Search found 99 matches

by Rhubarb
Thu Jan 07, 2010 5:17 pm UTC
Forum: Science
Topic: Confused about the interference of light
Replies: 14
Views: 1752

Re: Confused about the interference of light

The thing is you need a fixed phase relationship between the photons. Getting the same frequency is easy compared to fixing the phase. I think that is the main reason why different sources won't interfere quantum mechanically, it is just vanishingly likely that enough photons from each source will h...
by Rhubarb
Wed Dec 30, 2009 4:24 pm UTC
Forum: Science
Topic: Motion in a straight line (Physics)
Replies: 28
Views: 3119

Re: Motion in a straight line (Physics)

You know that the object in question starts out at s(0)=40m, and with an initial speed of v(0)=30m/s, and initial acceleration of a(0)=-9.81 ms^{-2} . So, it starts out somewhere above the ground traveling upwards, but with an acceleration pulling it back down. Try drawing the equation you have of s...
by Rhubarb
Mon Nov 02, 2009 1:26 pm UTC
Forum: Music
Topic: Post-rock thread...
Replies: 20
Views: 2352

Re: Post-rock thread...

Nobody's mentioned Slint yet. They were one of the first post rock bands (it wasn't really called post rock then I guess, but they sort of started it off), and Spiderland is an excellent album. Grails are good too- check out Black Tar Prophecies I,II and III. (Stray Dog = awesome) If you want to bra...
by Rhubarb
Fri Oct 30, 2009 12:41 pm UTC
Forum: Science
Topic: I cant do kinematics?
Replies: 15
Views: 1988

Re: I cant do kinematics?

Yeah I got 112.25s total time too. You must have picked up or missed out a minus sign. You have the two equations x=\frac{1}{2} a_1 t_1^2 +v_{02} t_2 +\frac{1}{2} a_2 t_2^2 where v_{02}=a_1 t_1 , and from v(x)=0, a_1 t_1 = -a_2 t_2 , eliminate t_2 to find t_1 , then use t=t_1 + t_2 = t_1 - \frac{a_1...
by Rhubarb
Sat Oct 17, 2009 1:30 pm UTC
Forum: Science
Topic: Time Travel and the Many Worlds Interpretation
Replies: 30
Views: 3438

Re: Time Travel and the Many Worlds Interpretation

Well the point is simply that there will be multiple yous each with different experiences. Some happy, some in pain and about to die, but there will presumably never be a you experiencing actually being dead. But why can't your experiences just stop at some point? Why are you guaranteed to find you...
by Rhubarb
Sat Oct 17, 2009 11:33 am UTC
Forum: Science
Topic: Time Travel and the Many Worlds Interpretation
Replies: 30
Views: 3438

Re: Time Travel and the Many Worlds Interpretation

I don't think quantum suicide is necessarily true, even if MWI is. Just because you might not die in some worlds doesn't mean you won't experience death in a world where you do die. I don't like the idea that consciousness is somehow quantum mechanical so that you somehow always experience one of th...
by Rhubarb
Sat Oct 17, 2009 12:45 am UTC
Forum: Science
Topic: Figures figures figures!
Replies: 12
Views: 1590

Re: Figures figures figures!

Inkscape is free and good for vector graphics.
by Rhubarb
Thu Oct 15, 2009 4:59 pm UTC
Forum: Mathematics
Topic: So, does this work as a prrof that e^pi*i=-1?
Replies: 39
Views: 4043

Re: So, does this work as a prrof that e^pi*i=-1?

I can get from \sum_{n=0}^\infty \frac{d^n}{dx'^n}\sin{(x')}\big |_{x'=0}\frac{x^n}{n!} to \sum_{n=0}^\infty (-1)^n\frac{x^{(2n+1)}}{(2n+1)!} alright, it's the bit where you show that sin(x) can even be written as a power series, and that the series above ...
by Rhubarb
Thu Oct 15, 2009 2:37 pm UTC
Forum: Mathematics
Topic: So, does this work as a prrof that e^pi*i=-1?
Replies: 39
Views: 4043

Re: So, does this work as a prrof that e^pi*i=-1?

