Field of Science

Gamma Ray Bursts Place Limit on Quantum Gravity

The right-most panel shows the discovery image made using the UKIRT Wide Field Infrared Camera with the K filter (centred at 2.15 μm) at a mid-time of about 30 min after the burst. The other three images (Y, 1.02 μm; J, 1.26 μm; H, 1.65  μm) were obtained approximately 1.5 h after the burst using Gemini North's Near Infrared Imager and Spectrometer (NIRI). The main panels are 40 arcsec to a side, oriented with north to the top and east to the left. Insets, regions around the GRB, smoothed and at higher contrast. The absence of any flux in Y implies a power-law spectral slope between Y and J steeper than Fν  ∝ ν-18 and, coupled with the blue colour at longer wavelengths (J-H(AB) ≈ 0.15 mag), immediately implies a redshift greater than about 7.8 for GRB 090423. Image credit: Nature.

In June the Fermi telescope detected a distant gamma ray burst (GRB) at a redshift of 8.2 which was called at the time the most distant object ever observed.  Today Nature has published papers on some of the results from the Fermi team. Here is a quick look at them; first up is that distant object GRB 090423, A gamma-ray burst at a redshift of  z=8.2.
Long-duration γ-ray bursts (GRBs) are thought to result from the explosions of certain massive stars, and some are bright enough that they should be observable out to redshifts of z > 20 using current technology. Hitherto, the highest redshift measured for any object was z = 6.96, for a Lyman-α emitting galaxy. Here we report that GRB 090423 lies at a redshift of z  ≈ 8.2, implying that massive stars were being produced and dying as GRBs ~630 Myr after the Big Bang. The burst also pinpoints the location of its host galaxy.
Another paper published today explores a tantalizing prospect for physicists: the unification of general relativity and quantum field theory, which seem to be fundamentally incompatible.  The observation of a single photon at ~31 GeV from GRB 090510 places limits on quantum gravity which predicts that Lorentz invariance breaks down at the Planck length.  This would cause different energy photons to travel at different speeds.  Observations of varied speeds of photons from GRB 090510 were not convincingly seen putting a damper on quantum-gravity theories. The Fermi team has gone on to derive A limit on the variation of the speed of light arising from quantum gravity effect .
A cornerstone of Einstein's special relativity is Lorentz invariance—the postulate that all observers measure exactly the same speed of light in vacuum, independent of photon-energy. While special relativity assumes that there is no fundamental length-scale associated with such invariance, there is a fundamental scale (the Planck scale, lPlanck  ≈ 1.62 ~ 10-33 cm or EPlanck = MPlanckc2 ≈ 1.22 x 1019 GeV), at which quantum effects are expected to strongly affect the nature of space–time. There is great interest in the (not yet validated) idea that Lorentz invariance might break near the Planck scale. A key test of such violation of Lorentz invariance is a possible variation of photon speed with energy. Even a tiny variation in photon speed, when accumulated over cosmological light-travel times, may be revealed by observing sharp features in γ-ray burst (GRB) light-curves. Here we report the detection of emission up to ~31 GeV from the distant and short GRB 090510. We find no evidence for the violation of Lorentz invariance, and place a lower limit of 1.2EPlanck on the scale of a linear energy dependence (or an inverse wavelength dependence), subject to reasonable assumptions about the emission (equivalently we have an upper limit of lPlanck/1.2 on the length scale of the effect). Our results disfavour quantum-gravity theories in which the quantum nature of space–time on a very small scale linearly alters the speed of light.
And that isn't all!  There is yet another interesting Fermi paper just out, The Fermi Haze: A Gamma-Ray Counterpart to the Microwave Haze.  This has implications for WIMP dark matter models which would explain the observation, though this is only a speculation, but it is exciting to speculate...

UPDATE: This video really nails what is going on here:

Goethe and Hemingway: Quantified

Photo by Martin C. Eisenloeffel 
Welcome to the digital Weimar. The theme: linking art and science. How does art influence science? How does science influence art? Beauty, elegance, simplicity? Lets ask Goethe, Goethe, the last great polymath!

