Archive for Ciencia

Observan un nuevo tipo de desintegración en núcleos ricos en protones

Una de las cuestiones básicas para la Física nuclear es entender la estructura del núcleo atómico, cómo protones y neutrones se mantienen unidos permitiendo la formación del núcleo. Esto, que se conoce bien en los núcleos estables que dan lugar … Continue reading

DOS ESTRELLAS DE NEUTRONES CONTRAPUESTAS

Las estrellas masivas ponen fin a sus días explotando como supernovas y liberando una gran cantidad de materia y energía. Todo lo que queda de ellas es un pequeño remanente extremadamente denso: una estrella de neutrones o un agujero negro. … Continue reading

Astrophysics at the edge of the Earth

Conducting research at the South Pole takes a unique level of commitment.

The sun sets but once a year at the South Pole, and it is a prolonged process. During a recent stay at the Amundsen-Scott South Pole Station, postdoctoral researcher Jason Gallicchio saw it hover along the horizon for about a week before dropping out of sight for six months. The station’s chefs prepared an eight-course meal to mark the occasion.

The South Pole is not the easiest place to mark the passage of time, but the spectacular view it offers of the night sky has made it one of the best places to study astrophysics—and a unique place to work.

Gallicchio, an associate fellow for the Kavli Insitute of Physics at the University of Chicago, is part of an astrophysics experiment at the South Pole Telescope. Last year he spent nearly a full year at the station, including a “winterover,” during which the crew for his experiment dwindled to just him and a colleague.

Life at the station

Making it to the South Pole took interviews and a rigorous training program that included emergency medical and firefighting training and a mandatory psychological evaluation, Gallicchio says.

“People were bombarding me with information—which grease to grease which parts with, how to analyze data in certain ways,” Gallicchio says. “It was totally intense every day. It was one of the best, most educational things in my life.”

Gallicchio landed at the South Pole in early January 2013 and remained there until mid-November.

“When you get off the plane at the South Pole, there is a feeling like you’re out in the ocean,” says University of Chicago physicist John Carlstrom, the principal investigator for the South Pole Telescope team, who has logged 15 round trips to the South Pole over the past two decades. “It’s just a featureless horizon. The snow is so dry it feels like Styrofoam.”

The living quarters at the South Pole station are comfortable and dorm-like, Gallicchio says. A brightly lit greenhouse provides an escape from the constant night and nosebleed-inducing dryness. It also supplies some greens to the daily menu, but no fresh fruit or nuts.

“One of the most popular things after dinner, ironically, is ice cream,” he says.

Gallicchio fashioned his sleeping schedule around his duties at the telescope. “I was always on-call,” he says. “A lot of people there were in that situation. It was totally acceptable to be eating or watching a movie and then to go off to work and come back.”

The living quarters are about a half-mile hike from the telescope building.

Because welding is challenging in the Antarctic chill, and because the long winter season limits construction time, the telescope was designed in pieces that could be quickly fastened together with thousands of structural bolts. The ski-equipped cargo planes that carry supplies to the South Pole station are limited to carrying 26,000 pounds per trip; the bolts practically required their own dedicated flight.

Much of the telescope’s instrumentation is tucked away in a heated building beneath the exposed dish. Its panels, machined to hair’s-width precision, are slightly warmed to keep them free of frost.

Earlier astrophysics experiments at the South Pole provided important lessons for how to best build, maintain and operate the South Pole Telescope, Carlstrom says. “Everything left out and exposed to the cold will fail in a way you probably hadn’t thought of.”

Measuring 10 meters across and weighing 280 tons, the South Pole Telescope precisely maps temperature variations in the cosmic microwave background, a kind of faint static left in the sky from the moment that light first escaped the chaos that followed the big bang.

The telescope was installed in 2007 and upgraded in 2012 to be sensitive to a type of pattern, called polarization, in the CMB. Studying the polarization of the CMB could tell scientists about the early universe.

Another South Pole experiment, BICEP2, recently reported finding a pattern that could be the first proof that our universe underwent a period of rapid expansion the likes of which we haven’t seen since just after the big bang. One of the goals of the South Pole Telescope is to further investigate and refine this result.

The South Pole Telescope’s next upgrade, which will grow its array from 1,500 to 15,000 detectors, is set for late 2015.

Icy isolation

During the winter months, the average temperature is negative 72 degrees, but “a lot of people find the altitude much worse than the cold,” Gallicchio says. No flights are scheduled in or out.

Gallicchio says he had never experienced such isolation. Even if you’re aboard the International Space Station, if something goes wrong you’re only a few hours away from civilization, he says. During a winter at the South Pole, there’s no quick return trip.

During the warmer months, up to about 200 scientists and support staff can occupy the South Pole station at any given time. During the winter, the group is cut to about 50.

