I know it doesn't really make sense if looking at the photon from the wave point of view, but is there any law of physics which prohibits a photon from stopping completely? Thanks.
Quite a few of the questions given on this site mention a photon in vacuum having a rest frame such as it having a zero mass in its rest frame. I find this contradictory since photons must travel at the speed of light in all frames according to special relativity.  Does a photon in vacuum have a rest frame?
How to properly indent PHP/HTML mixed code? derivative bounded by a constant multiple of the function $f$ is differentiable on $[a,b]$, $f&#39;(x) \leq A|f(x)|$ where $A$ is a non-negative constant.  If $f(a)=0$ show $f(x)=0, \forall x\in [a,b]$  I imagine the proof uses the Mean Value Theorem but I have not been able to get it to work.  I know $|f(x)|=|f&#39;(c)|(x-a)$ where $c \in [a,x]$, so $|f(x)| \leq A\  |f(c)|(x-a)$ where $c\leq x$ And I guess I could sort of iterate this to keep getting a smaller $c$ but I don't see why it must go all the way to zero. How do I know whether my bike can use disk brakes? A man condemned to serve his sentence in other times Does the regularization of a divergent infinite sum yield a unique value?  I.e. do different regularization schemes acting on the same infinite sum produce the same exact value independent of the regulator?  What, exactly, do these values mean?  Or what are they?  My understanding is that they are not "convergent" values.  (Sorry in advance for being a physicist. illustrates drag coefficients for several shapes:    It is generally accepted that some variation of the teardrop/airfoil shape has the lowest drag coefficient.  I was wondering what shape has the highest drag coefficient.  The image suggests that it is a flat plate, and that would seem to be an intuitively correct answer, but is that correct?  Is there some other shape (perhaps with a concave front or back relative to motion) that has an even higher drag coefficient? whether it be vs whether it is I brought the sentences from the speech about conversation tips.     They don’t just want to know about news and the weather.   They want to know about you.   So what are three things that you have going on right now, that you can talk about.   Whether it be school, whether it be a personal relationship, whether it be a hobby that you’re involved with.   My questions:     What is the difference in nuance between 'whether it is' and 'whether it be'?   Before posting this question, I googled, and some websites say 'whether it be' is subjunctive. I don't get why it is called 'subjunctive'. Because from what I know about subjunctive, it's supposed to be past of be verb.    If I say 'whether it should be' or whether it would be', is the meaning same? chrome disable or change keyboard shortcut ctrl+shift+c developer tools console? How can I disable the Keyboard Shortcut ctrl+shift+c in Google Chrome to bring up the Developer Tools console?  I find myself trying to copy+paste content from the browser and mistakenly typing ctrl+shift+c when I really want to do ctrl+c instead.  How can I disable the current keyboard binding or change ctrl+shift+c to do the same as ctrl+c in Google Chrome? Looking for sci-fi novel I read about humanity finding alien station on orbit of Earth I am looking for a novel that I'd love to re-read it with my wife (my 13-year old self must be proud of me I guess). Key Plot points The plot was about humanity finding an alien station on an orbit of Earth. (I'm not sure if it wasn't Moon itself). On this station there were thousands of ships ready to travel so there rose a company that paid people to get on those ships and explore the galaxy. The problem was humans didn't understand how to steer those ships so they had to rely on preset targets. Of course there was no telling where particular ship was to go and fair amount of them never returned. Chronology and other relevant information I read it as an early teenager back in early 2000s. It was Polish translation of a foreign (possibly English) story. I think (not sure) that the book wasn't new at the time. It was just one of those books you dig out in a library and take to see if it's good. I don't recall cover either and even if I did it'd be of the Polish version. Additional information could be that