Physics
Measuring the value and the impact of a scientist on her field of research using as data her scientific papers, the number of citations these papers got, and the prestige of the scientific journals where these were published is no easy matter.
Grading Researchers: The H-IndexThere is a large body of literature on how best to account for all these factors together: the discipline is called "scientometrics". Of course, the goal is to summarize the productivity of a scholar in a single number; possibly one with at most double digits, since decision-makers who hire or fund are usually incapable…
vongehr |
The fourth FQXi essay contest is underway. There is a lot questionable about FQXi and what it at times supports, but this year’s topic is just so clearly up my alley that I simply cannot resist:
Which of Our Basic Physical Assumptions Are Wrong?
I know which one, and if you know me, you know that I am all about that one and have a lot to say about it, but also, that I am uniquely idiosyncratic and incomprehensible. Here is the first half of my draft – please criticize it constructively and help me to get the message across. For most of you, this will simply mean to tell me where the…
The deeper we look into the universe, the deeper we look back in time. When in the night sky you see planets like Jupiter and Saturn, you look about an hour back in time. Look at the stars, and you are looking back in time anywhere from years to several centuries. Bring a binocular to a dark site and you will be able to see galaxies millions of years back in time. Get a decent telescope to the same site and you look even further back.
However, there is a limit to how deep you can peek. No matter what equipment you bring, and no matter what part of the electromagnetic spectrum you…
Was Einstein wrong about ?
No, the equation correctly relates an objects rest mass to its energy content. However, in 1952, Herbert Ives published Derivation of the Mass-Energy Relation in the Journal of the Optical Society of America. It purports to show that Einstein's derivation was invalid because Einstein committed the error of begging the question mathematically (its in the Appendix if you're curious). According to Ives, Einstein implicitly assumed that E=mc^2 in his derivation of E=mc^2. I believe Ives' mistake results from the false assumption that Einstein put in…
Top quarks are most often produced in pairs at hadron colliders. The reason of this fact is that the strong interaction, which produces most of the reactions between the projectiles, is flavor-blind, and it cannot create a single new flavor of quarks out of nothing. In other words, physical processes mediated by strong interactions conserve the quantum numbers describing the difference between the number of quarks and antiquarks of any given kind: U, D, C, S, T, and B.
Note that of the six mentioned "good quantum numbers" above only a subset are typically used. One would never go about…
In this blog I will derive the Einstein field equations starting from the Hilbert action. Since there are only two terms in the Hilbert action, one of which is left alone, there is not that much to do. Well, there is always way more to do - how well is this step really understood? Where does that factor come from? What kinds of variations could one do? The core of this blog is an extensive translation of the wikipedia page on the Einstein-Hilbert action written in my own personal style, doing minor variations so the steps made more sense to me. Go there if…
vongehr |
I like to explain stuff so that people like you and me think “aha!”, and not, “this guy knows a lot; I better agree though I have no clue what he is talking about”. In this manner, let me again briefly introduce one of those deeply complex and hugely controversial topics that supposedly require big sophisticated words, and then, like I hope you slowly come to expect from me, present the solution in a way that is obvious and that we all could have thought about a long time ago (if the conclusions were not so damn uncomfortable that people simply refuse even if it is presented on a silver…
Well, not really a "true" queen sacrifice, but it is still a nice little combination the one I played against a strong 1st category player today at the "Baracchi Memorial" in Venice, a one-day rapid chess tournament which is held every May in Venice in memory of a young and promising member of our chess club, who died in a car accident.
The position after black's 15th move (15. ...Be6) is the one shown below. I am white.
T.Dorigo - L.Pasqualetto, Memorial Baracchi 20/5/2012
The black knight has just been threatened by the pawn advance 15.e5, and black decided to interpose the developing move…
What I didn't account for in my last blog post was that there is a first order energy shift due to classical physics.. to IS NOT relativitstic in nature.
This can be understood using E=hf and the classical doopler shift which has v/c as a first appoximation and v^2/c^2 as a second approximation. The relativitc approx (1-v/c) (1+v/c +v^2/c^2) - (1+v/c)(1+v/c+v^2/c^2) gives 1+v^2/c^2. The first order effect cancels leaving only the second order purely relatvistic effect.
Without relativity
If the rays are pointed in the same direction this cancellation of first…