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Posted: 28 Nov 2012 09:36 AM PST
Referencia: Kurzweilai.net .
Por Steven Pinker, 25 de noviembre 2012
"La Tabla Rasa: la negación moderna de la naturaleza humana"
Autor: Steven Pinker
 Con su ingenio característico, lucidez y perspicacia, Pinker sostiene que el dogma de que la mente no tiene características innatas, una doctrina sostenida por muchos intelectuales durante el pasado siglo, niega nuestra humanidad común y nuestras preferencias individuales, reemplazando los análisis objetivos de los problemas sociales con eslóganes sensacionalistas, y distorsiona nuestra comprensión de la política, la violencia, la educación de los hijos y de las artes. Introducir calma y racionalidad en los debates, conocidos por pulverizar y ensuciar las argumentaciones, Pinker muestra la importancia del reconocimiento honesto de la naturaleza humana basada en la ciencia y el sentido común. - Puedes echar un vistazo al libro en Scribd.com o en Google.Books . - Imagen: Scribd.com.       |
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Posted: 27 Nov 2012 11:16 PM PST
Referencia: NewScientist.com .
Por Catherine Brahic 26 de noviembre 2012
 La edad de oroLos finales de 1990 y principios de 2000, fue una época dorada de descubrimientos para los paleoantropólogos. En el espacio de una década, fueron descubiertos los restos de tres homínidos nuevos en los desiertos de África oriental y central. El más completo fue Ardipithecus ramidus, un esqueleto de 4,4 millones de años de edad, en Afar, Etiopía, apodado Ardi. A éste se unieron más tarde el Sahelanthropus tchadensis, de hace 6 a 7 millones de años, y el Orrorin tugenensis, de unos 6 millones de años. El Ardipithecus es, con mucho, el más conocido de los tres. Aproximadamente del tamaño de un chimpancé, el esqueleto incluye dientes como los humanos, un cráneo pequeño y las extremidades inferiores de un animal que podía caminar en posición vertical (aunque también tenía un dedo gordo del pie oponible para agarrarse a las ramas). También fue identificada una posible relación, el Ardipithecus kadabba, por los dientes y fragmentos de unos pocos huesos, haciendo retroceder el origen del género alrededor de hace 5,8 millones de años. Del Sahelanthropus se conoce un solo cráneo en el Chad, apodado Toumaï. Tal que el Ardipithecus, sus dientes eran pequeños y de forma humana, y la mitad de su cara es corta, otro rasgo humano. La forma del agujero donde se inserta la columna vertebral en la base del cráneo sugiere que podría caminar sobre dos piernas, aunque esto es objeto de acalorados debates. Del Orrorin, por su parte, se sabe solamente de un puñado de dientes, además de algunos huesos de las piernas y los dedos, lo que da a entender que también caminaba erguido, pero que aún trepaba a los árboles. Todos los huesos juntos apenas llenarían dos cajas de zapatos, pero hicieron un gran ruido. En general, se pensaba que, cuando finalmente se lograra desenterrar los primeros homínidos, nos encontraríamos con algo que se parecía a un chimpancé. Y sin embargo, Ardi, Toumai y Orrorin tiene características netamente humanas. "Reina el desconcierto entre lo que sabemos", dice Tim White de la Universidad de California, Berkeley, quien dirigió el descubrimiento de Ardi. Algunos se apresuraron a reclamarlos como ancestros humanos. Pero el reloj de edad molecular decía otra cosa: era demasiado pronto. Y así, se les descartó como ramas laterales del árbol familiar, experimentos evolutivos sin salida con poca o ninguna relevancia para el evento principal. Ahora, con las nuevas estimaciones del reloj molecular, se les ha vuelto a dar la bienvenida al redil. "El argumento de que son demasiado tempranos se ha evaporado", apunta White, que piensa que los tres son miembros del mismo género. Con el tiempo ciertamente las cosas se ven mejor. "Si nos fijamos en el consenso de las recientes tasas de mutación, Sahelanthropus está casi en el límite", dice Scally, que recientemente publicó una revisión de las revisiones y de sus consecuencias para la evolución (Nature Review Genetics, vol 13, p 745) . "Si se trata de un humano, un proto-humano, o dentro de un período en el que los humanos se iban separando de los chimpancés, no creo que nadie pueda decirlo. Pero desde la perspectiva genética, desde luego que no creo que deba descartarse, que es lo que la gente solía hacer." La anatomía también tiene sentido, agrega White. "Parece que para aquellos de nosotros que estudiamos los fósiles, que la forma de obtener el último ancestro común es un Australopithecus, a través de algo parecido al Ardi. Se había vuelto una dirección preconcebida la del Australopithecus. Y dicho de otro manera, esto es posterior a la escisión". "¿Representa el Ardi una especie que está en línea directa?", continúa. "No lo sé, porque no tenemos suficientes fósiles de otros lugares todavía. Pero tampoco podemos descartarlo". Otra posibilidad, no descartable, es que la división sea aún más atrás en el tiempo. La lenta acumulación de mutaciones significa que las nuevas estimaciones de la tasa de mutación tengan incluso más grandes márgenes de error. En general, los genetistas y los paleoantropólogos se sienten cómodos con una cifra revisada de 7 a 8 millones de años. Algunos, incluso, van más allá. "Para mí, una división de 13 millones de años de antigüedad, podría en el fondo estar en lo cierto", dice Lovejoy. "Si te vas atrás 10 ó 15 millones de años, el planeta estaba cubierto de monos, muchos de empezaron a mostrar algunos tipos de adaptaciones anatómicas que se observan en los humanos modernos". Lovejoy, no obstante, va por su cuenta. Una semana después de que A. Kong y sus colegas publicaran su nueva estimación, otro equipo, incluyendo muchos de los mismos investigadores, publicaron otra. Ellos analizaron el ADN de más de 85.000 islandeses, centrándose en los tramos cortos de ADN llamados microsatélites. Según su coautor David Reich, de la Universidad de Harvard se trata del registro más fiable de mutaciones. La tasa que encontraron no era tan lenta como la de A. Kong. A consecuencia de ello, su estimación de la fecha de la escisión es más restringida, 7,5 millones años (Nature Genetics, vol 44, p 1161). Hay unos cuantos otros extremos sueltos a poner en orden. Otro problema con la estimación A. Kong, dice Reich, es que si se utiliza hasta la fecha la escisión entre orangutanes y monos africanos, humanos, chimpancés y gorilas, entonces conseguimos algo