Physics posts
- December 15, 2010
- 11:59 AM
- 792 views
Graphene – The Stuff of the Future!
by Paul Vallett in Electron Cafe
I’ve mentioned Graphene a few times in the blog and I wanted to spend some time explaining what sort of things people are doing with it, why it’s worthy of a Nobel Prize, and why it’s just plain cool! In fact, check out this picture: Read more below for additional reasons why graphene is awesome… [...]... Read more »
Novoselov, K. (2004) Electric Field Effect in Atomically Thin Carbon Films. Science, 306(5696), 666-669. DOI: 10.1126/science.1102896
Bae, S., Kim, H., Lee, Y., Xu, X., Park, J., Zheng, Y., Balakrishnan, J., Lei, T., Ri Kim, H., Song, Y.... (2010) Roll-to-roll production of 30-inch graphene films for transparent electrodes. Nature Nanotechnology, 5(8), 574-578. DOI: 10.1038/nnano.2010.132
Seol, J., Jo, I., Moore, A., Lindsay, L., Aitken, Z., Pettes, M., Li, X., Yao, Z., Huang, R., Broido, D.... (2010) Two-Dimensional Phonon Transport in Supported Graphene. Science, 328(5975), 213-216. DOI: 10.1126/science.1184014
Lin, Y., Dimitrakopoulos, C., Jenkins, K., Farmer, D., Chiu, H., Grill, A., & Avouris, P. (2010) 100-GHz Transistors from Wafer-Scale Epitaxial Graphene. Science, 327(5966), 662-662. DOI: 10.1126/science.1184289
- December 14, 2010
- 09:04 AM
- 1,403 views
other universes, found only on the arxiv blog…
by Greg Fish in weird things
Is it just me or is the CMBR becoming more like a Rorschach test for some theoretical physicists as of late? I mean, first we have Roger Penrose seeing traces of past Big Bangs and assembling them into a somewhat shaky and dubious model of cyclical cosmology, and now we have a team of astronomers [...]... Read more »
Stephen M. Feeney, Matthew C. Johnson, Daniel J. Mortlock, & Hiranya V. Peiris. (2010) First Observational Tests of Eternal Inflation. n/a. arXiv: 1012.1995v1
- December 13, 2010
- 11:14 AM
- 1,047 views
This “Week” in the Universe: November 30th – December 13th
by S.C. Kavassalis in The Language of Bad Physics
Astrophysics and Gravitation:
The Milky Way Project
The Milky Way Project aims to sort and measure our galaxy, the Milky Way. Initially we’re asking you to help us find and draw bubbles in beautiful infrared data from the Spitzer Space Telescope.
Understanding the cold, dusty material that we see in these images, helps scientists to learn how stars form and how our galaxy changes and evolves with time.
The GalaxyZoo project expands! Help astronomers out when you’re feeling in the mood to procrastinate.
GREAT10 Image Analysis Competitions for Cosmological Lensing
GREAT10, a simulation challenge that aims to improve image analysis algorithms for cosmic gravitational lensing.
GREAT10 is a way for astronomers, astrophysicists, computer vision, and AI people to come together and find new ways of solving problems. Contest details are online.
For more, see Computer Geeks: Compete to Help NASA Explain Dark Energy.
High Energy Physics and Particles:
2010 Ion Run Complete at CERN
From CERN Bulletin:
After a very fast switchover from protons to lead ions, the LHC has achieved performances that allowed the machine to exceed both peak and integrated luminosity by a factor of three. Thanks to this, experiments have been able to produce high-profile results on ion physics almost immediately, confirming that the LHC was able to keep its promises for ions as well as for protons.
Another milestone finished; it’s been a great year for the LHC.
For more, see CERN Bulletin.
General Relativity, Quantum Gravity, et al.:
GravityGeek for Christmas
GravityGeek is a cooperative project to help encourage interaction amongst physicists in gravitation/general relativity with journalists and the public.
