Recently went into Apple with my early 2011 MacBook Pro, was told that my hard drive was broken. So I decided to replace it myself with a Samsung 850 EVO, all went okay, but now when I turn it on all I get is a file with a question mark in it.  I couldn't upload anything to the SSD before installing as my Mac wasn't working at all and had a white screen with a spinning wheel. I had no new operating system on my Mac as I hadn't updated it in a while. A CD came with the drive but my laptop is having none of it it just turns on to a white screen with the mouse on it.  As you can see I'm not very technical so if any responses could be dulled down a bit that would be helpful!
I've just installed a new SSD replacing an HDD in my old (late 2008) iMac. When I switched it on all I got on screen was a question mark.   On the advice of my son I tried cmdR during switch on with no result.   I then tried alt which at least got me a cursor on the screen, but nothing else. Any suggestions? I've got everything backed up on an external Hard Drive, by the way.
With the confirmation that elements 113, 115, 117, and 118 are indeed fundamental elements that are now to be named on the periodic table, the next question is: what is the highest atomic number possible for an element? Feynman had a go at this years ago, and he derived (according to my limited understanding) that above element-137 (informally denoted 'Feynmanium') the electrons in the nearest orbit about the nucleus would be traveling at a velocity greater than the speed of light. (Note I am considering the Bohr model of the atom in this question.) I wished to demonstrate to my friends why this is and I came up with the following explanation.  According to Bohr's quantum condition, the angular momentum of an electron about the nucleus is given by $$ L=m_evr_n=n\hslash \implies r_n=\frac{n\hslash}{m_ev},$$ where $m_e$ is the mass of the electron, $v$ its velocity, $n$ an integer, and $r_n$ the radius of the $n$th possible orbit. Because we are concerned with the nearest orbit to the nucleus, $n=1$; and thus $$r=\frac{\hslash}{m_ev}.$$   Now, according to Coulomb's law, if the electron orbits about the nucleus the centripetal motion can be described by $$\frac{Ze^2}{4\pi\epsilon_or}=m_ev^2, $$ where $Z$ denotes the number of protons in the nucleus (the atomic number), and $e$ the elementary charge. Solving for $Z$ and substituting in $r$ from above yields $$Z=\frac{4\pi\epsilon_o \hslash v}{e^2}. $$ But what is $v$? Well, the maximum velocity an electron could ever have is the speed of light, and we wish to find the atomic number associated with an orbiting electron traveling at this speed, so we set $v=c$ and obtain our final result of $$Z=\frac{4\pi\epsilon_o\hslash c}{e^2}\approx 137.521,$$ which implies that for $Z&gt;137$, the electrons at a position of $n=1$ in the Bohr model would have a velocity $&gt;c$; and thus the highest atomic number achievable on the periodic table is 137.  Again, I just want to make sure this is a correct method for deriving element-137 before presenting. Perhaps one could explain how relativity plays a role here. I know Feynman used the Dirac equation to get this result...so could anyone (subsequently of course) expatiate on this in a simplistic manner? Thanks! g++ undefined reference to typeinfo Some time ago, we announced that . This has gone well and we're extremely thankful to everyone for their support and feedback. Because it has been successful so far, we're going to be extending the program to the majority of our graduated sites. Well, we've pretty much already done that, but there are quite a few sites that have ads enabled, yet still display nothing. The thing is, we don't really have an abundance of clients offering products that a  would find relevant, but Amazon has stand mixers, a selection of super fine chinois, deliciously sharp cutlery and enough cast iron to fill the Gulf Of Mexico with . Beginning as early as this week (week of 5 February 2018), our ad team is going to be hand selecting affiliate ads to be displayed on select sites. The use of inventory will of course depend on the availability of relevant ads to display which means:  Some sites might see very few, if any ads. Some topics simply don't come remotely close to orbiting anything worth advertising. Furthermore, while graduated, some sites simply don't have enough activity for ads to make sense.  Since these are hand-selected, it could take a while for ads to appear initially.  These would of course yield to inventory from clients if clients had products that were relevant to any given topic.   Nothing changes when it comes to the . If you're used to occasionally seeing a community promotion ad, you'll just notice that you'll also occasionally see an ad for something that is likely to be of interest to someone interested in the topic that your site covers. In fact, to be clear, this is simply a continuation of the announcement we made in November of 2016. We just wanted folks to know that we're going to be continuing the program where there's good potential to show relevant advertisements, even if we don't have clients lined up with a demand for it. Where can I give feedback about a certain ad on [site]? Open a meta post on your per-site meta and let us know. Please remember, the bulk of advertisements are an effort to get something small back from folks that hit the sites through search engines and are extremely unlikely to ever become contributors. Their soufflé stopped falling, and we'll probably never see them again. Maybe we can get a few bucks once they realized that copper ions help egg whites stiffen properly and buy a bowl or a proper bloom whisk. However, you're the experts on these topics and we're very likely going to listen to you. What sites, specifically? Are any sites exempt? If you're a former Stack Exchange 1.0 site and / or subsequently joined the network under a special charter, nothing changes - don't panic :) For the rest, we're just extending what we're currently doing with ads on graduated sites to also include those where there's an opportunity to make sensible use of affiliate ads. If a site has less than 15k (average) daily visits, or fewer than roughly 50k combined total posts - it might not yet be time to invest in selecting ads to be shown