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Comments:
<0> Good night and sleep well everyone! :)
<1> hi there!
<2> evil_insid1: yo
<1> Does anyone here know an equation of a function that correlates as few as possible with a caotic noise?
<3> heh
<1> If I have a chatic noise that carries a signal, it could be recovered by correlation. It would help if the signal would not correlate with the noise, so we need a function that correlates very few.
<4> hi
<5> Hi Wilibald!
<6> if i put a hot object in a vacum, does that mean it will cool off slower than if it wasn't in a vacum?
<4> I think much slower
<4> cooling means giving thermal energy to space around the object until both have same temperatures ... ich the space is totally empty then the object has no posibility to share its temperature and the only way to reduce the temp would be radiation (for example infrared light)
<6> i see... so in space, how is nasa cooling off their equipment?
<7> radiators afaik. perhaps aided by compression like a refridgerator
<7> doesn't seem to be a big problem
<7> plastic is a better radiator than metal btw
<7> afaik
<4> and space is never a perfect vacuum. and at the speed satellites fly through space even those few atomes reduce the temperature.
<7> no any impact would greatly increase the temperature
<7> if the vacuum wasn't really really close to perfect vacuum there would be problems
<7> it would slow down quickly and fall down out of orbit
<4> oh i see ... the ship gets really hot when it enters the atmosphere ... thats right ...
<7> yep
<4> i didn't thought of that.
<7> air shifts from a cooling effect to heating at around 900km/h and they are moving around 30000km/h in orbit
<4> what happens to those atomes that they greatly heat up when colliding ?
<4> anywhere the energy for that has to come from
<7> collision is basically what heat is
<4> another school-lie uncovered ...
<7> heat is random speed inside a body
<7> as far as I know at least
<4> they told us something like that ... the slower something is the slower the electrons move inside the atome's hull
<7> molecules jiggling about and hitting eachother
<4> and theoretically at zero Kelvin they would "fall" into the proton ???
<4> thats the part which confused me ...
<7> not sure how that works. something called bose einstein condensate can be made at very low temperature which has odd properties. but that's probably a quantum mechanics effects and not many who really know that and even fewer who can explain it well
<4> well but when the ship heats up through such collisions the atomes in space must cool down ... and they're in space very cool indeed
<7> nope body collision produces heat
<4> but where should that energy come from ? and how could we exist in this world ... when billion of atoms colliding within us every second produce heat ... that means everything heats up continuousely ...
<4> when the atomes are the same and suddenly warmer then before?
<7> the energy comes from the speed. orbit is very fast
<7> what all the rocket fuel is working for
<4> yes. another thing i didn't consider ...
<4> seems to be too late to think clearly ...
<7> porobably just new stuff to you
<7> probably
<4> i have that "why-do-you-ask-such-question-you-should-known-that" -feeling when reading my posts again ... i think i finally go to bed now
<7> np. sleep well
<4> thanks for the talk
<4> good night
<8> Can someone help me understand quantum computing?
<9> do you understand QM ?
<8> qdot, not really
<9> ahh.. well.. basically an object can be in multiple states simulatenously, with certain probabilities to coerce to either of those states upon measurement
<8> so a qubit can be 1 or 0 or both -- right?
<9> uhm
<8> Like a bit, a qubit can have only two possible values - normally a 0 or a 1. The difference is that whereas a bit must be either 0 or 1, a qubit can be 0, 1, or a superposition of both.
<9> yeah.. actually, it's easier to talk about it as superposition of both
<9> with 0 being 100% 0 and 0% 1 and 1 being 0% 0 and 100%1
<8> I think that's what's causing my problem - what does superposition of both mean?