GravityGeek, the beta collaboration/networking site for professionals in general relativity, quantum gravity, cosmology, etc., has recommendations for Christmas/other gift giving, in case you have a physicist to buy for (as well as non-technical recommendations for kids and those who just like good popular science literature).
For more, see The GravityGeek Mission.
Fun with 2D Blackholes
Abhay Ashtekar, Frans Pretorius, & Fethi M. Ramazanoğlu (2010). Surprises in the Evaporation of 2-Dimensional Black Holes arXiv arXiv: 1011.6442v1
The abstract:
Quantum evaporation of Callen-Giddings-Harvey-Strominger (CGHS) black holes is analyzed in the mean field approximation. The resulting semi-classical theory incorporates back reaction. Detailed analytical and numerical calculations show that, while some of the assumptions underlying the standard evaporation paradigm are borne out, several are not. Furthermore, if the black hole is initially macroscopic, the evaporation process exhibits remarkable universal properties. Although the literature on CGHS black holes is quite rich, these features had escaped previous analyses, in part because of lack of required numerical precision, and in part because certain properties and symmetries of the model were not recognized. Finally, our results provide support for the full quantum scenario recently developed by Ashtekar, Taveras and Varadarajan.
This is fairly nice for something so dense to read (it’s a lot crammed into four pages). The key result: for 2D black holes, information in the matter profile on Ī⁻R will not all be recovered at Ī⁺R, in generality. Slight twists on our understanding of 2D black holes might be suggestive of solutions in 4D. Of course, the usual problems of discussing anything in 2D are still there, but still…
Cyclic Circles in the Sky? Probably Not
The big topic of the past few weeks has been Roger Penrose and V.G. Gurzadyan’s November paper, suggesting there was evidence, via circle matching in the CMB, of a cyclic cosmology. There are so many papers being discussed right now, that this requires it’s own section. Now, because Penrose being a co-author makes any paper big news, mainstream media was all over this “evidence for time before time” (and other completely offensive and nonsensical catchphrases). What Gurzadyan and Penrose believed they had shown was that patterns in the CMB could not fit with standard inflationary cosmology and were strongly suggestive of a cyclic cosmology – ie. multiple “big bangs” (so our big bang wasn’t the first/didn’t start the cosmic clock, so to speak). Now, many people who’ve looked for circles in the CMB (because it could be very suggestive of the topology/geometry/history of the universe) were sceptical of this, because, unfortunately, patterns in the CMB are a little like bible codes. If you’re just looking for something, with a data set that big, you’re bound to find it and it doesn’t make it at all meaningful. Doubters appeared quickly on the arXiv and in blogs, and Gurzadyan and Penrose quickly responded in kind (see NASA, this is how it’s supposed to work). Below are the papers in the discussion as it stands, from November 16th to today:
The Original Paper
V. G. Gurzadyan, & R. Penrose (2010). Concentric circles in WMAP data may provide evidence of violent pre-Big-Bang activity arXiv arXiv: 1011.3706v1
Critique #1 by Wehus & Eriksen
I. K. Wehus, & H. K. Eriksen (2010). A search for concentric circles in the 7-year WMAP temperature sky maps arXiv arXiv: 1012.1268v1
Critique #2 by Moss, Scott & Ziblin
Adam Moss, Douglas Scott, & James P. Zibin (2010). No evidence for anomalously low variance circles on the sky ... Read more »
Abhay Ashtekar, Frans Pretorius, & Fethi M. Ramazanoğlu. (2010) Surprises in the Evaporation of 2-Dimensional Black Holes. arXiv. arXiv: 1011.6442v1
V. G. Gurzadyan, & R. Penrose. (2010) Concentric circles in WMAP data may provide evidence of violent pre-Big-Bang activity. arXiv. arXiv: 1011.3706v1
I. K. Wehus, & H. K. Eriksen. (2010) A search for concentric circles in the 7-year WMAP temperature sky maps. arXiv. arXiv: 1012.1268v1
Adam Moss, Douglas Scott, & James P. Zibin. (2010) No evidence for anomalously low variance circles on the sky. arXiv. arXiv: 1012.1305v1
V. G. Gurzadyan, & R. Penrose. (2010) More on the low variance circles in CMB sky. arXiv. arXiv: 1012.1486v1
- December 12, 2010
- 02:00 PM
- 777 views
Optics & stereopsis: how 3D vision is affected by retinal image quality?
