• Physics Discussion
    973 replies, posted
So, I finish High School this year and University will be next (If I'm accepted there, of course). The thing is, my objective is having a PhD. on Astronomy, and I can choose two paths (The other one is being a physics teacher but nah ty): Bachelor's degree in Astronomy or Bachelor's degree on Physics. Which one would be better for my goal? And considering things such as employement and salary? Thank you very much, and please mind that I live in Chile. So if you need some information to be able to answer my question I'll be glad to give it to you guys.
I can't comment on Chile's job market, but I'd say physics is much more adaptable of a major. It branches out easily into other computational subjects whereas astronomy is much more focused. You can do astronomy with a physics degree, but as an astronomer you can't do much else.
I'd imagine Physics would be harder than Astronomy though
I would end up dissatisfied if I just tried to do astronomy without the physics knowledge to make sense of many of the phenomena. I'd go for a bachelor's in physics and then a PhD in astrophysics or astronomy. You could also double major in astronomy and physics if possible.
How good is physics as a degree? Im halfway through mine but unbelievably tempted to switch to Comp Sci - at points I feel like I just completely lack the skill to understand what's going on in certain things, I still to this day do not see the use in binomial expansion and shit like that, still not entirely sure what the hell eigenvectors and values are.. it's frustrating. I try to read up on it and still reads like jargon. I used to have some enthusiasm for physics but now it feels like any interest has been murdered by complex maths and horrible reading / lecture material..
I often had/have that certain concepts only made sense after I saw them for a second time in a different course. Honestly I had no idea what I was doing during my Bachelor's :v: Things are coming a bit together now, although I also forgot about half of it.
[QUOTE=Instant Mix;48306869]How good is physics as a degree? Im halfway through mine but unbelievably tempted to switch to Comp Sci - at points I feel like I just completely lack the skill to understand what's going on in certain things, I still to this day do not see the use in binomial expansion and shit like that, still not entirely sure what the hell eigenvectors and values are.. it's frustrating. I try to read up on it and still reads like jargon. I used to have some enthusiasm for physics but now it feels like any interest has been murdered by complex maths and horrible reading / lecture material..[/QUOTE] Well, chances are you'll have to learn about those things anyway in computer science. Tbh physics is not a great degree to have on its own unless you do very well and go to grad school. It can be fine if it's supplemented with internships and/or major a second minor or minor in something lucrative like computer science. How far are you into your degree? A lot of these concepts will seem obvious in a year probably. And remember you can always ask people like us for intuition if it's just not clicking!
[QUOTE=JohnnyMo1;48307122]Well, chances are you'll have to learn about those things anyway in computer science. Tbh physics is not a great degree to have on its own unless you do very well and go to grad school. It can be fine if it's supplemented with internships and/or major a second minor or minor in something lucrative like computer science. How far are you into your degree? A lot of these concepts will seem obvious in a year probably. And remember you can always ask people like us for intuition if it's just not clicking![/QUOTE] About to go into third year, but have a shitload of resits in ~a fortnights time. I guess i'm mostly struggling with the mathematics side, specifically dynamics. There's a few things I get, like breaking down things to their core, but so far the course has been "if you get X, this is what to do" and the lecturer just shoves a load of jargon on the notes & board that feels completely alien and random at points, with little to no explanation of why that's the case. The only reason I didn't completely cunt the exam was because the other half was vector calculus, which I [i] sort of [/i] get; the minute it gets into cross product index notation / greene's theoerem / stoke's theorem I immediately nosedive. I completely suck at QM, mainly because the inability to visualise the system and the only way to "view" it is by equations, completely screws me up. It was literally only a week ago that I actually sort of understood what a potential well was..
For the QM, I liked this introduction to get a better understanding of the maths: [url]https://farside.ph.utexas.edu/teaching/qm/Quantumhtml/[/url]
[QUOTE=Instant Mix;48306869]How good is physics as a degree? Im halfway through mine but unbelievably tempted to switch to Comp Sci - at points I feel like I just completely lack the skill to understand what's going on in certain things, I still to this day do not see the use in binomial expansion and shit like that, still not entirely sure what the hell eigenvectors and values are.. it's frustrating. I try to read up on it and still reads like jargon. I used to have some enthusiasm for physics but now it feels like any interest has been murdered by complex maths and horrible reading / lecture material..[/QUOTE] If you study Physics and learn to program, then you are very good, trust me. You can program physics simulations, which include programming games (one of the many examples). Or another example: robotics. [editline]28th July 2015[/editline] [QUOTE=Number-41;48307659]For the QM, I liked this introduction to get a better understanding of the maths: [url]https://farside.ph.utexas.edu/teaching/qm/Quantumhtml/[/url][/QUOTE] Is this Quantum physics currently applicable, I mean you need very expensive material to something 'quantum'. Or is it confirmed, do those equations work in real space where we live?