<9> ok.. it is a state. when measurement is taken, the state will have to fall in either 0 or 1
<9> for example, the thought experiment of Schrodinger's cat was invented.. imagine a cat in a box which has a poison which has 50% lethality
<8> ok - so we are talking three values -- 0, 1, or 'not 0 or 1'
<9> until you open the box to see the cat, the cat is in superposition of both alive and dead
<9> and only by making the measurement we can determine which
<8> so a qubit is indeterminabl;e till read?
<9> yes
<9> however, it is well defined, too
<8> or a superposition of both till read
<9> uhm
<9> the superposition comes from the mathematical formulation of QM in which it's literally a sum of states
<9> |q> = a |0> + b |1>
<8> no formulas please
<9> ok
<8> so is it fair to say a qubit can be one of three states?
<9> well.. not really.. the moment we make a measurement we get a result.. it doesn't mean it is in that state anymore :)
<8> when making a measurement we can get a 0 or 1 only - correct?
<9> yes
<8> now I am super confused
<8> is it like a randon value
<8> random
<8> If the quantity is measured, the projection postulate states that the state will be randomly collapsed onto one of the values in the superposition
<8> Looking at Schrdinger's cat
<10> looking FOR ?
<7> some physics inspiration: http://www.ufoevidence.org/photographs/section/recent/photo328.htm press next. there are many more
<11> lol, are you ****ing kidding me?
<12> you read my mind .. but i'm not going to get into it anymore ;)
<11> This is great, I'm going to put Signs on
<12> the movie?
<12> cause that abomination must be the most boring movie about invading aliens i have *ever* seen
<13> morning /jreggelt!
<2> DanF_DrC: you're up early
<2> hey uv
<13> hi JohnFlux
<14> hello
<3> hello
<15> your favourite troll is back
<3> :)
<16> (:
<2> 8-D
<15> ?
<15> JohnFlux: still on page 2 of carrols text?
<2> Manyfold: i got to page 12 )
<2> :)
<2> i don't really get this summing notation
<2> Manyfold: so much work. and i'm so stupid
<2> sigh
<2> ;)
<2> at the moment i'm doing a write up paper though for a summer school :/
<15> why not
<15> ?
<15> so do you know what R_abc^d really means?
<2> is R a vector or matrix
<2> Manyfold: i don't
<15> well it's the curvature tensor
<2> :/
<2> A tensor is when you want to join two spaces together, right?
<15> a tensor is defined by how they behave under transformation
<15> so a tensor equatation is valid in any coordinate patch
<2> if you have a vector {a,b,c} in space A and a vector {d,e,f} in space B then the tensor of these is the vector {{a,b,c},{d,e,f}} in space AxB ?
<2> is that right? or something :/
<15> think of a scalar as a rank 0 tensor a vector as a rank 1 tensor and a matrix as a rank 2 tensor
<15> no
<2> hmm or was it {{a,d},{a,e},{a,f},{b,d},{b,e},{b,f},.....
<2> oh yeah i read that rank stuff
<2> i didn't get that either :-)
<2> i think because it used the summing notation
<15> think of multidimensional arrays
<2> okay
<15> so rank null would be the instance of an object
<15> rank 1 would be an array and rank 2 would be an 2-dimensional array
<15> do you know what a linear transformation is?
<2> rank 3 is a 3 dimensional array?
<15> yes
<2> it's a transformation such as a translation, rotation, sheer etc
<2> ones that can be described with multiplications and additions
<2> i.e. can be described as a matrix multiply
<2> for a vector x, if you do Ax where A is a matrix, then that's a linear transformation on x
<15> let V be a vectorspace over some field
<2> close?
<2> okay
<15> let A be a linear transformation which maps V to itself
<2> the identify matrix
<15> now write that linear transformation in maztrix form
<2> is V the values, or the type?
<15> JohnFlux: not necessarily
<2> if V is say my room and the field is the magnetic fields
<2> that would be a vector space over some field, right?
<2> i mean so V is the magnetic fields in my room
<15> V is the set of all v in V obeying the vector space axioms
<2> right
<15> no a field is something like R or C
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