by Pablo Artal in Optics confidential
Stereo (3D) vision is affected by the quality of the images in the retina. An adaptive optics instrument allows the testing of 3D vision and more...... Read more »
Fernández, E., Prieto, P., & Artal, P. (2010) Adaptive optics binocular visual simulator to study stereopsis in the presence of aberrations. Journal of the Optical Society of America A, 27(11). DOI: 10.1364/JOSAA.27.000A48
- December 11, 2010
- 10:53 AM
- 1,531 views
roger penrose’s cyclical cosmology revisited
by Greg Fish in weird things
A little while ago, we looked at the cyclical cosmology resurrected by Roger Penrose and his colleague Vahe Gurzadyan, and discussed the major problems it left unaddressed. Now, physicists have tried to replicate a cosmic map with wispy concentric circles of radiation and took to arXiv with their rebuttals. Yes, they could find the circles [...]... Read more »
V.G.Gurzadyan, & R.Penrose. (2010) More on the low variance circles in CMB sky. n/a. info:/1012.1486v1
Adam Moss, Douglas Scott, & James P. Zibin. (2010) No evidence for anomalously low variance circles on the sky. n/a. arXiv: 1012.1305v1
- December 10, 2010
- 03:02 PM
- 806 views
How to get rich fast with batteries
by Joerg Heber in All That Matters
The title of this blog post is a bit tongue in cheek, but the situation isn’t that far from the truth when it comes to rechargeable batteries such as lithium-ion batteries. Ever since lithium-ion batteries were first commercialized in 1991 by Sony, based on work by John Goodenough and others, they have been highly successful in the [...]... Read more »
Padhi, A., Nanjundaswamy, K.S., & Goodenough, J.B. (1997) Phospho-olivines as Positive-Electrode Materials for Rechargeable Lithium Batteries. Journal of The Electrochemical Society, 144(4), 1188. DOI: 10.1149/1.1837571
Chung, S., Bloking, J., & Chiang, Y. (2002) Electronically conductive phospho-olivines as lithium storage electrodes. Nature Materials, 1(2), 123-128. DOI: 10.1038/nmat732
Chan, C., Peng, H., Liu, G., McIlwrath, K., Zhang, X., Huggins, R., & Cui, Y. (2007) High-performance lithium battery anodes using silicon nanowires. Nature Nanotechnology, 3(1), 31-35. DOI: 10.1038/nnano.2007.411
Huang, J., Zhong, L., Wang, C., Sullivan, J., Xu, W., Zhang, L., Mao, S., Hudak, N., Liu, X., Subramanian, A.... (2010) In Situ Observation of the Electrochemical Lithiation of a Single SnO2 Nanowire Electrode. Science, 330(6010), 1515-1520. DOI: 10.1126/science.1195628
- December 9, 2010
- 01:04 PM
- 909 views
No Anomalous Enhancement of Nano-fluid Thermal Conductivity
by Arunn in nOnoScience (a.k.a. Unruled Notebook)
Nano was a buzz word a decade back in the USA. The buck was on anything prefixed with nano. Some useful technology did burgeon, identified now as nano-technology. Solar power, electronics and biotechnology were impacted with nano-engineered materials, capacitors and nano-probes and drug delivery methods. Chemistry and material science research in nano prospered with carbon [...]... Read more »
Buongiorno, J., Venerus, D., Prabhat, N., McKrell, T., Townsend, J., Christianson, R., Tolmachev, Y., Keblinski, P., Hu, L., Alvarado, J.... (2009) A benchmark study on the thermal conductivity of nanofluids. Journal of Applied Physics, 106(9), 94312. DOI: 10.1063/1.3245330
- December 6, 2010
- 05:37 PM
- 1,025 views
Saturn’s rings get spontaneously shaken up
by Kelly Oakes in Basic Space
From far away Saturn’s rings look pretty solid – I’m sure I’m not the only person who, as a child, imagined it’d be possible to skate around the planet on them. In reality, though, they’re made up of millions and … Continue reading →... Read more »
