viernes, 7 de octubre de 2011

UNIVERSE IS ACCELERATING

Discovery of Accelerating Universe Wins 2011 Nobel Prize in Physics

Dark energy wins out in the end: Three U.S. scientists have been honored for their observations that type Ia supernovae indicate that the expansion of the universe is accelerating

October 4, 2011 | 13 From Scientific American


Overview Discovering a Dark Universe: A Q&A with Saul Perlmutter
Overview From Slowdown to Speedup, by Adam Riess and Michael Turner

The 2011 Nobel Prize in physics was awarded today to Saul Perlmutter at the Lawrence Berkeley National Lab, Brian Schmidt at the Australian National Lab and Adam Reiss at Johns Hopkins University for their discovery of the accelerating expansion of the universe.

“In a universe which is dominated by matter, one would expect gravity eventually should make the expansion slow down, the Royal Swedish Academy’s Olga Botner said this morning at the announcement event in Stockholm. "Imagine then the utter astonishment when two groups of scientists headed by this year’s Nobel Laureates in 1998 discovered that the expansion was not slowing down, it was actually accelerating."

"By comparing the brightness of distant, far-away supernovae with the brightness of nearby supernovae," Botner continued, "the scientists discovered that the far-away supernovae were about 25 percent too faint. They were too far away. The universe was accelerating. And so this discovery is fundamental and a milestone for cosmology. And a challenge for generations of scientists to come.”

For a 2004 article in Scientific American by Riess about the use of distant supernovae to reveal the acceleration of the universe, click here.

And click here for a profile of Perlmutter and his work on dark energy.

Mundo real es identico a mundo virtual....

A raiz de este articulo que me comprueba la tesis esbozada: la similitud entre ambos mundos o "realidades " fisicas ,surgen elucubraciones- deducciones asombrosas:
a) Los seres humanos estamos "seteados" mediante los sentidos comunes para ver ,oler,gustar,tocar,sentir una realidad que es apenas una parte de toda la realidad
b) La realidad virtual esta implícita ,no desplegada a los sentidos,pero existe y es capaz de ser "sintonizada" por el cerebro (impulsos electromagnéticos).

c) Ergo si esto es asi-como lo demuestran muchos experimentos y lo termina de comprobar este, otros seres sintientes (restrinjamoslos por desconocimiento solo a plantas y animales) tienen sus propios programas para decodificar las realidades analogicas y las realidades virtuales. No necesariamente son coincidentes con las nuestras. Un ejemplo: la mosca ve en 360 grados,nosotros solo en 180 ,un murcielago y una ballena decodifican ondas sonoras con distinto umbral auditivo nuestro. Nosotros somos sordos a los sonidos de la naturaleza: hay una razon de fondo,nos volveriamos locos oyendo las estrellas,los pulsares, los meteoritos, las llamaradas solares, los llamados de las ballenas, los llamados de los murcielagos, y mucho etc.

d) Si esto es cierto-como lo es, el mundo cuantico con reglas distintas a las del mundo real es la puerta de entrada a otras realidades no percibidas por nuestros sentidos,ni siquiera por nuestra imaginacion.

e) Y lo que denominamos Espiritu es una realidad tan tangible como el dedo de mi mano que impulsa cada tecla de este escrito. Solo que esa realidad no se encuentra desplegada a nuestros sentidos. Ni siquiera la sintonizamos en nuestra oraciones dichas con la boca,con mente distraida.Solo se accesa con la Conciencia Expandida (como lo demuestran las practicas hindues). Solo que esas experiencias no son repetibles,tampoco transmisibles:son personalisimas.

f) Algunos fisicos plantean que el mundo real que sentimos,tocamos,medimos tiene tres dimensiones fisicas y una distinta ,llamada tiempo, que aun no sabemos definir mas que como el "lapso que media entre dos sucesos en el espacio". (hay una disputa acerca si el tiempo existe o no y si es solo una referencia espacial).
Pero ademas en muchas de las teorías actuales postulan que hay otras dimensiones replegadas sobre si mismas (no las captamos).

g) Los que hicieron esta asombrosa deduccion fueron dos físicos por aparte Klein y Kaluza y sus planeos fueron ignorados por muchísimo tiempo,hasta que ahora han sido redescubiertos por los fisicos de las llamadas teorias de cuerdas cósmicas...Asi el espacio tendria 3,4,5,7,10,11 dimensiones ( no hay coincidencia en las teorias formuladas al efecto) y solo visibles y cuantificables cuatro (tres espaciales,una temporal).

h) A lo anterior agreguemos que la matemática (lenguaje de la ciencia y no una ciencia per se) es la llave (digamos virtual) para entrar a esos mundos o realidades que luego pueden ser accedidos cuando se revelan físicamente ,mediante aparatos de medición expresamente diseñados a tales efectos.

i) De frente a estas situaciones realmente asombrosas da pena constatar que el ser humano ha perdido miserablemente el tiempo haciendo la guerra en vez de decidarse a desentrañar el Universo que nos rodea.

j) Y terminemos afirmando que el Universo ,no puede ser una mera concatenacion de accidentes y de acontecimiento al azar,sino un fino diseño de un ser superior.

