Boulder size and shape distributions on asteroid Ryugu

In 2018, the Japanese spacecraft Hayabusa2, arrived at the small asteroid Ryugu. The surface of this C-type asteroid is covered with numerous boulders whose size and shape distributions are investigated in this study. Using a few hundred Optical Navigation Camera (ONC) images with a pixel scale of approximately 0.65 m, we focus on boulders greater than 5m in diameter. Smaller boulders are also considered using five arbitrarily chosen ONC close-up images with pixel scales ranging from 0.7 to 6 cm. Across the entire surface area (~2.7 km2) of Ryugu, nearly 4400 boulders larger than 5m were identified. Boulders appear to be uniformly distributed across the entire surface, with some slight differences in latitude and longitude. At ~50 km−2, the number density of boulders larger than 20m is twice as large as on asteroid Itokawa (or Bennu). The apparent shapes of Ryugu's boulders resemble laboratory impact fragments, with larger boulders being more elongated. The ratio of the total volume of boulders larger than 5m to the total excavated volume of craters larger than 20m on Ryugu can be estimated to be ~94%, which is comparatively high. These observations strongly support the hypothesis that most boulders found on Ryugu resulted from the catastrophic disruption of Ryugu's larger parent body, as described in previous papers (Watanabe et al., 2019; Sugita et al.,2019). The cumulative size distribution of boulders larger than 5 m has a power-index of −2.65 ± 0.05, which is comparatively shallow compared with other asteroids visited by spacecraft. For boulders smaller than 4 m, the power-index is even shallower and ranges from −1.65 ± 0.05 to −2.01 ± 0.06. This particularly shallow power-index implies that some boulders are buried in Ryugu's regolith. Based on our observations, we suggest that boulders near the equator might have been buried by the migration of finer material and, as a result, the number density of boulders larger than 5 m in the equatorial region is lower than at higher latitudes

The Ship of Theseus Puzzle

Does the Ship of Theseus present a genuine puzzle about persistence due to conflicting intuitions based on “continuity of form” and “continuity of matter” pulling in opposite directions? Philosophers are divided. Some claim that it presents a genuine puzzle but disagree over whether there is a solution. Others claim that there is no puzzle at all since the case has an obvious solution. To assess these proposals, we conducted a cross-cultural study involving nearly 3,000 people across twenty-two countries, speaking eighteen different languages. Our results speak against the proposal that there is no puzzle at all and against the proposal that there is a puzzle but one that has no solution. Our results suggest that there are two criteria—“continuity of form” and “continuity of matter”— that constitute our concept of persistence and these two criteria receive different weightings in settling matters concerning persistence

The First Very Long Baseline Interferometry Image of 44 GHz Methanol Maser with the KVN and VERA Array (KaVA)

We have carried out the first very long baseline interferometry (VLBI) imaging of 44 GHz class I methanol maser (7_{0}-6_{1}A^{+}) associated with a millimeter core MM2 in a massive star-forming region IRAS 18151-1208 with KaVA (KVN and VERA Array), which is a newly combined array of KVN (Korean VLBI Network) and VERA (VLBI Exploration of Radio Astrometry). We have succeeded in imaging compact maser features with a synthesized beam size of 2.7 milliarcseconds x 1.5 milliarcseconds (mas). These features are detected at a limited number of baselines within the length of shorter than approximately 650 km corresponding to 100 Mlambda in the uv-coverage. The central velocity and the velocity width of the 44 GHz methanol maser are consistent with those of the quiescent gas rather than the outflow traced by the SiO thermal line. The minimum component size among the maser features is ~ 5 mas x 2 mas, which corresponds to the linear size of ~ 15 AU x 6 AU assuming a distance of 3 kpc. The brightness temperatures of these features range from ~ 3.5 x 10^{8} to 1.0 x 10^{10} K, which are higher than estimated lower limit from a previous Very Large Array observation with the highest spatial resolution of ~ 50 mas. The 44 GHz class I methanol maser in IRAS 18151-1208 is found to be associated with the MM2 core, which is thought to be less evolved than another millimeter core MM1 associated with the 6.7 GHz class II methanol maser.Comment: 19 pages, 3 figure

De Pulchritudine non est Disputandum? A cross-cultural investigation of the alleged intersubjective validity of aesthetic judgment

Since at least Hume and Kant, philosophers working on the nature of aesthetic judgment have generally agreed that common sense does not treat aesthetic judgments in the same way as typical expressions of subjective preferences—rather, it endows them with intersubjective validity, the property of being right or wrong regardless of disagreement. Moreover, this apparent intersubjective validity has been taken to constitute one of the main explananda for philosophical accounts of aesthetic judgment. But is it really the case that most people spontaneously treat aesthetic judgments as having intersubjective validity? In this paper, we report the results of a cross-cultural study with over 2,000 respondents spanning 19 countries. Despite significant geographical variations, these results suggest that most people do not treat their own aesthetic judgments as having intersubjective validity. We conclude by discussing the implications of our findings for theories of aesthetic judgment and the purpose of aesthetics in general.info:eu-repo/semantics/acceptedVersio