During Gallacchio’s winterover, he was generally responsible for the telescope’s data acquisition and software systems, though he occasionally assisted with “crawling around fixing things.” Gallacchio could work on some of the telescope’s computer and electronics systems from the main station, while his more seasoned colleague Dana Hrubes often spent at least eight hours a day at the telescope. “He really taught me a lot and was a great partner,” Gallachio says.

At one point, the power went out, and his emergency training kicked in. Gallicchio and Hrubes began the steps needed to dock the telescope to protect it from the elements in case its heating elements ran out of backup power.

“Power going out is a big deal, as all of the heat from the station comes from waste heat in the generators, and eventually there’s going to be no heat,” he says. “The circuit-breaker kept tripping and it took [the staff] a while to figure out that a control cable had frayed and shorted itself. It got a little scary.”

Once the power plant mechanics found the problem, they repaired it and got all systems back online. “They did a great job.”

A view like no other

Gallicchio recalls the appearance of the first star after the weeklong sunset. Gradually, more and more stars appeared. Eventually, the sky was aglow.

On some nights, the southern lights, the aurora australis, took over. “When the auroras are active they are by far the brightest thing,” he says. “Everything has a green tint to it, including the snow and the buildings.”

Besides missing family, friends, bike rides and working in coffee shops, Gallicchio says he did enjoy his time at the South Pole. “Nothing about the experience itself would keep me from doing it again.”

 

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What Hawking really meant

Fermilab physicist Don Lincoln explains the idea of a metastable universe, what it has to do with the Higgs boson, and why we're still in good shape.

If you’re a science enthusiast, this week you have likely encountered headlines claiming that physicist Stephen Hawking thinks the Higgs boson will cause the end of the universe.

This is a jaw-dropping misrepresentation of science. The universe is safe and will be for a very long time—for trillions of years.

To understand how abominably Hawking’s words have been twisted, first we need to understand his statement. To paraphrase just a little, Hawking said that in a world in which the Higgs boson and another fundamental particle—the top quark—have the masses that scientists have measured them to have, the universe is in a metastable state.

Basically, metastable means “kind of stable.” So what does that mean? Let’s consider an example. Take a pool cue and lay it on the pool table. The cue is stable; it’s not going anywhere. Take the same cue and balance it on your finger. That’s unstable; under almost any circumstances, the cue will fall over.

The analogy for a metastable object is a barstool. Under almost all circumstances, the stool will sit there for all eternity. However, if you bump the stool hard enough, it will fall over. When the stool falls, it is more stable than it was, just like the pool cue lying on the table.

Now we need to bring in the universe and the laws that govern it. Here is an important guiding principle: The universe is lazy—a giant, cosmic couch potato. If at all possible, the universe will figure out a way to move to the lowest energy state it can. A simple analogy is a ball placed on the side of a mountain. It will roll down the mountainside and come to rest at the bottom of the valley. This ball will then be in a stable configuration.

The universe is the same way. After the cosmos was created, the fields that make up the universe should have arranged themselves into the lowest possible energy state.

There is a proviso. It is possible that there could be little “valleys” in the energy slope. As the universe cooled, it might have been caught in one of those little valleys. Ideally, the universe would like to fall into the deeper valley below, but it could be trapped.

This is an example of a metastable state. As long as the little valley is deep enough, it’s hard to get out of. Indeed, using classical physics, it is impossible to get out of it.

However, we don’t live in a classical world. In our universe, we must take into account the nature of quantum mechanics. There are many ways to describe the quantum realm, but one of the properties most relevant here is “rare things happen.” In essence, if the universe was trapped in a little valley of metastability, it could eventually tunnel out of the valley and fall down into the deeper valley below.

So what are the consequences of the universe slipping from one valley to another? Well, the rules of the universe are governed by the valley in which it finds itself. In the metastable valley that defines our familiar universe, we have the rules of physics and chemistry that allow matter to assemble into atoms and, eventually, us.

If the universe slipped into a different valley, the rules that govern matter and energy would be different. This means, among other things, particles such as quarks and leptons might be impossible. The known forces that govern the interaction of those particles might not apply. In short, there is no reason to think we’d exist at all.

Would we have any warning if this transition occurred? Actually, we’d have no warning at all. If, somewhere in the cosmos, the universe made a transition from a metastable valley to a deeper one, the laws of physics would change and sweep away at the speed of light. As the shockwave passed over the solar system, we’d simply disappear as the laws that govern the matter that makes us up ceased to apply. One second we’d be here; the next we’d be gone.

Coming back to the original question, what does the Higgs boson tell us about this? It turns out that we can use the Standard Model to tell us whether we are in a stable, unstable or metastable universe.

We know we don’t live in an unstable one, because we’re here, but the other two options are open. So, what is the answer? It depends on two parameters: the mass of the top quark and the mass of the Higgs boson.

