El error como anacronismo en la enseñanza de la ciencia

La historia "canónica" de la ciencia es un relato anacrónico plagado de profundas dicotómías, sobredestacando los éxitos (descubrimientos, hallazgos, modelos teóricos triunfantes, hitos) y desestimando los fracasos. En la verdadera ciencia, hay discusión, debate y controversia constantes, alimentados por la dinámica propia de las comunidades disciplinares. En la enseñanza de la ciencia el análisis del "error" puede resultar mucho más interesante como constructo de la evolución del conocimiento, que su simple señalización como demarcación de teorías exitosas. Es igualmente valioso el estudio del fraude. Como la actividad científica depende fuertemente de la publicación, está por tanto condicionada por el discurso. La manipulación hábil de este discurso puede, en ocasiones, hacer especialmente difícil de identificar el artificio, el sesgo, el engaño. El enfoque conocido como "naturaleza de la ciencia" nos permite aprovechar estos elementos para comprender el funcionamiento interno e intrincado del ethos científico, y transmitir a los alumnos dimensiones controversiales de la ciencia como actividad social. La enseñanza de la ciencia puede sacar mucho provecho de estos dispositivos, que permiten segundas lecturas sobre hechos históricos. Traemos a consideración dos hechos científicos de principios del siglo XX, para examinar las complejas relaciones que una simple calificación de fraude o error impediría observar. Destacamos además el casi nulo tratamiento que tienen estos compromisos en los textos escolares de uso corriente. Realizamos sugerencias para que estos temas tengan inclusión en dispositivos didácticos con un enfoque epistemológico más actualizado, que revele el contexto y las tensiones a las que está sujeta la construcción del conocimiento

Age determination of sediment core MD99-2201

A marine sediment core from the leeward margin of Great Bahama Bank (GBB) was subjected to a multiproxy study. The aragonite dominated core MD992201 comprises the past 7230 years in a decadal time resolution and shows sedimentation rates of up to 13.8 m/kyr. Aragonite mass accumulation rates, age differences between planktonic foraminifera and aragonite sediments, and temperature distribution are used to deduce changes in aragonite production rates and paleocurrent strengths. Aragonite precipitation rates on GBB are controlled by exchange of carbonate ions and CO2 loss due to temperature-salinity conditions and biological activity, and these are dependent on the current strength. Paleocurrent strengths on GBB show high current velocities during the periods 6000-5100 years BP, 3500-2700 years BP, and 1600-700 years BP; lower current speeds existed during the time intervals 5100-3500 years BP, 2700-1600 years BP, and 700-100 years BP. Bahamian surface currents are directly linked to the North Atlantic atmospheric circulation, and thus periods with high (low) current speeds are proposed to be phases of strong (weak) atmospheric circulation.

Elevation Models of Antarctica and Greenland derived from CryoSat-2 in the period 2011 to 2013

This study focuses on the present-day surface elevation of the Greenland and Antarctic ice sheets. Based on 3 years of CryoSat-2 data acquisition we derived new elevation models (DEMs) as well as elevation change maps and volume change estimates for both ice sheets. Here we present the new DEMs and their corresponding error maps. The accuracy of the derived DEMs for Greenland and Antarctica is similar to those of previous DEMs obtained by satellite-based laser and radar altimeters. Comparisons with ICESat data show that 80% of the CryoSat-2 DEMs have an uncertainty of less than 3 m ± 15 m. The surface elevation change rates between January 2011 and January 2014 are presented for both ice sheets. We compared our results to elevation change rates obtained from ICESat data covering the time period from 2003 to 2009. The comparison reveals that in West Antarctica the volume loss has increased by a factor of 3. It also shows an anomalous thickening in Dronning Maud Land, East Antarctica which represents a known large-scale accumulation event. This anomaly partly compensates for the observed increased volume loss of the Antarctic Peninsula and West Antarctica. For Greenland we find a volume loss increased by a factor of 2.5 compared to the ICESat period with large negative elevation changes concentrated at the west and southeast coasts. The combined volume change of Greenland and Antarctica for the observation period is estimated to be -503 ± 107 km**3/yr. Greenland contributes nearly 75% to the total volume change with -375 ± 24 km**3/yr.

40Ar-39Ar geochronological studies on rocks at DSDP Leg 58 Holes

The technique of 40Ar-39Ar step-heating dating was applied to three rock samples from core of DSDP Site 443, one sample from Site 445, and four samples at Site 446. All sites were drilled during DSDP Leg 58. At Site 443 (Shikoku Basin), about 116 meters of basalt basement was drilled. Three samples were chosen for dating from different levels in the basalt; two samples are aphyric basalt, and the other is subophitic dolerite. At Site 445 (Daito Ridge), no basement rock was drilled; however, conglomeratic sandstone was cored in the lower part of the hole. 40Ar-39Ar dating was applied to a basalt pebble in the conglomerate. At Site 446 (Daito Basin), the lower cored sequence is clay stone interlayered with 16 basalt sills. Four samples were chosen from sills at different levels.