When you eventually learn how they did it, it will blow your mind. Trust me. Don't take my word for it. When you see it one day, you will literally defecate bricks. Well, almost literally Awesome. Well explained. I did physics at uni though, and I never actually learned how to do this. The Taylor e...
by Rhubarb
Wed Oct 14, 2009 10:49 am UTC
Forum: Science
Topic: [Help] Physics problem (changing radius and gravity)
Replies: 5
Views: 883

Re: [Help] Physics problem

Another way that might make things clearer is, instead of working out the new value of V, then the new value of M, then the new value of g, write g in terms of R, so that you can see what happens to g when R changes. The equations you need are g=GM/R^2 and M=\rho \frac{4}{3}\pi R^3 . You have to mak...
by Rhubarb
Mon Oct 12, 2009 12:24 pm UTC
Forum: Science
Topic: Equilibrium Statistical Mechanics Problem
Replies: 2
Views: 669

Re: Equilibrium Statistical Mechanics Problem

Maybe try expanding the log? [imath]\ln(1+x)\approx x[/imath], or [imath]\ln{\frac{1+x}{1-x}}\approx 2x[/imath].
by Rhubarb
Fri Oct 09, 2009 12:13 pm UTC
Forum: Science
Topic: Entropy from the canonical partition function
Replies: 6
Views: 1877

Re: Entropy from the canonical partition function

I think you are supposed to find a in terms of kT such that S is a maximum.

Also your expression for lnZ should be [imath]\ln Z = N\ln (1+e^{-\beta a}) -\ln (N!)[/imath]

edit: I think I've messed this up... D:
by Rhubarb
Tue Oct 06, 2009 1:43 pm UTC
Forum: Science
Topic: What are these formulas at the bottom of the periodic table?
Replies: 26
Views: 9125

Re: What are these formulas at the bottom of the periodic table?

Planck's constant is 6.626*10^-34 Js, not 10^-23. They must be measuring it in deciterajoule seconds. Or decakiloerg seconds. :P
by Rhubarb
Mon Sep 21, 2009 2:49 pm UTC
Forum: Music
Topic: Ranking: Best Albums Ever
Replies: 73
Views: 6985

Re: Ranking: Best Albums Ever

Add: Endtroducing..... - DJ Shadow
[-] OK Computer - Radiohead

:P
by Rhubarb
Tue Sep 15, 2009 11:44 am UTC
Forum: Music
Topic: Ranking: Best Albums Ever
Replies: 73
Views: 6985

Re: Ranking: Best Albums Ever

Add The Ascension - Glenn Branca
[+] The Ascension - Glenn Branca
by Rhubarb
Fri Sep 04, 2009 8:17 pm UTC
Forum: Science
Topic: Does light exert gravity?
Replies: 69
Views: 7465

Re: Does light exert gravity?

I think I sort of get what's going on now. Although, if the radial distance turns into time, what does time turn into? I'm having trouble visualizing it :P And if you fell into a black hole does the radial distance take on all the other aspects of time, e.g how you remember the past, don't know the ...
by Rhubarb
Wed Sep 02, 2009 10:30 pm UTC
Forum: Science
Topic: Does light exert gravity?
Replies: 69
Views: 7465

Re: Does light exert gravity?

I've been wondering about this actually. What if an infalling observer emits a photon on an exactly radial path, how would it ever reach the singularity? Wouldn't it approach the event horizon but never reach it- but from the inside- in the same way that external observers see everything fall toward...
by Rhubarb
Thu Aug 27, 2009 7:03 pm UTC
Forum: Science
Topic: Does light exert gravity?
Replies: 69
Views: 7465

Re: Does light exert gravity?

All the mass wouldn't be converted to photons. Some of the mass would be converted into neutrinos which have their own mass. (The Standard Model does indicate that neutrinos are massless but for neutrino oscillation to work, neutrinos would have some mass, even if the amount of mass is minute.) Not...
by Rhubarb
Fri Aug 07, 2009 5:30 pm UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2949
Views: 710254

Re: RELATIVITY QUESTIONS! (and other common queries)

Well, what is 0*(0+1)?? (I'm sure I've made the same mistake in the past!) I think the angular momentum is never zero in the Bohr model, but it is in the full QM theory. The balance between the containment energy and electric potential explains why the Bohr radius is so small. You just get it from t...
by Rhubarb
Thu Aug 06, 2009 7:29 pm UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2949
Views: 710254

