标签: einstein

In the extraordinary year of 1905, Einstein published five brilliant papers including his best-known one on special relativity . One of the other papers explained the mechanics of Brownian motion, the random motion of small particles in fluid first studied by Robert Brown in 1827 and easily observed with a microscope (Brown used spores).   Einstein combined diffusion analysis and thermodynamics to explain and then quantify this noise-like motion of particles ( figure ), which had previously been collectively measured although the underlying physics remained a mystery. While his analysis of Brownian motion has been experimentally confirmed, he noted that one parameter of his analysis—the instantaneous velocity of particles needed to verify their group-velocity distribution—would never be measurable, due to the tiny physical and time scales. Figure: Brown motion of particles is a random process like electrical noise, but Einstein showed how this motion could be analyzed in the aggregate using thermodynamic and diffusion principles to characterize observable factors such as mean travel distances and drift motion over time (from Florida State University, Department of Scientific Computation).   Forward to the 21st century and it looks as if the "it can't be done" measurement is being done. In a brief and fascinating article " The measurement Einstein deemed impossible " in January 2015 edition of Physics Today (always an interesting and readable publication), two professors have combined an optical tweezer with a pulsed laser for nanosecond data collection, to actually make that measurement.   Note: Einstein’s five papers of 1905 were on the kinetic theory of gases, Brownian motion, special relativity, the relationship between mass and energy, and the quantum nature of photoelectric effect (due to its "practicality," the last one was his cited accomplishment on the official rationale for his Nobel prize award). Einstein's Miraculous Year by John Stachel is an excellent book with complete translations of these five papers, as well as detailed technical explanations and in-depth historical perspective for each.   Developed in the 1970s, the optical tweezer is a focused laser beam that's now a standard tool in physics and biology experiments. It's used to trap and then move particles. This tweezer and a pulsed laser are, however, not enough to make the measurement. The article discussed how the particles under surveillance—here, they used tiny glass beads rather than the pollen that Brown and others used—and overall test bed were configured. The velocity measurement used a split-beam photodetector, with half of the emitted beam going to the test site and returning to the detector, while the other half is going directly to the detector via an equivalent optical-path length. This type of differential measurement enables cancellation of any intensity fluctuations in the laser.   The ability to extract meaningful data in difficult situations is one of the many attributes of the test and measurement domain. Sometimes, as in the Brownian-motion case here, the measurement challenge is inherent in the nature of the object under test and the subtleties of instantaneous velocity on this microscopic time and physical scale.   In many cases, however, the parameter is simple to measure in principle, but the reality of the making the measurement is hard. Think of all the challenging places we need to measure temperature despite its apparent simplicity, and all the creative, often ingenious contact and non-contact solutions used.   Or consider weight: the late Jim Williams, in his 1976 feature article for EDN , discussed in detail his design for an infant-weighing scale for the MIT nutrition lab, " This 30-ppm scale proves that analog designs aren't dead yet ." While a basic weigh scale is an almost trivial design, Williams faced some tough objectives: the scale had to be small and portable, offer absolute accuracy within 0.02% along with resolution to 0.01 pound over a 300-pound range, use only standard components, and never need calibration once put into use. To do this, he looked at every subtle source of error including thermal drift, component aging, and stray EM fields. In a thorough tour of engineering excellence, he worked out how to minimize, negate, or self-cancel their degrading effects.   Have you ever helped devise a solution to a measurement that "couldn't be done" or was deemed very difficult? How did you verify the validity of your approach?

