In Europe, travelers can buy a special rail pass that gives them unlimited train rides for a month. And some airlines offer tickets where a list of destinations is chosen in advance, but the flight dates are flexible and can be chosen on short notice.   Is there anything similar for traveling around the US by bus or train? Greyhound used to offer something like it, called the "Discovery Pass," but it seems to have been discontinued. And Amtrak only seems to offer unlimited passes on specific short routes, mainly targeting commuters.
Can you help me decide, what type of transport can I use to travel from one US town to another (it will be a big journey), without flying?  Are buses available, and is there any more suitable method of traveling?
Context  In one of his most popular books , Terry Pratchett makes an entropy joke:     Knowledge equals Power, which equals Energy, which equals Mass   Pratchett is a fantasy comedian and every third phrase in his book is a joke, therefore there is no good reason to believe it.  Pratchett uses that madness to make up that a huge library has a tremendous gravitational push.  The question  I work with computers and mostly with encryption.  My work colleagues believe Terry Pratchett's statement because of entropy.  On the other hand, I believe, it is incorrect since entropy of information is a different entropy than the one used in thermodynamics.  Am I correct?  And if so, why do use the same name (entropy) to mean two different things?  Also, what would be a good way to explain that these two "entropies" are different things to non-scientists (i.e. people without a chemistry or physics background)? So far, I understand that I have to look at each Jordan block. How do I prove that for a Jordan block with a value of x, $J_n(x)$, the Jordan decomposition of $(J_n(x))^2$ is $J_n(x^2)$ ? I have a feeling this will lead me to the solution. Thanks for your time. Cardinalities of the intervals $(-1,1)$ and $[-1,1]$ How often is the Golden Ratio actually used in modern design? The  is the stuff of legend () and is . My question is two-fold, really: Is the Golden Ratio really a good tool used in modern design (defined here as 20th century on forward), and if so, how often is it used outside of the aforementioned known uses?  EDIT: To @e100's first comment, examples of modern use of the Golden Ratio would be a great thing to add here if there any documented or arguably conclusive uses of it. Specifically, if diary Tom Riddle had succeeded, how would he have strengthened the present day Voldemort?   In , @Pearsonartphoto gives a quote from J.K. Rowling in his answer regarding what would have happened if Tom Riddle had succeeded in fully manifesting from his diary memory form to a full human form.     Q: In Harry Potter and the Chamber of Secrets, what would have happened if Ginny had died and Tom Riddle had escaped the diary?   J.K. Rowling: I can’t answer that fully until all seven books are finished, but it would have strengthened the present-day Voldemort considerably.    - FAQ - Wayback Machine   As well, I've read all seven Harry Potter books many, many times and I haven't been able to ferret out any overt details regarding exactly how the present day Voldemort would've been strengthened by co-existing with diary Tom Riddle.  Specifically, how would the reincarnation of 16-year-old Tom Riddle have strengthened the 67-year-old present-day Voldemort at the time of Chamber of Secrets?  &#9733; I would love an answer from canon, any of J.K. Rowling's interviews, or Pottermore, or an answer constructed within the spirit of canon. Winter Bash 2014 Secret Hats Take as an example the well-known . In the original paper, the regression model was used to model the amount people were willing to pay for improved air quality.  But the 'people' whose behaviour was being modelled was never specified. Presumably, it was not limited to 'residents of Greater Boston'. Only implausibly would it be 'humans anywhere on the planet'. Nor, 'all US residents'.   So what inference are we invited by the authors to draw about the scope they intend for their theory? Perhaps 'all residents of large US metro areas'. But - what about other First World metro areas? The first two sections of the Boston paper scrupulously avoid any reference which might suggest that they had a particular 'population' to which their 'sample' was to apply.  There is also the dimension of time - the data came from the 70s, whereas the theory is has no time limitations spelt out.  Plus - going back to first principles - how could the Boston data be treated as a sample of a population including, say, the Chicago metro area when no data from the Chicago area was considered?   Besides, lots of the covariates in the Boston regression weren't samples at all, but totals - so, for example, the proportion of blacks was supplied from census stats.  My question: how can we conceive the Boston data as supporting the geographically unlimited propositions in the paper? Is there a mathematical way of showing equivalence or approximation of the Boston data analysis to other cities? Or is it just assumed as a matter of common sense - such that the paper's authors would be amazed to think anyone could have any doubts on the matter? The age of the universe Stop Mathematica from giving imaginary solutions I recently traveled from the Basel area to Stuttgart for a weekend.  I had round-trip tickets including (paid) bicycle reservations.  At our first station change, we found that our EC train was canceled.  Information gave us a replacement train schedule, using slow RE trains which don't require reservations for bicycles.  As we continued our trip, every single train we boarded arrived late, eventually causing us to reach Stuttgart roughly 2 hours later than our initial itinerary.  