Do we know for sure that laws of physics are time invariant?
Do the laws of physics evolve?
A question about the idea of Laplace transform In Laplace integral transform equation one multiplies the function $f(t)$ by $e^{-st}$. I read in many tutorials that $e^{-st}$ decays much faster than any other function so the integral diverges.  But what I don't understand what makes one to think to multiply a function with  $e^{-st}$ to transform it in $s$ domain? What is the motivation behind it? Why would you suddenly come up with an idea as such: "Oh there is a function $f(t)$ in time domain what can I do to transform it to complex freq. ($s$) domain? Hmm let me multiply it with $e^{-st}$ and integrate it from zero to infinity" What would have motivated this idea of multiplying and integrating for transformation? It was suggested that I should get myself a polarizer filter to get over my reflection problem. (  )  I found out that a Nikon 52mm Circular Polarizing Filter CPL   while I can get another filter for less than half the price — . (Please note that I know nothing about these filters and googled them just for the example.)  What is the difference between polarizer filters?  I need to remove the glare and nothing else — would either of the two do the magic for me? What filter do you recommend for me? Agreement With Compound Subjects Joined by And I was surfing the internet the other day when I found this phrase: Instead your precious time and attention is wasted. To my ears, it sounds wrong. But I'm not a native English speaker, so I consulted with a number of them, and some of them said that it was "is" because the adjective modifies only the noun "time" and not "attention". Others said it "is" because that's just how it is. But I still believe it should be "are". Any help is appreciated. I am trying to print a large quantity (several megabytes) of UTF-8 encoded text which consists of Chinese and Latin characters (and maybe a sprinkling of others). I would like to print it in several columns per page, in a very small, condensed font, preferably with control over line spacing. I'd quite like inter-column lines, but I can live without them. The aim is to print to PDF for transfer, as well as to paper.  I have tried enscript and a2ps, but neither of these support Unicode.  I have also tried paps, but this produces bitmapped outputs which cannot be PDF'd effectively, and also look terrible.  Is there a modern way to print UTF-8 text like this without resorting to something like constructing it manually in Python? How can I go about determining the number of unique simple paths within an undirected graph? Either for a certain length, or a range of acceptable lengths.  Recall that a simple path is a path with no cycles, so I'm talking about counting the number of paths with no cycle. Primary question: A common speaking mistake is to exchange syllables of words, saying "It's trace rhyme!" instead of saying "It's race time!", or pronouncing "kickin' chackatory" instead of "chicken cacciatore." Is there an existing name in poetry, linguistics, or English studies for switching syllables of (quasi-)consecutive words? I am not especially interested in the case when switching syllables results in interpretable homonyms or portmanteaus, like in the first example.  Secondary question: if not, what would you call it?  Tertiary question: is there somewhere a (playful?) taxonomy of fruitful or unfruitful lingual aberrations? Automatically convert quotations in the form of "abc" to become ``abc" How does the double strike mechanic interact with other mechanics like lifelink or trample? I understand that the double strike mechanic allows a creature to attack in both a first strike combat damage step and a normal combat damage step.  It's clear that when a creature with no other abilities aside from double strike is blocked that even if the defender has lethal damage marked in the first strike step that the additional damage does not carry forward to the player.  How does this view of double strike change with relation to trample and lifelink?  I believe the correct interpretations are (not accounting for other effects or abilities) that 2 times the attacker's power is marked as damage on the defender.  For trample this amount is reduced by the defender's toughness and additional damage carries forward as normal.  Similarly for lifelink the active player gains life equal to 2 times the attacker's power.  Thus a 10/10 trampling double striking life linker blocked by a 1/1 creature would deal 19 points of trample damage and the active player would gain 20 life.  Is this interpretation correct? Convert list of ints to one number? I want to use the "BackSpace" button as a shortcut key on nautilus. I want to return to the previous folder whilst browsing the Home folder, just like windows 7.   