Tag: Physics (home)

University President: "Why is it that you physicists always require so much expensive equipment? Now the Department of Mathematics requires nothing but money for paper, pencils, and erasers . . . and the Department of Philosophy is better still. It doesn't even ask for erasers."

permalink source: Isaac Asimov
tags: Mathematics, Philosophy, Physics

God runs electromagnetics by wave theory on Monday, Wednesday,and Friday, and the Devil runs them by quantum theory on Tuesday, Thursday, and Saturday.

permalink source: William Bragg
tags: Physics, Science

Everything you've learned in school as "obvious" becomes less and less obvious as you begin to study the universe. For example, there are no solids in the universe. There's not even a suggestion of a solid. There are no absolute continuums. There are no surfaces. There are no straight lines.

permalink source: R. Buckminster Fuller
tags: Paradigms, Physics, Universe

All science is either physics or stamp collecting.

permalink source: E. Rutherford [who later won a Nobel prize in Chemistry]
tags: Physics, Pride

Had I known that we were not going to get rid of this damned quantum jumping, I never would have involved myself in this business.

permalink source: Schrodinger
tags: Physics

Flappity, floppity, flip, The mouse on the mobius strip; The strip revolved, The mouse dissolved In a chronodimensional skip.

permalink source: Anonymous
tags: Humor, Physics

186,282 miles per second: It isn't just a good idea, it's the law!

permalink source: Anonymous
tags: Humor, Physics

Nature and nature's laws lay hid in night, God said, "Let Newton be," and all was light. It did not last; the devil howling "Ho! Let Einstein be!" restored the status quo.

permalink source: Anonymous
tags: Humor, Physics

Time is an illusion perpetrated by the manufacturers of space.

permalink source: Anonymous
tags: Physics

Q: Why did the tachyon cross the road? A: Because it was on the other side.

permalink source: Anonymous
tags: Humor, Physics

Klein bottle for rent -- inquire within.

permalink source: Anonymous
tags: Humor, Physics

Heisenberg may have slept here.

permalink source: Anonymous
tags: Humor, Physics

The three laws of thermodynamics: The First Law: You can't get anything without working for it. The Second Law: The most you can accomplish by working is to break even. The Third Law: You can only break even at absolute zero.

permalink source: Anonymous
tags: Humor, Physics

Cole's Law: Thinly sliced cabbage.

permalink source: Anonymous
tags: Humor, Physics, Science

RELATIVISTIC SLEIGH RIDE. The December 11 1998 issue of Fermi News seeks to answer the perennial question of how Santa Claus can, in the course of a single night, deliver gifts to each of the world's 2 billion children. Even if a fullscale quantum computer were to work out the optimum course plan St. Nick must still cover a flight path of some 160 million km and stop at 800 million homes along the way. How does he do it? By traveling at close to the speed of light, of course, which, incidentally, also explains why (thanks to time dilation) Santa never seems to age. The Fermi News article helpfully addresses such questions as to how it is that the fat fellow can fit into Lorentz-contracted chimneys in the first place and how one can determine the color of the Doppler- shifted light emitted by Rudolph-the-rednosed-reindeer at sleigh velocities approching the speed of light.