Joseph N. Spitale, & Carolyn C. Porco. (2010) Free Unstable Modes and Massive Bodies in Saturn's Outer B Ring. Astron.J.140:1747-1757,2010. arXiv: 0912.3489v2
- December 6, 2010
- 03:19 AM
- 521 views
Blog: Qubits and Crypto
by Torah Kachur, Rheanna Sand and Brit Trogen in Science in Seconds
Secrets and lies define the government and military, that and being led by bumbling fools. There is no doubt that some military information should be kept secret like technological advances, battle locations and strategies and George W. Bush's IQ. For secrets to be kept away from Wikileaks, cryptography is essential. The new type of cryptography that is being tested by the US military research division, DARPA, is quantum cryptography. Because if codes like DaVinci's Last Supper weren't complicated enough, might as well throw in the most complicated scientific issue in the world today - quantum theory.
Quantum cryptography is based on using electromagnetic waves like light to carry information. Photons carry information as qubits (not Q-bert...unfortunately) and light can be polarized by only allowing a particular magnitude and phase of light through a specialized filter. This polarization gives light a specific binary (0 or 1) property depending on how it is polarized. You can polarize light at different angles and wavelengths thus the photons carry information. If two parties that send and receive the polarized light have detectors to receive and interpret the phase of photons, then a code is born.
The major advantage of using quantum bits for encryption is the Heisenberg Uncertainty Principle which says that if you try to intercept a quantum-coded message, the act of trying to measure one property of a quantum state will disturb another. In other words, if you touch this message (01001100) it will self-destruct in T-minus 1 second.
To add to the complexity, encryption can come in the form of quantum entanglement. Entanglement is the phenomenom that says that two or more separate but similar objects can be linked and respond to changes in eachother, even over a distance. So if a photon is split into two lesser energy photons (like UV into infrared) then those two photons are linked over a theoretically infinite distance. If point A (commonly called Alice) and point B (Bob) are separated but carry entangled photons then they can communicate by changing the properties of one photon and expecting its twin to respond similarly.
Most of this encryption isn't sending long-winded messages about military targets or whether or not Bill inhaled, instead the information sent and received is usually the key to decode encrypted messages sent over regular communication channels. So far, scientists have been able to send 1Mbit/s of information along an optical fiber 20kms in length. The hope is that transmission distances can be extended to even communicate through space to the International Space Station.
The newest rage in quantum encryption is using photons to encode more than just 0's and 1's. Now, in a recent paper published in Science, researchers have been able to measure more than just the phase of the photon but also the angle, which means that the possibilities are infinite for encryption. All of a sudden, entangled photons can communicate both the 0's and 1's and also an entire alphabet of angular information.
What will this mean to Bond, Langdon and Gagdet? Faster and more secure encryption for the military which means more secrets. It isn't clear if these secrets will include the "Don't Ask. Don't Tell" policy.