Como le llamemos es irrelevante.Lo relevante es que fuera o dentro de nuestras coordenadas existe y ha establecido las reglas universales que dominan Todo .

Que piensas al respecto.....
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Monkeys move and feel virtual objects with their minds

By Janet Fang | October 6, 2011, 12:52 PM

A new mind-machine interface translates brain signals into movements AND sends artificial touch feedback back to the brain.

This means monkeys can control objects on a computer display with a virtual arm controlled by their brain… while having the ability to ‘feel’ the textures of the objects on the screen.

The technique could lead to virtual prosthetic limbs and robotic bodysuits for amputees and patients with locked-in syndrome.

It’s designed by Duke’s Miguel Nicolelis and colleagues with the help of 2 rhesus monkeys named Mango and Tangerine.

First, the monkeys used their real hands to operate a joystick to move a virtual image of an arm on a computer screen.
Then team implanted 2 sets of electrodes into 2 parts of their brains: the motor cortex and somatosensory cortex. The motor cortex is involved in performing voluntary movement; the somatosensory cortex processes input received from cells in the body that are sensitive to touch.
The monkeys were trained to use only their brain to explore objects on a computer screen by moving the virtual arms.
Electrodes in the motor cortex record the monkeys’ intentions to move, and then relay that info to the computer.
As the virtual monkey hand sweeps over discs on the screen, electrical signals are fed into their somatosensory cortex through the second set of electrodes – providing tactile feedback of electrical pulses.

The monkeys were tasked to choose between visually identical objects; the only differences were in texture and treats (or lack of treats). Low frequency of pulses indicated a rough texture, high frequency indicated a fine texture.

They accurately distinguished between an object that produced an award (juice) – which was associated with an electrical stimulation when ‘touched’ – and objects that produced no electrical stimulation or treats, Nature News explains.

Watch a cool video with virtual monkey arms.

Nicolelis says that the combination of seeing an appendage that they control and feeling a physical touch tricks them into thinking that the virtual appendage is their own within minutes.

So really, its bidirectionality closes a loop, making this a brain-machine-brain interface, as well as a key component to future neuroprostheses.

Previous brain-machine interfaces have relied on visual feedback. But if you want to reach and grasp a glass, visual feedback won’t help you. It’s the sensory feedback that tells you if you have a good grip or if you are about to drop it.

Nicolelis’s ultimate goal, and that of the Walk Again Project, is to build an exoskeleton suit to restore mobility to severely paralyzed patients. They would not only be able to walk and move their arms and hands, says Nicolelis, but also to feel the texture of objects they hold or touch, and sense the terrain they walk on.

Nicolelis hopes that a suit will be demonstrated at the 2014 World Cup in his homeland, Brazil, with the opening kick of the ball being delivered by a young Brazilian with quadriplegia.

Source: The work was published in Nature yesterday. Via Nature News, ScienceNOW.

Images: Katie Zhuang / Duke

martes, 4 de octubre de 2011

DESCUBREN NUEVO BRAZO ESPIRAL EN NUESTRA GALAXIA

Descubren un nuevo brazo en los confines de la Vía Láctea
Tom Dame Descubren un nuevo brazo en los confines de la Vía Láctea
Se trata de un enorme fragmento con grandes concentraciones de gas hasta ahora desconocido

Un grupo de astrónomos británicos acaba de realizar un descubrimiento extraordinario. Un nuevo brazo espiral en nuestra galaxia o, más precisamente, un enorme fragmento hasta ahora desconocido de uno de los dos brazos principales de la Vía Láctea.

Igual que sucede con otras galaxias espirales, la Vía Láctea, la galaxia en que vivimos, está formada por un gran disco central de cuyos extremos surgen dos largos brazos repletos de estrellas, polvo y gas, que se curvan alrededor de un denso y alargado núcleo central. Entre todas las clases de galaxias que existen, la nuestra es una espiral barrada.

El Sol, la Tierra y el resto del Sistema Solar se encuentran en una pequeña ramificación de uno de esos brazos, una especie de "vía muerta" justo entre Perseo y el Escudo Centauro, los dos brazos principales, a unos 25.000 años luz del centro.

Sin embargo, y debido a que estamos dentro, no resulta fácil adivinar cuál es la verdadera forma de nuestra galaxia. La Vía Láctea contiene grandes cantidades de gases y polvo que obstaculizan la visión. Por eso, por nuestra posición, no podemos tener una imagen clara del conjunto y sólo podemos ver fragmentos aislados de los brazos.

Resulta mucho más sencillo estudiar galaxias distantes, que podemos ver enteras, que la nuestra propia. Por ejemplo, conocemos con mucha más exactitud las formas de Andrómeda, nuestra vecina, a dos millones de años luz de distancia, que las de nuestro propio hogar en el espacio.

Existen, es cierto, modelos teóricos de la Vía Láctea, y muchas razones para pensar que tiene la forma de un molinillo, con dos enormes brazos repletos de estrellas. Pero no hay forma de estar absolutamente seguros. Ni tampoco de estudiar directamente los detalles.