The Perimeter Institute's Quarks to the Cosmos festival presents Quantifying Goethe. Now experience simultaneously the Penderecki string quartet's quantum computer inspired music and an excerpt from Milan Kundera's Immortality chapter 17:

Strolling down a road in the other world, Hemingway saw a young man approaching him from a distance; he was elegantly dressed and held himself remarkably erect. As this dandy came closer, Hemingway could discern a slight, raffish smile on his face. When they were separated by just a few steps, the young man slowed his walk, as if he wanted to give Hemingway a last opportunity to recognize him.
    "Johann!" Hemingway exclaimed in surprise.
    Goethe smiled with satisfaction; he was proud that he head succeeded in producing such an excellent dramatic effect. Let's not forget that he had long been active as a theatrical director and had a sense of showmanship. He then took his friend by the arm (interestingly, even though he was now younger than Hemingway, he still behaved with the indulgence of the elderly) and took him on a leisurely walk.
    "Johann," said Hemingway, "today you look like a god." His friend's good looks caused him sincere joy, and he laughed happily: "Where did you leave you slippers? And that green eye shade? "And after he stopped laughing, he said, "That's how you should come to eternal trial. To crush the judges not with arguments but with you beauty!"
    "You know, I didn't say one single word at the eternal trial. Out of contempt.  But I couldn't keep myself from going there and listening to the proceedings. Now I regret it."
    "What do you want? You were condemned to immortality for the sin of writing books.  You explained it to me yourself."
    Goethe shrugged and said with some pride, "Perhaps our books are immortal, in a certain sense. Perhaps." He paused and then added softly, with great emphasis, "But we aren't."
    "Quite the contrary,"  Hemingway protested bitterly.  "Our books will probably soon stop being read. All that will remain of your Faust will be that idiotic opera by Gounod.  And maybe also that line about the eternal feminine pulling us somewhere or other..."
    "Das Ewigweibliche zieht uns hinan," recited Goethe.
    "Right. But people will never stop prying into your life, down to the smallest details."
    "Haven't you realized yet, Ernest, that figures they talk about have nothing to do with  us?"
    "Don't tell me, Johann, that you bear no relation to the Goethe about whom everybody writes and talks. I admit that the image that remained behind you is not entirely identical to you. I admit that it distorts you quite a bit. Still, you are present in it."
    "No, I'm not," Goethe said very firmly. "And I'll tell you something else. I am not even present in my books. He who doesn't exist cannot be present."
    "That's too philosophical for me."
    "Forget for a moment that you're an American and exercise your brain: he who doesn't exist cannot be resent. Is that so complicated? The instant I died I vanished from everywhere, totally. I even vanished from my books. Those books exist in the world without me. Nobody will ever find me in them. Because you cannot find someone who not exist."
    "I'd like to agree with you," said Hemingway, "but explain this to me: if the image you've left behind has nothing to do with you, why did you lavish so much care on it while you were still alive? Why did you invite Eckermann to join you? Why did you start writing Poetry and Truth?"
    "Ernest, resign yourself to the idea that I was as foolish as you. That obsession with one's own image, that's man's fatal immaturity. It is so difficult to be indifferent to one's image. Such indifference is beyond human strength. One becomes capable of it only after death. And even then it doesn't happen at once, but only a long time after death. You still haven't reached that point. You're still not mature. And yet you've been death... how long, actually?"
    "Twenty-seven years," said Hemingway.
    "That's nothing. You'll have to wait at least another twenty or thirty years before you become fully aware that man is mortal and be able to draw all the consequences from that realization. It won't happen any sooner. Just shortly before I died I declared that I felt such creative power within me, it was impossible for it to disappear without a trace. And of course I believed that I would live in the image I left behind me. Yes, I was just like you. Even after death it was hard to me to accept the idea that I no longer existed. You know, it's really very peculiar. To be mortal is the most basic human experience, and yet man has never been able to accept it, grasp it, and behave accordingly. Man doesn't know how to mortal. And when he dies, he doesn't even know how to be dead."
    "And do you know how to be dead, Johann?: asked Hemingway, in order to lighten the gravity of the moment. "Do you really believe that the best way to be dead is to waste time chatting with me?"
    "Don't make a fool of yourself, Ernest," said Goethe. "You know perfectly well that at this moment we are but the frivolous fantasy of a novelist who lets us say things we would probably never say on our own. But to conclude. Have you noticed my appearance today?"
    "Didn't I tell you the moment I set eyes on you? You look like a god!"
    "This is how I looked when all Germany considered me a pitiless seducer," Goethe said with an almost grandiose air. Then, moved, he added, "I wanted you to take me with you into your future years in precisely this way."
    "Hemingway looked at Goethe with sudden, gentle indulgence: "And you, Johann, how long have you lived since your death?"
    "One hundred and fifty-six," Goethe answered with some embarrassment.
    "And you still haven't learned how to be dead?"
    "Goethe smiled. "I know, Ernest. I've been behaving differently from what I've been telling you just a moment ago. But I permitted myself this childish vanity, because today we are seeing each other for the last time," And then, slowly, as one who would speak no more, he said these words: "You see, I have come to the definite conclusion that the eternal trial is bullshit. I have decided to make use of my death at least and, if I can express it with such an imprecise term, to go to sleep. To enjoy the delights of total nonexistence, which my great enemy Novalis used to say has a bluish color."
The entire Perimeter institute performance of Quantifying Goethe is shown below. The video above is an excerpt from the 29th minute.