que entra en el rango de 30 millones de años, salvajemente inconsistente con el máximo de 20 millones de años sugeridos por el registro fósil. En un intento de reconciliar ambos, Scally ha propuesto que a medida que nuestros ancestros evolucionaban desde los pequeños primates a monos de gran tamaño, el número de mutaciones acumuladas con cada generación decrecía. Esto concuerda con lo que se ve en otros mamíferos. "Se observa con bastante amplitud, incluso en primates, que las especies con mayor tamaño corporal tienden a tener tiempos más largos de generación", dice Scally. Las generaciones más largas significan menores tasas de mutación. Esto sería plausible, dice Reich, si no fuera porque, caso de tener razón, las tasas de mutación de nuestros antepasados y de los orangutanes habrían caído exactamente al mismo tiempo. "Me parece algo en extremo difícil de creer"; a pesar de ello, prosiguió Reich, "la hipótesis de Scally es probablemente la mejor que tenemos." Sutilezas aparte, lo que sí parece seguro es que nuestro linaje es considerablemente mayor de lo que se pensaba. Y eso tiene consecuencias para el resto de la prehistoria humana. El reloj molecular se ha utilizado hasta la fecha para una serie de eventos clave, no menos, al menos cuando nuestros ancestros salieron de África. Eso ha sido estimado observando las diferencias genéticas entre los Yoruba de Nigeria y los europeos y los asiáticos. Los primeros cálculos genéticos proponían que esto ocurrió hace 50.000 años. Así que cuando se descubrieron los restos fósiles de Israel y de los sitios arqueológicos de la India con alrededor de 100.000 años de antigüedad, hubo que dar algunas explicaciones. Los huesos israelíes fueron descartados como los restos de una solución temprana de una opción sin salida, y los sitios de la India como un error, puro y simple. El reloj molecular de nuevo resuelve la discrepancia, empujando la divergencia de vuelta entre 90.000 y 130.000 años atrás. Algo similar ocurre con la división entre nosotros y los neandertales. Los huesos descubiertos en una cueva en Atapuerca, España, y atribuidos al probable antepasado de los neandertales, el Homo heidelbergensis, datan de hace entre 400.000 y 600.000 años. Pero esto creó un problema, ya que el reloj molecular sugería que H. heidelbergensis apareció después de eso. Sin embargo, las nuevas estimaciones decen que, de hecho, tienen alrededor de 500.000 años de antigüedad. Otros hechos relevantes esperan revisión; no obstante, la principal conclusión está clara. El linaje humano es mucho mayor, y nuestros parientes más cercanos vivos son más lejanos de lo que se pensaba. Estamos acostumbrados a pensar en nosotros mismos como algo separado y distinto del resto del reino animal. Pues ya tenemos un poco más de separación, y un poco más claro. - Precisando nuestros orígenes (1) . - Precisando nuestros orígenes (2). - Artículo original: "Our true dawn: Pinning down human origins" - Imagen y diagrama: Istockphoto y New.Scientist.com .    |
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Posted: 27 Nov 2012 11:00 PM PST
Referencia: NewScientist.com .
Por Catherine Brahic, 26 de noviembre 2012
La argumentación sobre que nuestro linaje escindido del de los chimpancés está a punto de resolverse, con colosales consecuencias para la prehistoria. Esta es una de las cuestiones más importantes y más fuertes de la evolución humana. Sabemos que en algún momento compartimos un ancestro común con los chimpancés, pero el momento exacto, y cómo era ese antepasado, ha sido exasperadamente difícil de precisar. Los paleontólogos han buscado restos fósiles y los genetistas han hurgado en la documentación histórica que supone el ADN humano y el del chimpancé. Ambas disciplinas hicieron descubrimientos, pero no terminaban de llegar a un acuerdo. Las nuevas estimaciones en cuanto a la separación de nuestro linaje y el de los chimpancés sugieren que algunas de nuestras ideas establecidas están asombrosamente equivocadas. Si son correctas, exigen una reescritura de la prehistoria humana, empezando desde el principio. Pero, ¿cuándo fue ese principio? El primer lugar, obviamente, para buscar respuestas será en el registro fósil. Pero los fósiles humanos, o más estrictamente homínidos, que es el grupo que nos incluye tanto a nosotros como a todos nuestros parientes extintos desde que se produjo la escisión, son francamente pocos sobre la tierra, además de difíciles de interpretar. Los genetistas tienen que trabajar más. El ADN contiene trazos delatores de eventos del pasado de la especie, incluyendo información sobre la ascendencia común y la especiación. En teoría, el cálculo de temporización de un evento de especiación debería ser sencillo. Conforme dos especies divergen de un ancestro común, su ADN se vuelve cada vez más diferente, en gran parte debido a la acumulación de mutaciones aleatorias. La cantidad de diferencia genética entre dos especies relacionadas es proporcional a la longitud en el tiempo desde que se separaron. Para estimar cuándo se produjo la separación entre humano y chimpancé, los genetistas pueden, simplemente, contar las diferencias en los tramos coincidentes de ADN del chimpancé y el humano, se divide después por la velocidad a la que se acumulan las mutaciones. Esto se conoce como el método del reloj molecular. Pero hay trampa. Para llegar a esa respuesta debemos saber lo rápido que surgen las mutaciones. Y eso nos lleva de nuevo al punto de partida: primero necesitamos saber cuánto tiempo hace que nos separamos de los chimpancés. Para evitar este ‘catch-22', los genetistas volvieron su vista hacia los orangutanes. Los fósiles sugieren que la separación de nuestro linaje ocurrió hace 10 ó 20 millones de años. Usando este dulce dato, los genetistas llegaron a una tasa de unas 75 mutaciones por genoma y por generación. En otras palabras, la descendencia humana y la de chimpancés tiene, cada una, 75 nuevas mutaciones que no heredan de sus padres. Fósiles o ADN Este número se basa en varios supuestos importantes, igual de fiables que los registros fósiles del orangután, o sea, que no lo son. Pese a ello, se llevó a cabo la suposición de que los ancestros humanos se separaron de los chimpancés entre 4 a 6 millones de años atrás. Cuando los cazadores de fósiles oyen este número, lloran por el error. El extremo inferior de la estimación es particularmente difícil de tragar. El Australopithecus afarensis, un homínido temprano desde del este de África, que ya tiene