La imagen que acompaña estas líneas (realizada por Tom Dame, uno de los descubridores del nuevo brazo), muestra la estructura básica de la Vía láctea: dos largos brazos espirales que surgen de los extremos de una gran barra central. En gris aparecen los fragmentos que aún no han podido ser detectados. Arriba, a la izquierda, el nuevo brazo recién descubierto. Las ramificaciones menores, como en la que nosotros vivimos, han sido obviadas por el científico en aras de la claridad.
Una simetría sorprendente

Por suerte para la Ciencia, y más allá de los instrumentos ópticos, los astrónomos han desarrollado otras clases de "ojos" capaces de atravesar las densas nubes de polvo que nos rodean y "ver" lo que hay más allá de ellas. Esos instrumentos no buscan luz ordinaria, sino ondas de radio. Y resulta que las moléculas de monóxido de carbono, extraordinariamente abundantes en los brazos de las galaxias espirales, son excelentes emisoras de radio y, por lo tanto, la clase de objetos que los instrumentos pueden rastrear.

Utilizando un pequeño telescopio de apenas 1,2 metros, instalado el el tejado de su laboratorio de Cambridge, los astrónomos Tom Dame y Pat Thaddeus se centraron en las emisiones de radio de las moléculas de monóxido de carbono para buscar evidencias de brazos espirales en las zonas más distantes de la Vía Láctea. Y descubrieron un nuevo y enorme brazo, con grandes concentraciones de ese gas.

Los investigadores piensan que el nuevo brazo espiral es, en realidad, el tramo final y más distante de Escudo Centauro, una de las dos ramas principales. Si se confirma, Dame y Thaddeus habrán demostrado que la Vía Láctea posee una sorprendente simetría en sus formas. El nuevo brazo, en efecto, sería la contraparte simétrica del de Perseo.

Fuente: ABC,España , José Manuel Nnieves / madrid, Día 14/06/2011 - 09.00h

UNIVERSO ENTERO: imagen espectacular

El Universo entero, en una imagen espectacular
El telescopio Planck ha obtenido una fotografía sin igual en la que se aprecian los primeros momentos después del Big Bang
ABC / madrid , Día 05/07/2010 - 13.46h

«El telescopio Planck fue concebido para un momento como éste». David Southwood, director de Ciencia y Exploración Robótica de la Agencia Espacial Europea (ESA, por sus siglas en inglés), no puede evitar expresar su enorme satisfacción por el logro del ingenio espacial. La sonda ha captado su primera imagen de todo el Universo, lo que no sólo proporciona una nueva visión de cómo se formaron las estrellas y las galaxias, sino que nos muestra cómo el propio Cosmos se desarrolló después del Big Bang.
El Universo entero, en una imagen espectacular
ESA
Espectacular imagen del Universo tomada por el telescopio Planck

«No estamos dando una respuesta. Estamos abriendo las puertas a 'Eldorado', un paraíso donde los científicos pueden buscar las 'pepitas de oro' que les lleven a una mayor comprensión de la formación y el funcionamiento actual del Universo», explica Southwood.

Desde los tramos más cercanos de la Vía Láctea hasta los más lejanos confines del espacio y del tiempo, la nueva imagen de todo el cielo del Planck es un extraordinario tesoro de nuevos datos para los astrónomos, como puede apreciarse en la página web de la ESA. El disco principal de nuestra galaxia corre con el centro de la imagen. Inmediatamente, llaman la atención las «serpentinas» de polvo frío por encima y por debajo de la Vía Láctea. En esta red galáctica es donde las estrellas se forman. Precisamente, Planck ha encontrado muchos lugares donde las estrellas están a punto de nacer o apenas han comenzado su ciclo de desarrollo. Es fascinante.
La luz más antigua

Menos espectacular pero quizás aún más interesante es el telón de fondo moteado en la parte superior e inferior. Esta es la radiación de fondo cósmico de microondas. En otras palabras, la luz más antigua del Universo, los restos de la bola de fuego, del Big Bang, del que el Cosmos surgió hace 13,7 miles de millones de años. Estas microondas nos muestran cómo se veía el Universo casi cuando fue creado, antes de que nacieran las estrellas y las galaxias. Esta es, según la ESA, el corazón de la misión Planck, cuyo objetivo es descifrar lo que sucedió tras la explosión primigenia.

Cuando esté terminado el trabajo, Planck nos mostrará la imagen más precisa del fondo de microondas jamás obtenida. La gran pregunta es si estos nuevos datos revelarán la firma cósmica primordial del período llamado inflación, la época justo después del Big Bang que dio lugar a la expansión del Universo hasta alcanzar su enorme tamaño en un período muy corto. Al final de su misión en 2012, Planck habrá completado cuatro exploraciones de todo el cielo.

HILO COSMICO QUE NOS UNE...

Científicos han descubierto pruebas de un gran filamento de material que conecta la Vía Láctea con otras agrupaciones de galaxias y con el Universo entero
Fuente: abc.es / madrid , Día 03/10/2011 - 15.38h

El hilo cósmico que nos une, revelado
IC Irvine
Simulación de filamentos interconectados entre galaxias
Comentarios


Astrónomos de la Universidad Nacional de Australia han descubierto el hilo cósmico que teje la estructura del Universo. Se trata de un filamento con una gran cantidad de material que conecta nuestra galaxia, la Vía Láctea, a otras agrupaciones cercanas de galaxias que, a su vez, están interconectadas de la misma forma con el resto del Universo. La investigación, que muestra una especie de «escalera» al cielo, aparece publicada en Astrophysical Journal.