Other Worlds: Rare Astronomical Works

Image courtesy of the Harry Ransom Center at The University of Texas at Austin.
The Harry Ransom Center is a bastion of books. It is a research library located at the University of Texas at Austin; I used to work there and I must say it is a bibliophiles obsession. I remember that in the labyrinth of rare book stacks the fire alarms had signs posted saying something to the effect of, 'Warning: In case of fire the oxygen in this room will be removed' and below one of these warnings a page from the days of yore had scrawled, 'No one hears you scream in the stacks'. And they were right. There are so many books, so many rooms, and so many floors that I don't think anyone would hear you scream. But the authors in those books are a silent shout at an enduring literary, scientific, and artistic history.

The center is becoming something of a paragon in its field. And it is odd to ponder why do the archives of so many great writers end up in Texas? D. T. Max discusses the question in this article from the New Yorker. They also have a picture slide show on the tools of the trade.

Other Worlds: Rare Astronomical Works is a current exhibition showing at the center. They don't have an extensive web exhibition up for this collection (although they do have several other delightful online exhibits), but they do have a video discussing the collection and a nifty online preview which you may spin to visualize the Coronelli Celestial Globe. Their official blurb is below.
The Harry Ransom Center, a humanities research library and museum at The University of Texas at Austin, will present the exhibition "Other Worlds: Rare Astronomical Works," showcasing items from the center's science collection that survey some of the most important astronomical discoveries of the last 500 years.

Coinciding with the International Year of Astronomy, "Other Worlds" displays how the historical role of astronomy has come to influence the way the modern world is perceived.

With more than 40 rare editions of works by astronomers such as Johannes Kepler and Tycho Brahe, "Other Worlds" includes works by the individuals whose ideas revolutionized astronomical thought. From Nicolaus Copernicus's "De Revolutionibus," the first text to promote a heliocentric view of the solar system, to atlases of stars and constellations, the exhibition illustrates how early hypotheses laid the foundation for modern theories of the universe and its origins.

The exhibition also features items from the Ransom Center's papers of the Herschel family, a 19th-century English family of influential astronomers, including William Herschel, discoverer of the planet Uranus, and his sister Caroline Herschel, one of the first female astronomers. Highlights from the Herschel collection include the family's catalog of thousands of stars in the universe, William Herschel's 1836 account of Halley's Comet and a handmade astronomical device for locating heavenly bodies.

"Other Worlds" also examines the range of astronomy's influence on the broader culture, reflected in depictions of the moon and other worlds in literature, photography and popular works. From Jules Verne's novel "From the Earth to the Moon" to the 1923 moon illustration guide "Hutchinson's Splendour of the Heavens," the exhibition spans genres in revealing the breadth of astronomy's impact.

Read on...
Coronelli celestial globe, ca. 1688. Photo by Pete Smith. Image courtesy of
the Harry Ransom Center.