the narration was led along the psychoanalytics of the main protagonists where he relives his memories from inside the station and his journeys. How to use 'hover' in CSS "Print" and "ui.Label" return different strings in console and in the UI in Google Earth Engine I am working on a variable label in Google Earth Engine and noticed that the label as printed in the console is not the same as the label shown on the map. Why is that? Code below:  var aoi = ee.Geometry.Polygon([[[-106.75701284923326, 42.31332966408458],           [-106.75701284923326, 42.003856624775146],           [-106.31755972423326, 42.06913460511273]]]);  var chirpsSelect = ee.ImageCollection("UCSB-CHG/CHIRPS/DAILY")             .filterDate('1985-01-01','2018-01-01')             .filter(ee.Filter.dayOfYear(3,6))             .filterBounds(aoi)  var chirpsStartImage = ee.String(chirpsSelect.first().get('system:index')) var dateStartString = ((((chirpsStartImage.slice(6,8)).cat('/')).cat(chirpsStartImage.slice(4,6))).cat('/')).cat(chirpsStartImage.slice(2,4))   var sortChirpsSelect = chirpsSelect.sort('system:index',false)  var chirpsEndImage = ee.String(sortChirpsSelect.first().get('system:index')) var dateEndString = ((((chirpsEndImage.slice(6,8)).cat('/')).cat(chirpsEndImage.slice(4,6))).cat('/')).cat(chirpsEndImage.slice(2,4)) var dateTitle = ee.String((dateStartString.cat(' to ')).cat(dateEndString))  print(dateTitle)  var dateLabel = ui.Label({   value: dateTitle })  var panel = ui.Panel() panel.add(dateLabel) Map.add(panel) Deleting my own question back commandbutton in jsf I just saw Death in Paradise Season 5 Episode 3, which features a photographer using a DSLR to shoot a fashion runway performance.  He had a flash that was a ring around the lens.   I thought that was for macro shots only, where the extreme close-up has trouble with normal flash placement.  For normal photos you want the flash far from the lens, like on a boom on a separate handle framing the camera.  I've seen some recent trendiness in having ring-shaped catch lights, but I supposed those would be positioned in the normal manner: off-angle from the lens.  I suppose if an on-camera had any effect at all it would be for some subtle fill flash.  Is this a realistic thing to see from a pro? Or is it just a cool-looking prop that doesn't really fit the situation? Rufus nor any other software can fix my 16GB usb drive after using RUFUS I wanted to make a bootable USB drive using Rufus. I opened the program went with all the default options and I clicked start BUT what I forgot to do is to select an iso because I thought it would just make the disk bootable without selecting anything. Unfortunately it did not. It gave me an error. I do not remember it because this was about 6 months ago after I gave up in fixing it. Anyway I tried to reformat it again using diskpart and it fails. With Rufus it says "ERROR while partitioning drive" and I think that was the initial error as well. Also during the struggle I got messages from windows saying that the disk is write protected and NO, there is no switch for that on the USB pendrive.   More info:     Transcend 16 GB     Rufus 1.4.9,     Frustrated student :/ Index of the center of a group in the group is not a prime number The question is to prove index of $Z(G)$ in $G$ is not a prime number.    We know that $|G:Z(G)|=|G:C_G (x)||C_G (x):Z(G)|$ where $C_G (x)$ means centralizer of $x \in G$  I want to mention that we do not want to use $G⁄Z(G)$ theorem.   We may assume that $|G:Z(G)|=p$ where $p$ is a prime. A Linear Diophantine Equation is of the following form:                                                                                        $Ax+By+C=0$, where $x_1 \leq x \leq x_2$ and $y_1 \leq y \leq y_2$.  If the value of $A,B,C,x_1,x_2,y_1,y_2$ are given and $x_1 \leq x_2$ and $y_1 \leq y_2$, then how many solutions can be found? How can I find out the total number of solutions according to the above condition. How does gravity work underground? Would the effect of gravity on me change if I were to dig a very deep hole and stand in it? If so, how would it change? Am I more likely to be pulled downwards, or pulled towards the edges of the hole? If there would be no change, why not? How do I run two commands in one line in Windows CMD? Finding files by only knowing extension?