Also I want the same thing while using Firefox, In a way that when I press the shortcut key I will return to the previous web page. Allow Documentation in other Stack Exchange communities I'm a Salesforce developer and would love Documentation to be available in other Stack Exchange communities. The reason is  a lot of Salesforce developers get help, especially newer ones like myself. The developer forums and documentation on  is mediocre. It would be nice to allow users to create their own and give pack on How to modify a specified commit? I am looking for an Ubuntu version that consumes less Memory and CPU. I have read both Lubuntu and Xubuntu (The homepages, wikipedia, phoronix and other sites comparing both). But from experience, which one uses less memory and is less CPU intensive. I need to install them in very old hardware and want to persuade the owner of the hardware of the benefits of Ubuntu.  in this case I want to install 11.10 or 12.04 when it comes out. How are each behaving in those versions?  The 2 PCs I will be installing either Xubuntu or Lubuntu are:  Granpa PC:  CPU - Pentium 2 450Mhz RAM - 64MB DIMM Video - 16MB Used for - Documents and Internet. No listening to music, no looking at videos. Just using it for document writing.  The other old meat:  CPU - Pentium 3 550Mhz RAM - 128MB DIMM Video - 16MB Used for - Documents and Internet also but they want.. or maybe they are wishing for it to use it to see movies and listen to music. This one has internet. The other one does not.  UPDATE  Wanted to update this question with the test results for over 8 months worth of using Lubuntu and Xubuntu. When it comes to very old hardware, am talking about 64 MB, 128 MB or even 256 MB of RAM computers, Lubuntu is better than Xubuntu when comparing Memory usage. When it comes to CPU usage, both are the same.  This will not improve I/O Disk performance which will be the bottleneck for old computers. Also the difference in performance between Xubuntu and Lubuntu is about 10% to 20% percent in memory usage. Again, CPU usage is the same.  Now, when it comes to how responsive the Desktop is, LXDE (Lubuntu) has a much better response time than XFCE (Xubuntu). I would say about 50% or just simply noticeable to the eye. Lubuntu is similar to how Windows XP looks while Xubuntu is more like how Gnome 2 looked.  The computers (The old ones mentioned here) and 2 more are still working in excellent conditions thanks to the Ubuntu family. I also want to add I am using 13.10 for both distros. Finding information on German soldiers from World War I and World War II? Is there an uncountable family of infinite parts of $\mathbb N$ with two to two intersection finite? Support for OpenID ended on July 25, 2018 NOTE: Signing up or Logging in via OpenID is no longer officially supported from any of our sites. Currently,  is still on the internet, but we are in the process of completely removing it.    Stack Overflow was an early and strong supporter of . We built our sign up/log in flow around it. We were idealistic and had , but these hopes weren't realized. Over the years people have wondered if  is . We've had to remove support as OpenID providers  or .  The time has come to part ways. The reality is OpenID support has created a ton of complexity in our codebase and the number of users actively using OpenID simply don't justify that cost. Users have spoken with their actions. You prefer Google, Facebook and Stack Exchange (aka email/PW) based account auth.     Of our 9,813,747 accounts around one-tenth of a percent are actively using OpenID (defined as having visited a site in the past 12 months). 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If you don't see one of the three account types shown in the image below (Google, Facebook or Stack Exchange) then click the "add more logins" button to add one of them to your account.    Remember, SE OpenID accounts are really email/pw accounts handled through complicated OpenID code path. They will be migrated to a simpler email/pw only code path as a part of this change. No extra work required on your part. Capitalize fields of study? Find the subgroups of A4 I had a question I was hoping for some help on:     Find all of the subgroups of $A_4$   Here is what I know:  $A_4$ is the alternating group on 4 letters. That is it is the set of all even permutations. The elements are:  $(1), (12)(34), (13)(24), (14)(23), (123), (132), (124), (142), (134), (143), (234), (243)$   which totals to 12 elements. Which means, the subgroups should have order 1,2,3,4,6 and 12. The groups of order 1 and order 12 are trivial. I also know the groups of order 2 which are:  $[1,(12)(34)], [1, (13)(24)], [1, (14)(23)]$  but would someone be able to help me find the subgroups of order 3, 4 and 6 and be able to provide a good, easy explanation of how you got to them for me? I'm pretty sure there is no such groups of order 6, but I don't know how to explain why.  Thank you so much for your help in advance, I really appreciate it! How to derive addition of velocities without the Lorentz transformation? Installing Guest Additions causing problems