«Examinando las posiciones de antiguos grupos de estrellas, llamados cúmulos globulares, encontramos que los cúmulos forman un plano estrecho alrededor de la Vía Láctea en lugar de estar dispersos por todo el cielo», explica el astrónomo Stefan Keller. «Lo que hemos descubierto evidencia un hilo cósmico que nos conecta a la vasta extensión del Universo», explica. A su juicio, este hilo de cúmulos estelares y galaxias pequeñas alrededor de la Vía Láctea «es como el cordón umbilical que alimentó nuestra galaxia durante su juventud».

Existen dos tipos de materia que componen el Universo: la materia dominante -aquella que forma todo lo que conocemos, incluidos las galaxias, estrellas, planetas- y la predominante y enigmática materia oscura, que nadie puede ver pero de cuya existencia está convencida una buena parte de la comunidad científica.
Una esponja de cocina

«Una consecuencia del Big Bang y el dominio de la materia oscura es que la materia ordinaria es impulsada, como la espuma en la cresta de una ola, a una vasta extensión de hojas y filamentos interconectados sobre enormes vacíos cósmicos, al igual que la estructura de una esponja de cocina», explica Keller.

A diferencia de una esponja, sin embargo, la gravedad atrae el material sobre estos filamentos interconectados hacia el más grande de los conglomerados de materia, «y nuestros resultados muestran que los cúmulos globulares y las galaxias satélite de la Vía Láctea trazan este filamento cósmico».

«Los cúmulos globulares son sistemas de cientos de miles de antiguas estrellas apretadas en una bola. En nuestra imagen, la mayor parte de estos cúmulos de estrellas son los núcleos centrales de las galaxias pequeñas que se han elaborado a lo largo de los filamentos por la gravedad», continua Keller. Una vez que estas pequeñas galaxias se acercaron demasiado a la Vía Láctea fueron despojadas de la mayoría de las estrellas, que se añadieron a nuestra galaxia, dejando solo sus núcleos. «Se cree que la Vía Láctea ha crecido hasta su tamaño actual por el consumo de cientos de galaxias más pequeñas durante el tiempo cósmico».

Studies of Universe’s Expansion Win Physics Nobel

Studies of Universe’s Expansion Win Physics Nobel
By DENNIS OVERBYE

Three astronomers won the Nobel Prize on Tuesday for discovering that the universe is apparently being blown apart by a mysterious force that cosmologists now call dark energy, a finding that has thrown the fate of the universe and indeed the nature of physics into doubt.

They are Saul Perlmutter, 52, of the Lawrence Berkeley National Laboratory in Berkeley, Calif.; Brian P. Schmidt, 44, of the Australian National University in Weston Creek, Australia, and Adam G. Riess, 41, of the Space Telescope Science Institute and Johns Hopkins University in Baltimore.

“I’m stunned,” Dr. Riess said by e-mail, after learning of his prize by reading about it on The New York Times’s Web site.

The three men led two competing teams of astronomers who were trying to use the exploding stars known as Type 1a supernovas as cosmic lighthouses to limn the expansion of the universe. The goal of both groups was to measure how fast the cosmos, which has been expanding since its fiery birth in the Big Bang 13.7 billion years ago, was slowing down, and thus to find out if its ultimate fate was to fall back together in what is called a Big Crunch or to drift apart into the darkness.

Instead, the two groups found in 1998 that the expansion of the universe was actually speeding up, a conclusion that nobody would have believed if not for the fact that both sets of scientists wound up with the same answer. It was as if, when you tossed your car keys in the air, instead of coming down, they flew faster and faster to the ceiling. Subsequent cosmological measurements have confirmed that roughly 70 percent of the universe by mass or energy consists of this antigravitational dark energy, though astronomers and physicists have no conclusive evidence of what it is.

The most likely explanation for this bizarre behavior is a fudge factor that Albert Einstein introduced into his equations in 1917 to stabilize the universe against collapse and then abandoned as his greatest blunder.

Quantum theory predicts that empty space should exert a repulsive force, like dark energy, but one that is 10 to the 120th power times stronger than what the astronomers have measured, leaving some physicists mumbling about multiple universes. Abandoning the Einsteinian dream of a single final theory of nature, they speculate that there are a multitude of universes with different properties. We live in one, the argument goes, that is suitable for life.

“Every test we have made has come out perfectly in line with Einstein’s original cosmological constant in 1917,” Dr. Schmidt said.

If the universe continues accelerating, astronomers say, rather than coasting gently into the night, distant galaxies will eventually be moving apart so quickly that they cannot communicate with one another and all the energy would be sucked out of the universe.

Edward Witten, a theorist at the Institute for Advanced Study, Einstein’s old stomping grounds, called dark energy “the most startling discovery in physics since I have been in the field. It was so startling, in fact, that I personally took quite a while to become convinced that it was right.”

He went on, “This discovery definitely changed the way physicists look at the universe, and we probably still haven’t fully come to grips with the implications.”