Re: RELATIVITY QUESTIONS! (and other common queries)

I don't think angular momentum quantization quite explains it- the ground state of Hydrogen has zero angular momentum, which is why it's spherically symmetric. The uncertainty principle does come into it. It says \Delta x \Delta p \geq \hbar/2 . Let's assume for a minute the electron does crash into...
by Rhubarb
Sun Aug 02, 2009 9:28 am UTC
Forum: Mathematics
Topic: log x
Replies: 36
Views: 4490

Re: log x

We should invent new notation for different bases- if ln is natural log, shouldn't we have lb and ld for binary and decimal logs? Anything else would be [imath]\log_{base}[/imath].

Or we could just go by context...
by Rhubarb
Tue Jul 14, 2009 10:48 am UTC
Forum: Science
Topic: Quantum Entanglement
Replies: 64
Views: 8422

Re: Quantum Entanglement

I haven't forgotten this thread, I'm just trying to think up a good reply. I'm trying to get it straight in my head as well. :P You're right that the two observers had better agree on what results they get, but agreement of that type does not require realism, that is, the states of the entangled sys...
by Rhubarb
Tue Jul 07, 2009 11:19 am UTC
Forum: Science
Topic: Quantum Entanglement
Replies: 64
Views: 8422

Re: Quantum Entanglement

I still don't see how this differs from the example of the cat and a dog in a box. How are these particles entangled? What shows that they are not already opposites? If you create a particle pair with 50/50 chance of being up/down or down/up how can that be entanglement? (I still don't get how you ...
by Rhubarb
Mon Jul 06, 2009 8:20 pm UTC
Forum: Science
Topic: Quantum Entanglement
Replies: 64
Views: 8422

Re: Quantum Entanglement

Okay, number one, Quantum Mechanics doesn't "Make Sense" it accurately predicts effects in physical systems we have observed. Yeah, well, you know, that's just, like, your opinion, man. Personally I think quantum mechanics does make some kind of sense when you look at the relational inter...
by Rhubarb
Mon Jul 06, 2009 11:11 am UTC
Forum: Science
Topic: Quantum Entanglement
Replies: 64
Views: 8422

Re: Quantum Entanglement

The one bit here that I'm not sure about is whether current theory is stating that measuring the entangled property of one object actually FORCES the change to the other, or simply means that we know the other is the required value. If it's the second, then it's perfectly within the bounds of relat...
by Rhubarb
Thu Jul 02, 2009 7:21 pm UTC
Forum: Music
Topic: experimental/industrial bands
Replies: 4
Views: 946

Re: experimental/industrial bands

I'd recommend Big Black, they describe themselves as punk but have a kind of industrial sound. Kind of like noise rock as well I guess. They're Steve Albini's first band. Their album Songs About Fucking is a classic.
by Rhubarb
Fri Jun 26, 2009 3:14 pm UTC
Forum: Science
Topic: Quantum Physics: Wavefunctions
Replies: 11
Views: 1765

Re: Quantum Physics: Wavefunctions

Yeah I agree with you, although I don't see why A can't be complex- if it is you just end up with a global phase that cancels, the probabilities will still be real. i.e. if [imath]A=\sqrt{3}e^{i\theta}[/imath] for arbitrary [imath]\theta[/imath] nothing changes.
by Rhubarb
Mon Jun 22, 2009 8:55 pm UTC
Forum: Music
Topic: Music to drown yourself in
Replies: 50
Views: 5540

Re: Music to drown yourself in

Absolutego by Boris. I've never got stoned but I think I know what it's like now.
by Rhubarb
Mon Jun 22, 2009 8:43 pm UTC
Forum: Science
Topic: Absolute limits to computing
Replies: 33
Views: 3328

Re: Absolute limits to computing

Information and entropy aren't really determined by the messages themselves, but just by the probabilities of getting a particular message. So if the probability of getting a 0 or a 1 is 1/2, then 111111, 101010 and 100101 each carry the same amount of information, and have the same entropy. On the ...
by Rhubarb
Mon Jun 15, 2009 10:42 am UTC
Forum: Science
Topic: Miscellaneous Science Questions
Replies: 2949
Views: 710254

