Part 05: String Theory. David Gross - The Coming Revolutions in Fundamental Physics. Atoms are mini black holes? String Theory Basics. The Official String Theory Web Site. Relativity of Electric and Magnetic Fields. Previous home next Michael Fowler, University of Virginia A Magnetic Puzzle… Suppose we have an infinitely long straight wire, having a charge density of electrons of coulombs per meter, all moving at speed to the right (recall typical speeds are centimeters per minute) and a neutralizing fixed background of positive charge, also of course coulombs per meter. The current in the wire has magnitude (and actually is flowing to the left, since the moving electrons carry negative charge). Suppose also that a positive charge is outside the wire, a distance from the axis, and this outside charge is moving at the same exact velocity as the electrons in the wire.
What force does the positive charge feel? The wire is electrically neutral, since it contains equal densities of positive and negative charges, both uniformly distributed throughout the wire (the illustration above is of course schematic). However, since is moving, it will feel a magnetic force, so the force on the charge is of magnitude. Texas Science - News from the College of Natural Sciences & Blog...
Chapter 3. Classical physics could not explain the spectra of black bodies. It predicted that the intensity (power emitted at a given wavelength) of emitted light should increase rapidly with decreasing wavelength without limit (the "ultraviolet catastrophe"). In the figure below, the curve labeled "Rayleigh-Jeans law" shows the classically expected behavior. However, the measured spectra actually showed an intensity maximum at a particular wavelength, while the intensity decreased at wavelengths both above and below the maximum.
In order to explain the spectra, in 1900 the German physicist Max Planck (1858 - 1947) was forced to make a desperate assumption for which he had no physical explanation. As with classical physics, he assumed the body consisted of vibrating oscillators (which were actually collections of atoms or molecules). E = hf (Planck's formula) In classical physics, the electromagnetic field connects charged particles to each other (see Sections 2.4, 2.6). 3.2. L=h/p 3.3. 3.4. Physics. Brian Greene on string theory. Lectures. Antimatter:Mirror of the Universe. Quantum Mechanics. ScienceWorld. S Gravity Probe B confirms two Einstein theories. Artist concept of Gravity Probe B orbiting the Earth to measure space-time, a four-dimensional description of the universe including height, width, length, and time.
Stanford and NASA researchers have confirmed two predictions of Albert Einstein's general theory of relativity, concluding one of the space agency's longest-running projects. Known as Gravity Probe B, the experiment used four ultra-precise gyroscopes housed in a satellite to measure two aspects of Einstein's theory about gravity. The first is the geodetic effect, or the warping of space and time around a gravitational body. The second is frame-dragging, which is the amount a spinning object pulls space and time with it as it rotates. After 52 years of conceiving, building, testing and waiting, the science satellite has determined both effects with unprecedented precision by pointing at a single star, IM Pegasi, while in a polar orbit around Earth. The findings appear online in the journal Physical Review Letters. 0 Stumble. Brief Answers to Cosmic Questions.
Structure of the Universe Does the Universe have an edge, beyond which there is nothing? Are the galaxies arranged on the surface of a sphere? Why can't we see the whole universe? Does the term "universe" refer to space, or to the matter in it, or to both? Evolution of the Universe Did the Universe expand from a point? More about the Big Bang When they say "the universe is expanding," what exactly is expanding? Structure of the Universe Does the Universe have an edge, beyond which there is nothing?
Are the galaxies arranged on the surface of a sphere? Why can't we see the whole universe? If you could suddenly freeze time everywhere in the universe, and magically survey all of creation, you would find galaxies extending out far beyond what we can see today. Does the term "universe" refer to space, or to the matter in it, or to both? Today, the situation is reversed. Discovering the properties of space remains one of the deepest and most important problems in modern science. Physicists Slow Speed of Light. Physicists Slow Speed of Light By William J. Cromie Gazette Staff Light, which normally travels the 240,000 miles from the Moon to Earth in less than two seconds, has been slowed to the speed of a minivan in rush-hour traffic -- 38 miles an hour. An entirely new state of matter, first observed four years ago, has made this possible.
When atoms become packed super-closely together at super-low temperatures and super-high vacuum, they lose their identity as individual particles and act like a single super- atom with characteristics similar to a laser. Such an exotic medium can be engineered to slow a light beam 20 million-fold from 186,282 miles a second to a pokey 38 miles an hour. "In this odd state of matter, light takes on a more human dimension; you can almost touch it," says Lene Hau, a Harvard University physicist. In the future, slowing light could have a number of practical consequences, including the potential to send data, sound, and pictures in less space and with less power.
