If we can see billions of light years into space how do we know we're not looking at our galaxy in the past?
There is a possibility for our universe to be the surface volume of a (higher-dimensional) hyperspace. So if this possibility is true,then is there also a possibility that the other galaxies we see are our own galaxy after light has completed revolution around the three dimensional boundary (surface volume).  Know that we see different shapes for different galaxies.This can be perhaps due to other reasons like-   distance light travelled, the angle through which we look to see the other galaxy (possibly Milky Way) after     it made any number of revolutions, the part of the other galaxy (possibly Milky Way) which we see,and some other properties of light and space.   Only our Milky Way galaxy is just one possibility  Another possibilities are the number of galaxies are far less than we see because we see the same galaxy several times due to curved space.  Any possibilities for the above statements to be true?
Brackets in if condition: why am I getting syntax errors without whitespace? I am using the below script to move two days back when script runs at starting two days of the year and also check first and second days of every month and move two days back. if [$month=&quot;01&quot;] &amp;&amp; [$day=&quot;01&quot;]; then         date=&quot;$last_month/$yes_day/$last_year&quot;         fulldate=&quot;$last_month/$yes_day/$last_year&quot; else         if [$month=&quot;01&quot;] &amp;&amp; [$day=&quot;02&quot;]; then                 date=&quot;$last_month/$yes_day/$last_year&quot;                 fulldate=&quot;$last_month/$yes_day/$last_year&quot;         else                 if [ $day = &quot;01&quot; ]; then                         date=&quot;$last_month/$yes_day/$year&quot;                         fulldate=&quot;$year$last_month$yes_day&quot;                 else                         if [ $day = &quot;02&quot; ]; then                                 date=&quot;$last_month/$yes_day/$year&quot;                                 fulldate=&quot;$year$last_month$yes_day&quot;                         else                                 date=&quot;$month/$yes_day/$year&quot;                                 fulldate=&quot;$year$month$yes_day&quot;                         fi                 fi         fi fi  But my bad am getting the below error message Etime_script.sh: line 19: [06=01]: command not found Etime_script.sh: line 24: [06=01]: command not found I just moved to a new computer: Windows 10 with XAMPP. As far as I know I set everything up the same as it was on my old Windows 7 computer. But now, for some reason, much of the time when I run drush cc all or run update.php, the database gets corrupted. Most frequently, some cache tables' *.idb files (tablespaces) are deleted from my mysql directory, which makes those tables appear as "in use" in phpMyAdmin and prevents them from being edited or emptied. They are always cache tables and never tables that actually get modified by my update hooks. Restoring the database is the only way to fix it then. This is a mature site that I've been working on for a long time, and have never seen this until the new computer. What's happening here?  A sample error message when using update.php, caused by a missing *.idb file:  PDOException: SQLSTATE[HY000]: General error: 1812 Tablespace is missing for table '(null)': DELETE FROM {cache_field} WHERE (cid = :db_condition_placeholder_0) ; Array ( [:db_condition_placeholder_0] =&gt; field:message_type:6 ) in cache_clear_all() (line 168 of C:\&lt;path&gt;\includes\cache.inc).   My most recent drush cc all error message, which Google has never even heard of, was:  exception 'PDOException' with message 'SQLSTATE[HY000]: General      [error] error: 1030 Got error -1 "Internal error &lt; 0 (Not system error)" from storage engine InnoDB' As seen in this video: (Skip to 5:53)  When a player is slain, they drop an Enchanting Table on top of their inventory.  How was this achieved and how can I build a system (using command blocks) that does that? Come to think of it, what happens to a player's location when he/she dies? Does it reset to the spawnpoint? Stay the same (where they died) until they respawn? Or becomes a null value until they respawn? Question involving discriminant of quadratic congruence in elementary number theory. How to calculate the $H_2$ and $H_\infty$ norms of TransferFunctionModels or StateSpaceModels? listing files with pattern with starting and ending I want to list all files in a directory that start with 'abc' and end with '.zip'  I'm trying to use ls.  The directory has a lot of zip files starting with abc&lt;date&gt; and xvz&lt;date&gt;. I only want to get the list of the abc&lt;date&gt;.zip What is the difference between Shrink Database and File? DBCC ShrinkDatabase() DBCC ShrinkFile()    Do I need to run both DBCC commands in order to shrink the database? What is the difference between these two above? I`m using Firefox Sync on a bunch of computers.   