Copasetic Flow

Given the fascinating history of the author, I was very excited to read the book.  Agnew Hunter Bahnson Jr. is featured in the near sci-fi non-fiction book, "The Philadelphia Experiment".  A wealthy industrialist that fancied himself a potential astronaut, Bahnson funded fringe physics projects, (that's how he landed in The Philadelphia Experiment"), as well as mainstream general relativity research, (he raised the funds to sponsor the Institute for Field Physics at the University of North Carolina Chapel Hill). More on Agnew's history" The book alas, did not live up to the author.  While the story is more interesting if you allow yourself the gratuitous fantasy that Bahnson was dreaming about the ship he himself hoped to build, that's about all the book has to offer.  He had a potentially spectacular female character, a pilot the equal of the book's main character.  Unfortunately, Bahnson squandered her, using only as a romantic prop.  It...

If you can sneak away this afternoon and you want to see a fascinating history of physics video, this is the one!  This is a recording of the history roundtable at last December's 50th anniversary meeting of the  Texas Symposium on Relativistic Astrophysics.  The speaker include in no particular order: Roger Penrose Wolfgang Rindler Charles Misner Louis Witten Cecile DeWitt-Morette Joshua Goldberg Ezra Ted Newman and Roy Kerr, and those are just the ones I can remember off the top of my head. The agreed upon format was that each speaker had two or three minutes to introduce themselves and then the moderator would ask questions.  Fortunately, the format was completely abandoned!  What followed was over two hours of each speaker recounting their favorite stories about the history of relativistic astrophysics.  The whole video is worth watching.  Here's a link to the video on youtube queued to the beginning of Louis Witten's talk.  He ...

I transferred yesterday's Mathematica file with the Alcubierre warp drive[2] line element and space curvature calculations to the  +Sage Mathematical Software System  today, (the files been  added to the public repository [3]).  If you haven't used Sage before, it's a Python based software package that's similar in functionality to Mathematica.  Oh, and it' free.  I also worked a little more on understanding the theory, but frankly, I made far more progress with the software than the theory.  What follows will be a little more of the Alcubierre theory, plus, a cool Sage interactive demo of one of the Alcubierre functions[1], as well as a bit about my first experience with using Sage. Theory The theory is fun, but it's moving slowly.  Here's the chalk board from this morning's discussion Alcubierre setup the derivation using something called the 3+1 formalism which means we consider space to be flat, (in this case), slices that are labelled ...

I was able to play with the Alcubierre warp drive derivations for a bit today!  I'm still trying to absorb all the niceties, but here's what I understand so far.  I'm just getting started on all of this and everything is very shaky.  So, please, anyone who happens to be familiar with oh, I don't know, the 3+1 formalism of GR say, please feel free to jump in.  Actually the more involvement the merrier, whether it be with suggestions, corrections, or questions. Which brings up the Alcubierre github repository [1].  I went ahead and made an open access github project that for the moment holds only a mathematica file with the derivation details I've been able to compile so far, a wiki, and one open issue, (the space curvature graph looks a little too jaggy).  Here's the graph by the way, king of the 'Hello World' moment for Alcubierre work I suppose, (picture 1): I'd hoped to have more to say about this tonight, but hopefully I can check in again...

I jotted down a quick post on the Alcubierre Drive and faster than light travel.  I had assumed that like many FTL misconceptions, the media had been confused by speed measured as proper velocity, (space in the Earth's rest frame divided by time in the spaceships frame), as opposed to lab velocity.  +Jonah Miller quickly pointed out, however, that the claims for the drive were that it could go faster than the speed of light with regard to the laboratory frame, and hence with laboratory velocity.  I found the original paper by Alcubierre on arxiv[1], and... Jonah's absolutely right! The paper is amazingly well written and anyone that's had a grad level general relativity class should be able to easily traipse through it.  Alcubierre even shows that causality won't be violated.  I haven't had time to digest the material enough to say why causality isn't violated except with the very unsatisfying statement, "Well, the math works out."  Alcubierre w...

I'm reading an excellent article[3] by one of my all-time favorite authors, Wolfgang Rindler[1][2].  In the article, Rindler and Perlick show how to use a generalized form of the line element to derive the circular geodesics and the associated gyroscopic precessions of a number of different metrics including everyone's standby, the Schwarzschild metric. Using the Schwarzschild metric and his newly defined method for calculating circular geodesics, Rindler first derives the Thomas precession which was originally a special relativistic result having to do with the precession of the spin of an electron around an atomic nucleus.  He then goes on to show how the Fokker-De Sitter precession of a gyroscope orbiting a massive body, (like the sun), can be calculated. See reference [7] I'd never heard of the Fokker-De Sitter precession before, so I read on.  It turns out that this precession contains a component due to the geometry of the Schwarzschild metric as well as a...

I found something interesting yesterday, well interesting to me anyway.  What follows is a bit of a historical ramble and reference-fest.  Hyperbolic motion which is usually attributed to Wolfgang Rindler was actually first shown by Hermann Minkowski.  Rindler himself references Minkowski [2] in the first paragraph of his paper where hyperbolic motion under uniform acceleration in terms of special relativity is derived[1].  Not only did Minkowski show hyperbolic motion in his first lecture on spacetime, he also pointed out that you'd have to work kind of hard, actually setting all your acceleration components to zero to not exhibit hyperbolic motion, (picture 1). Hyperbolic motion, I think, is attributed to Rindler because of his fleshing out and full development of the idea including the concept of event horizons.  Rindler pointed out that when an object undergoes uniform acceleration in spacetime, that a light signal sent out after the object will never b...

For what's going on with research, scroll down.  But first, another study topic for the amateur radio extra class exam.  One of the questions asks what the purpose of a sense antenna is.  The correct answer is that "It modifies the the pattern of a DF antenna array to provide a null in one direction."  Whatever that means.  The DF referred to in the answer is direction finding.  Small loop antennas, like the one shown in the picture to the left (picture 1), can be used to find the direction that radio signals are transmitted from.  By rotating the loop until the received signal becomes the weakest, you can locate the direction.  There's only one problem, you can't tell whether the signal is coming from in front of, or behind the loop.  This is where the small vertical antenna in the picture comes in.  That's the 'sense antenna' or 'sense aerial'.  Its signal is added to the signal of the loop antenna and the net result is tha...

Good Morning!  While drinking my coffee after getting a full night's sleep, (hooray for happily sleeping seven month olds!!!), I came across a cute little satellite and some useful approximations. ESTCUBE 1 The Estonian University of Tartu has successfully placed a student built and student operated cubesat into orbit.  The satellite will deploy an electrodynamic tether and test the ability of the device to propel the space craft by exploiting the force between the electric charge placed on the tether by the satellite and charged particles in the solar wind.  For those that didn't know, the electronic tether propulsion concept was patented by Robert Forward, a physicist who worked for Hughes research during the '60s and went on to become a famous scifi author[5][6].  Folks with ham radios can listen in on the satellite at 437.250 MHz and 437.505 MHz.  M5AKA did a great write up on the little cubesat [1].  The satellite tracker here at Co...