Dr. Perlmutter, who led the Supernova Cosmology Project out of Berkeley, will get half of the prize of 10 million Swedish kronor ($1.4 million). The other half will go to Dr. Schmidt, leader of the rival High-Z Supernova Search Team, and Dr. Riess, who was the lead author of the 1998 paper in The Astronomical Journal, in which the dark energy result was first published. All three were born and raised in the United States; Dr. Schmidt is also a citizen of Australia. They will get their prizes in Stockholm on Dec. 10.

Since the fate of the universe is in question, astronomers would love to do more detailed tests using supernovas and other observations. So they were dispirited last year when NASA announced that cost overruns and delays on the James Webb Space Telescope had left no room in the budget until the next decade for a satellite mission to investigate dark energy that Dr. Perlmutter and others had been promoting for almost a decade.

Cosmic expansion was discovered by Edwin Hubble, an astronomer at the Mount Wilson Observatory in Pasadena, Calif., in 1929, but the quest for precision measurements of the universe has been hindered by a lack of reliable standard candles, objects whose distance can be inferred by their brightness of some other observable characteristic. Type 1a supernovas, which are thought to result from explosions of small stars known as white dwarfs, have long been considered uniform enough to fill the bill, as well as bright enough to be seen across the universe.

In the late 1980s Dr. Perlmutter, who had just gotten a Ph.D. in physics, devised an elaborate scheme involving networks of telescopes tied together by the Internet to detect and study such supernovas and use them to measure the presumed deceleration of the universe. The Supernova Cosmology Project endured criticism from other astronomers, particularly supernova experts, who doubted that particle physicists could do it right.

Indeed, it took seven years before Dr. Perlmutter’s team began harvesting supernovas in the numbers they needed. Meanwhile, the other astronomers had formed their own team, the High-Z team, to do the same work.

“Hey, what’s the strongest force in the universe?” asked Robert Kirshner, of the Harvard-Smithsonian Center for Astrophysics, and a mentor to many of the astronomers on the new team, told a reporter from this newspaper once, “It’s not gravity, it’s jealousy.”

In an interview with the Associated Press, Dr. Perlmutter described the subsequent work of the teams as “a long aha.” The presence of dark energy showed up in an expected faintness on the part of some distant supernovas: the universe had sped up and carried them farther away from us than conventional cosmology suggested.

As recounted by the science writer Richard Panek in his recent book, “The 4% Universe, Dark Matter, Dark Energy, and the Race to Discover the Rest of Reality,” neither team was eager to report such a strange result.

In January 1998, Dr. Riess took time off from his honeymoon to go over the results one more time and then e-mailed his comrades, “Approach these results not with your heart or head but with your eyes. We are observers after all!”

In the years since, the three astronomers have shared a number of awards, sometimes giving lectures in which they completed each other’s sentences. A Nobel was expected eventually.

“No more waiting!” Dr. Kirshner said Tuesday.

This article has been revised to reflect the following correction:

Correction: October 4, 2011

An earlier version of this article incorrectly stated the publication in which Adam G. Riess's 1998 paper on dark energy appeared. It was The Astronomical Journal, not Science. The article also stated incorrectly the amount of the prize. It is 10 million Swedish kronor ($1.4 million).

Source: New York Times, October 4, 2011

NOBEL DE FISICA PARA ACELERACION DEL UNIVERSO

Nobel de Física para la aceleración del universo

Tres científicos que descubrieron el efecto, que puede ser debido a la denominada energía oscura, reciben el galardón .


Los científicos Saul Perlmutter, Brian Schmidt y Adam Riess, reciben el Premio Nobel de Física 2011 por sus observaciones cosmológicas, al descubrir que la expansión del universo, el Big Bang, está acelerándose, según ha informado el comité Nobel de Física de la Real Academia de Ciencias sueca. Es un fenómeno que los científicos no han logrado aún explicar pero que se ha comprobado en diferentes observaciones realizadas después de los trabajos pioneros de los tres galardonados, hace más de una década. Es el misterio de la energía oscura del universo y la mejor interpretación, según muchos expertos, es la constante cosmológica de Einstein. Perlmutter y Riess trabajan en EE UU y Schmidtt, en Australia. Su hallazgo tiene implicaciones directas en el destino del universo, ya que esa aceleración de la expansión indica que el cosmos acabará completamente helado.


Schmidt ha declarado en una conexión en directo con la sala de la Fundación Nobel donde se ha presentado el premio, que, aunque la posibilidad de que su trabajo obtuviera el galardón se comentaba de vez en cuando en su entorno, no se lo esperaba. Por supuesto está encantado. La mitad del premio (un millón de euros) es para Perlmutter y la otra mitad, compartida entre Schmidt y Riess.

Los descubrimientos premiados se remontan a 1998, y fueron una sorpresa general en la comunidad científica. Además, para mayor solidez del hallazgo, fue logrado por dos grupos competidores trabajando independientemente, uno liderado por Perlmutter (el Supernova Cosmology Project) y otro por Schmidt (High-Z supernova Research Team), en el que Riess desempeña un papel clave.

