Let's say I have a time independent Hamiltonian so my system conserves energy. It's initially in an energy eigenstate with $E=1$ in whatever energy units you like. I measure a different observable that doesn't commute with $H$, then I measure $H$ again. I have some probability now of finding my system in an energy eigenstate with $E\neq1$.  What gives? If this was a harmonic oscillator for example, it could be the case that I end up in a state with hugely more energy. Where does this extra energy come from?  In this question, the accepted answer says that the probe particle imparts the energy:   I get that idea, but after the probe interacts with the system and I measure the energy again, then my energy may go down, stay the same or go up. How does this relate to the energy of the probe particle? I feel I'm missing something fundamental here.
Consider a particle in a potential well. Let’s assume it’s a simple harmonic oscillator potential and the particle is in its ground state with energy E0 = (1/2) &#8463;&omega;0. We measure its position (measurement-1) with a high degree of accuracy which localises the particle, corresponding to a superposition of momentum (and therefore energy) states.  Now we measure the particle’s energy (measurement-2) and happen to find that it’s E10 = (21/2) &#8463;&omega;0. Where did the extra energy come from?  In the textbooks it’s claimed that the extra energy comes from the act of observation but I wonder how that could work. Measurement-1 which probed the position of the particle can’t have delivered to it a precise amount of energy, while measurement-2 might just have been passive. No doubt there is entanglement here between the particle state and the measuring device but where, and which measurement?
I just attempted to fix a typo on a question on cooking.stackexchange.com and saw this     Oops! Your edit couldn't be submitted because:         Your edit summary must be at least 10 characters   This edit is less than 6 characters; surely more can be improved with your edit?      So, misspelled words have to just be left misspelled?  That could prevent the post from being found in a search. I am a first year Ph. D student, and I have been working on a new topic of research.  I worked day and night to prove something new and verified it. I began my Ph. D while my supervisor was on travel, but he returned before I had been here for long.  When he returned, he told me we have to stop and not continue without any reasonable reasons.  After a few months he began treating me poorly---always belittling and underestimating---although I got two grants from a top conference, made videos and podcasts, and constantly received praise for my good work and personality.    It seems that I have been treated as a competitor, not a collaborator.  Although agreeing with my approaches in private, my supervisor said false words to the committee to take the decision and stop my Ph. D work!  It is not surprising, as there was another former senior Ph. D student who I met on campus, who was not allowed to defend his Ph. D: this same supervisor claimed he was not able to finish his dissertation although he had published in a peer reviewed journal and having citation as well, it was scary and not familiar.  In front of committee, he lied, and said something without proving. I asked if he can make a detailed constructive criticism, but he could not.  All I can say that they are a gang literally, and he said words that show that he is jealous and doesn't want to see me having self confidence in my self. I know no one will believe me, but this is the truth.  Honestly, I am distressed and I'm losing sleep.  I had this dream where there were many people who saw me fail.  All things considered, I don't know whether what happened is good or bad, and I definitely don't know what I should do next!  I would be grateful for your advice and whether there is someone has encountered any similar situation. Suppose $G$ is a semigroup and it holds both left and right cancellation. Suppose $G$ is a semigroup and it holds both left and right cancellation. Also for each $a,b\in G$, $xa=b$ has solution in $G$. Prove G is a group.   I know this question looks very "old" style. First I think it's easy for me too since I already practice probelems like "semigroup, $xa=b$ and $ax=b$ have solution , then group" Or "finite semigroup, both left and right cancellation hold, then group ". But I still get stuck... My try:  First of course, for $xa=a$ , there exists $e_a$ such that $e_aa=a$. Now we need to proof $e_a$ is left identity for all elements. Then left inverse exists hence $G$ is a group. But the key is to proof $e_ab=b$ for all $b\in G$. Triggering actions when a variable is set Simple way to see a list of installed iOS apps with their storage space size? The storage on my iPhone is nearly full. Most of the space is used by apps. I'd like to see which apps consume the most space on my device.  