This is might come out a tad cynical, but we continue to marvel at how much texting young people seem to do these days. It's almost like they are oblivious to the world around them. However, there is one advantage as you will see when you reach the bottom... Having coffee with friends .   A day at the beach.   Cheering on your team.     Having dinner out with your friends.   Out on an intimate date.   Having a conversation with your BFF .   A visit to the museum .   Enjoying the sights .   Nuff said?   Of course, one of the benefits of all this texting is that innocent bystanders (people sitting at the next restaurant table, people sitting in the next bus seat etc.) don't have to listen to these young people's inane telephone conversations anymore! So it's true—every cloud does have a silver lining :-)  

I just finished reading George Dyson's Turing's Cathedral: The Origins of the Digital Universe. I was going to write a review on it, but – sad to relate – I really couldn't rouse the enthusiasm... One of the reason's I got Turing's Cathedral in the first place (apart from the fact that I love learning about the history of computing) is that I really enjoyed the biography Einstein: His Life and Universe by Walter Isaacson. (I mistakenly recollected the Einstein book as also being a work of George Dyson's). You can read the reviews of Turing's Cathedral on Amazon. I pretty much agree with all of them – both "for" and "against". This isn't a book about Alan Turing, although he does get a few good mentions. This is more of a description of the pioneering development of computing in America during the decade after World War II. The central character is the Hungarian-American mathematician and polymath John von Neumann, but we also get introduced to a "cast of thousands". The book is replete with interesting details – but it's also jam-packed with boring details. The bottom line is that (a) I'm glad I read it and (b) I won't be reading it again (grin). By comparison, if you are interested in learning more about the life and works of Albert Einstein, then I most heartily recommend Walter Isaacson's biography of the great man. The book is almost completely without equations ( E = mc 2 might creep in there), but by the end you really have a "feel" for what a staggering achievement Einstein's work was and how incredibly difficult it was to get there. But that's not what I wanted to talk about... I also just finished re-reading Shakespeare – The World as Stage by Bill Bryson. I'm much more used to seeing Bryson's humorous accounts of his life and travels around England, Europe, Australia, and America, so I must admit that I was a tad dubious when I first saw that he'd written a book on Shakespeare. Now, I can drop Shakespearian quotes into the conversation as readily as the next man, and I've slogged my way through a fair number of his plays, but – truth to tell – I would be more than happy if I was never exposed to another one of his works during the rest of my stay on this plane of existence (grin). When I was at high school, the thought that I would one day read a book about Shakespeare for my own pleasure would have had me rolling on the floor laughing. Bill Bryson's skill is that he can write a book about the Bard that is incredibly informative ... and still has me rolling on the floor laughing. Now, it's important to note that this is not a biography of Shakespeare per se. As we soon discover in Bill's book, what we really and truly know about Shakespeare as a person would fit on the back of a postcard. Even the spelling of Shakespeare's name is problematical. As Bryson says: We are not sure how best to spell his name – but then neither, it appears, was he, for the name was never spelled the same way twice in the signatures that survive. The curious thing is that the one spelling Shakespeare didn't actually use himself is the one that is now universally attached to his name. Bryson also points out that one of the reason's Shakespeare remained so well-known (when so many of his peers have been lost in the mists of time) is that, seven years after his death, two of his friends published a compendium of his works that is now known as the First Folio . Now, you might think that the First Folio would be the definitive word (pun intended), but as Bryson says: In fact, however, the First Folio was a decidedly erratic piece of work. Even to an inexpert eye its typographical curiosities are striking. The problem was that there was no "master" copy of any of the plays. There was instead a bunch of different copies for each play, where each copy reflected a different state of development as the play was acted out and revisions were made on the fly. So what Shakespeare's friends had to do was to go through all of the versions they had available to them and create a synthesis of what they thought was best. The results sometimes left something to be desired. One of many examples offered by Bryson is as follows: A crucial line of dialog in King Lear is abbreviated by the character name "Cor.," but it is impossible to know whether "Cor." Refers to Cornwall or Cordelia. Either one works, but each gives a different shadow to the play. The issue has troubled directors ever since. Having said all of this, the fact that we know so little about Shakespeare in no way detracts from the fact that this is a very interesting, informative, and amusing book. As one review on Amazon says: What Bryson does is provide an excellent background piece on what little we do know of "the English Language's Greatest Writer" by exploring where he came from, what life was like generally in his time and how the theater and actor/writers worked as they entertained the masses in London and the countryside. I couldn't have said it better myself. The bottom line is that this is a really good book that I would recommend highly. Even if you have no interest whatsoever in reading Shakespeare's plays, or any of his myriad other writings, I am fully confident that you would really enjoy this work on the man himself.