Leach J, Jack B, Romero J, Jha AK, Yao AM, Franke-Arnold S, Ireland DG, Boyd RW, Barnett SM, & Padgett MJ (2010). Quantum correlations in optical angle-orbital angular momentum variables. Science (New York, N.Y.), 329 (5992), 662-5 PMID: 20689014
... Read more »
Leach J, Jack B, Romero J, Jha AK, Yao AM, Franke-Arnold S, Ireland DG, Boyd RW, Barnett SM, & Padgett MJ. (2010) Quantum correlations in optical angle-orbital angular momentum variables. Science (New York, N.Y.), 329(5992), 662-5. PMID: 20689014
- December 5, 2010
- 08:25 AM
- 1,733 views
searching for wormholes with general relativity
by Greg Fish in weird things
When you’re reading sci-fi stories in which some of the characters find themselves in need to cover hundreds or thousands of light years very quickly without a warp drive, they manage to make it through time and space via a convenient wormhole. It’s not the worst way to go since wormholes are supposed to exist, [...]... Read more »
Abe, F. (2010) Gravitational microlensing by the Ellis wormhole. The Astrophysical Journal, 725(1), 787-793. DOI: 10.1088/0004-637X/725/1/787
- December 4, 2010
- 06:34 PM
- 846 views
Quantum Teleportation: Science Fiction? NOPE! It's been here, is real, is documented, here's the proof, and here's how it works!
by DJ Busby in Astronasty
An in depth look at Quantum Teleportation... Read more »
DJ Busby. (2010) Quantum Teleportation: Science Fiction? NOPE! It's been here, is real, is documented, here's the proof, and here's how it works!. http://www.astronasty.com. info:/
- December 3, 2010
- 11:16 PM
- 759 views
Re (not the sun god) hypothesizes a solar atom (1903)
by gg in Skulls in the Stars
It is fair to say that the decade surrounding the start of the 20th century was an amazingly perplexing time to be a physicist. Mounting experimental evidence strongly suggested that something was amiss with classical physics, especially in the understanding … Continue reading →... Read more »
Fillipo Re. (1903) Hypothése sur la nature des corps radioactifs. Comptes rendus hebdomadaires des séances de l'Académie des sciences, 1393-1395. info:other/
- December 2, 2010
- 05:07 AM
- 951 views
An electric motor made from a single molecule
by Michael Berger in nanowerk
For the visionary goals of nanotechnology, functional and perhaps autonomous molecular motors will play an essential part, just like electric motors can be found in many appliances today. These nanomachines could perform functions similar to the biological molecular motors found in living cells, things like transporting and assembling molecules, or facilitating chemical reactions by pumping protons through membranes. Although applications of molecular motors are still in the future, the results of early-day studies are already spectacular: well-designed molecules or supramolecules show different kinds of motion - fueled by different driving forces such as light, heat, or chemical reactions - resulting in molecular shuttles, molecular elevators and rotating motors. A team of researchers is now proposing a conceptually new design of molecular motor based on electric field actuation and electric current detection of the rotational motion of a molecular dipole embedded in a three-terminal single-molecule device.... Read more »
Seldenthuis, J., Prins, F., Thijssen, J., & van der Zant, H. (2010) An All-Electric Single-Molecule Motor. ACS Nano, 4(11), 6681-6686. DOI: 10.1021/nn1021499
- November 30, 2010
- 09:27 AM
- 1,425 views
50 years of metallic glasses
by Joerg Heber in All That Matters
This week I am attending the 2010 Materials Research Society Fall Meeting in Boston — one of the key meetings in materials science. One of the sessions is on bulk metallic glasses and their applications, which this year is a little special. It is organised in honour of the 50 year anniversary of the first demonstration [...]... Read more »
KLEMENT, W., WILLENS, R., & DUWEZ, P. (1960) Non-crystalline Structure in Solidified Gold–Silicon Alloys. Nature, 187(4740), 869-870. DOI: 10.1038/187869b0
- November 29, 2010
- 08:25 PM
- 2,175 views
This Week in the Universe: November 23rd – November 29th
by S.C. Kavassalis in The Language of Bad Physics
Astrophysics and Gravitation:
Lensing of Black Holes Can Determine the Metric Around Them?