[QUOTE=Fourier;48309235]Is this Quantum physics currently applicable, I mean you need very expensive material to something 'quantum'. Or is it confirmed, do those equations work in real space where we live?[/QUOTE] I don't think I understand your question. Are you asking if quantum mechanics is an accurate theory?
I'm going into 10th grade, which means I'm going to take physics. Alongside that, I'm also taking AP Chem. Can these two subjects compliment each other or not at all? I'm also taking Calculus this year. So I want to know if ANY of these subjects can intermingle.
[QUOTE=JaspertheDoxie;48310803]I'm going into 10th grade, which means I'm going to take physics. Alongside that, I'm also taking AP Chem. Can these two subjects compliment each other or not at all? I'm also taking Calculus this year. So I want to know if ANY of these subjects can intermingle.[/QUOTE] Calculus and physics certainly go well. Physics and chem do, but not at the level you'll be learning them at.
[QUOTE=Instant Mix;48307438]About to go into third year, but have a shitload of resits in ~a fortnights time. I guess i'm mostly struggling with the mathematics side, specifically dynamics. There's a few things I get, like breaking down things to their core, but so far the course has been "if you get X, this is what to do" and the lecturer just shoves a load of jargon on the notes & board that feels completely alien and random at points, with little to no explanation of why that's the case. The only reason I didn't completely cunt the exam was because the other half was vector calculus, which I [i] sort of [/i] get; the minute it gets into cross product index notation / greene's theoerem / stoke's theorem I immediately nosedive. I completely suck at QM, mainly because the inability to visualise the system and the only way to "view" it is by equations, completely screws me up. It was literally only a week ago that I actually sort of understood what a potential well was..[/QUOTE] You only get better with time as long as you're willing (eager even) to do so; you have to put the effort in, but if you do you'll get there. Eventually small bits and pieces will click into place, and before you know it an entire subject area that once upon a time seemed alien will seem like a familiar old friend. If you enjoy what you do and actually want to keep doing it, then just keep at it; you'll get there eventually.
Just sat one of my resits (yay, fuck no) and it was an absolute cunter. Revised everything vaguely complicated to do with gauss' shit (kq/r^2, del(E)da = q/epsilon_{0} , all that shit), same with magnetics, and what bloody comes up apart from stupidly simple parallel plate capacitor that I couldn't remember any of the formulae for, so may have done shitly. A question came up later in the exam that actually caught my interest, regarding permanent magnets. I think it went something along the lines of this: "By Gauss' Law, magnetic fields can only be generated by the presence of a changing electrical current, or *something else* , state why permanent magnets exist and why they do not violate gauss' law". This was a pretty high marking question, about a quarter / third of the entire marks of the question block, but this was almost not remotely covered in the course. Could someone explain how this actually works? My thought was that permanent magnets are made of paramagnetic material, and that it's something to do with the combined alignment of the molecules that add up to a net total magnetic field, but then the whole "changing electric current" thing stumped me and I thought it may be something due to a free electron in the material itself?
Was this a classical electromagnetism course? Because it turns out permanent magnetism cannot be explained classically.
