egg|nomz|egg changed the topic of #kspacademia to: https://gist.github.com/pdn4kd/164b9b85435d87afbec0c3a7e69d3e6d | Dogs are cats. Spiders are cat interferometers. | Космизм сегодня! | Document well, for tomorrow you may get mauled by a ネコバス. | <UmbralRaptor> egg|nomz|egg: generally if your eyes are dewing over, that's not the weather. | <ferram4> I shall beat my problems to death with an engineer.
<kmath>
<shubhamkanodia> Interesting strategy of using existing Cerenkov telescopes for Optical Laser searches. #technosignatures… https://t.co/NB5PWhl6nZ
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* egg
stabs ctrl+w
<egg>
UmbralRaptor: черенков?
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<UmbralRaptor>
egg: Черенко́в!
<UmbralRaptor>
Mainly surprise at a cosmic ray airshower detector being used for SETI.
<UmbralRaptor>
!u Чч
<Qboid>
U+0427 CYRILLIC CAPITAL LETTER CHE (Ч)
<Qboid>
U+0447 CYRILLIC SMALL LETTER CHE (ч)
* UmbralRaptor
sighs, and adds "magnetohydrodynamics" to the phone dictionary.
<kmath>
<eggleroy> "cancellation isnt real," i assure myself as i close my Белоусов and ram the degree 90 legendre polynomial with my… https://t.co/C3j5b9FBlB
<ferram4>
I don't understand this meme, but it makes too little sense to not be one
<kmath>
<dril> "jail isnt real," i assure myself as i close my eyes and ram the hallmark gift shop with my shitty bronco
<ferram4>
Ah. It sounded like dril
<egg>
ferram4: and then, as shown in the picture, it's a terrible idea to evaluate high-degree Legendre polynomials in the monomial basis
<egg>
ferram4: because the coefficients are exponentialish and alternating
<ferram4>
Those are words
<ferram4>
And in other contexts I understand them
<ferram4>
But not here, unfortunately. :P
<egg>
ferram4: the polynomial looks like (big) * x**(2n) - (bigger) * x**(2*(n+1)) + (even bigger) * x**(2*(n+3)) + ...
<egg>
ferram4: which means catastrophic cancellation unless x is very small
<egg>
x being sin latitude
<egg>
ferram4: the image here is a (gravity) map of the world, and you may notice that everything north of Hawaii is garbage and similarly in the south
<egg>
ferram4: one should instead evaluate the Legendre polynomials using a recurrence formula that doesn't entail repeatedly subtracting giant numbers from each other
<egg>
ferram4: as for Белоусов, he wrote tables of Legendre polynomials in 1956
<ferram4>
I see
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<egg>
ferram4: so, what will the name of the next FAR version be
<ferram4>
Not sure yet
<ferram4>
Will figure that out when it's ready to be released
<egg>
whitequark: also do you have additional котенькаpics
<kmath>
<✔rtphokie> Received an email from my ISP claiming I was downloading "copyrighted content such as music, movies, video or softw… https://t.co/1DcOGdA2iG
<egg>
!wpn bofh
* Qboid
gives bofh an exceptional nephroid
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<egg>
!wpn hillexed
* Qboid
gives hillexed an injective pentagon
<hillexed>
angles so sharp they have only a trivial kernel
<UmbralRaptor>
If we embed the pentagon in a hyperbolic surface…
<egg>
pentagon at infinity!
<egg>
what's the area of one of those again
<egg>
oh we can just cut the pentagon into triangles
<hillexed>
Does the Euclidean metric extend in a well-defined way to a projective plane?
<egg>
that triangulates with three triangles, so the area is 3п
<egg>
3π rather
<egg>
the hyperbolic plane is fun
<egg>
the n-gon at infinity has area (n-2)π
<egg>
okay but what about the right-angled n-gon
<egg>
(obviously n > 3)
<egg>
n = 4, the area is 0
<egg>
(square are Euclidean, so it has to be smol)
<egg>
s/quare/quares/
<Qboid>
egg meant to say: (squares are Euclidean, so it has to be smol)
<egg>
but we can derive that by triangulating, cutting two of the corners as α+β=π/2 and γ+δ=π/2, yielding an area of (π-π/2-α-γ) + (π-π/2-β-δ)= π-π/2 + π-π/2 - 2(π/2)
<egg>
hm, so I suppose (n-2)π - n(π/2) ultimately
<egg>
so the right-angled n-gon has area (n-4)/2 π, and in particular the right-angled hexagon has area π (like the triangle at infinity! and thus the pair of pants has area 2π
<egg>
from which one can deduce the area of the connected sums of k tori (k > 1) with constant curvature -1
<egg>
(since they are made by stitching pairs of pants)
<egg>
UmbralRaptor: you appear to have nerd-sniped me :-p
<UmbralRaptor>
oops :D
<bofh>
and on my way back to Paris at last~
<bofh>
!wpn egg
* Qboid
gives egg a csh modified [REDACTED]
<egg>
!wpn bofh
* Qboid
gives bofh a harmful Bose-Einstein condensate/icosahedron hybrid
<kmath>
<✔Laelaps> That’s when the attack comes not from the front, but behind, from the other Pallas cat kitten you didn’t even know… https://t.co/NFyB6vLnq4
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<UmbralRaptop>
⚴🐈
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* egg
stabs things
<egg>
bofh: UmbralRaptor: whitequark: note: the pngs and animations I made of the geopotential were the radial acceleration minus the constant term and C20, on a sphere of equatorial radius. Compared to the properly-computed gravity disturbance with respect to a reference ellipsoid, this has lower values as the latitude increases. I'm recomputing that with the proper* gravity disturbance on the ellipsoid GRS80 right now.