Bin-Nun, A. (2010). Gravitational lensing of stars orbiting Sgr A* as a probe of the black hole metric in the Galactic center Physical Review D, 82 (6) DOI: 10.1103/PhysRevD.82.064009
From the abstract:
We show that a possible astrophysical experiment, detection of lensed images of stars orbiting close to Sgr A*, can provide insight into the form of the metric around a black hole. We model Sgr A* as a black hole and add in a 1/r2 term to the Schwarzschild metric near the black hole. … This knowledge will be useful in constraining any modified gravity theory that adds a similar term into the strong field near a black hole.
Sounds too good to be true? It’s hard to say, but a technique to observationally determine the spacetime metric would be awfully exciting (and huge – to classical/quantum relativists, that is).
For more, see Black Hole May Offer Clues to Extra Dimensions.
Dark Energy and the Geometry of the Universe
Marinoni, C., & Buzzi, A. (2010). A geometric measure of dark energy with pairs of galaxies Nature, 468 (7323), 539-541 DOI: 10.1038/nature09577
From the abstract:
There is a purely geometric test of the expansion of the Universe (the Alcock–Paczynski test), which would provide an independent way of investigating the abundance () and equation of state () of dark energy. … Here we report an analysis of the symmetry properties of distant pairs of galaxies from archival data. This allows us to determine that the Universe is flat…
Speaking of observing metrics… this is a lot less exciting, however, as it takes in many more assumptions about the basic nature of the universe, galaxy distances, and, of course, dark energy.
For more, see Distant Galaxies Confirm Dark Energy’s Existence and Universe’s Flatness, Dark Energy Theory Gets a Boost From New Galactic Measurements, Cosmology: Geometry of the Universe.
Unified Origin of Matter and Dark Matter?
Davoudiasl, H., Morrissey, D., Sigurdson, K., & Tulin, S. (2010). Unified Origin for Baryonic Visible Matter and Antibaryonic Dark Matter Physical Review Letters, 105 (21) DOI: 10.1103/PhysRevLett.105.211304
The abstract:
We present a novel mechanism for generating both the baryon and dark matter densities of the Universe. A new Dirac fermion X carrying a conserved baryon number charge couples to the standard model quarks as well as a GeV-scale hidden sector. CP-violating decays of X, produced nonthermally in low-temperature reheating, sequester antibaryon number in the hidden sector, thereby leaving a baryon excess in the visible sector. The antibaryonic hidden states are stable dark matter. A spectacular signature of this mechanism is the baryon-destroying inelastic scattering of dark matter that can annihilate baryons at appreciable rates relevant for nucleon decay searches.
This is a surprisingly practical one (and really should be classified as high energy): A UBC team has proposed a new fermion that could explain dark matter, while linking to regular matter and the Standard Model. Signatures related to this fermion X should be detectable, in the right experiment, making it a target for future searches.
For more, see The X factor, UBC physicists make atoms and dark matter add up.