[QUOTE=JohnnyMo1;48464754]Was this a classical electromagnetism course? Because it turns out permanent magnetism cannot be explained classically.[/QUOTE] Absolutely no idea, it was just called "Physics of Fields & Matter", the latter part being mostly thermodynamics. Taken from the course description: [quote] This course is designed for pre-honours physics students. It provides an introduction to electromagnetic fields and the properties of matter. It serves both as a preparation for further study in physics-based degree programmes, and as a standalone course for students of other disciplines, including mathematics, chemistry, geosciences, computer science and engineering. The course consists of lectures to present new material, and workshops to develop understanding, familiarity and fluency. Physics of Fields (20 lectures) - Introduction and why electromagnetism is important. - Electric charge, Coulomb's Law. - Electric field from changes, dipoles and charge distributions. - Gauss's Law in integral form and briefly in div form. - Electrostatic potential from point changes and charge distributions and link to work. - Capacitors, dielectric materials, energy stored in electric fields. - Current, resistance, RC circuits. - Magnetic field, Lorentz force of charges and current, magnetic moment and torque on current loops. - Ampere's Law in integral form, magnetic field in solenoid and toroids. - Induction, magnetic Flux, Faraday's Law, Lenz's Law. - Inductance, current in inductor, RL circuits, energy in magnetic field. - Magnetic materials. Dia/Para/Ferro-magnetism. The Earth's magnetic field. - LC , LRC circuit, ac current, forced LRC circuit and resonance. - Maxwell's equations in integral form and discussion of physical implications. [/quote] Turns out it is in our course notes, and that the ferromagnetism is due to aligned paramagnetism - but still don't see how Gauss' theorems and such can be applied to that
Ironically I was about to say "well, really that's only true on a macro scale when you take thermodynamics into account," but if they taught you thermo... lol. See here: [url]https://en.wikipedia.org/wiki/Bohr%E2%80%93van_Leeuwen_theorem[/url] [editline]15th August 2015[/editline] Mind quoting the course notes?
[QUOTE=JohnnyMo1;48464834]Ironically I was about to say "well, really that's only true on a macro scale when you take thermodynamics into account," but if they taught you thermo... lol. See here: [URL]https://en.wikipedia.org/wiki/Bohr–van_Leeuwen_theorem[/URL] [editline]15th August 2015[/editline] Mind quoting the course notes?[/QUOTE] I am almost certain that did not appear in our notes at all. I'll quote a few bits from both fields & matter ( this isn't a breach of copyright, surely??) Fields has this: [quote]Within a full electron shell there are electrons with all allowed angular momentum and spin combinations with the total angular moment and spin, and thus the magnetic moments sum to zero. • However with partially filled electron shells there is a net angular moment and/or spin, so a net magnetic moment. Therefore certain atoms can have a permanent magnetic moment.[/quote] There's a couple equations tied with this but It's all in latex so I can't copy & paste. So is this actually just completely ignoring Gauss' theorem altogether ( as in not using it at all as part of a proof) and just mentioning that as there is a net non-zero magnetic moment, it can be present without an external current? They say there are two forms of Magnetic moment, one being from orbital angular momentum ( [img]https://latex.codecogs.com/gif.latex?%5Cdpi%7B120%7D%20%5Cvec%7B%5Cmu%7D_%7Borb%7D%20%3D%20-%5Cfrac%7Be%7D%7B2m%7D%5Cvec%7BL%7D_%7Borb%7D[/img] ) and one from spin magnetic moment ([img]https://latex.codecogs.com/gif.latex?%5Cdpi%7B120%7D%20%5Cvec%7B%5Cmu%7D_%7Bs%7D%20%3D%20-%5Cfrac%7Be%7D%7Bm%7D%5Cvec%7BS%7D[/img] ) In matter the only thing I could find regarding anything to do with magnets was this adiabatic demagnetization which doesn't appear to have any connection to it at all. I don't know why but I find thermodynamics incredibly, incredibly mind-numbing and dull. Have no idea wether it's our monotonous boring lecturer, our shitly made and laid out lecture notes, or just my plain hatred for jargon with no explanation.
I'm not sure why Gauss matters at all. A loop of current (e.g. an "orbiting" electron in a simplified atomic model) will create a magnetic field. This is no violation of Gauss' law. It's not just you. I also really hate thermo. It's just so hard to picture anything going on, and if I can't get [I]some[/I] kind of picture in my head I can't intuit anything very well. I did okay when I took it, but it bored me quite a bit. If you want to give it a go, David Tong's statistical physics lecture notes, like all of his notes, are actually quite readable: [url]http://www.damtp.cam.ac.uk/user/tong/statphys/sp.pdf[/url]
[QUOTE=JohnnyMo1;48464938]I'm not sure why Gauss matters at all. A loop of current (e.g. an "orbiting" electron in a simplified atomic model) will create a magnetic field. This is no violation of Gauss' law. It's not just you. I also really hate thermo. It's just so hard to picture anything going on, and if I can't get [I]some[/I] kind of picture in my head I can't intuit anything very well. I did okay when I took it, but it bored me quite a bit. If you want to give it a go, David Tong's statistical physics lecture notes, like all of his notes, are actually quite readable: [url]http://www.damtp.cam.ac.uk/user/tong/statphys/sp.pdf[/url][/QUOTE] My god those are actually really good notes, totally understand what you mean about being readable - thank you very much! The ones we recieved were literally bulletpointed from the getgo; it went straight into PVT diagrams with little to no exposition, just going "this is x, this is y". Felt like a dictionary rather than lecture notes; this was literally our first page in the lecture notes. See : [img]https://dl.dropboxusercontent.com/u/888382/thebestnotesever.jpg[/img] These also had huge chunks missing, to which the lecturer would scribble over and then upload as an "after-lecture" handout, so you had to really hope you could read his awful handwriting. Navigating these for revision was an absolute [i] bitch [/i].