If we follow our understanding of the Standard Model, combined with our best measurements, it appears that we live in a metastable universe that could one day disappear without warning. You can be forgiven if you take that pronouncement as a reason to indulge in some sort of rare treat tonight.

But before you splurge too much, take heed of a few words of caution. Using the same Standard Model we used to figure out whether the cosmos is metastable, we can predict how long it is likely to take for quantum mechanics to let the universe slip from the metastable valley to the stable one: It will take trillions of years.

Mankind has only existed for about 100,000 years, and the sun will grow to a red giant and incinerate the Earth in about 5 billion years. Since we’re talking about the universe existing as a metastable state for trillions of years, maybe overindulging tonight might be a bad idea.

It is important to note that finding the Higgs boson has no effect on whether the universe is in a metastable state. If we live in a metastable cosmos, it has been that way since the universe was created. The discovery of the Higgs boson has no effect at all on whether the universe is in a metastable state.

Returning to the original, overly hyped media stories, you can see that there was a kernel of truth and a barrel full of hysteria. There is no danger, and it’s completely OK to resume watching with great interest the news reports of the discovery and careful measurement of the Higgs boson. And, yes, you have to go to work tomorrow.


A version of this article was published in Fermilab Today.

 

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The Dawn of the standard revolution

Author(s) DE RUJULA, Alvaro (speaker) (Consejo Superior de Investigaciones Cientificas (CSIC) (ES)) Corporate author(s) CERN. Geneva Imprint 2014-06-06. - Streaming video. Series (Public Events) (The dawn of the standard revolution) Lecture note on 2014-06-06T15:30:00 Subject category Public Events Copyright/License © … Continue reading

CERN 2nd Anniversary of the Discovery of the Higgs

2nd Anniversary of the Discovery of the Higgs The ATLAS & CMS Experiments Celebrate the 2nd Anniversary of the Discovery of the Higgs boson. Here, are some i...
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2nd Anniversary of the Discovery of the Higgs

2nd Anniversary of the Discovery of the Higgs The ATLAS & CMS Experiments Celebrate the 2nd Anniversary of the Discovery of the Higgs boson. Here, are some images of the path from LHC startup to Nobel Prize, featuring a musical … Continue reading

Eventos para celebrar el 60 aniversario del CERN en septiembre

El 29 de septiembre de 1954 entró en vigor la Convencióndel CERN, estableciendo oficialmente la Organización Europea para la Investigación Nuclear con 12 estados miembros de Europa. Convertido ahora en el mayor laboratorio del mundo de física de partículas, el … Continue reading

Un algoritmo permite la detección vía satélite de diferentes grupos de fitoplancton en el mar Mediterráneo

El mar Mediterráneo presenta unas características ópticas diferentes al resto de los océanos que hacen que los algoritmos globales de detección no funcionen de forma precisa. Ahora un grupo de investigadores del Consejo Superior de Investigaciones Científicas (CSIC) ha adaptado … Continue reading

Voyager HD (original)

Voyager HD (original)
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Proyectos de la NASA – Los Viajeros del Universo

Proyectos de la NASA - Los Viajeros del Universo
Blog del canal : http://documaniacosesp.blogspot.com.esSe denomina Voyager a cualquiera de las dos sondas espaciales estadounidenses enviadas a los planetas exteriores. La Voyager 1 fue lanzada el 5 de septiembre de 1977 desde Cabo Cañaveral. Pasó por Júpiter en 1979 y por Saturno en 1980. La Voyager 2 fue enviada el 20 de agosto de 1977, pasando por Júpiter y Saturno para llegar a Urano en 1986 y Neptuno en 1989. La Voyager 2 es la única sonda que ha visitado esos dos planetas.Ambas sondas llevan consigo un disco de oro con una selección de hora y media de duración de música proveniente de varias partes y culturas del mundo, saludos en 55 idiomas humanos, un saludo del entonces Secretario General de las Naciones Unidas y el ensayo Sonidos de la Tierra, que es una mezcla de sonidos característicos del planeta. También contiene 115 imágenes (+1 de calibración) donde se explica en lenguaje científico la localización del Sistema Solar, las unidades de medida que se utilizan, características de la Tierra y características del cuerpo y la sociedad humana. Este disco fue ideado por un comité científico presidido por el astrónomo Carl Sagan quien, refiriéndose al mensaje, asegura que su objetivo principal no es el ser descifrado, por el hecho de que su simple existencia pone de manifiesto la existencia de los humanos, así como sus esfuerzos por contactar a otras especies inteligentes que pudiesen existir fuera del Sistema Solar.
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La sexta extinción

Alertan sobre la la sexta gran extinción que está induciendo el ser humano en la biosfera. Como ya sabemos todos, a lo largo de estos 550 millones de años evolución biológica compleja ha habido cinco extinciones masivas. Alguna de ellas, … Continue reading