permalink source: Anonymous
tags: Humor, Physics, Christmas

> There was still one aspect of the whole concept of a ravioli-loaded railgun type wepon which we, lolling about late on a weeknight, with only a few neurons randomly firing, could not resolve. Would a chunk of metal (can of ravioli) impacting another, larger, rest mass structure (star destroyer) produce an "explosion" effect, or simply punch an appropriately shaped hole as it passed through? Bill? What am I, the neighborhood blast physicist??? Well, maybe... :-) It all depends on speed of impact versus the speed of sound in the target (what is called the Mach number, where Mach 1 means the speed of sound, Mach 2 is twice the speed of sound, etc), and the speed of the ravioli versus the speed of light in the target (which I'll call the Cerenkov number, where Cerenkov 1 is the speed of light in anything; Cerenkov 1.3 is the speed of high-energy protons in a water-cooled reactor (that's why you get that nifty blue glow), and you can get up to Cerenkov 2.4 using diamonds and nuclear accellerators. In the late 40's people used to talk about Cerenkov numbers, but they don't anymore. Pity.). Lastly, there's the ravioli velocity expressed as a fraction of the speed of light in a vacuum (that is, as a fraction of "c"). "C" velocities are always between 0 and 1. At low speeds (REAL low) the ravioli will simply flow over the surface, yielding a space-cruiser with a distinctly Italian paint job. Faster (still well below speed-of-sound in the target) the metal of the space-cruiser's skin will distort downward, making what we Boston drivers call a "small dent". Faster still, you may have a "big dent" or maybe even a "big dent with a hole in the middle", caused by the ravioli having enough energy to push the dent through, stretching and thinning the hull metal till the metal finally tears in the middle of the dent. Getting up past Mach 1 (say, 5000 feet/sec for steel), you start to get punch-a-hole-shaped-like-the-object effects, because the metal is being asked to move faster than the binding forces in the object can propagate the "HEY! MOVE!" information. (After all, sound is just the binding forces between atoms in a material moving the adjacent atoms -- and the speed of sound is how fast the message to "move" can propagate.) From this, we see that WileE Coyote often reached far-supersonic speeds because he often punched silhouette-type holes in rocks, cliffs, trucks, etc. Around Mach 4 or so, another phenomenon starts -- compressive heating. This is where the leading edge of the ravioli actually starts being heated by compression (remember PV=nRT, the ideal gas law?) Well, ravioli isn't a gas, but under enough pressure, ravioli behaves as a gas. It is compressed at the instant of impact and gets hot -- very hot. Likewise, the impact point on the hull is compressed and gets hot. Both turn to gasses -- real gasses, glowing-white-hot gasses. The gasses expand spherically, causing crater-like effects, including a raised rim and a basically parabolic shape. In the center of the crater, some material is vaporized, then there's a melt zone, then a larger "bent" zone, and the raised rim is caused because the gas expansion bubble center point (the bending force) is actually *inside* the hull plate. If the hull plate isn't thick enough, then the gas-expansion bubble pushes through to the other side, and you get a structural breach event (technically speaking, a "big hole") in the side of the space-cruiser. Compressive heating really hits the stride up around 20,000 feet/sec (Mach 4 in steel, Mach 15 in air) and continues as a major factor all the way up to the high fractional Cerenkov speeds, where nuclear forces begin to take effect. Aside: the "re-entry friction heating" that spacecraft endure when the reenter the atmosphere is NOT friction. It's really compressive heating of the air in the path. As long as the spacecraft is faster than Mach 1, the air can't know to get out of the way, so it bunches up in front of the spacecraft. When you squeeze any gas, it gets hot. So, the glowing "reentry gas" is really just squeezed air, which heats the spacecraft heat shield by conduction and infrared. The hypersonic ravioli can be expected to behave similarly. As we increase speed from the high Mach numbers (about 10 miles/sec) all the way up to about 150,000 miles/sec, not much different happens except that the amount of kinetic energy (which turns into compressive heat) increases. This is a huge range of velocity, but it's uninteresting velocity. At high fractional Cerenkov speeds, the ravioli is now beginning to travel at relativistic velocities. Among other things, this means that the ravioli is aging more slowly than usual, and the ravioli can looks compressed in the direction of travel. But that's really not important right now. As we pass Cerenkov 1.0 in the target, we get a new phenomenon -- Cerenkov radiation. This is that distinctive blue glow seen around water-cooled reactors. It's just (relatively) harmless light (harmless compared to the other blast effects, that is). I mention it only because it's so nifty... At around .9 c (Cerenkov 1.1) , the ravioli starts to perceptibly weigh more. It's just a relativistic mass increase -- all the additional weight is actually energy, available to do compressive heating upon impact. The extra weight is converted to heat energy according to the equation E=mc^2; it looks like compressive heating but it's not. [Here's where I'm a little hazy on the numbers; I'm at work and don't have time to rederive the Lorentz transformations.] At around .985 c (Cerenkov 1.2 or so), the ravioli now weighs twice what it used to weigh. For a one pound can, that's two pounds... or about sixty megatons of excess energy. All of it turns to heat on impact. Probably very little is left of the space-cruiser. At around .998 c, the impacting ravioli begins to behave less like ravioli and more like an extremely intense radiation beam. Protons in the water of the ravioli begin to successfully penetrate the nuclei of the hull metal. Thermonuclear interactions, such as hydrogen fusion, may take place in the tomato sauce. At around .9998 c, the ravioli radiation beam is still wimpy as far as nuclear accellerator energy is concerned, but because there is so much of it, we can expect a truly powerful blast of mixed radiation coming out of the impact site. Radiation, not mechanical blast, may become the largest hazard to any surviving crew members. At around .9999999 c, the ravioli radiation may begin to produce "interesting" nuclear particles and events (heavy, short-lived particles). At around .999999999999 c, the ravioli impact site may begin to resemble conditions in the original "big bang"; equilibrium between matter and energy; free pair production; antimatter and matter coexisting in equilibrium with a very intense gamma-ray flux, etc.[1] Past that, who knows? It may be possible to generate quantum black holes given a sufficiently high velocity can of ravioli. --Bill [1]According to physicist W. Murray, we may also expect raining frogs, plagues of locusts, cats and dogs living together, real Old Testament destruction. You get the idea...