Is there a way to get a list of the apps with their corresponding used space? By "used space I mean the installation size (bonus for added user data). How can we know that all of the results for entangled photons are not chosen when the pair is created? I have to teach the Bayes formula to some undergraduates, in the form:  $$ P(A|B) = \frac{P(A \cap B)}{P(B)} = \frac{P(B|A)P(A)}{P(B)} $$  I was wondering if anyone had any really thoughtful or alternative ways of teaching it instead of the standard approach. Vertical placing of wide accents in superscript The following code  $\widetilde{aaa} \quad L^{\widetilde{aaa}}$  $\tilde{aaa} \quad L^{\tilde{aaa}}$  $\widehat{aaa} \quad L^{\widehat{aaa}}$  $\hat{aaa} \quad L^{\hat{aaa}}$  $\overline{aaa} \quad L^{\overline{aaa}}$  $\bar{aaa} \quad L^{\bar{aaa}}$   produces the following output:    What is the reason for additional vertical spacing for \widetidle and \widehat in superscript and what can one do about it? Is there a single word that is a more vicious connotation of "competition"? Modiagram will not compile How do I make Div Container 100% width only on homepage of site? Why did Voldemort hide two Horcruxes in Hogwarts? Win32: How to hide 3rd party windows in taskbar by hWnd Force MacBook to drain the battery while connected to charger I leave my MacBook Pro on my desk nearly all the time, connected to the charger with the lid closed, connected to an external display.  I've heard this is bad for the battery health, and everyone in my office have to replace swollen batteries every couple of years. I want to regularly discharge the battery, per , but I don't want to physically unplug it because that temporarily turns off the external monitor, and then I have to reconnect the monitor.  So I am looking for a software method of disabling the power input, to force the laptop to discharge its battery to 20% and then re-enable the power input. Why haven't I received the "Curious" badge? How to get hardware specs of Android device? How can I find information on the hardware of my Android device like processor architecture, RAM, etc? I am not from EU. I have Spanish partner and we live in Spain and, because of our official relationship, I have a Spanish family resident permit. We are going to travel to the UK together for tourism. I am confused whether I need an EEA family permit or not.  I will not live there and I'm going to travel with my partner. I was told that I don't need a visa, that showing our civil union document will be sufficent. Is this correct, or do I need a visa to enter the UK?    Thank you so much for your answer. Let me give you more detail.  I hold Turkish citizenship.  My resident card exactly says that Residence Card of a Family Member of a Union Citizen " tarjeta de familiar de la union.   my case is like For example, a non-EEA spouse of a German national living in Germany will usually hold a residence permit issued under German domestic law. Therefore, a United Kingdom EEA family permit is required for travel and entry to the UK , therefore I should consider that I need to EEA Family Permit even if for touristic trip with my partner. I am trying to automate these steps so that I don't need to do this on every machines manually. I need to install latest app server software (abc.tar.gz) on all the unix boxes.  I need to do this in around 12 machines - "machine1" ... "machine12". I have a master machine "machine0" which has abc.tar.gz file so I was thinking to run my script from this machine only and install abc.tar.gz software by following below steps in all those 12 machines one by one. My unix account id is david and my process runs as golden user.  This is the steps I follow if I am installing abc.tar.gz in "machine1":  david@machine1:~$ sudo scp david@machine0:/home/david/abc.tar.gz . david@machine1:~$ sudo stop test_server david@machine1:~$ sudo su - golden golden@machine1:~$ cd /opt/process golden@machine1:/opt/process$ rm -rf * golden@machine1:/opt/process$ exit david@machine1:~$ sudo cp abc.tar.gz /opt/process david@machine1:~$ sudo chown -R golden /opt/process david@machine1:~$ sudo su - golden golden@machine1:~$ cd /opt/process golden@machine1:/opt/process$ tar -xvzf abc.tar.gz golden@machine1:/opt/process$ exit david@machine1:~$ sudo start test_server   How can I automate this so that it can do the same steps in all 12 machines one bye one? I mean install abc.tar.gz in machine1 first, then install on machine2 and go on..  I want to run this script from machine0 only.  Is there any way to automate this? Map display not filling window in QGIS on Mac? In this screenshot of QGIS, you can see that the map is not filling the window. I have tried resizing the window in various ways.   Am I missing something obvious, or is this a bug?  Versions:   MacBook Pro MacOS High Sierra 10.13.5 QGIS version 3.2.1-Bonn QGIS code branch Release 3.2 Compiled against Qt 5.9.6 Running against Qt 5.9.6 Compiled against GDAL/OGR 2.2.4 Running against GDAL/OGR 2.2.4 Compiled against GEOS 3.6.2-CAPI-1.10.2 Running against GEOS 3.6.2-CAPI-1.10.2 4d2925d6 PostgreSQL Client Version 9.6.6 SpatiaLite Version 4.4.0-RC0 QWT Version 6.1.3 QScintilla2 Version 2.10.7 PROJ.4 Version 493 Python 3.6.6 What is the simplest way to prove the Earth is round? Assume you've come in contact with a tribe of people cut off from the rest of the world, or you've gone back in time several thousand years, or (more likely) you've got a numbskull cousin.  How would you prove that the Earth is, in fact, round?