Accurate Measurement in the Field of the Earth of the General-Relativistic Precession
Lucchesi, D., & Peron, R. (2010). Accurate Measurement in the Field of the Earth of the General-Relativistic Precession of the LAGEOS II Pericenter and New Constraints on Non-Newtonian Gravity Physical Review Letters, 105 (23) DOI: 10.1103/PhysRevLett.105.231103
From the abstract:
The pericenter shift of a binary system represents a suitable observable to test for possible deviations from the Newtonian inverse-square law in favor of new weak interactions between macroscopic objects. We analyzed 13 years of tracking data of the LAGEOS satellites with GEODYN II software but with no models for general relativity. From the fit of LAGEOS II pericenter residuals we have been able to obtain a 99.8% agreement with the predictions of Einstein’s theory
It’s always nice to see confirmations of general relativity, especially when they help put limits on poss... Read more »
Bin-Nun, A. (2010) Gravitational lensing of stars orbiting Sgr A* as a probe of the black hole metric in the Galactic center. Physical Review D, 82(6). DOI: 10.1103/PhysRevD.82.064009
Marinoni, C., & Buzzi, A. (2010) A geometric measure of dark energy with pairs of galaxies. Nature, 468(7323), 539-541. DOI: 10.1038/nature09577
Davoudiasl, H., Morrissey, D., Sigurdson, K., & Tulin, S. (2010) Unified Origin for Baryonic Visible Matter and Antibaryonic Dark Matter. Physical Review Letters, 105(21). DOI: 10.1103/PhysRevLett.105.211304
Lucchesi, D., & Peron, R. (2010) Accurate Measurement in the Field of the Earth of the General-Relativistic Precession of the LAGEOS II Pericenter and New Constraints on Non-Newtonian Gravity. Physical Review Letters, 105(23). DOI: 10.1103/PhysRevLett.105.231103
Eugenio Bianchi. (2010) Black Hole Entropy, Loop Gravity, and Polymer Physics. arXiv. arXiv: 1011.5628v1
- November 29, 2010
- 09:51 AM
- 1,242 views
how to navigate in deep space with dead stars
by Greg Fish in weird things
Not only are GPS devices useful, they’re also an ongoing experiment that keeps confirming special relativity’s spot on descriptions of how time flows for fast-moving objects. Without constant adjustments, GPS would be quickly rendered unusable because accurate timing of the signals being sent between the satellites and the moving object they’re supposed to track is [...]... Read more »
Angelo Tartaglia, Matteo Luca Ruggiero, & Emiliano Capolongo. (2010) A null frame for spacetime positioning by means of pulsating sources. Advances in Space Research. arXiv: 1001.1068v3
- November 24, 2010
- 02:12 PM
- 417 views
Paragliding With Pterodactyls
by Michael Gutbrod in A Scientific Nature
The pterosaurs, or pterodactyls as you might recognize them, flew like no creature has ever flown before. Leave it to a reptile to do things differently. While today’s high-fliers have wings with multiple boney “fingers” providing structure, these anomalies of the skies possessed wings with only one long wing finger and a fibrous membrane that [...]... Read more »
Colin Palmer. (2010) Flight in slow motion: aerodynamics of the pterosaur wing. Proceedings of the Royal Society B. info:/10.1098/rspb.2010.2179
- November 24, 2010
- 01:16 PM
- 813 views
Light does matter
by Joerg Heber in All That Matters
Light is special. In our everyday experience it behaves like a wave, which gets reflected, refracted and shows interference with other light of the same wavelength. At the same time, light also consists of particles, so-called photons. This duality is quite fundamental: the Hanbury Brown and Twiss experiment for example only works because of the [...]... Read more »
Klaers, J., Schmitt, J., Vewinger, F., & Weitz, M. (2010) Bose–Einstein condensation of photons in an optical microcavity. Nature, 468(7323), 545-548. DOI: 10.1038/nature09567
- November 24, 2010
- 10:56 AM
- 1,641 views
This “Week” in the Universe: November 9th – November 22nd
by S.C. Kavassalis in The Language of Bad Physics
Astrophysics and Gravitation:
Fundamental constants: Big G revisited
Davis, R. (2010). Fundamental constants: Big G revisited Nature, 468 (7321), 181-183 DOI: 10.1038/468181b
Credit: Nature. a, A spherical 'source mass' (ms) is brought near a pendulum's spherical bob (the 'test mass', mt) and causes the bob to move a small distance z from its usual resting position (grey). The gravitational force between the two masses (left side of equation), which depends on Newton's constant (G), can be obtained from a measurement of z provided that k is known (see b). b, The value of k is found by measuring the period (P) of the freely swinging pendulum. To compute the value of G, we need measurements of L, z, ms and P (but not mt). Parks and Faller's experiment was based on four cylindrical source masses of 100 kilograms each, two pendulums and many other refinements.