Los dos equipos, en los años noventa, estaban investigando supernovas de un determinado tipo, denominado Ia. Son explosiones finales de estrellas viejas compactas, de la masa del Sol pero el tamaño de la Tierra. Estos científicos observaron que medio centenar de tales supernovas lejanas en el cielo brillaban menos de lo esperado, lo que indicaba que estaban más lejos. Esto indicaba, por increíble que pareciera, que la expansión reciente (en términos cósmicos) del universo se está acelerando. "Comunicamos al mundo que teníamos este resultado loco, que el universo se estaba acelerando", ha recordado Schmidt. "Parecía demasiado loco para ser correcto y creo que estabamos un poco asustados". La expansión del universo, no esta, como cabía esperar, ralentizándose desde la gran explosión, hace unos 13.700 millones de años, sino que está acelerándose.

Los cosmólogos, tras la sorpresa inicial de este hallazgo corroborado por dos grupos competidores, empezaron a analizarlo, buscando explicaciones.

La teoría más generalmente aceptada es que está en acción la llamada constante cosmológica de Einstein, una fuerza de repulsión (algo parecido a la atracción gravitacional, pero de signo contrario) que el gran sabio alemán introdujo en su teoría para frenar el universo y hacerlo estable, como se pensaba entonces que era. Cuando se descubrió que el cosmos estaba en expansión y que, por tanto, no hacía falta frenarlo, Einstein dijo que la constante cosmológica era su mayor error. Décadas después los científicos han desempolvado la idea para explicar, con esa fuerza de repulsión, la aceleración del universo.

En un lenguaje más reciente, la constante cosmológica es la llamada energía oscura y las investigaciones posteriores a los trabajos de los tres galardonados con el Premio Nobel de Física 2011 han determinado que juega el papel fundamental en el universo: el 72% del cosmos es energía oscura, el 26% es materia oscura y sólo el 4,6% es materia normal y corriente, los átomos conocidos.

Perlmutter, estadounidense, nacido en 1959, es profesor de la Universidad de California en Berkeley y del Laboratorio Nacional Lawrence Berkeley. Schmidt, con nacionalidad estadounidense y australiana, nacido en 1967, es profesor de la Universidad Nacional Australiana en Weston Creek. Riess, estadounidense, nacido en 1969, es profesor en la Universidad Johns Hopkins (Baltimoere, EE UU) e investigador del Instituto Científico del Telescopio Espacial.
Trabajo en equipo

Este descubrimiento se debe a un trabajo de equipo, ha insistido hoy uno de los premiados con el Nobel, Saul Perlmutter, destacando el esfuerzo colectivo de los investigadores en estudios teóricos de las supernovas, las observaciones astronómicas fundamentales, los análisis de datos y su interpretación. Casi medio centenar de especialistas integran el Supernova Cosmology Project , que él dirige. Otra treintena forman el equipo rival, High-Z Supernova Search Team, cuyo líder, Brian P. Schmidt y el experto Adam g.Riess, también reciben el máximo galardón científico compartido con Perlmutter.

A mediados de los años noventa, estos investigadores se propusieron medir la geometría del universo utilizando las supernovas 1a como señales para medir distancias en el cosmos. La cuestión en aquel momento era saber, por la geometría, si el universo seguiría expandiéndose eternamente o si llegaría un momento en que se detendría esa expansión y empezaría a colapsar sobre sí mismo, recuerda Perlmutter en un comunicado de la Universidad de Berkeley.

La idea era utilizar esas explosiones de supernova en concreto, las de tipo 1a, porque todas tienen aproximadamente el mismo brillo intrínseco, por lo que su brillo aparente visto desde la tierra se puede utilizar para calcular a qué distancia están. Pero los resultados fueron un bombazo: la aceleración de la expansión del universo. La primera reacción general fue de escepticismo, pero los dos equipos rivales hicieron más observaciones con más supernovas obteniendo los mismos resultados. Además, otros trabajos con enfoques diferentes del mismo problema los corroboraron. La aceleración se impuso, mientras los cosmólogos teóricos buscaban -y siguen buscando— explicaciones, con la energía oscura como mejor candidato.

"No había ningún indicio de todo esto cuando empezamos el proyecto", dijo Riess en 1998. "Esperábamos ver el universo ralentizándose y, sin embargo, todos los datos encajaban en una aceleración". Si uno lanza al aire una pelota y esta sigue subiendo en lugar de lugar de caer al suelo, te llevas una sorpresa, y "así estabamos de sorprendidos cuando sacamos aquellos resultados", recuerda ahora. Se retomó entonces la idea propuesta por Einstein de que una energía de "anti-gravedad" estaría en acción, añade.

Fuente : Alicia Rivera, El Pais.com

lunes, 3 de octubre de 2011

Quantum life: The weirdness inside us

Quantum life: The weirdness inside us

03 October 2011 by Michael Brooks
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Ideas from the stranger side of physics could explain some long-standing mysteries of biology

EVER felt a little incoherent? Or maybe you've been in two minds about something, or even in a bit of delicate state. Well, here's your excuse: perhaps you are in thrall to the strange rules of quantum mechanics.

We tend to think that the interaction between quantum physics and biology stops with Schrödinger's cat. Not that Erwin Schrödinger intended his unfortunate feline - suspended thanks to quantum rules in a simultaneous state of being both dead and alive - to be anything more than a metaphor. Indeed, when he wrote his 1944 book What is Life?, he speculated that living organisms would do everything they could to block out the fuzziness of quantum physics.