características específicas humanas según nuestros datos se remonta por lo menos a 3,85 millones de años. Sus caninos eran pequeños, por ejemplo. Y caminaban erguidos. Ambos rasgos se consideran homínidos, lo que significa que desarrollaron nuestro linaje después de la escisión y no aparecen al lado del chimpancé. Sin embargo, es difícil ver cómo podrían haber evolucionado tan rápidamente, en tan sólo 150.000 años después de la separación. "Los genetistas ignoraron por completo a los paleontólogos", señala Owen Lovejoy de la Universidad Estatal de Kent, en Ohio. "Nos gustaría obtener estimaciones de hace alrededor de 4 millones de años; no obstante hay homínidos inconfundibles y altamente evolucionados que se remontan a casi 4 millones de años. Pero indicar una fecha para la divergencia de 4 millones años es, simplemente, una tontería." Incluso en 5 ó 6 millones de años, la separación fue recibida con escepticismo. Esto es debido en gran parte a tres fósiles recientemente descubiertos en África que datan de la misma época. Los tres Australopithecus son anteriores, pero portaban las marcas inconfundibles de la humanidad. Aunque la interpretación de los restos es controvertido, muchos los consideran como post-escisión. Dicho de otra manera, los paleontólogos estaban seguros de que había pocas probabilidades de exactitud de los resultados de ADN. La humanidad, afirmaron, tenía que ser más vieja de lo que los genetistas clamaban. La historia parece haberles dado la razón. En los últimos tres años, los investigadores que estudian las poblaciones humanas, por primera vez han podido observar mutaciones casi a medida de que ocurrieran. Y eso crea toda una diferencia. En lugar de depender de una estimación basada en los fósiles raros, ahora podemos ver el tic-tac del reloj molecular en tiempo real. "Hasta que no fueron capaces de comparar los genomas de los niños con sus padres, no pudieron estimar la tasa de mutación de los humanos", añadió Aylwyn Scally, del Wellcome Trust Sanger Institute de Cambridge, Reino Unido. En septiembre, Augustine Kong, de Decode Genetics en Reykjavik, Islandia, y sus colegas, publicaron un innovador estudio. Después de escanear los genomas de 78 niños y sus padres, para contar el número de nuevas mutaciones en el genoma de cada niño, hallaron que cada niño portaba un promedio de 36 nuevas mutaciones (Nature, vol 488, p 471). Es crucial entender que es la mitad de lo que se suponía anteriormente, es decir, el reloj molecular es más lento de lo que pensábamos, reajustando la división humano-chimpancé más atrás en el tiempo (ver diagrama).  Pero, ¿cuánto tiempo atrás exactamente? A principios de este año, Kevin Langergraber, de la Universidad de Boston y sus colegas, resolvieron otra pieza del rompecabezas. Las tasas de mutación en estudios como los de A. Kong se miden por generación. Para convertir esto en una estimación de la separación de los chimpancés, lo que necesitamos saber es cuánto tiempo dura una generación, en otras palabras, la edad media de reproducción. Tenemos un buen control sobre esto para los humanos, pero no en otros primates. Para los chimpancés, las estimaciones oscilaron entre 15 a 25 años. Utilizando datos de 226 crías nacidas en ocho poblaciones de chimpancés salvajes, Langergraber encontró que, de media, los chimpancés se reproducían con 24 años y medio (PNAS, vol 109, p 15716). Basándose en estas nuevas cifras, el equipo estimó que el linaje humano siguió su camino por separado hace al menos 7 millones de años, y posiblemente una fecha tan lejana como 13 millones de años. "Está claro que si esto es correcto, la mayoría de los libros de texto que tratan de la historia de nuestra especie tendrán que reescribirse", apunta Klaus Zuberbühler, de la Universidad de St Andrews, Reino Unido, que ayudó a la recopilación de datos para el estudio. "La importancia de esto apenas puede sobreestimarse". John Hawks, de la Universidad de Wisconsin-Madison, está de acuerdo. "Creo que esto afectará a prácticamente todos los acontecimientos de la evolución humana, desde la divergencia inicial de nuestro linaje a la dispersión fuera de África." Quizás la consecuencia más significativa la hallemos en la búsqueda de los primeros miembros de una tribu humana. Por ahora, el Australopithecus es el más antiguo homínido aceptada, aunque una división anterior nos trae a escena a otras especies. - Precisando nuestros orígenes (1) . - Precisando nuestros orígenes (2). - Artículo original: "Our true dawn: Pinning down human origins" - Imagen y diagrama: Istockphoto y New.Scientist.com |
Mostrando entradas con la etiqueta Cosmovision. Mostrar todas las entradas
Mostrando entradas con la etiqueta Cosmovision. Mostrar todas las entradas
miércoles, 2 de enero de 2013
Posted: 01 Nov 2012 03:02 AM PDT
Referencia: Scientific.American.com .
Por Eugenie Samuel Reich, 30 octubre 2012
Un marco basado en las matemáticas de nivel universitario podría describir lo que sucede a las partículas en los llamados desgarros del espacio-tiempo, las fluctuaciones de gravedad, como los que ocurren durante el nacimiento de un agujero negro.
La tarea de ajustar la mecánica cuántica, que se ocupa del comportamiento de las partículas fundamentales, con la teoría general de Einstein de la relatividad, que describe la gravedad en términos de un espacio-tiempo curvo, ha demostrado ser un enorme desafío. Una de las dificultades es que no resulta adecuada para describir lo que le ocurre a las partículas cuando el espacio-tiempo que ocupan sufre cambios drásticos, como los producidos con el nacimiento de un agujero negro. Sin embargo, en un artículo publicado en arXiv el 15 de octubre (A. D. Shapere et al. http://arxiv.org/abs/1210.
El análisis no tiene un modelo de gravedad explícito, por lo que no es un intento de formular una teoría de "gravedad cuántica" que aune la relatividad general y la mecánica cuántica bajo un mismo paraguas. En cambio, los autores, entre ellos el premio Nobel Frank Wilczek, del Instituto de Tecnología de Massachusetts (MIT) en Cambridge, sugieren que su trabajo podría proporcionar un marco simplificado para la comprensión de los efectos de la gravedad sobre las partículas cuánticas, así como la descripción de otras situaciones en las que el espacios por donde se mueven las partículas cuánticas se pueden alterar radicalmente, tal como en los experimentos de física de materia condensada. "Esto es excitante", dice Wilczek, "Tenemos que ver hasta dónde nos puede llevar".