Nothing at Stake in Knowledge

Many philosophers hold that stakes affect ordinary knowledge ascriptions. Here’s a version of a pair of cases aimed at supporting this: Bob and his wife are driving home on Friday and considering whether to stop at the bank to deposit a check. The lines at the bank are very long and so Bob considers coming back on Saturday. In the low stakes version, nothing of importance hinges on whether the check is deposited; in the high stakes version, it is very important that the check be deposited. Bob’s wife asks whether the bank will be open on Saturday. Bob says he drove past the bank last Saturday, and it was open. However, his wife points out that banks sometimes change their hours. Bob says “I know the bank will be open tomorrow”. In the low stakes case, many philosophers maintain that Bob does indeed know that the bank will be open; in the high stakes case, these philosophers maintain that Bob is ignorant – his statement that he knows the bank will be open tomorrow is false. These philosophers also maintain that this pattern of judgments is what we would expect from competent speakers confronted with this and similar cases (e.g., Cohen, 1999, 2013; DeRose, 1992, 2009; Fantl and McGrath, 2002; Nagel, 2008; Rysiew, 2001; Stanley, 2005). Though many philosophers agree that stakes play a role in ordinary knowledge ascriptions, there is disagreement about what explains this. One view, epistemic contextualism, holds that “to know” is a context sensitive verb and that the truth conditions for knowledge ascriptions can vary across conversational contexts (e.g., DeRose, 2009). For instance, Bob’s statement “I know the bank will be open tomorrow” can be true in low stakes contexts and false in high stakes contexts. Another view, interest-relative invariantism, denies that “to know” is a context sensitive verb and that the truth conditions for knowledge ascriptions vary according to conversational contexts. Instead, cases like the Bank cases show that practical factors—i.e., stakes—play a distinctive role in determining whether the knowledge relation obtains (e.g., Stanley, 2005). Yet another alternative, which we’ll call classical invariantism, denies that “to know” is a context sensitive verb and that practical factors, such as stakes, play a direct role in determining whether the knowledge relation obtains. Instead, stakes affect knowledge ascriptions only by affecting our assessment of factors that have traditionally been taken to constitute or be necessary for knowledge, such as e.g., belief, quality of evidence, etc. (e.g., Bach, 2005; Weatherson, 2005; Ganson, 2007; Nagel, 2008). If this is right, then the role of stakes in knowledge ascriptions fails to motivate such surprising views as epistemic contextualism or interest-relative invariantism. Naturally, epistemic contextualists and interest-relative invariantists deny this, claiming that even when the factors that have traditionally been taken to constitute or be necessary for knowledge are held fixed, stakes continue to play a role in ordinary knowledge ascriptions (e.g., DeRose, 2009; Lawlor, 2013). So we see a dispute over what best explains the role of stakes in ordinary knowledge ascriptions. It is thus extremely surprising that a wide range of empirical evidence suggests that ordinary knowledge ascriptions fail to display any sensitivity to stakes (e.g., Buckwalter, 2010; Buckwalter and Schaffer, 2015; Feltz and Zarpentine, 2010; May, Sinnott-Armstrong, Hull, and Zimmerman, 2010; Turri, forthcoming; though see e.g., Pinillos, 2012; Pinillos and Simpson, 2014; Sripada and Stanley, 2012). If stakes really do not play any role in ordinary knowledge ascriptions, one of the main motivations for epistemic contextualism and interest relative invariantism would be undermined. Perhaps these different explanations of the role of stakes in ordinary knowledge ascription are born out of nothing more than a myth (Schaffer and Knobe, 2009). If so, classical invariantism about knowledge might be best supported—not because it provides the best explanation of the role of stakes in ordinary knowledge ascriptions, but rather because the failure of stakes to play a role in ordinary knowledge ascription would undercut an important motivation for its two competitors, epistemic contextualism and interest-relative invariantism. These radical alternatives to classical invariantism, lacking evidence in support of one of their important motivations, should perhaps then fall. Classical invariantism would stand. In the remainder of this article, we’ll disarm an important motivation for epistemic contextualism and interest-relative invariantism. We’ll accomplish this by presenting a stringent test of whether there is a stakes effect on ordinary knowledge ascription. Having shown that, even on a stringent way of testing, stakes fail to impact ordinary knowledge ascription, we will conclude that we should take another look at classical invariantism. Here is how we will proceed. Section 1 lays out some limitations of previous research on stakes. Section 2 presents our study and concludes that there is little evidence for a substantial stakes effect. Section 3 responds to objections. The conclusion clears the way for classical invariantism