I would generally consider fields to not be substances, since substances are generally associated with matter. I know that energy is not a substance. Are electromagnetic waves a substance?
There was a reason why I constantly failed physics at school and university, and that reason was, apart from the fact I was immensely lazy, that I mentally refused to &quot;believe&quot; more advanced stuff until I understand the fundamentals (which I, eventually, never did). As such, one of the most fundamental things in physics that I still don't understand (a year after dropping out from the university) is the concept of . No one cared to explain what a field actually is, they just used to throw in a bunch of formulas and everyone was content. The school textbook definition for a field (electromagnetic in this particular case, but they were similar), as I remember it, goes like:  An electromagnetic field is a special kind of substance by which charged moving particles or physical bodies with a magnetic moment interact.  A special kind of substance, are they for real? This sounds like the authors themselves didn't quite understand what a field is so they decided to throw in a bunch of buzzwords to make it sounds right. I'm fine with the second half but a special kind of substance really bugs me, so I'd like to focus on that. Is a field material? Apparently, it isn't. It doesn't consist of particles like my laptop or even the light. If it isn't material, is it real or is it just a concept that helps to explain our observations? While this is prone to speculations, I think we can agree that in scope of this discussion particles actually do exist and laws of physics don't (the latter are nothing but human ideas so I suspect Universe doesn't &quot;know&quot; a thing about them, at least if we're talking raw matter and don't take it on metalevel where human knowledge, being a part of the Universe, makes the Universe contain laws of physics). Any laws are only a product of human thinking while the stars are likely to exist without us homo sapiens messing around. Or am I wrong here too? I hope you already see why I hate physics. Is a field not material but still real? Can something &quot;not touchable&quot; by definition be considered part of our Universe by physicists? I used to imagine that a &quot;snapshot&quot; of our Universe in time would contain information about each particle and its position, and this would've been enough to &quot;de&quot; it but I guess my programmer metaphors are largely off the track. (Oh, and I know that the uncertainty principle makes such (de)serialization impossible — I only mean that I thought the Universe can be &quot;defined&quot; as the set of all material objects in it). Is such assumption false? At this point, if fields indeed are not material but are part of the Universe, I don't really see how they are different from  except for perhaps a more geeky flavor. When I talked about this with the teacher who helped me to prepare for the exams (which I did pass, by the way, it was before I dropped out), she said to me that, if I wanted hardcore definitions,  a field is a function that returns a value for a point in space.  Now this finally makes a hell lot of sense to me but I still don't understand how mathematical functions can be a part of the Universe and shape the reality.
Why $\sqrt{-1 \times -1} \neq \sqrt{-1}^2$? Auto size image to page size in InDesign I've got an InDesign document with 100 A4 pages.   I've got 100 assets (a mixture of .jpg and .pdf files) and I want to place 1 per page. If an image is not the proportion of the A4 page I would like to get it as big as it can be on the page before it hits into the margin. Ex. if it's a portrait image it should be as large as it can be before hits the top/bottom margin. If it's a landscape image it should be as large as it can be before hits the left/right margin.   At the moment I'm dragging each file across and resizing them manually. Is it possible just drop them on the page and get them auto resized ? How to get the current time in Python header and footer of the first page of every chapter It maby be weird, I want to make header and footer for every page including the first page of each chapter, how can I do this? What exactly happens when a Weeping Angel is quantum locked? Writing C# debug output to .txt file "compare with" or "compare to" Please check both sentences and let me know, which one is correct and why?   She compares me with her boyfriend.  She compares me to her boyfriend. Dual Channel RAM vs. Quad Channel RAM I just bought a motherboard that says it supports Dual-Channel RAM. The RAM I'm looking at says it's a "Quad-Channel Kit" . Will it work with my motherboard?  EDIT: Thanks all for the replies. Here is some more info:    Here is the RAM I'm looking at:    It all looks compatible to me, I just was curious about the four channel thing. How are Contacts in Marketing Cloud counted? Salesforce bills Marketing Cloud on total number of Contacts within the system. I'd like to know what exactly is used to count these? Is this the Email Studio > All Subscribers list or the Contact Builder > All Contacts list?  