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Comments:
<0> JohnFlux: are you there?
<1> Manyfold: ah wb
<0> JohnFlux: has the integration of muslims into british society failed?
<0> a manifold is something that looks locally like R^n
<0> or
<0> perhaps better to say a manifold is something that could be wholly covered by open patches which look like open subsets of R^n
<1> Manyfold: uh?
<0> what uh integration or manifold
<1> Manyfold: i spent the day picking apples
<1> ;)
<1> Manyfold: how was your day? :)
<1> integration ;)
<0> i spend the day learning pascal and the boundry interior test
<2> in relativity theory are there such things as moving frames of reference?
<1> hermes: ....
<1> hermes: frames of reference can move relative to each other
<1> hermes: you can't say one frame is "moving" and one isn't
<0> i also sdownloaded the book semantics with applications a formal introduction
<2> is the following statement correct?
<2> Reference frames can only be said to be moving relative to other ones, in the sense that the transformation between two changes with time.
<2> When this is the case two frames may be said to be moving relative to one another
<2> In and of themselves, reference frames do not change. A chosen frame of reference will not vary with time.
<2> is that statement correct?
<1> hermes: it's trying to make you understand frames of reference
<2> i want to know if my statement is right or wrong?
<1> hermes: you can't look too closely at it since it doesn't really make sense in the way its phrased
<2> i'm a layman who stupidly got ****ed into an argument
<1> hehe
<2> can pinpoint what i said is wrong?
<1> " Reference frames can only be said to be moving relative to other ones, in the sense that the transformation between two changes with time."
<1> that is correct
<2> ok
<1> "When this is the case two frames may be said to be moving relative to one another"
<1> correct also
<1> "In and of themselves, reference frames do not change. A chosen frame of reference will not vary with time." that... I'm not sure what it strictly means
<2> it means a freference frame remains the same as time progresses
<1> remain the same how
<2> well it doesn't really mean anything does it
<1> exactly
<1> i can't say it's right or wrong
<2> i think that philosophically speaking its meaningful enough
<1> well even then it's kinda wrong
<1> you can have an accelerating frame of reference
<1> or a frame of reference that changes however you want it to
<2> i still don't think acceleration is meaningful except in the sense of F=ma not working in the frame of refernece
<1> general relativity for example deals specifically with accelerating frames of reference
<2> they're just non-inertial in the sense of F=ma not holding
<2> absent some other frame to compare it to it cannot be said to be moving or not moving
<2> or accelrating or not accelerating
<1> iirc, einstein put it that a non-inertial frame is one in which there are forces you can't account for
<1> which it what you said
<2> they would be accelerating as measured against non-inertial frames
<1> s/it/is/
<2> not not accelerating per se
<2> am in on the money?
<1> you mean to "the frame would be accelerating as measured as inertial frames" ?
<1> *say
<2> yes
<1> argh. you mean to say "the frame would be accelerating as measured against inertial frames" ?
<2> that's what i did mean
<2> i guess the transnformation would be changing at a non-constant rate
<2> the transformation between the frames
<1> you do have accelerating frames
<1> that's not relative
<1> a frame is accelerating or it isn't
<1> it's not like movement which is relative
<1> otherwise, how would you know what an inertial frame is?
<2> you know when a frame is non-inertial by observing F=ma not holding
<2> for instance the corialis effect
<2> without some other frame to compare it to saying its acceleraing or not isn't meaningful
<2> but i figure for a non-inertial frame it would be accelerating vis a vis inertial frames
<2> through rotation or anything
<1> surely if you observe F=ma is not holding, then you can say it is accelerating
<1> i don't see the problem?
<2> its not the frame that's accelerating. its stuff in it
<2> a frame is a frame is a frame, without some other frame to compare it to you can't say its doing anything
<1> if you look at the stuff in the frame, and see it has forces you can't account for, then you can deduce the frame is accelerating
<2> accelerating vis a vis what?
<0> accelerating means ddot(x) neq 0
<1> hermes: spacetime :)
<2> JohnFlux, that's not a good answer
<2> in some sense it can probably be said to be accelerating vis a vis inertial frames i think
<2> relative to i mean
<0> JohnFlux: spacetime concept surfaces in special relativity not general
<0> acceleration means curved spacetime not flat
<0> hello folks
<3> hi Manyfold. I'm off to bed. laters. I wish you a good night Manyfold
<4> I'd like to have my own interstellar travel and cargo shipping business.
<4> between mars, earth, moon, maybe mercury
<5> .
<4> oh and a computer company that could fix everything between here and there.
<5> iamtheobject: sir, i seem to remember something being in the topic not too long ago about no crackpots.
<4> lol
<4> :-P
<4> dream big.
<4> I know huge rock, possibly made up of quartz, 500 kelvin or something
<6> morning | jreggelt!
<7> I'm just here because I saw "torque is not a vector" in the channel title
<7> why so?
<7> T = r x F surely...
<8> who knows
<1> irbdavid: it's because it's a psuedo-vector
<1> irbdavid: the force isn't in the direction of the vector
<1> irbdavid: the vector part of torque is the line around which it is rotated
<9> i spose, but the _torque_ is in the direction of the vector
<9> surely this is just semantics :D
<1> nah. more technically, it's a psuedo-vector because the sign changes as you change the coordinate system
<1> irbdavid: you can sort of see that, say, gravitational force causes movement in the direction of the force
<1> whereas torque doesn't
<9> yeah, but that doesnt really conflict with the definition of a vector
<9> i see your point, but i think it's a semantic argument. should you then not call a B field a vector field, since an electron doesnt move in the same direction of it?
<1> it's not a semantic argument because of the fact that it's not invariant when you reverse the direction of axises
<1> so it does have real effects that you have to deal with
<1> axis's
<1> hmm
<1> axeses
<1> bah
<9> ah well
<9> i'm not going to loose sleep over it
<9> :D
<1> irbdavid: well it's so you know when people ask about it
<1> http://en.wikipedia.org/wiki/Pseudovector
<9> heheh
<1> irbdavid: btw
<9> sup?
<1> irbdavid: you are right that a magnetic field is also a psuedo vector
<1> pseudo
<9> in that it's invariant of reference frame?
<1> this actually does have real consequences
<1> p***ing light through a magnetic field is the only optical way to change light in a way such that it's not reversible by sending light the opposite way through
<9> er....eh?
<1> consider a lens or mirror system
<9> doesnt that violate parity laws
<9> yeah, i understand what you're saying
<1> if you send light in one direction through it
<1> then the output is a certain way
<1> ah okay
<1> in a laser, you want the light to only go one way round
<1> inside the cavity
<1> so you need a way to block light that goes the wrong way round
<9> by wrong way round you mean out of phase?
<1> no no, physically the wrong way round
<1> imagine a ring cavity laser
<1> hmm a bit hard to describe on irc hehe
<1> /------------\
<1> \----[ ]----/
<1> something like that heh - imagine i had lined it up properly
<1> the [ ] bit is the laser crystal - the lasing material
<1> so that emits light, in both clockwise and anticlockwise direction
<1> the mirrors bounce the light round in a circle
<9> okay, think i follow you
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