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12:55 AM
Couldn't you build a telescope on mars or just fly it away. Have it take a picture of an spot and at the same time have a telescope in farther back such as an ground telescope in the same direction take a image of the same spot at the same time? To tell if the universe is bigger than our observable universe?
And yeah I just copy and paste that since I am too lazy to rewrite it.
 
 
7 hours later…
7:44 AM
Hm
How does the configuration space work exactly in Lagrangian mechanics
Is it "The space of functions with values at $t_a, t_b$ set to the boundaries"
I'm not sure of the exact formal way to put "the variation from the Gâteau derivative is zero at the boundary"
Because that function space doesn't form a vector space
Unless the boundary is zero
Since if $x(0) = 1$, then the sum of two such functions $x_1(t) + x_2(t)$ will be $2$ at the boundary
 
 
2 hours later…
9:21 AM
> So, per pound, coal has more energy per kg.
ouch
 
9:49 AM
:-/
 
10:03 AM
@Loong you maybe interested in this
 
10:14 AM
that's why my smartphone runs on coal
 
as opposed to ?/kg :P
 
@skullpetrol omg :-(
 
yikr
interested in depressed by
 
11:13 AM
@skullpetrol I put my usual reply as an answer since it's too long for a comment.
 
thanks pal :-)
+1
 
cya
 
11:52 AM
¬¬
=|
damn
@DanielSank and his tribe have won
 
did you hear, the boxing legend César Chávez got mugged at gunpoint in Mexico City?
:(
 
@skullpetrol Cesar Chávez?
(The boxer is Julio César Chavez, and no, it's not the same name if you randomly drop bits from it)
In any case
"person gets mugged at gunpoint in Mexico City" stopped being newsworthy many decades ago, I'm afraid
 
> Mexico is currently suffering from record murder levels that have made the capital, long regarded as a relatively safe haven, increasingly prone to outbreaks of violent crime.
 
> long regarded as a relatively safe haven
lol
no
sorry
that's some amazingly short-termed memory
Mexico City was long regarded as one of the least safe cities in the country
definitely through the nineties and into the early 2000s
it's only in the late 2000s and early 2010s that the crime level elsewhere rose enough to overtake the capital
crime in Mexico City never really went down
 
12:09 PM
hmmm
 
but in any case, "oldish guy gets mugged" is pretty far down the agenda these days
 
lol
oldish boxing legend :-)
 
cases of police officers raping women are a bit more of a pressing concern
 
>8(
 
↑ exactly
so, sorry if I can't work up an indignation about a watch getting stolen
¯\ _(ツ)_/¯
 
@skullpetrol 2018 data is aging extremely fast
 
the crime level everywhere rose to overtake the capital :O
 
the new government started on 1 December 2018
so we don't have a full year of data yet
and it will take some time to process
but the environment is different now
(not necessarily for the better, though)
so any data prior to 2019 needs to be understood within that frame
@skullpetrol ::facepalm::
what?
there's more governments than the US government, you know
 
oops, i keep thinking about the silly "wall" :-)
sorry
 
sorry, but
 
12:27 PM
lol
 
I thought this was a serious conversation
that's my cue, though
see you around.
 
cya
 
 
2 hours later…
2:10 PM
@Slereah why does the value taken at the boundary matter, e.g. in extremizing the arc length $S = \int_a^b \sqrt{1+y'^2}dx$ it doesn't matter what values $y$ takes at $a$ and $b$
 
2:26 PM
@bolbteppa well there is a boundary term to the EL equation
The $h$ in $S[\phi + \varepsilon h]$ would not cancel out if we didn't have that all functions on that function space vanish at the boundary
I do recall that the Wiener process (heheheh) is defined on functions with compact support on $[a,b]$, which may be related
 
Oh right, hmm
 
I do suppose you could decompose any function with boundary condition $x(0) = x_1$ and $x(T) = x_2$ by some random function with those boundary conditions + the vector space of functions with compact support on [0,T]
mb that is the trick
 
That's a good point
About the functional being defined on a set of functions with specific values at the endpoints, is it a vector space
 
Well, as I said
it is if the boundary is zero
It seems like a fairly basic issue but I can't find anything specifically on the topic
it might be because I look it up with physicist words
and they don't care too much
 
I'm looking in Gelfand's COV
It begins by setting up linear functionals on normed function spaces and defining a norm useful for COV but then when discussing EL eq's it just talks about the 'set of functions with boundary conditions $y(a) = A, y(b) = B$' i.e. the subset within that normed vector space satisfying the BC's, I don't think they have to be a subspace
The EOM don't have to be linear so no reason why they should form a subspace in general right
 
2:56 PM
Hm
Maybe
 
ABC
3:12 PM
image url: https://ibb.co/5vpZ3bP

Text:
A point mass m rotates with an angular velocity omega around a rotation axis, which in turn rotates with angular velocity Omega in the same direction around a second axis (see figure). Identify the point where the absolute speed of the mass m assumes the minimum value and calculate the absolute speed and acceleration values at that point.

I know from relative motion that $v = v'+v_{O \ '}+ \Omega \times r'$
I our case $v = v' + \omega \times r'$ where $v'$ is velocity of mass m in the rotational system and $r'$ is position of mass in the rotational
 
 
2 hours later…
4:49 PM
Howdy hoo
I'm looking into Matsubara frequencies at the moment and I'm trying to understand it completely, sadly my condensed matter course kind of skipped the details on this
 

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