Tag Archives: physics

The Mystery of Empty Space

Get ready to re-think your ideas of reality. Join UCSD physicist Kim Griest as he takes you on a fascinating excursion, addressing some of the massive efforts and tantalizing bits of evidence which suggest that what goes on in empty space determines the properties of the three-dimensional existence we know and love, and discusses how that reality may be but the wiggling of strings from other dimensions.

Big Bangless and Endless Universe

A new the theory does away with the big bang and dark energy by having space, time and energy and no beginning and no ending.

Big Bang Abandoned in New Model of the Universe

Wun-Yi Shu at the National Tsing Hua University in Taiwan has developed an innovative new description of the Universe in which the roles of time space and mass are related in new kind of relativity.

Shu’s idea is that time and space are not independent entities but can be converted back and forth between each other. In his formulation of the geometry of spacetime, the speed of light is simply the conversion factor between the two. Similarly, mass and length are interchangeable in a relationship in which the conversion factor depends on both the gravitational constant G and the speed of light, neither of which need be constant.

So as the Universe expands, mass and time are converted to length and space and vice versa as it contracts. This universe has no beginning or end, just alternating periods of expansion and contraction. In fact, Shu shows that singularities cannot exist in this cosmos.

It’s easy to dismiss this idea as just another amusing and unrealistic model dreamed up by those whacky comsologists.

That is until you look at the predictions it makes. During a period of expansion, an observer in this universe would see an odd kind of change in the red-shift of bright objects such as Type-I supernovas, as they accelerate away. It turns out, says Shu, that his data exactly matches the observations that astronomers have made on Earth.
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That’s not to say Shu’s theory is perfect. Far from it. One of the biggest problems he faces is explaining the existence and structure of the cosmic microwave background, something that many astrophysicists believe to be the the strongest evidence that the Big Bang really did happen. The CMB, they say, is the echo of the Big bang.

How it might arise in Shu’s cosmology isn’t yet clear but I imagine he’s working on it.

Science is useful in letting us understand the world better. But it also is an evolving understanding as we learn more and search for answers to more questions. Many attempts to put forth new ideas and have them gain acceptance are made. Most fail to gain traction. But even many of the ideas that are not accepted are interesting.

Read Cosmological Models with No Big Bang by Wun-Yi Shu (on the wonderful open access arXiv).

All About Circuits

All About Circuits is an online textbook covering electricity and electronics. Topics covered include: Basic Concepts of Electricity’ OHM’s Law; Electrical Safety; Series and Parallel Circuits; Physics of Conductors and Insulators; Solid-State Device Theory; Binary Arithmetic; Logic Gates; Switches; Digital Storage? It is a great resource. Enjoy.

Friday Fun: Amazing Goal

This amazing goal illustrates what is possible with an amazing football (soccer) player and some physics.

Gravity Emerges from Quantum Information, Say Physicists

One of the hottest new ideas in physics is that gravity is an emergent phenomena; that it somehow arises from the complex interaction of simpler things.
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perhaps the most powerful idea to emerge from Verlinde’s approach is that gravity is essentially a phenomenon of information.
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Over recent years many results in quantum mechanics have pointed to the increasingly important role that information appears to play in the Universe. Some physicists are convinced that the properties of information do not come from the behaviour of information carriers such as photons and electrons but the other way round. They think that information itself is the ghostly bedrock on which our universe is built.

Gravity has always been a fly in this ointment. But the growing realisation that information plays a fundamental role here too, could open the way to the kind of unification between the quantum mechanics and relativity that physicists have dreamed of.

This speculative physics is fascinating. Open access paper: Gravity from Quantum Information.

Invisible Worlds: Fastest Thing on the Planet

Fun with Fungi.

New Funding for arXiv Online Scientific Repository

The Cornell University Library is broadening the funding base for the arVix online scientific repository. Nearly 600,000 e-prints – research articles published online in physics, mathematics, statistics, computer science and related disciplines – now reside in arXiv, which is an open information source for hundreds of thousands of scientific researchers.

arXiv will remain free for readers and submitters, but the Library has established a voluntary, collaborative business model to engage institutions that benefit most from arXiv. “Keeping an open-access resource like arXiv sustainable means not only covering its costs, but also continuing to enhance its value, and that kind of financial commitment is beyond a single institution’s resources,” said Oya Rieger, Associate University Librarian for Information Technologies. “If a case can be made for any repository being community-supported, arXiv has to be at the top of the list.”

The 200 institutions that use arXiv most heavily account for more than 75 percent of institutional downloads. Cornell is asking these institutions for financial support in the form of annual contributions, and most of the top 25 have already committed to helping arXiv.

arXiv’s original dissemination model represented the first significant means to provide expedited access to scientific research well ahead of formal publication. Researchers upload their own articles to arXiv, and they are usually made available to the public the next day. arXiv, founded by physics professor Paul Ginsparg, has about 400,000 users and serves more than 2.5 million article downloads per month. Its 101,000 registered submitters live in nearly 200 countries.

arXiv is interconnected with many other scholarly information resources. These include the INSPIRE system being developed by supporting high-energy physics laboratories CERN, DESY, Fermilab and SLAC, as well as the Astrophysics Data System at Harvard University, another supporting institution. Read details about the operating principles of the new structure.

