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Category: physics – Page 206

So young and already so evolved: Thanks to observations obtained at the Large Binocular Telescope, an international team of researchers coordinated by Paolo Saracco of the Istituto Nazionale di Astrofisica (INAF, Italy) was able to reconstruct the wild evolutionary history of an extremely massive galaxy that existed 12 billion years ago, when the universe was only 1.8 billion years old, less than 13% of its present age. This galaxy, dubbed C1-23152, formed in only 500 million years, an incredibly short time to give rise to a mass of about 200 billion suns. To do so, it produced as many as 450 stars per year, more than one per day, a star formation rate almost 300 times higher than the current rate in the Milky Way. The information obtained from this study will be fundamental for galaxy formation models for objects it for which it is currently difficult to account.

The most in the universe reach masses several hundred billion times that of the sun, and although they are numerically just one-third of all galaxies, they contain more than 70% of the in the universe. For this reason, the speed at which these galaxies formed and the dynamics involved are among the most debated questions of modern astrophysics. The current model of galaxy formation—the so-called hierarchical model—predicts that smaller galaxies formed earlier, while more massive systems formed later, through subsequent mergers of the pre-existing smaller galaxies.

On the other hand, some of the properties of the most massive galaxies observed in the local universe, such as the age of their stellar populations, suggest instead that they formed at early epochs. Unfortunately, the variety of evolutionary phenomena that galaxies can undergo during their lives does not allow astronomers to define the way in which they formed, leaving large margins of uncertainty. However, an answer to these questions can come from the study of the properties of massive galaxies in the early universe, as close as possible to the time when they formed most of their mass.

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Though it sounds like something straight out of science fiction, controlling the speed of light has in fact been a long-standing challenge for physicists. In a study recently published in Communications Physics, researchers from Osaka University generated light bullets with highly controllable velocities.

According to Albert Einstein’s principle of relativity, the is constant and cannot be exceeded; however, it is possible to control the group velocity of optical pulses.

Currently, the spatiotemporal coupling of optical pulses provides an opportunity to control the of three-dimensional non-diffraction optical wave-packets, known as “light bullets,” in free space.

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The history of the Universe thus far has certainly been eventful, marked by the primordial forging of the light elements, the birth of the first stars and their violent deaths, and the improbable origin of life on Earth. But will the excitement continue, or are we headed toward the ultimate mundanity of equilibrium in a so-called heat death? In The Janus Point, Julian Barbour takes on this and other fundamental questions, offering the reader a new perspective—illustrated with lucid examples and poetically constructed prose—on how the Universe started (or more precisely, how it did not start) and where it may be headed. This book is an engaging read, which both taught me something new about meat-and-potatoes physics and reminded me why asking fundamental questions can be so fun.

Barbour argues that there is no beginning of time. The Big Bang, he maintains, was just a very special configuration of the Universe’s fundamental building blocks, a shape he calls the Janus point. As we move away from this point, the shape changes, marking the passage of time. The “future,” he argues, lies in both directions, hence the reference to Janus, the two-faced Roman god of beginnings and transitions.

Barbour illustrates his main points with a deceptively simple model known as the three-body problem, wherein three masses are subject to mutual gravitational attraction. In this context, the Janus point occurs when all three masses momentarily occupy the same point, in what is called a total collision. The special shape at the Janus point, explains Barbour, is an equilateral triangle, which is his model’s version of the Big Bang. I found this imagery helpful when trying to understand the more abstract, and necessarily less technical, application of this concept to general relativity.

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The observation of a chemical reaction at the molecular level in real time is a central theme in experimental chemical physics. An international research team has captured roaming molecular fragments for the first time. The work, under the supervision of Heide Ibrahim, research associate at the Institut national de la recherche scientifique (INRS), was published in the journal Science.

The research group of the Énergie Matériaux Télécommunications Research Centre of INRS, with support of Professor François Légaré, has used the Advanced Laser Light Source (ALLS). They have succeeded in shooting the first molecular film of “roamers”—hydrogen fragments, in this case—that orbit around HCO fragments) during a chemical reaction by studying the photo-dissociation of formaldehyde, H2CO.

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Researchers at Oregon State University are making key advances with a new type of optical sensor that more closely mimics the human eye’s ability to perceive changes in its visual field.

The sensor is a major breakthrough for fields such as image recognition, robotics and artificial intelligence. Findings by OSU College of Engineering researcher John Labram and graduate student Cinthya Trujillo Herrera were published today in Applied Physics Letters.

Previous attempts to build a human-eye type of device, called a retinomorphic sensor, have relied on software or complex hardware, said Labram, assistant professor of electrical engineering and computer science. But the new sensor’s operation is part of its fundamental design, using ultrathin layers of perovskite semiconductors—widely studied in recent years for their solar energy potential—that change from strong electrical insulators to strong conductors when placed in light.

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For now, it looks like our best bet for going interstellar is to rely on robotic spacecraft that are optimized for speed.

For countless generations, the idea of traveling to an extrasolar planet has been the stuff of dreams. In the current era of renewed space exploration, interest in interstellar travel has understandably been rekindled. However, beyond the realm of science fiction, interstellar space travel remains a largely theoretical matter.

Between the sheer expense involved, the need for technological developments to happen first, and the nature of spacetime itself, sending people to another star system is something that is not likely to happen for a long time – if ever. But in spite of the challenges, the hope remains.

Continue reading “Reaching for the Stars: The Case for Interstellar Travel” | >

The Voyager probes have detected an entirely new kind of electron burst outside the solar system.

It is the first time this “unique physics” have been detected by a spacecraft, and could allow for new breakthroughs in our understanding of the “interstellar medium”, or the space between the stars.

The two Voyager spacecraft were launched by NASA more than 40 years ago, with the aim of flying to the far reaches of our solar system. They have now gone even further than that, reaching interstellar space, and exploring the gaps between the stars, giving us the first glimpses of what it might be like in that mysterious zone.

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