What monetary compensation am I justified in requesting from Deutsche Bahn in this case?  In particular:   It seems clear I should get back the bicycle reservation money, since the train we reserved on was canceled. I know DB offers compensation for late travels.  I'm not sure whether we were 2 hours late or more, or just shy of 2 hours.  But does this apply if we weren't traveling by our original trains? If we had originally scheduled our journey with RE trains and other local transport, we could have bought a Baden-Württemberg ticket for much cheaper than our tickets including an EC cost.  Can I ask them to refund the difference? Am I entitled to any other type of compensation? Correct usage of "see" vs. "watch" Why should edits be at least six non-space characters? Earlier today I got this message:  Oops! Your edit couldn't be submitted because:   Edits must be at least 6 non-space characters; is there something else to improve in this post?   However, the purpose of my edit was to change the formatting for a message to show code.  There may have been other grammatical mistakes that could have been, but in general it is possible that there would not be.  What's the correct protocol to handle a situation like this? What registers to save in the ARM C calling convention? It's been a while since I last coded arm assembler and I'm a little rusty on the details. If I call a C function from arm,  I only have to worry about saving r0-r3 and lr, right?  If the C function uses any other registers, is it responsible for saving those on the stack and restoring them? In other words, the compiler would generate code to do this for C functions.   For example if I use r10 in an assembler function, I don't have to push its value on the stack, or to memory, and pop/restore it after a C call, do I?  This is for arm-eabi-gcc 4.3.0. SQL Server compatibility with New TLS Standards I occasionally update my kernel from this web site    I have been always downloading 3 deb files for installing  linux header all, linux image and linux headers. I noticed one more deb file recently for 64 bit kernel called Linux-image-extra.  I would like to know what does kernel file Linux-image-extra do and should I also install it? When I run:  tex algorithms.dtx   for example, I get this message.    ! Undefined control sequence. l.34 \documentclass                    {ltxdoc} ?   Help? Doing a little reading over the break (The Probabilistic Method by Alon and Spencer); can't come up with the solution for this seemingly simple (and perhaps even a little surprising?) result:     (A-S 1.6.3) Prove that for every two independent identically distributed real random variables $X$ and $Y$,   $$Pr[|X-Y| \leq 2] \leq 3 Pr[|X-Y| \leq 1].$$ Bottom to top explanation of the Mahalanobis distance? I'm studying pattern recognition and statistics and almost every book I open on the subject I bump into the concept of Mahalanobis distance. The books give sort of intuitive explanations, but still not good enough ones for me to actually really understand what is going on. If someone would ask me "What is the Mahalanobis distance?" I could only answer: "It's this nice thing, which measures distance of some kind" :)   The definitions usually also contain eigenvectors and eigenvalues, which I have a little trouble connecting to the Mahalanobis distance. I understand the definition of eigenvectors and eigenvalues, but how are they related to the Mahalanobis distance? Does it have something to do with changing the base in Linear Algebra etc.?  I have also read these former questions on the subject:       I have also read .  The answers are good and pictures nice, but still I don't really get it...I have an idea but it's still in the dark. Can someone give a "How would you explain it to your grandma"-explanation so that I could finally wrap this up and never again wonder what the heck is a Mahalanobis distance? :) Where does it come from, what, why?   UPDATE:   Here is something which helps understanding the Mahalanobis formula: "When I grow up, I am going to be a doctor"- Is it correct? When I grow up, I am going to be a doctor.   Is this sentence correct? Personally I think my growing up will happen in future and "I am going to be a doctor" sounds like it is going to happen in next month! But the sentence clearly indicates the speaker is a child. So according to me, "I am going to be a doctor" should be replaced by "I will be a doctor". So I think a more clear sentence would be     When I will grow up, I will be a doctor.   Is my concept correct here? Plotting several 2d functions in a 3d graph I am trying to reproduce a similar figure to the following one. My first guess was to use pgfplots but I didn't find any example that I could use as a starting point. At the moment I am unsure if pgfplots is actually the right package or I should rely on something else e.g. TikZ.   Since I don't really know where to start, I would appreciate any piece of code that points me in the right direction.    EDIT  Here is some dummy data for the plots.  plot1   plot2   plot3   plot4 0       0       0       0 3.466   2.058   0       0 4.262   2.976   0.001   0 3.822   3.168   0.006   0.008 2.953   2.936   0.019   0.063 2.065   2.492   0.046   0.265 1.332   1.977   0.092   0.734 0.797   1.478   0.164   1.508 0.443   1.045   0.268   2.44 0.228   0.698   0.412   3.219 0.107   0.438   0.598   3.524 0.046   0.256   0.831   3.219 0.017   0.138   1.109   2.44 0.006   0.067   1.429   1.508 0.002   0.029   1.78    0.734 0       0.01    2.141   0.265 0       0.003   2.479   0.063 0       0.001   2.736   0.008 0       0       2.808   0 0       0       2.465   0 0       0       0       0