there. But, part of this exercise is also seeing what works best. I don't really have feedback, just some suggestions Ads aren't just an opportunity to sell stuff, they're an opportunity to really show people that we understand a given topic. That, of course, makes suggestions from people that do that stuff every day quite valuable. Post on your per-site meta and our community / ad critters will take a look. Questions? Comments? Kvetches? Let us know in an answer or comment below. If anything about the plan changes, we'll update this post to let folks know. I have been following  tutorial until I started adding nodes. The problem is that he has completely different nodes than I have. Even nodes that are created at start are different (I have Material and Output and he has Render Layers and Composite). Have I missed something or should I use different nodes than he? Does using the Console Commands negatively affect me? I'm wondering in case I get stuck in an area that I'm unable to get out of or if I clip into a wall and I suddenly can't move. I've had to disable clipping to get out of certain areas in Skyrim before but I want to make sure that things like my achievements and stuff won't shut out on my playthrough.  If I enable something, spawn an item that didn't spawn for me, or just basically use the console command to fix any bugs, what will happen achievement and game-wise? Balloons and lifting gases Hydrogen is the lightest element, so it's cable of lifting the most weight in out atmosphere (probably not the best terminology there, but you get the picture)  Would hot hydrogen (in the same sense as hot air) be able to lift even more mass? Would a higher or lower density of hydrogen in a ballon lift more? If you could have a balloon which had nothing in it (it was a vacuum inside) would that lift more than a hydrogen balloon?  Basically what are the physics to balloons and lifting?  (really not sure what to tag this, so if someone else could that'd be great) In what order are the dated ordered by? Certainly not alphanumeric order.  ls -lt sorts by modification time. But I need creation time. I was googling unsuccessfully.   I've created Aura components without any problem, but I can't figure out how enabled this:     I'm trying to enable that feature in a Dev Winter 15. Let $R$ be a ring (unital, not necessarily commutative), $M$ a finitely presented left $R$ module. Suppose $m_1,\ldots,m_n\in M$ generate $M$. This determines a surjection $f:R^n\to M$.     Must the kernel of $f$ be finitely generated?   This is true by definition if the generating set $m_1,\ldots,m_n$ is the one coming from the finite presentation of $M$. Let $a, b$ be elements of a group $G$. Suppose that a has order $5$ and that $a^3b = ba^3$. I want to show that that $ab = ba$.  Here is what I think:   We know that we have $a^1, a^2, a^3, a^4, a^5 = 1$. So, $a^4 = a^{-1}$ and $a^3 = a^{-2}$ and $a^{2} = a^{-4}$. Now,   $a^3b = ba^3$ then $a^{-2}b = ba^{-2}$ then $ba^2 = a^2b$ then $ba^{-4} = a^{-4}b$ then $a^{-1}b = ba^{-1}$ then multiply on the left and right by $a$ to get $ba=ab$. Is this correct or is there a simpler approach? Functional Analysis. Continuous extensions of linear functionals. I would like to show that a continuous functional on a subspace $W$ of a normed space $(V,\|\cdot \|)$ has a unique continuous extension to $V$ iff $W$ is dense in $V$.  I have proved $(\Leftarrow$). But the converse is currently eluding me! Help would be much appreciated! Is there a word for someone with the same name? If a person shares my name, in Dutch there is the word &quot;naamgenoot&quot;, meaning roughly 'member of the same name'.  John A: Hi, my name is &quot;John&quot;  John B: O, then we're insert solution word here!  Similarly,  'classmate' is 'klasgenoot' in Dutch 'roommate' is 'kamergenoot' in Dutch  I'm pretty sure I cannot call someone with the same name as mine a 'namemate' :)  Edit Because sceptics appear to be frustrated mightily by an apparent lack of research, there was  in chat, with no satisfactory conclusion. /Merriam Webster namesake appears to be linked to intentional name correspondance (being named after someone). There may be a US/UK English divide there.  &quot;I was named after my grandfather. I am his namesake.&quot; -   Also, the introduction seems to hint at much broader meaning:  &quot;Namesake is a term used to characterize a person, place, thing, quality, action, state, or idea that has the same, or a similar, name to another&quot;   Do you know of a better word/phrase to describe this succinctly? Sending Email via gmail smtp server in JAVA Is there a database of Linux compatible hardware? I want to know if there is a centralised community site where all Hardware is listed in terms of compatability with Linux. Something like AppDB for Wine. What is the difference between an "API," a "framework," an "IDE," and an "engine?" I know this has probably been asked before, but I couldn't find it with Google.   Given   Linux Kernel No configurations that change $HOME bash   Will ~ == $HOME be true? "This box of matches is empty" There are several Japanese books teaching Japanese students how to write in English. I found this example in  (Correcting Errors in English Composition Manuals) by Michio Kawakami and J.D. Monkman.  The authors of this book claim that this sentence is incorrect:     This box of matches is empty.   They note that a “box of matches” is a box containing matches (and not a box made for keeping matches), hence the sentence should instead be:     This matchbox is empty.   Likewise, an “empty bottle of beer” should instead be an “empty beer bottle.”  Is this actually an error that I should avoid in writing English? If so, is it a grammatical error or something else? Simple georeferenced 3D data format for building models Kill the [bugs] tag? It seems most of the questions tagged  on Stack Overflow are just intended to indicate "there's something wrong with my program", which would cover probably at least 80% of all questions on Stack Overflow.  There are some questions where it seems to refer to a possible bug in a framework or utility. I'm not sure the tag is really all that useful in that case either.  What does meta think? Is there a dollar amount that, when adding Massachusetts Sales Tax, precisely equals $200?