LIGO Gravitational wave discovery - how did they know the cause of spike? I understand how unbelievably lucky the discoverers were to catch the wave produced billions of years ago by an event that happens so rarely one hour into a test run of their equipment. But one thing is still not clear to me – how did they know what exactly caused the spike? Was that merely a conclusion that this must have been two black holes colliding or there was any additional astronomical observation done that spotted the collision?  EDIT:   is similar, and one of the answers mentions that LIGO observation can not be interpreted as evidence of WHAT the actual event was, but it also never directly tells me if any proven-to-work ways of observation parallely detected the black hole merger.  Because if only LIGO was involved in detection, than how do we know WHEN and WHERE the merger happen? As far as I understand, LIGO technology does not communicate any space-time coordinates of the event. Or am I wrong?   and other articles insist that event took place 1.3 billion years ago.
Are the LIGO observations proof of a black hole merger, and what happened to the black holes? Recent reports claim that the gravitational waves detected by LIGO match up with the signal expected from two black holes merging as predicted by general relativity.  Additionally, the masses of both black holes were estimated. Questions:  How certain are we that the detected of gravitational waves are necessarily from two black holes merging?  Since supermassive black holes are typically at the center of a host galaxy, what happened to the galaxies that contained the two merging black holes?  For example, did their host galaxies merge?    Edit After reading the answers, I understand that the signals detected by LIGO are proof of the validity of gravitational wave generational artifacts as predicted by general relativity.  When additionally gravitational waves, caused by the merger of the supermassive black holes (those which ARE indeed located in the centers of the merging galaxies) will be detected, since mergers of galaxies could be observed by the methods independent of gravitational waves such as registering the fact of the quasar appearance (). Additional questions:  Could someone offer me the historical ASTRONOMY precedent when the second degree of inference (from the mathematical model, being associated with the theory of Physics) was accepted as the discovery of the astronomical object?  Could someone give a reference to trustable scientific publication, with the subject of study being discussion of requirements satisfying claim of astronomical discovery of an astronomical object?  Have independent scientific sources (outside of members of the LIGO team) analyzed methodology and results of the LIGO signal detection, and published their conclusions with regards of what was actually discovered?
Does the shebang determine the shell which runs the script? This may be a silly question, but I ask it still. If I have declared a shebang  #!/bin/bash    in the beginning of my_shell_script.sh, so do I always have to invoke this script using bash  [my@comp]$bash my_shell_script.sh   or can I use e.g.  [my@comp]$sh my_shell_script.sh   and my script determines the running shell using the shebang? Is it the same happening with ksh shell? I'm using AIX. Layover at Narita, Japan. Do I need a transit visa? I will be transferring between two international flights at Tokyo Narita airport. I'm scheduled to depart the same day I arrive. I am planning to stay within the airport during the layover. Does anyone know if I will require a transit visa at Narita? Objective-C and Swift URL encoding How to update to the latest numpy and scipy on Ubuntu 14.04LTS On my Ubuntu 14.04LTS, for python3, I have   &gt;&gt;&gt; import numpy  &gt;&gt;&gt; import scipy  &gt;&gt;&gt; numpy.__version__  '1.8.2'  &gt;&gt;&gt; scipy.__version__  '0.13.3'   I want to update numpy and scipy to the most , I tried with the following commands  sudo pip3 install --upgrade numpy sudo pip3 install --upgrade scipy   both commands ran successfully, but the version numbers didn't change to 1.9.2 and 0.16.0 at all for both python packages (after restarting the computer). Anyone knows how to update to the most version? Thank you very much!! Monic $f(x)\in\Bbb Z[x]$ has no rational root if $f(0)\ \&\ f(1)$ odd [Parity Root Test, Modular Root Test] A polynomial problem from my old algebra textbook:     $f(x)\in\Bbb Z[x]$ with leading coefficient $1$, $\deg f(x)\ge 1$, and both $f(0)$ and $f(1)$ are odd numbers, prove:   $f(x)$ has no root within $\Bbb Q$   Eisenstein's criterion seems to be of little help here because we know virtually nothing about the coefficients. So I tried some other approach. Let $$f(x)=a_0+a_1x+a_2x^2+\cdots+a_{n-1}x^{n-1}+x^n\in \Bbb{Z}[x]$$ What we have known so far is $$f(0)=a_0\text{ is an odd number}$$ and $$f(1)=a_0+a_1+a_2+\cdots+a_{n-1}+1 \text{ is an odd number}$$ from which we can also conclude that $$f(1)-f(0)=a_1+a_2+\cdots+a_{n-1}+1\text{ is an even number}$$ To be honest I don't know how to proceed now. It isn't until just now that I realized "irreduicible" is not equivalent to "has no roots".. So all my previous attempt is fundamentally wrong.. Can anybody help or drop a hint? Best regards! More than one optional argument for newcommand The \newcommand macro allows to use an optional argument for the first parameter #1 with:  \newcommand{\mycommand}[3][defaultfor1]{blah blah blah}   Is it possible to have more than one option with \newcommand? Integer solutions to the equation $a^3+b^3+c^3=30$ No command 'bla' found, did you mean:? So, when a command is not found, by what means is the "did you mean:" list populated? What program finds these alternate commands?  