About twenty years ago (so, late 90s, but the book could've been older) I remember my mother read me a book. The basic premise was that for some reason, modern society had collapsed, been destroyed, or otherwise been forgotten, and a new human civilization had developed. Humans from this far future then rediscovered various items from modern times and tried to interpret what they were used for; this book described their findings.   I remember this being a picture book, but not being very colorful. Possibly it was going for a sort of Victorian/Planet-of-the-Apes aesthetic. I recall the future society being less advanced than our own, and they ascribed religious significance to a lot of the things they found (and were generally wrong about everything). I think the idea of the book was to be satirical and/or humorous, but also as a young child I was freaked out by the idea of everyone dying in some cataclysm.   I'd like to find this book again because I think I'd more appreciate the humor and I want to see if it's still as unsettling as I remember, but I have no idea how to even begin to look for it.
I read it in Reader's Digest in the seventies. Archaeologists interpreted everyday objects as the TV set and the toilet seat to be sacred and precious.
If APS-C and similar crop-sensor digital cameras have a focal length multiplying effect such that a 50mm lens has an apparent focal length closer to the field of view of an 80mm on a full frame camera, and yet at the same time the depth of field for the smaller sensor camera is more like the depth of field a 50mm lens would produce on a full frame camera (using the same aperture), then this would seem to suggest the concept of an "aperture dividing effect."  In other words, a 50mm f/1.8 lens on an APS-C camera would act more like a 80mm f/2.8 (approx. 1.8 * 1.6x) lens in 35mm equivalent — for depth of field, not considering exposure.  Can someone with a better understanding of the physics involved clarify this for me.  I've never seen this concept explicitly mentioned anywhere, so I am a bit suspect of it. Fantasy book with shape shifting dragon warriors Set in a fantasy world with shape shifting Dragon kings and their warriors. They terrorize the humans, and kill those with magic.   The protagonist is the great-grandson of a powerful warlock. He finds out that he has magic, and fights with it to save his new friends, the Griffin, Blackhorse (I think that's his name), some creepy necromancer who is immortal, and Gwen (fellow sorceress), along with the kingdom that the Griffin rules in.   They fight the protagonist's father, the leader of the Dragon kings, the king's Duke, and the creepy sorcerer, who has a curse (when he dies, he changes side from good to bad, or bad to good). I have no clue what this is called, but I want to find out, since I'm out of things to read. Spy from Earth studies Galactic Empire nobility and prevents plot to depose Emperor For various such sentences in many cases I get confused, it seems different for different cases. I want to know if someone left doing something for permanantly then what should be used? Also give some examples for different cases. Suppose... "I left my bag" means "I forgot my bag". but If I want to say the same for permanentaly "I left bringing my bag". Where should we use "stop" and "quit" then? Should the personal/research statement be technical? Related:   I know I must describe my past and current research in my personal/research statement or statement of purpose. But do I use technical terms?  I was given the advice that since the people reading my statement are mathematicians (I am applying to US for applied mathematics), they should know what I am talking about.  Although I am applying to applied mathematics, it would also be nice to hear from other fields (biology, computer science, engineering etc) about this. SHA-256 "almost unique"? I have seen numerous references on the internet of people describing SHA-256 as generating an "almost unique" hash.  . there are more.  Is there some mathematical basis to the almost uniqueness? I would have thought that as SHA-256 is an evenly-distibuted (?) hash algorithm which can accept any message (infinitely many) as an input and produces a fixed length (finite) hash - then there will in fact be an infinite number of each possible output - which I would think hardly qualifies as "almost unique".  Is there a basis for this statement? I'm using ArcGIS 10.1 and would like to export a map to a pdf, preserving feature's attributes. I would like to be able to identify, for example, a point feature from the map on pdf with its underlying features (essentially hyperlink to a document or URL). I know one can export to such a pdf in ArcMap, with an advanced option of exporting features with attributes. I use Adobe Acrobat Pro v.10, and cannot seem to be able to find a way to bring these attributes up.   Is this possible? How to open pdf file in Windows Phone 8? I have two passports/nationalities. How do I use them when I travel? How to create a bootable Ubuntu USB flash drive from terminal? Is there any way to create a bootable Ubuntu USB flash drive from the terminal without using any third-party applications like , , ,  etc.  I tried to create a bootable Ubuntu flash drive with dd method,  sudo umount /dev/sdb sudo dd if=/path/to/ubuntu.iso of=/dev/sdb bs=1M   It creates files on the USB disk, but when I try to boot the USB disk it shows an Operating System Not Found error. In a field that is the direct product of two fields, why isn't it a field? Suppose that we have the direct product of two fields, defined as: $\mathbb{F}^2 = \mathbb{F} \ \times\ \mathbb{F}$. Then, this is obviously not a field because we can take $(1,0)$, and this doesn't have a multiplicative inverse. However, I saw a mention to this today in a book, and the reasoning was:     "$\mathbb{F} \ \times\ \mathbb{F}$ has the zero-divisor $(1,0) \neq  (0,0)$, hence it is not a field".   (Lectures on Rings and Modules by Joachim Lambek, pg. 17).  I am not sure what they mean by zero-divisor here nor what $(1,0) \neq  (0,0)$ has anything to do with the direct product of fields not being a field. I always assumed there wasn't a multiplicative inverse, and that was it. Am I missing something deeper? Is it legal to add your publications to ResearchGate? I recently created a profile on . And to add your publications list it requires you to upload the paper. Is it legal to upload published journal articles on public servers, where everyone can download it for free? How to use siunitx with non numerical values? I understand that something like \SI{5}{\meter\per\second} defines a certain space between the number (5) and units (m/s). What should I use if instead of a numerical quantity I want a variable: R m/s? \SI{R}{\meter\per\second} fails because it expect a number in first parameter, and R \si{\meter\per\second} or $R$ \si{\meter\per\second} show different space.  Which is the correct use?  \documentclass{standalone} \usepackage{siunitx} \sisetup{per-mode=symbol} \begin{document} \begin{tabular}{r} \SI{5}{\meter\per\second}\\ $R$ \si{\meter\per\second}\\ R \si{\meter\per\second}\\ \end{tabular} \end{document} system wide keyboard hook on X under linux I drew a parallelepiped that is spanned by three vectors, and we know the volume is given by the absolute value of the determinant of the matrix - with the three vectors arranged in rows (or columns, since $detA = detA^T$).  How can I draw the tetrahedron from this parallelepiped to convince myself it is indeed 1/6th of the volume, i.e., 1/6 * |detA|?  Thanks, How to find relevant and new open research topics? How can one find relevant and new open research topics?  When working on my PhD thesis, I find it hard to find open questions in my very specific research area. Which approach do you take to find new and relevant topics? When I gain control of a creature, do I also gain control of any auras or equipment attached to it? What would happen if I 'd a creature that had been enchanted by a bestow creature and cast a spell to give it protection from the enchantment's color on it to remove the bestowed creature?  For instance:  They have just bestowed a  on a  and passes the turn. I use Portent of Betrayal to take control of the Asphodel Wanderer, attack and in the second main I cast Gods Willing to give the Asphodel Wanderer protection from black. Nighthowler detaches and where does it go, my control, opponents control or graveyard?  As an additional question, in the same vein:  What if I destroyed the creature while it was on my side? So change the gods willing to a hero's downfall in the example.  Relevent (under state-based actions):     704.5n If an Aura is attached to an illegal object or player, or is not attached to an object or player, that Aura is put into its owner's graveyard. How to create a GUID/UUID in Python How do I create a GUID in Python that is platform independent? I hear there is a method using ActivePython on Windows but it's Windows only because it uses COM. Is there a method using plain Python? notify-osd replaced with dunst after switching back to unity from i3wm I was testing i3wm (sudo apt-get install i3 is what I ran, and chose i3 from the log in screen) on my machine and after a while, decided to switch back to Unity. Upon switching back, I noticed that notifications came in the top right corner similar to i3 even though I was using Unity.  I'd really like it to use the normal Unity notification bubbles instead.  I looked into it and turns out instead of notify-osd, dunst is being used.   I tried using sudo vim /usr/share/dbus-1/services/org.freedesktop.Notifications.service and editing the file, but it has the correct line (i.e. Exec=/usr/lib/x86_64-linux-gnu/notify-osd) as expected.  I also tried unity-tweak-tool --reset-unity but that didn't do anything.  Is it possible for me to return to the normal notifications? Any help would be greatly appreciated. Thanks :)  Edit: I was able to return to the normal notifications by removing i3wm itself (and dunst). What I am actually asking is: is it possible to change to normal notifications while still keeping i3 and dunst on my system?  Note: This is NOT a duplicate of . The solution there is to remove dunst and I would like to keep dunst and have that work when I choose i3, and have notify-osd work when I choose Unity. Is there a convergent, alternating series that fails the AST? The alternating series test (AST) says, briefly, that if   $a_k&gt;0$ $a_k \geq a_{k+1}$, and $a_k \to 0$ as $k \to \infty$   then $\sum_k (-1)^k a_k$ converges.  This seems to be a one-way test (that is, if an alternating series fails the test, we don't know that it diverges).   document says so explicitly. It then gives an example of an alternating series which fails the AST. That doesn't prove the series is divergent (but it turns out to be divergent, anyway, by $n$th term test).  Is there a convergent, alternating series that fails the AST?  Of course, if the series fails condition 3, then it also fails the $n$th term test, and must diverge. And if it fails the first condition, then it's not strictly alternating, anyway.  So it must be a series that is not getting smaller (condition 2), but still converges.