Ew. [editline]15th August 2015[/editline] On the side of good pedagogy, here are the rest of David Tong's lecture notes if you want them: [url]http://www.damtp.cam.ac.uk/user/tong/teaching.html[/url] He's got some damn fine notes. The QFT ones especially are a really good (condensed) explanation of a ridiculously tough subject.
Advanced quantum mechanics (mainly perturbation/scattering theory) must be my least enjoyable course I've ever had. I just hate the calculations & the results. Especially partial waves, holy fuck eww :v: It's an obligatory course in my Uni though (my last one ever)...
[QUOTE=Number-41;48478343]Advanced quantum mechanics (mainly perturbation/scattering theory) must be my least enjoyable course I've ever had. I just hate the calculations & the results. Especially partial waves, holy fuck eww :v: It's an obligatory course in my Uni though (my last one ever)...[/QUOTE] Yeah. The math is pretty inelegant. I never learned scattering theory in my undergrad quantum. I tried to learn a little and got so bored. [editline]17th August 2015[/editline] Learn the highlights and move on to something fun like QFT :v:
Yeah the second part is relativistic QM (Klein-Gordon, Dirac equations) and some QFT, that's a lot neater. Instead of conclusions like "yeah look this spectrum will look a bit different because of our shitty fucking ugly approximate solution with ten billion constants that you should keep in mind" you have "will you look at that, spin appeared out of nowhere just because we tried factoring the KG equation"... [Editline]17th August[/editline] isn't this what a large part (I know it's a very diverse project) of CERN physicists do, i.e. work out cross sections? I get it that it's an awesome project, but I don't get how they could stand doing stuff like that all day :v: fucking masochists [Editline]17th August[/editline] ew ew ew [IMG]http://i.imgur.com/RGjDxrX.png[/IMG]
I think when you're working at the energies they do, you're doing cross sections in QFT since particle creation is a distinct possibility, and the formalism is pretty different (as far as I can tell).
[QUOTE=Number-41;48478596]Yeah the second part is relativistic QM (Klein-Gordon, Dirac equations) and some QFT, that's a lot neater. Instead of conclusions like "yeah look this spectrum will look a bit different because of our shitty fucking ugly approximate solution with ten billion constants that you should keep in mind" you have "will you look at that, spin appeared out of nowhere just because we tried factoring the KG equation"... [Editline]17th August[/editline] isn't this what a large part (I know it's a very diverse project) of CERN physicists do, i.e. work out cross sections? I get it that it's an awesome project, but I don't get how they could stand doing stuff like that all day :v: fucking masochists [Editline]17th August[/editline] ew ew ew [IMG]http://i.imgur.com/RGjDxrX.png[/IMG][/QUOTE] What is there hard to understand, it's black on white symbols :v: [sp]just kidding, don't kill me[/sp] [editline]20th August 2015[/editline] One question for you guys. Imagine one big coil, that is closed (both terminals are short circuited). Would dropping it down in one huge B (magnetic) field brake/stop it? [editline]20th August 2015[/editline] [QUOTE=Falubii;48309851]I don't think I understand your question. Are you asking if quantum mechanics is an accurate theory?[/QUOTE] Yes.