When we have Marketing Cloud connector and synchronise the Contacts object, is this counted towards that number? (or only when they have been inserted into the All Subscribers / All Contacts list, as they are not done so automatically) Find the value of $\left[\frac{1}{\sqrt 2}+\frac{1}{ \sqrt 3}+......+\frac{1}{\sqrt {1000}}\right]$ Find the value of $$\left[\frac{1}{\sqrt 2}+\frac{1}{\sqrt 3}+.....+\frac{1}{\sqrt {1000}}\right]$$.Where [•] denote the greatest integer function.   I am very confused about this problem. I tried to find the upper and lower bound of the function. But I can't find any formulas to find the bounds. Somebody please help me. I was trying to dual boot elementary os with windows on my laptop (Asus Zenbook UX305). To do that I shrank the windows partition using the windows disk manager, and then used the Elementary installer's "install alongside windows" option to set up the linux partitions automatically. When I rebooted after installing I was put into the grub console. I was able to boot linux manually with the commands  grub&gt; set root=(hd0,gpt4) grub&gt; linux /boot/vmlinuz-3.19.0-26-generic root=/dev/sda4 grub&gt; initrd /boot/initrd.img-3.19.0-26-generic grub&gt; boot     and I found that running the command  grub&gt; configfile (hd0,gpt4)/boot/grub/grub.cfg   would load the normal grub menu as is supposed to happen - so there don't seem to be any problems with the config file itself. I also found that the root and prefix are on (hd0,gpt1), so running  grub&gt; set root=(hd0,gpt4) grub&gt; set prefix=(hd0,gpt4)/boot/grub grub&gt; insmod normal grub&gt; normal   also loaded the normal grub menu. So possibly the problem is that grub is looking on the wrong partition?  In my BIOS, I have a choice between using grub and the windows bootloader to boot. Selecting the windows bootloader boots me directly into windows without any problems.  However, I can't find any way to get any fixes to stick after a reboot. I've tried rerunning grub-install /dev/sda, recreating the config file with grub-mkconfig, and using the Ubuntu boot repair gui tool - none of these have worked. Is there any way to fix this short of reinstalling either or both OSs? I'd rather not have to reinstall windows if possible. Localizing Dynamic Plural Noun messages (e.g. "5 Items Processed") on iPhone using Objective-C \xymatrix undefined How to know when to change a chain? A bike shop employee used a tool he said would check the wear on the chain, and said that it should be changed.   He said it took a measurement that meant the chain had expanded, but it is still hard for me understand why I should change the chain.   He said that the reason was that the expanded chain links will cause the chain rings to wear down.   That is one argument and I have no experience with it, to know if it is true.   But are there more reasons? How do I know when the chain should be changed?   My first thought is to use it until it breaks, but it probably is not the wisest option. Checking for a file and whether it is readable and writable I'm trying to write a script that will look for a certain .txt file saved to my desktop.  I want the script to be able to check if this file exists and then check to see if it is readable and writable.  Any hints? I cast  on my opponent, whose hand has two Mountain cards. Wistful Thinking resolves and my opponent draws a  and another Mountain.  Can my opponent cast Shock before discarding it? [Firmware Bug]: TSC_DEADLINE disabled due to Errata - what should I do about this? I saw several bugs and error messages when I was looking by chance into the tool called "logs".  Being a newbie in Ubuntu I have no idea how to deal with these bugs, where to report them or how to fix them.  Any help to guide me here?  The bug I have (which is listed under important) reads:  [Firmware Bug]: TSC_DEADLINE disabled due to Errata; please update microcode to version: 0x52 (or later) I have just migrated from Windows environment. I have installed Python 3.2 in a separate directory. How can I get the python installation path in Ubuntu shell?  Is there any way I can let the shell know/choose at runtime which python version is to be used for further code execution?  Are there any environment variables and search path kind of things in Ubuntu Linux as well? If Durmstrang and Beauxbatons were hidden from common knowledge, how did people from other schools go to them for the Triwizard tournament? So in GoF, they state that Beauxbatons and Durmstrang are hidden from view and don't have their locations public.     “Durmstrang’s another wizarding school?” said Harry      “Yes,” said Hermione sniffily, “and it’s got a horrible reputation.      According to An Appraisal of Magical Education in Europe, it puts a   lot of emphasis on the Dark Arts.”      “I think I’ve heard of it,” said Ron vaguely. “Where is it? What   country?”      “Well, nobody knows, do they?” said Hermione, raising her   eyebrows.      “Er — why not?” said Harry.      “There’s traditionally been a lot of rivalry between all the magic   schools. Durmstrang and Beauxbatons like to conceal their whereabouts   so nobody can steal their secrets,” said Hermione matter-offactly.   So how do students get to the other school for the Triwizard tournament? Intersect (analysis) of polygons generating empty output