La idea está atrayendo la atención no sólo por el alcance de sus posibles aplicaciones, sino por el grado de nivel de matemáticas. "Su trabajo comienza con el marco más elemental", indica Brian Greene, teórico de cuerdas de la Universidad de Columbia en Nueva York. "Es inspirador hasta dónde se puede llegar sin necesidad de ningún mecanismo de lujo."
Wilczek y sus coautores, han establecido un sistema hipotético de una sola partícula cuántica en movimiento a lo largo de una conexión que se divide abruptamente en dos. El despojado escenario es efectivamente la versión unidimensional de un encuentro con un espacio-tiempo desgarrado, el cual sucede cuando la topología de un espacio cambia de manera radical. Los teóricos se concentran en lo que ocurre en los extremos de la conexión, estableciendo las "condiciones límite" para los estados anteriores y posteriores de la onda cuántica asociada a la partícula. A continuación, ellos muestran que la onda puede evolucionar de forma continua sin ninguna interrupción, tal como las condiciones límite cambian de una geometría a otra, sin incompatibilidad. "Se puede seguir sin problemas el proceso", señala Al Shapere, de la Universidad de Kentucky en Lexington, y co-autor del artículo, y agrega que, como con los anillos de un mago, la transformación es imposible de visualizar, pero tiene sentido matemático.
El deseo de escapar de los dolores de cabeza matemáticos causados por tales transformaciones, es una de las motivaciones para la teoría de cuerdas, que permite cambios suaves en la topología del espacio-tiempo, aduce Greene, y sugiere que el enfoque desarrollado por Wilczek, Shapere y el estudiante de pregrado del MIT, Zhaoxi Xiong, podría aplicarse también dentro de la teoría de cuerdas.
Aunque originalmente Wilczek pensaba que el resultado era nuevo, un documento de 1995, de Aiyalam Balachandran, de la Universidad de Syracuse en Nueva York, ya propuso una estrategia similar para describir los cambios de topología en la mecánica cuántica (A. P. Balachandran et al. Nucl. Phys. B 446, 299-314 ; 1995). Balachandran reconoce que su trabajo no ha afectado a la corriente principal, y espera que el artículo de Wilczek induzca a otros a echar una mirada más cercana. "Los enfoques convencionales para este problema no llegan muy lejos", dice. "Esto abre una nueva técnica."
El marco también podría servir de inspiración para los experimentadores que trabajan en la materia condensada. Rob Myers, un teórico de cuerdas en el Instituto Perimeter de Física Teórica, en Waterloo, Canadá, también espera que sea relevante a un área denominada cuántica sofocada, en la que se desarrollan sistemas cuánticos aislados del medio ambiente y luego se desequilibran por la acción del experimentador. Los físicos de materia condensada han desarrollado diversos sistemas cuánticos, incluyendo trampas de átomos fríos y circuitos de superconductores, que se pueden utilizar para probar esta idea.
Aunque los autores han diseñado su solución en una sola dimensión, Myers espera que el enfoque se pueda generalizar fácilmente a la hora de describir experimentos reales en tres dimensiones, aunque advierte que el documento sólo representa un primer paso. "Está por ver en el tiempo, el impacto real de este trabajo."
- Fuente: Reproducido desde Magazine Nature.
- Imagen: Frank Wilczek estudia cómo las partículas fundamentales responden a los cambios drásticos en el espacio-tiempo.
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domingo, 16 de septiembre de 2012
Musings on chemistry and the history and philosophy of science
The Curious Wavefunction HomeAboutContact
Theories, models and the future of science
September 5, 2012
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Dark
matter and dark energy: Models for accounting for the distribution of
matter and the acceleration of the universe (Image: Edelweiss)
But what is equally interesting is the ignorance that the prizewinning discovery reveals. The prize was awarded for the observation of an accelerating universe, not the explanation. Nobody really knows why the universe is accelerating. The current explanation for the acceleration consists of a set of different models incorporating entities like dark energy, none of which has been definitively proven to explain the facts well enough. And this makes me wonder if such a proliferation of models without accompanying concrete theories is going to embody science in the future.
The twentieth century saw theoretical advances in physics that agreed with experiment to an astonishing degree of accuracy. This progress culminated in the development of quantum electrodynamics, whose accuracy in Richard Feynman’s words is equivalent to calculating the distance between New York and Los Angeles within a hairsbreadth. Since then we have had some successes in quantitatively correlating theory to experiment, most notably in the work on validating the Big Bang and the development of the standard model of particle physics. But dark energy- there’s no theory for it as of now that remotely approaches the rigor of QED when it comes to comparison with experiment.
Of course it’s unfair to criticize dark energy since we are just getting started on tackling its mysteries. Maybe someday a comprehensive theory will be found, but given the complexity of what we are trying to achieve (essentially explain the nature of all the matter and energy in the universe) it seems likely that we may always be stuck with models, not actual theories. And this may be the case not just with cosmology but with other sciences. The fact is that the kinds of phenomena that science has been dealing with recently have been multifactorial, complex and emergent. The kind of mechanical, reductionist approaches that worked so well for atomic physics and molecular biology may turn out to be too impoverished for taking these phenomena apart. Take biology for instance. Do you think we could have a complete “theory” for the human brain that can quantitatively calculate all brain states leading to consciousness and our reaction to the external world? How about trying to build a “theory” for signal transduction that would allow us to not just predict but truly understand (in a holistic way) all the interactions with drugs and biomolecules that living organisms undergo? And then there’s other complex phenomena like the economy, the weather and social networks. It seems wise to say that we don’t anticipate real overarching theories for these phenomena anytime soon.
Molecular models - such as that of a ribosome depicted here - are already an integral part of chemistry and biology (Image: MRC)
Admittedly these and other models are still far behind theory and experiment which have had head starts of about a thousand years. But there can be little doubt that such models can only become more accurate with increasing computational firepower and more comprehensive inclusion of data. How accurate remains to be seen, but it’s worth noting that there are already books that make a case for an independent, study-worthy philosophy of modeling and simulation; a recent book by the University of South Florida philosopher Eric Winsberg for instance extols philosophers of science to treat models not just as convenient applications and representations of theories (which are then the only fundamental things worth studying) but as ultimate independent explanatory devices in themselves that deserve separate philosophical consideration.
