The magic of physics.
The magic of physics.
The new book, Einstein's Puzzle Universe, by Tim Dedopulos, is a compendium of good physics and logic problems. Here's one for you to solve:
Imagine that there is an even rope of negligible weight draped over a wheel, which permits it to slide perfectly freely. Equal lengths of the rope descend from either side. On the left side, the rope ends in a 10 kg weight. On the other side, perfectly level with the weight, is a young chimp, also weighing 10 kg.
When you give a signal, the chimp will start climbing the rope. Which of the two, the chimp or the weight, will reach the top first?
The European Organization for Nuclear Research, or CERN, has been releasing portions of its research to the public for years. This week's massive 300 terabyte dump of Large Hadron Collider (LHC) data is the biggest yet by a long shot -- and it's all out there, open source, free for the exploration.
MinutePhysics responds to CGP Grey's video "The Trouble with Transporters," below.
Gravitational waves are real, and scientists have detected them. In the video above, PBS Space Time explains the discovery by researchers at the Laser Interferometer Gravitational-Wave Observatory (LIGO). From the New York Times:
A team of physicists who can now count themselves as astronomers announced on Thursday that they had heard and recorded the sound of two black holes colliding a billion light-years away, a fleeting chirp that fulfilled the last prophecy of Einstein’s general theory of relativity.
That faint rising tone, physicists say, is the first direct evidence of gravitational waves, the ripples in the fabric of space-time that Einstein predicted a century ago (Listen to it here.). And it is a ringing (pun intended) confirmation of the nature of black holes, the bottomless gravitational pits from which not even light can escape, which were the most foreboding (and unwelcome) part of his theory.
More generally, it means that scientists have finally tapped into the deepest register of physical reality, where the weirdest and wildest implications of Einstein’s universe become manifest.
Below, NASA's animated simulation of the black holes merging and releasing the gravitational radiation (background here):
above image credits: R. Hurt/Caltech-JPL Read the rest
Brian, a graduate student of Applied Mathematics at Columbia University, has a Tumblr called Fouriest Series where he posts his math and physics visualizations. His explanations are clearly written. He also provides the Mathematica code he used to create his animations. From his post about chaos and double pendulums:
Summarized by mathematician Edward Lorenz, "Chaos [is] when the present determines the future, but the approximate present does not approximately determine the future.“ There’s an important distinction to make between a chaotic system and a random system. Given the starting conditions, a chaotic system is entirely deterministic. A random system, on the other hand, is entirely non-deterministic, even when the starting conditions are known. That is, with enough information, the evolution of a chaotic system is entirely predictable, but in a random system there’s no amount of information that would be enough to predict the system’s evolution. The simulations above show two slightly different initial conditions for a double pendulum — an example of a chaotic system. In the left animation both pendulums begin horizontally, and in the right animation the red pendulum begins horizontally and the blue is rotated by 0.1 radians (≈ 5.73°) above the positive x-axis. In both simulations, all of the pendulums begin from rest.
Julldozer created an amazingly clever digital sundial ("Cadran Solaire Numérique") that precomputes the angle of the sun throughout the day and uses those computations to make hundreds of precise holes calibrated to cast a shadow displaying the present time. Read the rest
Have you ever tried to draw a brain? I find it hard to get the wrinkles to look right. Scientists at at the University of Jyväskylä in Finland made a solid model of a fetal brain out of gel that developed its own realistic furrows just by dunking it into a solvent.
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They made a solid replica of a foetal brain, still smooth and unfolded, and coated it with a second layer which expanded when dunked into a solvent.
That expansion produced a network of furrows that was remarkably similar to the pattern seen in a real human brain.
This suggests that brain folds are caused by physics: the outer part grows faster than the rest, and crumples.
The tl;dr: hit the water at a 20% angle. But the answer isn't as interesting as the question…
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Bocquet’s quest to understand how this happens — how a solid object can skim along water without immediately sinking — began more than a decade ago, while he was skipping stones on the Tarn River in southern France with his young son. ‘‘He turns to me,’’ Bocquet says, ‘‘and asks, ‘Why does the stone bounce on the water?’ ’’ To answer that question satisfactorily, Bocquet and his colleagues built a mechanical stone skipper and analyzed the angle of each toss using high-speed video. They also created a set of mathematical equations to predict the number of skips.
Can't get enough of nude, 3D-modelled humans with the internal physics of bags of jelly interacting with physics simulations? We've got you covered with Albert Omoss's Plug Party 2K3. (via JWZ) Read the rest
In a gorgeous animation, Malin Christersson shows how much simpler it is to plot out celestial mechanics when you assume that all the bodies in our solar system are in orbit around the sun, rather than the other way around. Read the rest
AP physics teacher Dan Burns gave a fun demonstration about spacetime curvature in 2012 at Los Gatos High School. Here's the 10 minute video.
Here's another good one from Burns: the "Pole and Barn Paradox":
This is my favorite Special Relativity paradox. It will blow your student's minds. A runner traveling at 0.87c with a 20 m long pole runs through a 10 m long barn. To the barn FOR the pole shrinks and the barn doors can be closed for an instant with the ole completely inside. From the runner's frame of reference the barn contracts to 5 m and the pole can NOT fit with both doors closed! How is this resolved? You can use the slides and associated videos to go though this mind-bender with an added twist at the end.
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Cambridge University today said that Stephen Hawking is cancelling several public appearances because of ill health.
Watch these three guys discuss "God, The Universe and Everything Else," which includes extraterrestrials, creativity, science fiction, education, the Cold War, fractals, and so much more.
You are kidnapped by political-science majors (who are upset because you told them political science is not a real science). Although blindfolded, you can tell the speed of their car (by the whine of the engine), the time of travel (by mentally counting off seconds), and the direction of travel (by turns along the rectangular street system). From these clues, you know that you are taken along the following course: 50 km/h for 2.0 min, turn 90° to the right, 20 km/h for 4.0 min, turn 90° to the right, 20 km/h for 60 s, turn 90° to the left, 50 km/h for 60 s, turn 90° to the right, 20 km/h for 2.0 min, turn 90° to the left, 50 km/h for 30 s. At that point, (a) how far are you from your starting point, and (b) in what direction relative to your initial direction of travel are you? – From Halliday & Resnick Fundamentals of Physics Extended 9th Edition Read the rest