I would like to manage my account, by removing some computers. I can't find the place to do this, it should be on the Firefox Sync page, but the official page only has the privacy and download information. Expected value of sums Suppose we draw cards out of a deck without replacement. How many cards do we expect to draw out before we get an ace? How to show every field is a Euclidean Domain. I'm having trouble proving this. This is what I have so far:  Let $F$ be a field. Let $v(x) \rightarrow 1$ for all $x$ not equal to $0$.  So if we let $x$ be in $F$ where $x$ not zero then we can write $x$ as: $x=qy+r$ for some $y$ in $F$. If $r$ not zero then $V(r)=1$.  Not sure what to do from here. I know eventually I'm supposed to get no remainder $(r=0)$ but I'm stuck at applying the definition and valuation map. Can $n!$ be a perfect square when $n$ is an integer greater than $1$? Can $n!$ be a perfect square when $n$ is an integer greater than $1$?  Clearly, when $n$ is prime, $n!$ is not a perfect square because the exponent of $n$ in $n!$ is $1$.  The same goes when $n-1$ is prime, by considering the exponent of $n-1$. What is the answer for a general value of $n$?  (And is it possible, to prove without Bertrand's postulate. Because Bertrands postulate is quite a strong result.) Enumerate non-isomorphic graphs on n vertices In the following the graphs are assumed to be undirected and simple.  1.Enumerate the number of non-isomorphic graphs on $n$ vetrices where $n$ is fixed.  Here are some ideas I had:  The number of labeled graphs is $ 2^{\frac{n(n-1)}{2}} $.  So it is enough to find the number unlabeled graphs on $n$ vertices.I have no idea for this.  2.Enumerate the number of non-isomorphic graphs on $n$ vertices and $m$ edges where $n,m$ are fixed.   Can we find a closed formula for each of this?  Any help?   Thank you! A continuous function that attains neither its minimum nor its maximum at any open interval is monotone Let $f: \mathbb R\to \mathbb R$ be a continuous function such that $f$ attains neither its minimum nor its maximum at any open interval $I \subseteq  \mathbb R$ , then how to prove that $f$ is monotone ? How do I prove that $S^n$ is homeomorphic to $S^m \Rightarrow m=n$? This is what I have so far:  Assume $S^n$ is homeomorphic to $S^m$. Also, assume $m≠n$. So, let $m&gt;n$.  From here I am not sure what is implied. Of course in this problem $S^k$ is defined as:  $S^k=\lbrace (x_0,x_1,⋯,x_{k+1}):x_0^2+x_1^2+⋯+x_{k+1}^2=1 \rbrace$ with subspace topology. Influence of the scale factor on the projection Why doesn't archive.ubuntu.com use HTTPS? I always see instructions for adding the Universe and Multiverse repositories that look something like the following:  sudo add-apt-repository -y "deb http://archive.ubuntu.com/ubuntu $(lsb_release -sc) main universe restricted multiverse"   Recently I tried editing this to use HTTPS instead and was dismayed to find that archive.ubuntu.com doesn't appear to respond to HTTPS. Now I wonder how feasible it would be, or what damage could be done, if an attacker were to successfully perform a man-in-the-middle attack here?  Am I being too paranoid, considering the role these repositories perform on a system? What is the name of the operation $v^T H v$? To find out how something is called is the one thing I don't know how to use Google for.  If I have a vector $v$ and a symmetric matrix $H$, then the operation $v^T H v$ gives me some sort of projection of the matrix $H$ on the vector $v$. For example if $H$ is the Hessian, the operation gives me the second derivative in the direction of $v$.  What is the name of this operation? Transit Visas for South Africa Undesirable-Overstay Tourists I received an undesirable status for overstaying a SA visa while hospitalized for injuries sustained in Lesotho. I had to cross into SA from Lesotho. Now I am banned entry into SA until Feb 2016 and though I have submitted a waiver request to remove the undesirable status, I hear from some the waiver request may take 4-5 months or even take longer than the time of banishment.  I have a pre-paid safari planned in October in which I need to fly through Johannesburg to get to Botswana. The Jburg border control requires tourists to pass through SA immigration even when simply changing planes.  1) Will SA grant me "transit" access if I don't leave the airport?  2) Will SA allow me to spend a night in the airport as the layover is 12 hours>  Thanks for passing on any info. What is the difference between implication symbols: $\rightarrow$ and $\Rightarrow$? I do not understand the difference between $\rightarrow$ and $\Rightarrow$. Sometimes I see implication truth tables labeled with the former, sometimes with the latter.  Aren't they synonyms of logical implication or is there any difference? Custom Adapter for List View