But is that the case? Might particles that occupy two states at once, that interact seemingly inexplicably over distances and exhibit other quantum misbehaviours actually make many essential life processes tick? Accept this notion, say its proponents, and we could exploit it to design better drugs, high-efficiency solar cells and super-fast quantum computers. There's something we need to understand before we do, though: how did the quantum get into biology in the first place?

On one level, you might think, we shouldn't be surprised that life has a quantum edge. After all, biology is based on chemistry, and chemistry is all about the doings of atomic electrons - and electrons are quantum-mechanical beasts at heart. That's true, says Jennifer Brookes, who researches biological quantum effects at Harvard University. "Of course everything is ultimately quantum because electron interactions are quantised."

On another level, it is gobsmacking. In theory, quantum states are delicate beasts, easily disturbed and destroyed by interaction with their surroundings. So far, physicists have managed to produce and manipulate them only in highly controlled environments at temperatures close to absolute zero, and then only for fractions of a second. Finding quantum effects in the big, wet and warm world of biology is like having to take them into account in a grand engineering project, says Brookes. "How useful is it to know what electrons are doing when you're trying to build an aeroplane?" she asks.

Might this received wisdom be wrong? Take smellMovie Camera, Brookes's area of interest. For decades, the line has been that a chemical's scent is determined by molecular shape. Olfactory receptors in the nose are like locks opened only with the right key; when that key docks, it triggers nerve signals that the brain interprets as a particular smell.

Is that plausible? We have around 400 differently shaped smell receptors, but can recognise around 100,000 smells, implying some nifty computation to combine signals from different receptors and process them into distinct smells. Then again, that's just the sort of thing our brains are good at. A more damning criticism is that some chemicals smell similar but look very different, while others have the same shape but smell different. The organic compound benzaldehyde, for example, comes in two almost identical molecular arrangements, vanillin and isovanillin, that have very distinctive smells.

There is an alternative explanation. Around 70 years ago, even before the lock-and-key mechanism was suggested, the distinguished British chemist Malcolm Dyson suggested that, just as the brain constructs colours from different vibrational frequencies of light radiation, it interprets the characteristic frequencies at which certain molecules vibrate as a catalogue of smells.

The idea languished in obscurity until 1996, when Luca Turin, a biophysicist then at University College London, proposed a mechanism that might make vibrational sensing work: electron tunnelling. This phenomenon results from the basic fuzziness of quantum mechanics, and is a staple of devices from microchips to microscopes. When an electron is confined in an atom, it does not have an exactly defined energy but has a spread of possible energies. That means there is a certain probability that it will simply burrow through the energy barrier that would normally prevent it escaping the atom.

Turin's idea is that when an odorous molecule lodges in the pocket of a receptor, an electron can burrow right through that molecule from one side to the other, unleashing a cascade of signals on the other side that the brain interprets as a smell. That can only happen if there is an exact match between the electron's quantised energy level and the odorant's natural vibrational frequency. "The electron can only move when all the conditions are met," Turin says. The advantage, though, is that it creates a smell without the need for an exact shape fit.

It was a controversial notion. In 2007 Brookes, then also working at University College London, and colleagues showed that the mechanism is physically plausible: the timescales are consistent with the speed with which the brain responds to smell, and the signals generated are large enough for the brain to process (Physical Review Letters, vol 98, p 038101). And in January this year Turin, now at the Alexander Fleming Biomedical Sciences Research Centre in Vari, Greece, and his colleagues delivered what looks like evidence for vibrational sensing. They showed that fruit flies can distinguish between two types of acetophenone, a common base for perfumes, when one contains normal hydrogen and the other contains heavier deuterium. Both forms have the same shape, but vibrate at different frequencies (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1012293108). That sensitivity can only mean electron tunnelling, says Andrew Horsfield of Imperial College London, a co-author on Brookes's paper: in classical models of electron flow the electron would not be sensitive to the vibrational frequency. "You can't explain it without the quantum aspect."

Smell is not the only thing that proponents of quantum biology think it might explain: there's also the mechanism that powers the entire animal kingdom. We all run on adenosine triphosphate, or ATP, a chemical made in cells' mitochondria by moving electrons through a chain of intermediate molecules. When we attempt to calculate how speedily this happens, we hit a problem. "In nature the process is much faster than it should be," says Vlatko Vedral, a quantum physicist at the University of Oxford.

Vedral thinks this is because it depends on the quality of "superposition" which allows the sort of quantum-mechanical wave that describes electrons to be in two places at once. He reckons quantum omnipresence might speed the electrons' passage through the reaction chain. "If you could show superposition is there and it's somehow also important for the electron flow, that would be very interesting," he says.

Vedral's first calculations support the idea, but he says it is too early to make any claims. It is hard to estimate all the parameters involved in electron transport, and it is possible that the classical calculations just used the wrong numbers. "And as yet we have no experimental proof," he says. Such proof might be quite close by - in how plants and some bacteria get their energy. It seems photosynthesis might be very much a quantum game.
Quantum marines

Direct evidence that this is so came in 2007, when a group led by Graham Fleming at the University of California, Berkeley, took a close look at photosynthesis in the green sulphur bacterium Chlorobium tepidum. They detected "beating" signals characteristic of quantum wave interference in the photosynthesising centres of bacteria cooled to 77 kelvin (Nature, vol 446, p 782). In January last year, a group led by Gregory Scholes of the University of Toronto, Canada, showed a similar effect at room temperature in light-harvesting proteins from two marine algae (Nature, vol 463, p 644).