Could this then be at least part of the future of science? A future where robust experimental observations are encompassed not by beautifully rigorous and complete theories like general relativity or QED but only by different models which are patched together through a combination of rigor, empirical data, fudge factors and plain old intuition? This would be a new kind of science, as useful in its applications as its old counterpart but rooting itself only in models and not in complete theories. Given the history of theoretical science, such a future may seem dark and depressing. That is because as the statistician George Box famously quipped, although some models are useful, all models are in some sense wrong. What Box meant was that models often feature unrealistic assumptions about the details of a system, and yet allow us to reproduce the essential features of reality. They are subject to fudge factors and to the whims of their creators. Thus they can never provide the certain connection to “reality” that theories seem to. This is especially a problem when disparate models give the same answer to a question. In the absence of discriminating ideas, which model is then the “correct” one? The usual, convenient answer is “none of them”, since they all do an equally good job of explaining the facts. But this view of science, where models that can be judged only on the basis of their utility are the ultimate arbiters of reality and where there is thus no sense of a unified theoretical framework, feels deeply unsettling. In this universe the “real” theory will always remain hidden behind a facade of models, much as reality is always hidden behind the event horizon of a black hole. Such a universe can hardly warm the cockles of the heart of those who are used to crafting grand narratives for life and the cosmos. However it may be the price we pay for more comprehensive understanding. In the future, Nobel Prizes may be frequently awarded for important observations for which there are no real theories, only models. The discovery of dark matter and energy and our current attempts to understand the brain and signal transduction could well be the harbingers of this new kind of science.
Should we worry about such a world rife with models and devoid of theories? Not necessarily. If there’s one thing about science that we know, it’s that it evolves. Grand explanatory theories have traditionally been supposed to be a key part- probably the key part- of the scientific enterprise. But this is mostly because of historical precedent as well a psychological urge for seeking elegance and unification. And even historically sciences have progressed much without complete theories, as chemistry did for hundreds of years before the emergence of the atomic and structural theories. The belief that a grand theory is essential for the true development of a discipline has been resoundingly validated in the past but it’s utility may well have plateaued. I am not advocating some “end of science” scenario here – far from it – but as the recent history of string theory and theoretical physics in general demonstrates, even the most mathematically elegant and psychologically pleasing theories may have scant connection to reality. Because of the sheer scale and complexity of what we are trying to currently explain, we may have hit a roadblock in the application of the largely reductionist traditional scientific thinking which has served us so well for half a millennium
Ultimately what matters though is whether our constructs- theories, models, rules of thumb or heuristic pattern recognition- are up to the task of constructing consistent explanations of complex phenomena. The business of science is explanation, whether through unified narratives or piecemeal explanation is secondary. Although the former sounds more psychologically satisfying, science does not really care about stoking our egos. What is out there exists, and we do whatever’s necessary and sufficient to unravel it.
This is a revised version of a past post.
About the Author:
Ashutosh (Ash) Jogalekar is a chemist interested in the nature of the
"central science" and its intersection with philosophy, history and
culture. He is also more generally interested in the history and
philosophy of science and is particularly fascinated by how science
tries to mirror reality by building models. Follow on Twitter @curiouswavefn.
lunes, 6 de agosto de 2012
Is Death An Illusion? Evidence Suggests Death Isn’t the End
Robert Lanza, MD -
BIOCENTRISM
CHIEF SCIENTIFIC OFFICER OF ADVANCED CELL TECHNOLOGY
Autor: Robert Lanza M.D.
After the death of his old friend, Albert Einstein said “Now Besso has departed from this strange world a little ahead of me. That means nothing. People like us … know that the distinction between past, present and future is only a stubbornly persistent illusion.”
New evidence continues to suggest that Einstein was right – death isan illusion.
Our classical way of thinking is based on the belief that the world has an objective observer-independent existence. But a long list of experiments shows just the opposite. We think life is just the activity of carbon and an admixture of molecules – we live awhile and then rot into the ground.
We believe in death because we’ve been taught we die. Also, of course, because we associate ourselves with our body and we know bodies die. End of story. But biocentrism – a new theory of everything – tells us death may not be the terminal event we think. Amazingly, if you add life and consciousness to the equation, you can explain some of the biggest puzzles of science. For instance, it becomes clear why space and time – and even the properties of matter itself – depend on the observer. It also becomes clear why the laws, forces, and constants of the universe appear to be exquisitely fine-tuned for the existence of life.
Until we recognize the universe in our heads, attempts to understand reality will remain a road to nowhere.
Consider the weather ‘outside’: You see a blue sky, but the cells in your brain could be changed so the sky looks green or red. In fact, with a little genetic engineering we could probably make everything that is red vibrate or make a noise, or even make you want to have sex like with some birds. You think its bright out, but your brain circuits could be changed so it looks dark out. You think it feels hot and humid, but to a tropical frog it would feel cold and dry. This logic applies to virtually everything. Bottom line: What you see could not be present without your consciousness.
In truth, you can’t see anything through the bone that surrounds your brain. Your eyes are not portals to the world. Everything you see and experience right now – even your body – is a whirl of information occurring in your mind. According to biocentrism, space and time aren’t the hard, cold objects we think. Wave your hand through the air – if you take everything away, what’s left? Nothing. The same thing applies for time. Space and time are simply the tools for putting everything together.
Consider the famous two-slit experiment. When scientists watch a particle pass through two slits in a barrier, the particle behaves like a bullet and goes through one slit or the other. But if you don’t watch, it acts like a wave and can go through both slits at the same time. So how can a particle change its behavior depending on whether you watch it or not? The answer is simple – reality is a process that involves your consciousness.
Or consider Heisenberg’s famous uncertainty principle. If there is really a world out there with particles just bouncing around, then we should be able to measure all their properties. But you can’t. For instance, a particle’s exact location and momentum can’t be known at the same time. So why should it matter to a particle what you decide to measure? And how can pairs of entangled particles be instantaneously connected on opposite sides of the galaxy as if space and time don’t exist? Again, the answer is simple: because they’re not just ‘out there’ – space and time are simply tools of our mind.
Death doesn’t exist in a timeless, spaceless world. Immortality doesn’t mean a perpetual existence in time, but resides outside of time altogether.