permalink source: Bill somebody from Fun_People
tags: Humor, Physics

Elementary Physics: work = f.d force = m.a Therefore work = m.a.d

permalink source: Neil Price
tags: Humor, Physics

"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled."

permalink source: Richard Feynmann
tags: Physics, Truth, Science

"What I am going to tell you about is what we teach our physics students in the third or fourth year of graduate school... It is my task to convince you not to turn away because you don't understand it. You see, my physics students don't understand it... That is because I don't understand it. Nobody does."

permalink source: Richard Feynmann QED, The Strange Theory of Light and Matter
tags: Physics

"The young specialist in English Lit... lectured me severely on the fact that in every century people have thought they understood the Universe at last, and in every century they were proved to be wrong. It follows that the one thing we can say about our modern 'knowledge' is that it is wrong. ...My answer to him was, ...when people thought the Earth was flat, they were wrong. When people thought the Earth was spherical they were wrong. But if you think that thinking the Earth is spherical is just as wrong as thinking the Earth is flat, then your view is wronger than both of them put together."

permalink source: Isaac Asimov, The Relativity of Wrong
tags: Physics, Truth, Tolerance, Relativism

NOT ALL CHAOS ON THE WEATHER MAP IS EQUAL, researchers have found, providing insights that are hoped to improve weather forecasting. Researchers usually assume that all spots on a weather map are equally chaotic, meaning that small uncertainties in initial conditions grow to the point at which the conditions become unpredictable. Now, a multidisciplinary University of Maryland team of meteorologists, physicists, and computer scientists (DJ Patil, 301-405-4842, dpatil@ipst.umd.edu) has developed a technique that identifies what can be considered as chaos "hotspots," regions in which small changes in conditions are believed to magnify most quickly into large perturbations in the weather. Chaos hotspots shift their location on a regular basis, but tend to cover only about 20% of the global map at any given time. Making more meteorological observations in hotspots can help reduce forecasting errors, the researchers believe. Since 1992, the National Weather Service has provided "ensemble forecasts," in which a computer model generates a main forecast and several slightly adjusted forecasts providing a range of possible outcomes for the weather. The Maryland researchers look at global wind predictions from five of these forecasts at a particular level in the atmosphere (where the pressure is 500 millibars). Placing these five forecasts on the map, the researchers then look at wind vectors, which specify how each forecast deviates from the main forecast in wind strength and direction. Analyzing 1100 km-by- 1100 km squares in a global map, they identify regions where the vectors tend to line up with one another (see figure at http://www.aip.org/mgr/png). The aligned wind vectors have "low dimensionality," transforming the regions in which they reside into chaos hotspots where good initial observations become most crucial for reducing forecasting errors. All other points on the map are less important for forecasting, the authors say. (Patil et al., Phys. Rev. Lett., 25 June 2001; text at http://www.aip.org/physnews/select.)

permalink source: The American Institute of Physics Bulletin of Physics News Number 543 June 13, 2001
tags: Physics, Systems

How many seconds are there in a year? If I tell you there are 3.155 x 10^7, you won't even try to remember it. On the other hand, who could forget that, to within half a percent, pi seconds is a nanocentury.

permalink source: Tom Duff, Bell Labs
tags: Physics, Time Management

Opening scene from "Contact" is a good illustration of the insignificance of man in the universe

permalink source: Anonymous
tags: Atheism, Physics

Our two greatest problems are gravity and paper work. We can lick gravity, but sometimes the paper work is overwhelming.

permalink source: Dr. Wernher von Braun
tags: Beauracracy, Physics

THE eminent Russian physicist Andrei Linde once found himself on a long flight seated beside a businessman nose-deep in A Brief History of Time. Without having been introduced and before the usual small talk, they struck up a conversation about it. “What do you think of it?” Linde asked. “Fascinating,” said the businessman. “I can’t put it down.” “Oh, that’s interesting,” the scientist replied. “I found it quite heavy going in places and didn’t fully understand some parts.” At which point the businessman closed the book on his lap, leaned across with a compassionate smile, and said, “Let me explain. . . .”

permalink source: http://books.nap.edu/books/0309084105/html/251.html#pagetop
tags: Physics, Humility

What Science Really Tells Us

The first gulp from the glass of natural sciences will turn you into an atheist, but at the bottom of the glass God is waiting for you. (original - "Der erste Trunk aus dem Becher der Naturwissenschaft macht atheistisch, aber auf dem Grund des Bechers wartet Gott.")

permalink source: Werner Heisenberg, Hildebrand, Ulrich. 1988. "Das Universum - Hinweis auf Gott?", in Ethos (die Zeitschrift für die ganze Familie), No. 10, Oktober. Berneck, Schweiz: Schwengeler Verlag AG. Reprinted by permission of the publisher, Schwengeler Verlag AG.
tags: Apologetics, Atheism, Physics