Smithsonian Air and Space Posters


The Smithsonian National Air and Space Museum has digitized their poster collection online. Above are some of my favorite picks and below a blurb about the posters.

Throughout their history, posters have been a significant means of mass communication, often with striking visual effect. Wendy Wick Reaves, the Smithsonian Portrait Gallery Curator of Prints and Drawings, comments that "sometimes a pictorial poster is a decorative masterpiece-something I can't walk by without a jolt of aesthetic pleasure. Another might strike me as extremely clever advertising … But collectively, these 'pictures of persuasion,' as we might call them, offer a wealth of art, history, design, and popular culture for us to understand. The poster is a familiar part of our world, and we intuitively understand its role as propaganda, promotion, announcement, or advertisement."

Reaves' observations are especially relevant for the impressive array of aviation posters in the National Air and Space Museum's 1300+ artifact collection. Quite possibly the largest publicly-held collection of its kind in the United States, the National Air and Space Museum's posters focus primarily on advertising for aviation-related products and activities. Among other areas, the collection includes 19th-century ballooning exhibition posters, early 20th-century airplane exhibition and meet posters, and twentieth-century airline advertisements.

The posters in the collection represent printing technologies that include original lithography, silkscreen, photolithography, and computer-generated imagery. The collection is significant both for its aesthetic value and because it is a unique representation of the cultural, commercial and military history of aviation. The collection represents an intense interest in flight, both public and private, during a significant period of its technological and social development.

Hip-Hop Physics

The Ising and Hubbard models are really clever physical approximations from statistical physics. The Wikipedia page on the Ising model is extensive and every physicist should preform the 1D solution at some point in their life, and for others just taking a look at these models and considering their application to the social sciences is worth considering. Anyways onto Hip-Hop Physics from the American Scientist (by Brian Hayes who also runs the bit-player) which discusses the challenges inherent in solving even these simple mathematical models (I first saw this link on 3QuarksDaily and have shamelessly reproduced it here, but good science writing must be propogated):
Mathematical models and computer simulations usually begin as aids to understanding, introduced when some aspect of natural science proves too knotty for direct analysis. Facing an intractable problem, we strip away all the messy details of the real world and build a toy universe, one simple enough that we can hope to master it. Often, though, even the dumbed-down model defies exact solution or accurate computation. Then the model itself becomes an object of scientific inquiry—a puzzle to be solved.
A good example is the Ising model in solid-state physics, which attempts to explain the nature of magnetism in materials such as iron. (I wrote about the Ising model in an earlier Computing Science column; see “The World in a Spin,” September–October 2000.) The Ising model glosses over all the intricacies of atomic structure, representing a magnet as a simple array of electron “spins” on a plain, gridlike lattice. Even in this abstract form, however, the model presents serious challenges. Only a two-dimensional version has been solved exactly; for the three- dimensional model, getting accurate results requires both algorithmic sophistication and major computer power.
Read on...

Space Exploration Missions

The image above is a link to a huge diagram showing space exploration missions. I have no idea how comprehensive of missions it is. I think the original source was National Geographic so it must be rather complete. Regardless the image is stunning in a visual design sense and it makes a good desktop background. Enjoy.

A Dream

In a deserted place in Iran there is a not very tall stone tower that has neither door nor window. In the only room (with a dirt floor and shaped like a circle) there is a wooden table and a bench. In that circular cell, a man who looks like me is writing in letters I cannot understand a long poem about a man who in another circular cell is writing a poem about a man who in another circular cell . . . The process never ends and no one will be able to read what the prisoners write.

A Dream by Jorge Luis Borges (Translated, from the Spanish, by Suzanne Jill Levine.)
En un desierto lugar del Irán hay una no muy alta torre de piedra, sin puerta ni ventana. En la única habitación (cuyo piso es de tierra y que tiene la forma del círculo) hay una mesa de madera y un banco. En esa celda circular, un hombre que se parece a mí escribe en caracteres que no comprendo un largo poema sobre un hombre que en otra celda circular escribe un poema sobre un hombre que en otra celda circular . . . El proceso no tiene fin y nadie podrá leer lo que los prisioneros escriben.
Un Sueño por Jorge Luis Borges