[QUOTE=Fourier;48309235] Is this Quantum physics currently applicable, I mean you need very expensive material to something 'quantum'. Or is it confirmed, do those equations work in real space where we live?[/QUOTE] I'm not sure (not really a quantum physicist but I did just have my third compulsory QM course :v:) but I think it is regarded as one of the most successful (accurate) theories ever in physics, at least on a very small and non relativistic scale, so the problem is that the QM regime is far from our every day environment which might explain why you asked this question. It is [URL="http://www.scientificamerican.com/article/everyday-quantum-physics/"]extremely applicable[/URL], as a very large part of our contemporary electronics required QM in their development. As for scientific areas, Magnetic Resonance Imaging, Electron Paramagnetic Resonance and Nuclear MR are also very QM-dependent. Their most basic experiments can be explained classically, but as soon as you start with more complex pulse sequences you need the density matrix formalism, which is pure QM. Compared to the equipment needed to experimentally test subatomic scale things (CERN) or sending a satellite into space, QM experiments are rather cheap I think. It's a very broad question and I'm sure there's also super-expensive QM experiments (things that require high magnetic fields are super expensive, I'm talking again MRI, NMR, ...), but in undergrad experimental physics courses there are simple experiments that have a quantum mechanical basis (the Zeeman effect, for example). [URL="https://www.youtube.com/watch?v=zPqEEZa2Gis"]Super conductivity/flux pinning[/URL] is also one of those typical and relatively cheap experiments that are based on QM. Stack Exchange has [URL="http://physics.stackexchange.com/questions/65397/quantum-mechanics-and-everyday-nature"]similar questions[/URL] with great answers: [URL="http://physics.stackexchange.com/questions/112615/why-is-it-said-that-without-quantum-mechanics-we-would-not-have-modern-computers"]Why is it said that without quantum mechanics we would not have modern computers?[/URL] [URL="http://physics.stackexchange.com/questions/70541/canonical-everyday-life-example-of-a-technology-that-could-not-work-without-huma"]Canonical everyday-life example of a technology that could not work without humans mastering QM[/URL] [editline]20th August 2015[/editline] Speaking of which, I want to brush up on electromagnetism, specifically perhaps a concise review of classical EM that transitions into electromagnetism that requires QM (superconductivity, etc.), any suggestions? Griffiths is usually pretty good.
I see, it's actually more common and "hidden" that I have previously thought. Thanks!
[QUOTE=Number-41;48501497]I'm not sure (not really a quantum physicist but I did just have my third compulsory QM course :v:) but I think it is regarded as one of the most successful (accurate) theories ever in physics, at least on a very small and non relativistic scale, so the problem is that the QM regime is far from our every day environment which might explain why you asked this question. It is [URL="http://www.scientificamerican.com/article/everyday-quantum-physics/"]extremely applicable[/URL], as a very large part of our contemporary electronics required QM in their development. As for scientific areas, Magnetic Resonance Imaging, Electron Paramagnetic Resonance and Nuclear MR are also very QM-dependent. Their most basic experiments can be explained classically, but as soon as you start with more complex pulse sequences you need the density matrix formalism, which is pure QM. Compared to the equipment needed to experimentally test subatomic scale things (CERN) or sending a satellite into space, QM experiments are rather cheap I think. It's a very broad question and I'm sure there's also super-expensive QM experiments (things that require high magnetic fields are super expensive, I'm talking again MRI, NMR, ...), but in undergrad experimental physics courses there are simple experiments that have a quantum mechanical basis (the Zeeman effect, for example). [URL="https://www.youtube.com/watch?v=zPqEEZa2Gis"]Super conductivity/flux pinning[/URL] is also one of those typical and relatively cheap experiments that are based on QM. Stack Exchange has [URL="http://physics.stackexchange.com/questions/65397/quantum-mechanics-and-everyday-nature"]similar questions[/URL] with great answers: [URL="http://physics.stackexchange.com/questions/112615/why-is-it-said-that-without-quantum-mechanics-we-would-not-have-modern-computers"]Why is it said that without quantum mechanics we would not have modern computers?[/URL] [URL="http://physics.stackexchange.com/questions/70541/canonical-everyday-life-example-of-a-technology-that-could-not-work-without-huma"]Canonical everyday-life example of a technology that could not work without humans mastering QM[/URL] [editline]20th August 2015[/editline] Speaking of which, I want to brush up on electromagnetism, specifically perhaps a concise review of classical EM that transitions into electromagnetism that requires QM (superconductivity, etc.), any suggestions? Griffiths is usually pretty good.[/QUOTE] I don't know where you'd find that. Most classical EM books I know of don't touch QM. Effects that involve both get relegated to the later sections of QM books. If you want undergrad level, Griffiths is good for EM. Jackson is the scary standard for graduate level, Zangwill is a bit of a more user friendly Jackson.
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