Re: RELATIVITY QUESTIONS! (and other common queries)

Well inversion is in the Lorentz group, so its conserved charge would be given by the angular momentum. From x^\mu->x^\mu+\epsilon^\mu{}_\nu x^\nu where \epsilon^\mu{}_\nu is antisymmetric the conserved current is M^\rho_{\mu\nu} = x_\mu T^\rho_\nu-x_\nu T^\rho_\mu where T is the stress energy tenso...
by Rhubarb
Mon May 11, 2009 7:11 pm UTC
Forum: Music
Topic: Discover new bands game.
Replies: 56
Views: 5214

Re: Discover new bands game.

Sun City Girls - Torch of the Mystics.
by Rhubarb
Mon May 11, 2009 8:04 am UTC
Forum: Music
Topic: Discover new bands game.
Replies: 56
Views: 5214

Re: Discover new bands game.

The Shaggs - Philosophy of The World.

:P
by Rhubarb
Sat May 09, 2009 11:02 am UTC
Forum: Music
Topic: Discover new bands game.
Replies: 56
Views: 5214

Re: Discover new bands game.

Captain Beefheart and His Magic Band - Trout Mask Replica.
by Rhubarb
Wed May 06, 2009 2:20 pm UTC
Forum: Music
Topic: Discover new bands game.
Replies: 56
Views: 5214

Re: Discover new bands game.

Electric Masada - At The Mountains of Madness.

Such a good album. :)
by Rhubarb
Mon May 04, 2009 7:53 am UTC
Forum: Mathematics
Topic: Stirling's approx from method of steepest decent
Replies: 2
Views: 625

Re: Stirling's approx from method of steepest decent

Ahh I see, thanks very much. I always forget about the limits of integration. :oops:
by Rhubarb
Sat May 02, 2009 9:38 pm UTC
Forum: Mathematics
Topic: Stirling's approx from method of steepest decent
Replies: 2
Views: 625

Stirling's approx from method of steepest decent

OK, so have been given the task of using the method of steepest decent on the gamma function to find Stirling's approximation. I have basically got all the way there except for one of those annoying factors of 1/2 that always manage to crop up- except I'm certain I am doing it right, and I can't fig...
by Rhubarb
Tue Apr 21, 2009 11:41 am UTC
Forum: General
Topic: The ToneMatrix
Replies: 38
Views: 2450

Re: The ToneMatrix

Wow this is addictive! Sine waves are so pretty.

16416,32896,0,1024,32768,512,65536,256,16384,0,576,65544,288,65536,8256,0

8976,17544,34884,69666,8976,17544,34884,70434,70434,34884,17544,8976,69666,34884,17544,8976
by Rhubarb
Mon Apr 13, 2009 7:59 pm UTC
Forum: General
Topic: Matrix themed sigs for the 10th Aniversary
Replies: 11
Views: 1117

Re: Matrix themed sigs for the 10th Aniversary

Best line, Agent Smith sees Neo outside with the minigun in the chopper, and goes "No" with utter hate and contempt. Perfect. One word conveyed such an utter and pure hatred, a refusal to believe that what was about to happen was about to happen. Ahhh and then at the end Neo says 'no'... ...
by Rhubarb
Sun Apr 12, 2009 9:51 am UTC
Forum: Music
Topic: Music you put off listening to and now love
Replies: 29
Views: 2939

Re: Music you put off listening to and now love

Sonic Youth. My friend lent me a couple of their CDs a few years ago, but they didn't do anything for me. Recently I got Spotify though and I've had a chance to listen again, and now I think they're really good.
by Rhubarb
Sun Apr 12, 2009 9:36 am UTC
Forum: Language/Linguistics
Topic: Every man is a bacon lover - even Chaucer
Replies: 20
Views: 2520

Re: Every man is a bacon lover - even Chaucer

I'm vegetarian. I don't eat bacon. :) In fact, I'm pretty sure I have never had bacon (otherwise, how would I have become vegetarian? It must be the food of the gods! :P). Have you ever smelled bacon? I had a friend a few years ago who was vegetarian, but one day she smelled bacon cooking... and th...

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