What is the meaning of: "(main), (universe)..."? Can I change which program finds these? Using the same code behind file for multiple .aspx pages What is meant by a continuous-time white noise process? I have Opportunity-lookup field on Opportunity (self),  Scenario:   Opportunity A if select Opportunity B using lookup then Opportunity B's same lookup field automatically populate with Opportunity A.   I tried to achieve this using trigger - before insert/update but its failing as:  System.DmlException: Update failed. First exception on row 0 with id 006G000000DHaBlIAL; first error: SELF_REFERENCE_FROM_TRIGGER, Object (id = 006G000000DHaBl) is currently in trigger Oppy_before_INSUPD, therefore it cannot recursively update itself: [] What is the daily reputation cap and how can I hit it? I've found some questions and those two badges "Epic" and "Legendary" regarding the "daily reputation cap". What is it and how can I hit it? how to prove the chain rule? I have just learnt about the chain rule but my book doesn't mention a proof on it. I tried to write a proof myself but can't write it. So can someone please tell me about the proof for the chain rule in elementary terms because I have just started learning calculus. Laplace transform of integral constant Why didn't Isildur's Heir come forward sooner? Can I be my own trusted CA via an signed intermediate certificate? Can I get a certificate from a root CA that I can then use to sign my own web server certificates? I would, if possible, use a signed certificate as an intermediate to sign other certs.  I know that I would have to configure my systems in a certain way with "my" intermediate certificate in order to supply information about the chain of trust to my clients.   Is this possible? Are root CAs willing to sign a certificate like this? Is it expensive?  BACKGROUND  I'm familiar with the basics of SSL as it pertains to securing web traffic over HTTP. I also have a basic understanding of the way the chain of trust works, in that web traffic is secured "by default" if you encrypt with a certificate that has a valid chain all the way back to a root CA, as determined by the browser/OS vendor.  I am also aware that many of the root CAs have begun signing certificates for end users (like me) with intermediate certificates. That may require a bit more setup on my end, but otherwise, those certificates will work fine. I guess this has to do with protecting their all-valuable private key for the CA and the disaster that it would be if i were ever compromised.  EXAMPLES        Now, we are definitely not the size of any of those organizations, but they seem to be doing something like this. It would definitely make the management of these certificates a lot more palatable, especially considering one way we are expanding the reach of our e-commerce platform. Connecting multiple screens to the 2016 MacBook Pro with Touch Bar I'm thinking about buying the new MacBook Pro with 4 USB-C ports.  I want to attach two screens, mouse and keyboard and ethernet to the MacBook Pro while using the fewest number of USB-C ports possible.  So what I need is an adaptor with:   two DP or HDMI ports (or one DP port with daisy chaining support) two or more USB ports an ethernet port   Best case would be a hub to which all devices are connected with a single connection to the MacBook Pro, including power supply. Worst case if attaching the MacBook Pro to the devices would require me to use all four of USB-C ports.  Given the answers up to far, I can tell that:   Daisy chaining might or might not work with the MacBook Pro (since it requires DP1.2 which is supported by the graphics chipset, but it's uncertain if it's supported by the MacBook Pro itself) I can attach the monitors with two cables as a last resort, leaving me with two ports for the remaining peripherals.   What I still don't know:   Would daisy chaining work with a hub or does it require the first monitor to be directly attached to the MacBook Pro? Does some kind of hub exist supporting attachment of all listed devices with a single upstream connection to the MacBook Pro? How to schedule jobs in Sql server 2008 for less than 10 sec? I want to run a job every 3 seconds, however in SQL Server 2008 we cannot define an interval of less than 10 seconds.  The job is used to insert/update visitor information, and segmentation information into a database which is tracked by google search.   There are up to about 100 rows inserted in a 2 or 3 seconds. That job inserts and update the table in a database. Is there any way to schedule it using sp job scheduling configuration? I tried many ways to make a bigger screen in VirtualBox because I do not like the small size of the guest window? Is there is a way to make it big? Is there an American English equivalent of the British idiom "carrying coals to Newcastle"? I'm an American living in the Netherlands who is learning Dutch. There's an idiom in Dutch that describes performing a needless/futile activity, "water naar de zee dragen," which literally translates to "carrying water to the sea." My Dutch parents-in-law asked me if there was an English equivalent, but I couldn't think of one.  In doing   , I found that the English translation given for the this idiom is always "carrying coals to Newcastle." This was the first time I'd ever come across the phrase, and subsequent searches revealed that it was indeed of  , though one site I found did . However, neither I nor any of my culturally American friends have ever heard of this phrase.   Is there an American English idiom or phrase that carries the same connotations for carrying out a futile activity?