<egg>
which is actually significantly different, they say it's similar to the spherical approximation for the gravity anomaly, which has a max error of 302 mGal and wrms of 4.39 mGal
<egg>
still, it should at least not introduce biases towards the poles
<kmath>
<iximeow> @whitequark @0xabad1dea the documentation i was reading yesterday from a hardware vendor described I/O to a part en… https://t.co/prB0q5yE3V
<iximeow>
vb6 is fine! vb6 to describe your hardware is not fine!
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<egg>
iximeow: my third language was Ada 95 though
<egg>
iximeow: sadly from discussing the grammar with rqou it seems that VHDL has gone in a very weird direction from Ada
<rqou>
oh yeah
<rqou>
vhdl is pretty cursed
<egg>
I mean, it does have some nice bits from Ada
<egg>
(not nice on the compiler writer, but nice in the language)
<egg>
but it seems that they grew weird warts on top of that
<egg>
Ada 95's bounded error is a really nice concept though
<egg>
(I think VHDL grows on top of 83 so it probably doesn't have that)
<egg>
rqou: wherever possible, Ada 95 doesn't have the equivalent of UB (called erroneous in Ada), it has bounded errors
<egg>
which you can still reason about
<egg>
e.g., an uninitialized variable has a value of its type
<rqou>
vhdl doesn't have that
<rqou>
it's kinda yolo
<rqou>
especially for synthesis
<egg>
using it doesn't poison the execution, it just has a value of its type
<rqou>
vhdl doesn't explicitly describe how synthesis is supposed to work
<egg>
so if some integer is uninitialized and you multiply it by 0, you get 0
<egg>
if you add 1, you get an integer or a Constraint_Error
<egg>
you don't get ~nothing can be proven about this program past or future~
<rqou>
but this inhibits potential optimizations :P
<egg>
rqou: for uninitialized variable, not that much
<rqou>
but now the compiler can't delete null checks and re-introduce vulns into the kernel :P
<egg>
rqou: note that you have much richer semantics than C or C++, so you can mark parameters as out rather than in out, and *that* is something the optimizer can play with
<egg>
rqou: the language really gives the optimizer a lot to play with
<egg>
rqou: e.g. unless you go very far out of your way, you generally don't tell the compiler what size your integers are in hardware
<rqou>
oh right
<egg>
you just say "I want an integer that will work in at least this range", and get range checks, but the compiler is free to decide that 128 bits is the fastest option
<rqou>
vhdl has both that and their std_logic_vector crap
<egg>
(if you really want it to be a specific size there are representation clauses of course)
<egg>
<rqou> but now the compiler can't delete null checks and re-introduce vulns into the kernel :P << Ada 2005 has not null pointers!
<egg>
not null access
<rqou>
i mean, so does c++ but you can still make them null and cause UB
<egg>
and you can't reassign them
<egg>
they're really not like pointers morally
<rqou>
but overall yes, ada is surprisingly good
<egg>
rqou: they're a bit like Ada renames when used for local variables, and like in out parameters when used as function parameters
<egg>
rqou: Principia has actual not_null<T*> with checks because we wanted that
<egg>
<rqou> i mean, so does c++ but you can still make them null and cause UB << very technically it is by dereferencing the nullptr that you fed into it that you cause UB, you can't make the reference null without already being in UBland
<egg>
(but the fact that dereferencing the pointer doesn't always come with the nullcheck means this is academic)
<egg>
(Ada will yell Constraint_Error at you in that when dereferencing a null, because it likes yelling Constraint_Error :-p)
* egg
yells Constraint_Error at rqou
<iximeow>
!wpn rqou
* Qboid
gives rqou a titanium expression
* egg
meows at rqou
* rqou
meows back
<egg|phone|egg>
喵
<egg>
เหมียว
<egg>
!u ″ā
<Qboid>
U+2033 DOUBLE PRIME (″)
<Qboid>
U+0101 LATIN SMALL LETTER A WITH MACRON (ā)
<kmath>
<bofh453> @funimag @volatile_void My response is here's a pic from, uh, yesterday. Taken with essentially a potato with a UVC… https://t.co/oK9QExJaQV