Book about terraforming Venus and crossing it on foot
Short story, domed refuges
Find the general solution of $y'= a^{x + y}$ where y is the function How should I approach this problem? Should I put ln logarithm on both sides and move factor of variable of lnx on right side in front of the ln, or do somehing else? I understand general solving and types of solving these differential equations of first order, but I have no idea what my next step should be. Start a longtable in Latex at top of next page I want to use the longtable environment for a table. However, I do not know how to place it at the top of the next page, as I can do with the table environment. Do you know how to do it? Why do people go to the Wall in Game of Thrones? Is the wall a bad or a good place to be? Some people are sent there as punishment, others go because they want to (Jon Snow), others to get away from harm (Arya).  If I am not completely correct, it is because I have only started watching the series recently, and it is a bit confusing!  Please also correct me if I am wrong with any facts! In many C/C++ macros I'm seeing the code of the macro wrapped in what seems like a meaningless do while loop.  Here are examples.  #define FOO(X) do { f(X); g(X); } while (0) #define FOO(X) if (1) { f(X); g(X); } else   I can't see what the do while is doing.  Why not just write this without it?  #define FOO(X) f(X); g(X) View progress towards Announcer, Booster, and Publicist badges I shared a link to a question and now I am wondering whether I am almost going to get an announcer badge.  Can I somehow see which links I shared and how many clicks were on it for the last days?  Update:  Maybe this would be a nice feature. Next to any question you can see who has promoted it the most (number of fresh hits from a referer link) and also the amount of new ip's through search engine's and other referring sites.  Note the progress feature should include the Announcer, Booster, and Publicist badges. Currently in my last year of high school, and I have always been told that  does not exist by my physics teachers. Today my girlfriend in the year below asked me what centrifugal force was, I told her it didn't exist, and then she told me her textbook said it did, and defined it as "The apparent force experienced towards the outside of a circle is the centrifugal force and is due to the mass of the object resisting the inward centripetal acceleration that the object is experiencing". I was pretty shocked to hear this after a few years of being told that it does not exist.  I did some reading and found out all sorts of things about pseudo forces and reference frames. I was wondering if someone could please explain to me what is going on? Is it wrong to say that centrifugal force does not exist?   This has always nagged me a bit as I often wonder that if every force has a reaction force then a centripetal force must have a reaction centrifugal force, but when I asked my teachers about this they told me that centrifugal force does not exist. Extended Euclidean Algorithm: backward vs. forward I'm confused about how to do the extended algorithm. For example, here's the gcd part gcd(8000,7001)  $$\begin{align}8000 &amp;= 7001\cdot1 + 999\\ 7001&amp;=999\cdot 7+8\\ 999&amp;=8\cdot 124+7\\ 8&amp;=7\cdot 1+1\\ 7&amp;=1\cdot 7+0\\ \gcd(8000,7001)&amp;=1\end{align}$$    Now, the extended algorithm  $$\begin{align}1 &amp;= 8 - 1\cdot7\\ &amp;= 8 - 1\cdot(999 - 8\cdot124)\\ &amp;= -1\cdot999 + 8\cdot125\end{align}$$  How do you get this 8*125 from the previous line? Extract reply addresses from all emails in an outlook folder (sent on behalf of) I've got to send a bulk email out to a bunch of people in reply to emails they sent me. I've got all the original emails stored in a single outlook folder. I want to extract all of the reply addresses from the emails in that folder so I can send an email to all of them.  The article  shows you how to export the FROM address of these emails, however a large amount of them came from a web service that sends emails 'on behalf of' the person I'm trying to mail to. So I need the reply-to address, and the export wizard doesn't do that.  Does anyone have a tip on how to do this? This is Outlook 2007 on Exchange 2010. I know I'm late with this; this could be the last bug report about the old topbar. But the text on the privilege progress indicator (on your profile page) appears above the dropdown menu coming from the Stack Exchange button, as can be seen in the picture below.     Changing the z-index property of .s-progress-bar._badge .-info, .s-progress-bar._privilege .-info from 2 to 1 solves the problem.    The new menu seems to have a high enough z-index so that this is no longer a problem anymore: How to distribute objects in a circular pattern on a surface (Radial Array, Polar Array) Border with a transparent centred arrow Allow User to input HTML in ASP.NET MVC - ValidateInput or AllowHtml Showing a Sequence and its Limit are Closed Let $(X, d)$ be a metric space, and $(x_n)_{n \in \mathbb{N}}$ a sequence in $X$, with $x_n \rightarrow x$ w.r.t. $d$ for some $x \in X$. Show that the set $\{x_n : n \in \mathbb{N}\}\cup\{x\}$ is closed in $(X, d)$.   I figured I should use $\overline{F} = F \cup F'$ to show the above set is closed. Let $(x_n)_{n \in \mathbb{N}} = F$. Then, all elements of the sequence are in  $F$, which is equal to $\{x_n : n \in \mathbb{N}\}$. Clearly, the sequence (or $F$) has only one accumulation point, $x$. So, $F' = \{x\}$. This shows $\{x_n : n \in \mathbb{N}\}\cup\{x\} = \overline{F}$, and thus is closed.  Is this sufficient in proving the problem? Or would I have to show that $x$ is the only accumulation point as well (figured I don't have to because we know limits are unique)? Any advice would be very helpful. Thank you. A shell tool to "tablify" input data A long time ago I remember using a command that makes its input into a nicely formatted table.  For example, for this input,  apple 1 100 orange 20 19 pineapple 1000 87 avocado 4 30   The output will be similar to this:  apple     1    100 orange    20   19 pineapple 1000 87 avocado   4    30   I'd like to know the name of this tool. Find longest repeating string based on input in perl (using subroutines) I am wondering why matrix factorization techniques in the machine learning domain almost always expect the provided matrix to be non-negative. What is the advantage of this constraint?  Background: I want to use matrix factorization algorithms for a sparse user-item matrix containing positive and negative implicit feedback. Is there any another possibility to set interactions with negative indications apart from fields that denote that no interaction happened between the user and the item? Show bounded and convex function on $\mathbb R$ is constant How to load a .NET assembly for reflection operations and subsequently unload it? Attempting to create a tag wiki when a user has hit the suggested edit limit should alert the user that no more edits can be suggested at this time I ran into an issue on Gaming.SE where I attempted to create a tag wiki and wiki excerpt for a tag which did not have one already while I already have the maximum of five suggested edits in the queue.  Navigating to the tag page for the  provides a link to  for this tag. This link redirects to the  for this tag, without telling me that I can't submit an edit because I've reached the maximum number of suggested edits. Instead of silently redirecting, the page should alert me that I can't suggest any more edits until my suggestions are reviewed. Short story identification: society partitioned off by high wall Reading another question today reminded me of a short story I read in the early 90s (probably written in 60s or 70s though). A society is blocked off by a really high wall; the story follows a girl who tries to get over the wall. I think she manages it with a hot air balloon. When she reaches the other side she meets an older man who had managed to scale the wall in his youth - his solution had been to use a flock of birds to carry him.  UPDATE  I seem to recall that it splits off an elite group of people - getting over the wall is like a rite of passage. Most people don't even bother to get over it (or even be concerned by its existence at all), but a few try. There might be some magic involved (on the other / better side), or they might just be more advanced technologically.  FINAL UPDATE  As pointed out in the answer, and confirmed by me re-reading the story, I was mistaken in a few details. The main protagonist is not a girl, it's a boy called Porgie. He doesn't use a balloon, it's a glider he made, assisted with a broom. Magic is involved, but it's on the inside, with technology on the outside.