From the abstract:
Measuring Newton’s constant of gravitation is a difficult task, because gravity is the weakest of all the fundamental forces. An experiment involving two simple pendulums provides a seemingly accurate but surprising value.
For more, see Fundamental constants: Big G revisted.
Galaxy Zoo Supernovae
Galaxy Zoo (2010). Galaxy Zoo Supernovae arXiv arXiv: 1011.2199v2
This paper presents the first results from a new citizen science project: Galaxy Zoo Supernovae which, with 2500 volunteers, has categorized almost 14,000 supernovae candidates.
For more, see Galaxy Zoo paper goes supernova.
“Youngest” Nearby Black Hole
Credits: X-ray: NASA/CXC/SAO/D.Patnaude et al, Optical: ESO/VLT, Infrared: NASA/JPL/Caltech
From the Press Release:
This composite image shows a supernova within the galaxy M100 that may contain the youngest known black hole in our cosmic neighborhood. In this image, Chandra’s X-rays are colored gold, while optical data from ESO’s Very Large Telescope are shown in red, green, and blue, and infrared data from Spitzer are red. The location of the supernova, known as SN 1979C, is labeled… This approximately 30-year age, plus its relatively close distance, makes SN 1979C the nearest example where the birth of a black hole has been observed, if the interpretation by the scientists is correct.
Sure, black holes can have finite age, that seems perfectly reasonable… well no, not really. The “age” of a black hole is an exceptionally complicated, verging on philosophical, matter that I’ll have to write about.
For more, see Black Hole Baby Spotted Being Born, Youngest nearby black hole found, Youngest Nearby Black Hole.
High Energy Physics and Particles:
Trapped Antihydrogen
Andresen, G., & et al. (2010). Trapped antihydrogen Nature DOI: 10.1038/nature09610
From the abstract:
Antihydrogen, the bound state of an antiproton and a positron, has been produced2, 3 at low energies at CERN (the European Organization for Nuclear Research) since 2002. Antihydrogen is of interest for use in a precision test of nature’s fundamental symmetries. … Here we demonstrate trapping of antihydrogen atoms. …This result opens the door to precision measurements on anti-atoms, which can soon be subjected to the same techniques as developed for hydrogen.
For more, see Antiatoms Bottled for First Time, Antimatter atoms held captive by physicists.
General Relativity, Quantum Gravity, et al.:
Pre-Big-Bang Penrose
V. G. Gurzadyan, & R. Penrose (2010). Concentric circles in WMAP data may provide evidence of violent pre-Big-Bang activity arXiv arXiv: ... Read more »
Davis, R. (2010) Fundamental constants: Big G revisited. Nature, 468(7321), 181-183. DOI: 10.1038/468181b
Galaxy Zoo. (2010) Galaxy Zoo Supernovae. arXiv. arXiv: 1011.2199v2
Andresen, G., & et al. (2010) Trapped antihydrogen. Nature. DOI: 10.1038/nature09610
V. G. Gurzadyan, & R. Penrose. (2010) Concentric circles in WMAP data may provide evidence of violent pre-Big-Bang activity. arXiv. arXiv: 1011.3706v1
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- November 23, 2010
- 08:00 AM
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Reconciling Einstein and Schroedinger
by David Bradley in SciScoop Science Forum
SciScoop contact Nykolai Bilaniuk brought an intriguing paper to our attention recently, that at first glance looks like a typical cracked conjecture of the kind SciScoop has reported in the past, but, says Bilaniuk, this one has a certain credibility. The idea is that of UC Berkeley’s Petr Horava, Bilaniuk tells us, and it’s one [...]Reconciling Einstein and Schroedinger is a post from: SciScoop Science News
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Hořava, P. (2009) Quantum gravity at a Lifshitz point. Physical Review D, 79(8). DOI: 10.1103/PhysRevD.79.084008
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