Our linear way of thinking about time is also inconsistent with another series of recent experiments. In 2002, scientists showed that particles of light “photons” knew – in advance – what their distant twins would do in the future. They tested the communication between pairs of photons. They let one photon finish its journey – it had to decide whether to be either a wave or a particle. Researchers stretched the distance the other photon took to reach its own detector. However, they could add a scrambler to prevent it from collapsing into a particle. Somehow, the first particle knew what the researcher was going to do before it happened – and across distances instantaneously as if there were no space or time between them. They decide not to become particles before their twin even encounters the scrambler. It doesn’t matter how we set up the experiment. Our mind and its knowledge is the only thing that determines how they behave. Experiments consistently confirm these observer-dependent effects.
Bizarre? Consider another experiment that was recently published in the prestigious scientific journal Science (Jacques et al, 315, 966, 2007). Scientists in France shot photons into an apparatus, and showed that what they did could retroactively change something that had already happened in the past. As the photons passed a fork in the apparatus, they had to decide whether to behave like particles or waves when they hit a beam splitter. Later on – well after the photons passed the fork – the experimenter could randomly switch a second beam splitter on and off. It turns out that what the observer decided at that point, determined what the particle actually did at the fork in the past. At that moment, the experimenter chose his past.
Of course, we live in the same world. But critics claim this behavior is limited to the microscopic world. But this ‘two-world’ view (that is, one set of physical laws for small objects, and another for the rest of the universe including us) has no basis in reason and is being challenged in laboratories around the world. A couple years ago, researchers published a paper in Nature (Jost et al, 459, 683, 2009) showing that quantum behavior extends into the everyday realm. Pairs of vibrating ions were coaxed to entangle so their physical properties remained bound together when separated by large distances (“spooky action at a distance,” as Einstein put it). Other experiments with huge molecules called ‘Buckyballs’ also show that quantum reality extends beyond the microscopic world. And in 2005, KHC03 crystals exhibited entanglement ridges one-half inch high, quantum behavior nudging into the ordinary world of human-scale objects.
We generally reject the multiple universes of Star Trek as fiction, but it turns out there is more than a morsel of scientific truth to this popular genre. One well-known aspect of quantum physics is that observations can’t be predicted absolutely. Instead, there is a range of possible observations each with a different probability. One mainstream explanation, the “many-worlds” interpretation, states that each of these possible observations corresponds to a different universe (the ‘multiverse’). There are an infinite number of universes and everything that could possibly happen occurs in some universe. Death does not exist in any real sense in these scenarios. All possible universes exist simultaneously, regardless of what happens in any of them.
Life is an adventure that transcends our ordinary linear way of thinking. When we die, we do so not in the random billiard-ball-matrix but in the inescapable-life-matrix. Life has a non-linear dimensionality – it’s like a perennial flower that returns to bloom in the multiverse.
“The influences of the senses,” said Ralph Waldo Emerson “has in most men overpowered the mind to the degree that the walls of space and time have come to look solid, real and insurmountable; and to speak with levity of these limits in the world is the sign of insanity.”
The Most Amazing Experiment
From Biocentrism (Robert Lanza and Bob Berman)
Quantum theory has unfortunately become a catch-all phrase for trying to prove various kinds of New Age nonsense. It’s unlikely that the authors of the many books making wacky claims of time-travel or mind-control, and who use quantum theory as “proof,” have the slightest knowledge of physics or could explain even the rudiments of QT. The popular 2004 film, What the Bleep Do We Know? is a good case in point. The movie starts out claiming quantum theory has revolutionized our thinking – which is true enough – but then, without explanation or elaboration, goes on to say that it proves people can travel into the past or “choose which reality you want.”
QT says no such thing. QT deals with probabilities, and the likely places particles may appear, and likely actions they will take. And while, as we shall see, bits of light and matter do indeed change behavior depending on whether they are being observed, and measured particles do indeed appear to amazingly influence the past behavior of other particles, this does not in any way mean that humans can travel into their past or influence their own history.
Given the widespread generic use of QT, plus the paradigm-changing tenets of biocentrism, using QT as evidence might raise eyebrows among the skeptical. For this reason, it’s important that readers have some genuine understanding of QT’s actual experiments — and can grasp the real results rather than the preposterous claims so often associated with it. For those with a little patience, this chapter can provide a life-altering understanding of the latest version of one of the most famous and amazing experiments in the history of physics.
The astonishing “double-slit” experiment, which has changed our view of the universe – and serves to support biocentrism — has been performed repeatedly for many decades. This specific version summarizes an experiment published in Physical Review A, (65, 033818) in 2002. But it’s really merely another variation, a tweak to a demonstration that has been performed again and again for three quarters of a century.
It all really started early in the 20th century when physicists were still struggling with a very old question – whether light is made of particles called photons, or whether instead they are waves of energy. Isaac Newton believed “particles.” But by the late 19th century, waves seemed more reasonable. In those early days, some physicists presciently and correctly thought that even solid objects might have a “wave nature” as well.
To find out, we use a source of either light or particles. In the classic double-slit experiment, the particles are usually electrons, since they are small, fundamental (they can’t be divided into anything else) and easy to beam at a distant target. A classic TV set, for example, directs electrons at the screen. We start by aiming light at a detector wall. First, however, the light must pass through an initial barrier with two holes. We can shoot a flood of light or just a single indivisible photon at a time – the results remain the same. Each bit of light has a 50-50 change of going through the right or the left slit. After awhile, all these photon-bullets will logically create a pattern – falling preferentially in the middle of the detector with fewer on the fringes, since most paths from the light source go more-or-less straight ahead. The laws of probability say that we should see a cluster of hits like this:
When plotted on a graph (in which number of hits is vertical, and position on the detector screen horizontal) the expected result for a barrage of particles is to indeed have more hits in the middle and fewer near the edges, which produces a curve like this:
But that’s not the result we actually get. When experiments like this are performed – and they have been done thousands of times during the past century – we find that the bits of light instead create a curious pattern:
Plotted on a graph, the pattern’s “hits” look like this:
In theory, those smaller side peaks around the main one should be symmetrical. In practice, we’re dealing with probabilities and individual bits of light, so the result usually deviates a bit from the ideal. Anyway, the big question here is: Why this pattern?
Turns out, it’s exactly what we’d expect if light is made of waves, not particles. Waves collide and interfere with each other, causing ripples. If you toss two pebbles into a pond at the same time, the waves of each meet each other and produce places of higher-than-normal, or lower-than-normal water-rises. Some waves reinforce each other, or, if one’s crest meets another’s trough, they cancel out at that spot.