Feynman “is a second Dirac, only this time human”

Oppenheimer recommendation of Feynman, page 1

Great quotes from Oppenheimer’s recommendation of Richard Feynman

“He is by all odds the most brilliant young physicist here, and everyone knows this. He is a man of thoroughly engaging character and personality, extremely clear, extremely normal in all respects, and an excellent teacher with a warm feeling for physics in all its aspects. He has the best possible relations both with the theoretical people of whom he is one, and with the experimental people with whom he works in very close harmony.”

“Bethe has said that he would rather lose any two other men than Feynman from this present job, and Wigner said, ‘He is a second Dirac, only this time human.”

Oppenheimer recommendation of Feynman, page 2

Images of letter from Oppenheimer to the University of California – Berkeley Recommending Richard Feynman for a position, November 4, 1943 (from Big Science at Berkeley).

via: He is a second Dirac, only this time human.

Related: Vega Science Lectures: Feynman and More – The Feynman Lectures on Physics by Richard P. Feynman and Robert B. Leighton and Matthew Sands – posts on physics

Friday Fun: Longest Basketball Shot

Amazing basketball shot from Texas. Popular Science looked at the physics involved:

The horizontal distance to the basket from the launch point is approximately 50 meters, and the launch angle Î¸ is about 20 degrees.
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Looking at the horizontal part of the motion and accounting for the launch angle we can then determine the initial speed (v0) of the basketball necessary to cover the horizontal distance in 3.8 seconds. We get

Î”x = vhorizontal t = v0cosÎ¸t

and therefore v0 = Î”x/cosÎ¸t = 50 m /[cos 20 (3.8 s)] = 14 m/s

Now if we look at the vertical part of the motion we can determine how far the ball would drop in 3.8 seconds. We’ll then compare our theoretical result to the actual vertical distance from the third deck down to the basket that we observe in the video. (We estimate that drop to be similar to the horizontal distance of about 50 meters.) Therefore, based on the time of flight and the initial velocity that we determined above we calculate a vertical drop of

Î”y = v0vertical t + Â½ at2 = v0 sin t — Â½ gt2 = 14m/s(sin 20)(3.8 s) — Â½ (-9.8m/s2 )(3.8)2 = -53 m

Well, this corresponds pretty well to what we see in the video. Even accounting for the effects of air resistance (which we did not address above to keep things simple) the result isn’t altered drastically. The motion recorded in the video (in what appears to be a continuous frame) certainly appears possible according to the laws of physics.

See more videos of circus basketball shots by Dude Perfect.

The Nobel Prize in Physics 2009

The 2009 Nobel Prize in Physics honors three scientists, who have had important roles in shaping modern information technology, with one half to Charles Kuen Kao and with Willard Sterling Boyle and George Elwood Smith sharing the other half. Kao’s discoveries have paved the way for optical fiber technology, which today is used for almost all telephony and data communication. Boyle and Smith have invented a digital image sensor – CCD, or charge-coupled device – which today has become an electronic eye in almost all areas of photography. The Nobel prize site includes great information on the science behind the research that has been honored:

The first ideas of applications of light guiding in glass fibers (i.e. small glass rods) date from the late 1920’s. They were all about image transmission through a bundle of fibers. The motivation was medicine (gastroscope), defense (flexible periscope, image scrambler) and even early television. Bare glass fibers were, however, quite leaky and did not transmit much light. Each time the fibers were touching each other, or when the surface of the fibers was scratched, light was led away from the fibers. A breakthrough happened in the beginning of the 1950’s with the idea and demonstration that cladding the fibers would help light transmission, by facilitating total internal reflection.
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Optical communication of today has reached its present status thanks to a number of breakthroughs. Light emitting diodes (LEDs) and especially diode lasers, first based on GaAs (800-900 nm) and later on InGaAsP (1-1.7 ïm), have been essential. The optical communication window has evolved from 870 nm to 1.3 ïm and, finally, to 1.55 ïm where fiber losses are lowest. Gradient-index fibers were used in the first optical communication lines. However, when moving towards longer wavelengths and longer communication distances, single-mode fibers have become more advantageous.

Nowadays, long-distance optical communication uses single mode fibers almost exclusively, following Kao’s vision. The first such systems used frequent electronic repeaters to compensate for the remaining losses. Most of these repeaters have now been replaced by optical amplifiers, in particular erbium-doped fiber amplifiers. Optical communication uses wavelength division multiplexing with different wavelengths to carry different signals in the same fiber, thus multiplying the transmission rate. The first non-experimental optical fiber links were installed in 1975 in UK, and soon after in the US and in Japan. The first transatlantic fiber-optic cable was installed in 1988.