Astronomers have shown that the objects in the universe from galaxies a million times smaller than ours to the largest clusters of galaxies are held together by a form of matter that is not what we are made of and that gives off no light. This matter probably consists of one or more as-yet-undiscovered elementary particles, and aggregations of it produce the gravitational pull leading to the formation of galaxies and large-scale structures in the universe. At the same time, these particles may be streaming through our Earth-bound laboratories. Other, as yet undiscovered, particles might exist; for example, a new symmetry called supersymmetry predicts a large new class of particles, some of which could explain dark matter.
There are many documentaries, forums, blogs and more dedicated to . I have been frantically searching for an answer to my question however none of my sources have clarity to the matter of hand. I would really love a clear explanation to: What exactly is Dark Matter? Please help me to have a clear understanding.
How to draw a fish? I would like to draw an image like the following.     This is what I've done so far (I used tikz, but any other package is welcome):  \documentclass{article} \usepackage{tikz}  \begin{document}     \begin{tikzpicture}         \draw[fill=blue] (.5,0) rectangle (4,2);         \draw[fill=red] (1,1) to[bend left=50] (3,1) to[bend left=50] (1,1);         \draw[fill=red] (3,1) -- (3.5,1.5) -- (3.3,1) -- (3.5,.5) -- cycle;         \draw[fill=white] (1.6,1.1) circle (.15cm);          \draw[fill=blue] (1.55,1.1) circle (.05cm);              \end{tikzpicture} \end{document}     Edit: April 2nd, Time for explanation  In Italy (but I also think in other countries), a practical joke done on April 1st is called "pesce d'Aprile" (= April's fish, that is an ) and is often related to fishes.  The usual one is to stick a drawing of a fish on someone's back without he/she realizes it.  Some years ago a colleague of mine stuck some "pesci d'Aprile" with written below "sono disponibile" (= I'm easy) on the rear of all the cars in our company car parking. Some other colleagues didn't realize it, and they had gone around with that drawing for days.  Another funny example happened in Milan . Someone put on the windshield of a lot of cars a false fine for illegal parking. On the fine sheet was written "per il pagamento rivolgersi agli uffici comunali di via Gadio, 2" (= for payment, please contact the municipal offices in via Gadio, 2), the address of the Civic Aquarium.  Hence, this question was simply a way to put    P.S. = Since I earned a lot of reputation points with this trick question, I decided to give them back to the Community awarding a bounty to the two answers posted on April, 1st.  Moreover, I accepted Robert's one since he guessed without spoiling, and I thank the other two answerers.  To the downvoters: you're probably technically right, but:   there's already too much sadness in the world, let's laugh now and then! humor is part of the LaTeX philosophy, Prof. Knuth himself docet if only serious questions are accepted, why did they create a fun tag? When will my device get the Android 4.2 update (Jelly Bean)? R: loading a table with number as the column heading all were wrongly added a X, how to solve it? Can you help me with my software licensing issue? I was looking for a tree or graph data structure in C# but I guess there isn't one provided.  explains a bit about why.  Is there a convenient library which is commonly used to provide this functionality?  Perhaps through a strategy pattern to solve the issues presented in the article.  I feel a bit silly implementing my own tree, just as I would implementing my own ArrayList.     I just want a generic tree which can be unbalanced.  Think of a directory tree.  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I cannot find enable-interactive-search in    gsettings set org.gnome.nautilus.preferences enable-interactive-search true.     I searched using    gsettings list-recursively | grep search     and    gsettings list-recursively | grep interactive     but no such option.  Can you help me disable this in Ubuntu 17.10 and later? Getting "System program problem detected" pops up regularly after upgrade How do I assign the output of a command into an array? Drush hangs when trying to bootstrap Drupal Duplicate application icons in Ubuntu dock upon launch I'm using Ubuntu 17.10 with GNOME shell and Numix-Circle icon theme.   When I hover over the Numix icon for Nightly Web Browser, which is pinned to the dock I get the title "Nightly Web Browser".      But when I launch the program, another icon pops up at the bottom, with the name "Nightly". Is it correct to use "their" instead of "his or her"? SQL Server Escape an Underscore How do I escape the underscore character?  I am writing something like the following where clause and want to be able to find actual entries with _d at the end.  Where Username Like '%_d' With an  of archive/compression file formats, is there a single free/open-source command line tool to rule them all? Perhaps something with a consistent / unified set of flags? (note my  friendly )  I once run into a set of aliases meant to largely simplify the task of compressing/de-compressing files with bindings to tar and other utils, but I can't find this anymore.  Update: How can I configure something like atool to not use unzip to extract zip files (which apparently can't handle files larger than 4GB) and to use gunzip instead?  $ aunpack large_file.zip error:  Zip file too big (greater than 4294959102 bytes) Archive:  large_file.zip warning [large_file.zip]:  1491344848 extra bytes at beginning or within zipfile   (attempting to process anyway) error [large_file.zip]:  start of central directory not found;   zipfile corrupt.   (please check that you have transferred or created the zipfile in the   appropriate BINARY mode and that you have compiled UnZip properly) aunpack: unzip ...: non-zero return-code Deleting Lines Containing a Specified String in Different Files Suppose there are two files in web/ named foo.php and bar.php. The 1st line of foo.php is "sdajgeSTRINGdsad" and the 10th line of bar.php is "gdfhu98324STRING". The task is to first locate these two files, then delete 1st line of foo.php and 10th line of bar.php given that the specified string is "STRING". How good is Hard AI? 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.