatory
LISA. The waves from such inspirals will probe the extreme strong-field nature
of the Kerr metric. In this paper, I investigate the properties of a restricted
family of such inspirals (the inspiral of circular, inclined orbits) with an
eye toward understanding observable properties of the gravitational waves that
they generate. Using results previously presented to calculate the effects of
radiation reaction, I assemble the inspiral trajectories (assuming that
radiation reacts adiabatically, so that over short timescales the trajectory is
approximately geodesic) and calculate the wave generated as the compact body
spirals in. I do this analysis for several black hole spins, sampling a range
that should be indicative of what spins we will encounter in nature. The spin
has a very strong impact on the waveform. In particular, when the hole rotates
very rapidly, tidal coupling between the inspiraling body and the event horizon
has a very strong influence on the inspiral time scale, which in turn has a big
impact on the gravitational wave phasing. The gravitational waves themselves
are very usefully described as ``multi-voice chirps'': the wave is a sum of
``voices'', each corresponding to a different harmonic of the fundamental
orbital frequencies. Each voice has a rather simple phase evolution. Searching
for extreme mass ratio inspirals voice-by-voice may be more effective than
searching for the summed waveform all at once.Comment: 15 pages, 11 figures, accepted for publication in PRD. This version
incorporates referee's comments, and is much less verbos
Empty Rivers: The Decline of River Herring and the Need to Reduce Mid-Water Trawl Bycatch
Examines the effects of industrial mid-water trawlers on river herring populations along the East Coast and makes recommendations for how to protect herring stocks
Striking NYNEX
[Excerpt] The four-month strike by 60,000 telephone workers at NYNEX in 1989 was one of the largest and most significant anti-concession struggles of the decade.
In an era when many unions have lost highly publicized contract fights and been forced to make give-backs, the NYNEX strikers successfully resisted management demands that they pay hundreds and eventually thousands of dollars a year for their medical coverage. They also defeated the company\u27s drive for new forms of flexible compensation designed to replace base wage increases and COLAs with lump-sum payments and profit-sharing.
Successful union resistance to these concessions would not have been possible without an unprecedented pre-strike program of membership education and internal organizing. The contract campaign conducted by the 30 NYNEX local unions within the Communications Workers of America (CWA) and their allies in NYNEX units represented by the International Brotherhood of Electrical Workers (IBEW) reflects CWA\u27s nationwide commitment to rankand- file mobilization through the one-on-one approach
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