This is a trick we might like to learn from. Although photosynthesis is not particularly efficient overall, the initial stage of converting incoming photons into the energy of electrons within a photosynthesising organism's light-gathering pigment molecules is extremely effective. When sunlight is weak, plants are able to translate more than 90 per cent of photons into an energy-carrying electron; in strong sunlight plants have to dump about half the energy to avoid overheating.

Scholes's explanation for this is that when sunlight hits electrons, they are kicked into a quantum superposition that allows them to be in two places at once. That effectively "wires" light-gathering molecules to the reaction centre where the photosynthesis takes place for a few hundred femtoseconds. During that time, an electron can, according to quantum rules, take all paths between the two places simultaneously. Probing the process more closely causes the superposition to collapse - and reveals the electron to have taken the path that lost it the least energy.

Might we take a leaf out of biology's book? Scholes thinks so. "Every year there are thousands of papers published on energy transfer," he says. "It sounds harsh but we haven't learned a thing apart from the obvious." A better understanding of what is going on might also help us on the way to building a quantum computer that exploits coherent states to do myriad calculations at once. Efforts to do so have so far been stymied by our inability to maintain the required coherence for long - even at temperatures close to absolute zero and in isolated experimental set-ups where disturbances from the outside world are minimised.

This remains the central conundrum for the physicists studying quantum aspects of biology. If we can't do these things in our isolated labs, how can a leaf in your less-than-isolated garden do it? If only the European robin could do more than warble chirpily. Perhaps then it could tell us - and explain its own apparent quantum superpowers, too (see "Bird's eye view").

At the moment we have little more than educated guesses. One is that it is simply a wonder of evolution. Scholes thinks that proteins around algae's light-harvesting equipment might have evolved structures that shield disturbances from the environment and so allow processes within to exploit the magic of quantum physics to give them a selective advantage. Vedral thinks something similar, although why and how nature would do this, he says, is "completely unclear".

Turin shrugs his shoulders, too. "Life's 4 billion years of nanoscale R&D will have engineered many miracles," he says. We should learn to accept what we see and try to mimic it, he says - and not just in solar cells and quantum computers. While what makes a drug effective or ineffective is far from clear, for instance, we do know that the operation of things like neurotransmitters in our brains depends on redox reactions, which are all to do with electron flow. If those flows occur in weirder ways than we have hitherto imagined, that could open up a new path to design drugs to treat some of our most pernicious ailments.

Others think nature is leading us up the garden path. Is photosynthesis, for example, really made more efficient by exploiting quantum interference and superposition effects? "I think the jury is still out on this question," says Robert Blankenship of Washington University in St Louis, Missouri. "I think it is possible that, depending on the details of the system, it could just as easily decrease the efficiency." Simon Benjamin, a colleague of Vedral's at the University of Oxford, wonders how we can really put long-lived quantum states to work if indeed they do pop up in natural systems. "It's certainly too early to be making dramatic claims," he says.

All those stepping gingerly around this new field agree that caution is needed - yet there is a palpable sense of excitement. Max Planck first discovered quantum theory more than a century ago because of odd observations that could be explained in no other way. That led to the laser and the semiconductor and all the technological revolutions they have seeded. Quantum biology is at that early stage of inexplicable observations. Turin for one believes something big is emerging. "I can't help thinking we are seeing just a small part of a far, far bigger iceberg," he says.
Bird's eye view

Another instance of quantum effects in biology might be in how birds sense Earth's magnetic field (New Scientist, 27 November 2010, p 42). In 2004, Thorsten Ritz of the University of California, Irvine, showed how magnetic disturbances that would only show up on systems that could detect transitions between particular quantum-mechanical atomic spin states could disrupt the compass of the European robin, Erithacus rubecula.

Ritz suggested that birds come equipped with a sensor system containing spin states that flip in response to changes in Earth's magnetic field, producing signals that the bird's brain in some way detects. But how?

The first proposal was that some apparatus in the eye initiates a chemical response. But this would require a constant, fast flipping of spins to keep chemical information flowing, whereas the birds seemed to maintain delicate spin states for extraordinarily long times of up to 100 microseconds.

According to the late Marshall Stoneham of University College London and his colleagues, the problem might be overcome if the birds used something similar to a human visual peculiarity that detects light polarisation. Known as Haidinger's brush, this superimposes a faint, yellow bow-tie shape on our visual field, and is thought to result from the way blue light-absorbing lutein molecules are arranged in concentric circles within our eye. Stare at a blank piece of paper and a polarising filter or a blank document on a laptop screen and you can see it for yourself.

Stoneham calculated that a magnetic field could produce a similar distortion in a bird's visual field, the orientation of which would change with a change in magnetic field. Crucially, that would occur only if quantum states lasted long enough to affect many of the bird's light sensing molecules at the same time. Birds might see the result, Stoneham suggested, in a kind of a head-up display of the kind that is embedded in the windscreens of some luxury cars (arxiv.org/abs/1003.2628).

Michael Brooks is a consultant for New Scientist. His latest book is Free Radicals: The secret anarchy of science (Profile, 2011)