So this early 20th-century result of an interference pattern, which can only be caused by waves, showed physicists that light is a wave, or at least acts that way when this experiment is performed. The fascinating thing is that when solid physical bodies like electrons were used, they got exactly the same result. Solid particles have a wave-nature too! So, right from the get-go, the double slit experiment yielded amazing information about the nature of reality. Solid objects have a wave nature!
Unfortunately, or fortunately, this was just the appetizer. Few realized that true strangeness was only beginning. The first oddity happens when just one just photon or electron is allowed to fly through the apparatus at a time. After enough have gone through and been individually detected, this same interference pattern emerges. But how can this be? With what is each of those electrons or photons interfering? How can we get an interference pattern when there’s only indivisible object in there at a time?
A single photon hits the detector.
A second photon hits the detector.
A third photon hits the detector.
Somehow, these individual photons add up to an interference pattern!
There has never been a truly satisfactory answer for this. Wild ideas keep emerging. Could there be other electrons or photons “next door” in a parallel universe, from another experimenter doing the same thing? Could their electrons be interfering with ours? That’s so far-fetched, few believe it.
The usual interpretation of why we see an interference pattern is that photons or electrons have two choices when they encounter the double slit. They do not actually exist as real entities in real places until they are observed, and they aren’t observed until they hit the final detection barrier. So when they reach the slits, they exercise their probabilistic freedom of taking bothchoices. Even though actual electrons or photons are indivisible, and never split themselves under any conditions whatsoever, their existence as “probability waves” are another story. Thus, what goes “through the slit” are not actual entities but just probabilities. . THE PROBABILITY WAVES OF THE INDIVIDUAL PHOTONS INTERFERE WITH THEMSELVES! When enough have gone through, we see the overall interference pattern as all probabilities congeal into actual entities making impacts and being observed – as waves.
Sure it’s weird, but this, apparently, is how reality works. And this is just the very beginning of Quantum Weirdness. QT, as we mentioned last chapter, has a principle called complementarity which says that we can observe objects to be one thing or another – or have one position or property or another, but never both. It depends on what one is looking for, and what measuring equipment is used.
Now, suppose we wish to know which slit a given electron or photon has gone through, on its way to the barrier. It’s a fair enough question, and it’s easy enough to find out. We can use polarized light (meaning light whose waves vibrate either horizontally or vertically or else slowly rotate their orientation) and when such a mixture is used, we get the same result as before. But now let’s determine which slit each photon is going through. Many different things have been used, but in this experiment we’ll use a “quarter wave plate” in front of each slit. Each quarter wave plate alters the polarity of the light in a specific way. The detector can let us know the polarity of the incoming photon. So by noting the polarity of the photon when it’s detected, we know which slit it went through.
Now we repeat the experiment, shooting photons through the slits one at a time, except this time we know which slot each photon goes through. Now theresults dramatically change. Even though QWPs do not alter photons except for harmlessly shifting their polarities (later we prove that this change in results is not caused by the QWPs), now we no longer get the interference pattern. Now the curve suddenly changes to what we’d expect if the photons were particles:
Something’s happened. Turns out, the mere act of measurement, of learning the path of each photon, destroyed the photon’s freedom to remain blurry and undefined and take both paths until it reached the barriers. Its “wave function” must have collapsed at our measuring device, the QWPs, as it instantly “chose” to become a particle and go through one slit or the other. Its wave nature was lost as soon as it lost its blurry probabilistic not-quite-real state. But why should the photon have chosen to collapse its wave-function? How did it know that we, the observer, could learn which slit it went through?
Countless attempts to get around this, by the greatest minds of the past century, have all failed. Our knowledge of the photon or electron path alone caused it to become a definite entity ahead of the previous time. Of course physicists also wondered whether this bizarre behavior might be caused by some interaction between the “which-way” QWP detector or various other devices that have been tried, and the photon. But no. Totally different which-way detectors have been built, none of which in any way disturbs the photon. Yet we always lose the interference pattern. The bottom line conclusion, reached after many years, is that it’s simply not possible to gain which-way information and the interference pattern caused by energy-waves.
We’re back to QT’s complementarity – that you can measure and learn just one of a pair of characteristics, but never both at the same time. If you fully learn about one, you will know nothing about the other. And just in case you’re suspicious of the quarter wave plates, let it be said when used in all other contexts, including double slit experiments but without information-providing polarization-detecting barriers at the end, the mere act of changing a photon’s polarization never has the slightest effect on the creation of an interference pattern.
Okay, let’s try something else. In nature, as we saw in the last chapter, there are “entangled particles” or bits of light (or matter) that were born together and therefore “share a wave function” according to QT. They can fly apart – even across the width of the galaxy – and yet they still retain this connection, this knowledge of each other. If one is meddled with in any way so that it loses its “anything’s possible” nature and has to instantly decide to materialize with, say, a vertical polarization, its twin will instantaneously then materialize too, and with a horizontal polarity. If one becomes an electron with an up spin, the twin will too, but with a down spin. They’re eternally linked in a complementary way.
So now let’s use a device which shoots off entangled twins in different directions. Experimenters can create the entangled photons by using a special crystal called beta-barium borate (BBO). Inside the crystal, an energetic violet photon from a laser is converted to two red photons, each with half the energy (twice the wavelength) of the original, so there’s no net gain or loss of energy. The two outbound entangled photons are sent off in different directions. We’ll call their paths direction p and s.
We’ll set up our original experiment with no which-way information measured. Except now, we add a “coincidence counter.” The role of the coincidence counter is to prevent us from learning the polarity of the photons at detector S unless a photon also hits detector P. One twin goes through the slits (call this photon s) while the other merely barrels ahead to a second detector. Only when both detectors register hits at about the same time do we know that both twins have completed their journeys. Only then does something register on our equipment. The resulting pattern at detector S is our familiar interference pattern:
This makes sense. We haven’t learned which slit any particular photon or electron has taken. So the objects have remained probability waves.
But let’s now get tricky. First we’ll restore those QWPs so we can get which-way information for photons traveling along path S.
As expected, the interference pattern now vanishes, replaced with the particle pattern, the single curve.