Antihydrogen could lead to antigravity - National Technology. The Antihydrogen Laser Physics Apparatus (ALPHA) at the CERN particle physics laboratory announced that they have been able to hold 309 atoms of antihydrogen in a magnetic trap for 1000 seconds, approximately 10,000 times longer than before. When they experimented with the anti-atoms last year they verified that they were in fact antihydrogen atoms by releasing them from the trap and observing them being annihilated by hydrogen atoms. During that experiment they were only able to contain the atoms for 170 milliseconds.
They have repeated this experiment, but have made a few changes. By cooling the antiprotons that create the antihydrogen they were able to lower their energy, this allowed for more atoms to be contained with a longer life span. The longer life will allow scientists to do more experiments, like checking if antihydrogen has the same energy level as hydrogen. Scientist also want to find out if the anti-atoms exhibit antigravity effects. For more info: Cornell. Relativity Explained in a Nutshell - Global One TV.
Physics Flash Animations. We have been increasingly using Flash animations for illustrating Physics content. This page provides access to those animations which may be of general interest. The animations will appear in a separate window. The animations are sorted by category, and the file size of each animation is included in the listing. Also included is the minimum version of the Flash player that is required; the player is available free from The categories are: In addition, I have prepared a small tutorial in using Flash to do Physics animations. LInks to versions of these animations in other languages, other links, and license information appear towards the bottom of this page. The Animations There are 99 animations listed below. Other Languages and Links These animations have been translated into Catalan, Spanish and Basque: En aquest enllaç podeu trobar la versió al català de les animacions Flash de Física.
Einstein for Everyone. Einstein for Everyone Nullarbor Press 2007revisions 2008, 2010, 2011, 2012, 2013 Copyright 2007, 2008, 2010, 2011, 2012, 2013 John D. Norton Published by Nullarbor Press, 500 Fifth Avenue, Pittsburgh, Pennsylvania 15260 with offices in Liberty Ave., Pittsburgh, Pennsylvania, 15222 All Rights Reserved John D. An advanced sequel is planned in this series:Einstein for Almost Everyone 2 4 6 8 9 7 5 3 1 ePrinted in the United States of America no trees were harmed web*bookTM This book is a continuing work in progress.
January 1, 2015. Preface For over a decade I have taught an introductory, undergraduate class, "Einstein for Everyone," at the University of Pittsburgh to anyone interested enough to walk through door. With each new offering of the course, I had the chance to find out what content worked and which of my ever so clever pedagogical inventions were failures. At the same time, my lecture notes have evolved. This text owes a lot to many.
I i i. An Essay by Einstein -- The World As I See It. "How strange is the lot of us mortals! Each of us is here for a brief sojourn; for what purpose he knows not, though he sometimes thinks he senses it. But without deeper reflection one knows from daily life that one exists for other people -- first of all for those upon whose smiles and well-being our own happiness is wholly dependent, and then for the many, unknown to us, to whose destinies we are bound by the ties of sympathy. A hundred times every day I remind myself that my inner and outer life are based on the labors of other men, living and dead, and that I must exert myself in order to give in the same measure as I have received and am still receiving... "I have never looked upon ease and happiness as ends in themselves -- this critical basis I call the ideal of a pigsty.
The ideals that have lighted my way, and time after time have given me new courage to face life cheerfully, have been Kindness, Beauty, and Truth. "My political ideal is democracy. We come from the future. This is, for the most part, an accurate article, except for a few statements. "Exactly what makes a fermion a fermion is a bit complicated, but suffice it to say that fermions are all the particles that deal with matter. So what about the last group of elementary particles, the ones that don't deal with matter? These are the bosons, and they deal with the fundamental forces of the universe. " The statements above can be misinterpreted as suggesting that fermions are defined as particles that deal with matter and bosons are defined as particles that deal with forces. And that is not true. It's actually the other way around. Particles that deal with matter are fermions and particles that carry the fundamental forces are bosons.
What fermions and bosons really are have to do with two apparently unrelated (but actually related) particle properties: spin and statistics. "There are four known bosons" See, this is an example of the misconception I just mentioned. Actually, that isn't true.