So far so good. But now let’s destroy our ability to measure the which-way paths of the s photons, but without interfering with them in any way. We can do this by placing a polarizing window in the path of the other photon P, far away. This plate will stop the second detector from registering coincidences. It’ll measure only some of the photons, and effectively scramble up the double-signals. Since a coincidence-counter is essential here in delivering information about the completion of the twins’ journeys, it has now been rendered thoroughly unreliable. The entire apparatus will now be uselessly unable to let us learn which slit individual photons take when they travel along path S because we won’t be able to compare them with their twins – since nothing registers unless the coincidence counter allows it to. And let’s be clear: We’ve left the QWPs in place for photon S. All we’ve done is to meddle with the p photon’s path in a way that removes our ability to use the coincidence counter to gain which-way knowledge. (The set-up, to review, delivers information to us, registers “hits,” only when polarity is measured at detector S AND the coincidence counter tells us that either a matching or non-matching polarity has been simultaneously registered by the twin photon at detector P). The result:
They’re waves again. The interference pattern is back. The physical places on the back screen where the photons or electrons taking path s hit have now changed. Yet we did nothing to these photons’ paths, from their creation at the crystal all the way to the final detector. We even left the QWPs in place. All we did was meddle with the twin photon far away so that it destroyed our ability to learn information. The only change was in our minds. How could photons taking path S possibly know that we put that other polarizer in place — somewhere else, far from their own paths? And QT tells us that we’d get this same result even if we placed the information-ruiner at the other end of the universe.
(Also, by the way, this proves that it wasn’t those QWP plates that were causing the photons to change from waves to particles, and to alter the impact points on the detector. We now get an interference pattern even with the QWPs in place. It’s our knowledge alone that the photons or electrons seem concerned about. This alone influences their actions.)
Okay, this is bizarre. Yet these results happen every time, without fail. They’re telling us that an observer determines physical behavior of “external” objects. Could it get any weirder? Hold on: Now we’ll try something even more radical – an experiment only first performed in 2002. Thus far the experiment involved erasing the which-way information by meddling with the path of p and then measuring its twin s. Perhaps some sort of communication takes place between photon p and s, letting s know what we will learn, and therefore giving it the green light to be a particle or a wave and either create or not create an interference pattern. Maybe when photon p meets the polarizer it sends s an IM (instant message) at infinite speed, so that photon s knows it must materialize into a real entity instantly, which has to be a particle since only particles can go through one slit or the other and not both. Result: No interference pattern.
To check out whether this is so, we’ll do one more thing. First we’ll stretch out the distance p photons have to take until they reach their detector, so it’ll take them more time to get there. This way, photons taking the S route will hit their own detectors first. But oddly enough, the results do not change! When we insert the QWPs to path S the fringes are gone; and when we insert the polarizing scrambler to path P and lose the coincidence-measuring ability that lets us determine which-way info for the S photons, the fringes return as before. But how can this be? Photons taking the S-path already finished their journeys. They either went through one or the other slit, or both. They either collapsed their “wave function” and became a particle or they didn’t. The game’s over, the action’s finished. They’ve each already hit the final barrier and were detected – before twin p encountered the polarizing scrambling device that would rob us of which-way information.
The photons somehow know whether or not we will gain the which-way information in the future. They decide not to collapse into particles before their distant twins even encounter our scrambler. (If we take away the P scrambler, the S photons suddenly revert to being particles, again before P’s photons reach their detector and activate the coincidence counter.) Somehow, photon s knows whether the “which-way” marker will be erased even though neither it, nor its twin, have yet encountered an erasing mechanism. It knows when its interference behavior can be present, when it can safely remain in its fuzzy both-slits ghost reality, because it apparently knows photon p — far off in the distance — is going to eventually hit the scrambler, and that this will ultimately prevent us from learning which way p went.
It doesn’t matter how we set up the experiment. Our mind and its knowledge or lack of it is the only thing that determines how these bits of light or matter behave. It forces us, too, to wonder about space and time. Can either be real if the twins act on information before it happens, and across distances instantaneously as if there is no separation between them?
Again and again, observations have consistently confirmed the observer-dependent effects of QT. In the past decade, physicists at the National Institute of Standards and Technology have carried out an experiment that, in the quantum world, is equivalent to demonstrating that a watched pot doesn’t boil. “It seems,” said Peter Coveney, a researcher there, “that the act of looking at an atom prevents it from changing.” (Theoretically, if a nuclear bomb were watched intently enough, it would not explode, that is, if you could keep checking its atoms every million trillionth of a second. This is yet another experiment that supports the theory that the structure of the physical world, and of small units of matter and energy in particular, are influenced by human observation.)
In the last couple of decades, quantum theorists have shown, in principle, that an atom cannot change its energy state as long as it is being continuously observed. So, now, to test this concept, the group of laser experimentalists at the NIST held a cluster of positively charged beryllium ions, the “water” so to speak, in a fixed position using a magnetic field, the “kettle”. They applied “heat” to the kettle in the form of a radio-frequency field that would boost the atoms from a lower to a higher energy state. This transition generally takes about a quarter of a second. However, when the researchers kept checking the atoms every four milliseconds with a brief pulse of light from a laser, the atoms never made it to the higher energy state, despite the force driving them toward it. It would seem that the process of measurement gives the atoms “a little nudge,” forcing them back down to the lower energy state–in effect, resetting the system to zero. This behavior has no analog in the classical world of everyday sense awareness and is apparently a function of observation.
Arcane? Bizarre? It’s hard to believe such effects are real. It’s a fantastic result. When quantum physics was in its early days of discovery in the beginning of the last century, even some physicists dismissed the experimental findings as impossible or improbable. It is curious to recall Albert Einstein’s reaction to the experiments: “I know this business is free of contradictions, yet in my view it contains a certain unreasonableness.”
It was only with the advent of quantum physics and the fall of objectivity, that scientists began to consider again the old question of the possibility of comprehending the world as a form of mind. Einstein, on a walk from The Institute for Advanced Study at Princeton to his home on Mercer street, illustrated his continued fascination and skepticism about an objective external reality, when he asked Abraham Pais if he really believed that the moon existed only if he looked at it. Since that time, physicists have analyzed and revised their equations in a vain attempt to arrive at a statement of natural laws that in no way depends on the circumstances of the observer. Indeed, Eugene Wigner, one of the 20th century’s greatest physicists, stated that it is “not possible to formulate the laws of [physics] in a fully consistent way without reference to the consciousness [of the observer].” So when quantum theory implies that consciousness must exist, it tacitly shows that the content of the mind is the ultimate reality, and that only an act of observation can confer shape and form to reality– from a dandelion in a meadow, to sun, wind and rain.
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