Invariance of the speed of light Updated +Created
This single experimental observation/idea is the basis for all of special relativity.
Special relativity is the direct result of people bending their backs to accommodate for this really weird fact.
Isomer Updated +Created
Isomers were quite confusing for early chemists, before atomic theory was widely accepted, and people where thinking mostly in terms of proportions of equations, related: Section "Isomers suggest that atoms exist".
Law of physics Updated +Created
Stack Overflow Vote Fraud Script Updated +Created
It is OK to treat things as black boxes Updated +Created
You don't need to understand the from first principles derivation of every single phenomena.
And most important of all: you should not start learning phenomena by reading the from first principles derivation.
Instead, you should see what happens in experiments, and how matches some known formula (which hopefully has been derived from first principles).
Only open the boxes (understand from first principles derivation) if the need is felt!
E.g.:
Physics is all about predicting the future. If you can predict the future with an end result, that's already predicting the future, and valid.
Japanese company Updated +Created
Jasraj Updated +Created
This dude is amazing. He apparently has many devotional songs.
Video 1.
Pandit Jasraj and Ustad Zakir Hussain - 1987 - Haveli Sangeet, Malkauns, and Bhairavi
. Source.
Mechanics Updated +Created
This section is more precisely about classical mechanics.
Physics conference Updated +Created
JavaScript Updated +Created
The language all browsers converted to as of 2019, and therefore the easiest one to distribute and most widely implemented programming language.
Hopefully will be killed by WebAssembly one day.
Because JavaScript is a relatively crap/ad-hoc language, it ended up some decent tooling to make up for that, e.g. stuff like linting via ESLint and reformatting through Prettier is much more widespread than in other languages.
JavaScript data structure are also quite a bit anemic, which makes libraries such as lodash incredibly popular. But most of that stuff should be in the stdlib.
Our JavaScript examples can be found at:
Big O notation family Updated +Created
This is a family of notations related to the big O notation. A good mnemonic summary of all notations would be:
CIA 2010 covert communication websites / 2012 Internet Census hostprobes Updated +Created
Hostprobes quick look on two ranges:
208.254.40:
... similar down

208.254.40.95	1334668500	down	no-response
208.254.40.95	1338270300	down	no-response
208.254.40.95	1338839100	down	no-response
208.254.40.95	1339361100	down	no-response
208.254.40.95	1346391900	down	no-response
208.254.40.96	1335806100	up	unknown
208.254.40.96	1336979700	up	unknown
208.254.40.96	1338840900	up	unknown
208.254.40.96	1339454700	up	unknown
208.254.40.96	1346778900	up	echo-reply (0.34s latency).
208.254.40.96	1346838300	up	echo-reply (0.30s latency).
208.254.40.97	1335840300	up	unknown
208.254.40.97	1338446700	up	unknown
208.254.40.97	1339334100	up	unknown
208.254.40.97	1346658300	up	echo-reply (0.26s latency).

... similar up

208.254.40.126	1335708900	up	unknown
208.254.40.126	1338446700	up	unknown
208.254.40.126	1339330500	up	unknown
208.254.40.126	1346494500	up	echo-reply (0.24s latency).
208.254.40.127	1335840300	up	unknown
208.254.40.127	1337793300	up	unknown
208.254.40.127	1338853500	up	unknown
208.254.40.127	1346454900	up	echo-reply (0.23s latency).

208.254.40.128	1335856500	up	unknown
208.254.40.128	1338200100	down	no-response
208.254.40.128	1338749100	down	no-response
208.254.40.128	1339334100	down	no-response
208.254.40.128	1346607900	down	net-unreach
208.254.40.129	1335699900	up	unknown

... similar down
Suggests exactly 127 - 96 + 1 = 31 IPs.
208.254.42:
... similar down

208.254.42.191	1334522700	down	no-response
208.254.42.191	1335276900	down	no-response
208.254.42.191	1335784500	down	no-response
208.254.42.191	1337845500	down	no-response
208.254.42.191	1338752700	down	no-response
208.254.42.191	1339332300	down	no-response
208.254.42.191	1346499900	down	net-unreach

208.254.42.192	1334668500	up	unknown
208.254.42.192	1336808700	up	unknown
208.254.42.192	1339334100	up	unknown
208.254.42.192	1346766300	up	echo-reply (0.40s latency).
208.254.42.193	1335770100	up	unknown
208.254.42.193	1338444900	up	unknown
208.254.42.193	1339334100	up	unknown

... similar up

208.254.42.221	1346517900	up	echo-reply (0.19s latency).
208.254.42.222	1335708900	up	unknown
208.254.42.222	1335708900	up	unknown
208.254.42.222	1338066900	up	unknown
208.254.42.222	1338747300	up	unknown
208.254.42.222	1346872500	up	echo-reply (0.27s latency).
208.254.42.223	1335773700	up	unknown
208.254.42.223	1336949100	up	unknown
208.254.42.223	1338750900	up	unknown
208.254.42.223	1339334100	up	unknown
208.254.42.223	1346854500	up	echo-reply (0.13s latency).

208.254.42.224	1335665700	down	no-response
208.254.42.224	1336567500	down	no-response
208.254.42.224	1338840900	down	no-response
208.254.42.224	1339425900	down	no-response
208.254.42.224	1346494500	down	time-exceeded

... similar down
Suggests exactly 223 - 192 + 1 = 31 IPs.
Let's have a look at the file 68: outcome: no clear hits like on 208. One wonders why.
It does appears that long sequences of ranges are a sort of fingerprint. The question is how unique it would be.
First:
n=208
time awk '$3=="up"{ print $1 }' $n | uniq -c | sed -r 's/^ +//;s/ /,/' | tee $n-up-uniq
t=$n-up-uniq.sqlite
rm -f $t
time sqlite3 $t 'create table tmp(cnt text, i text)'
time sqlite3 $t ".import --csv $n-up-uniq tmp"
time sqlite3 $t 'create table t (i integer)'
time sqlite3 $t '.load ./ip' 'insert into t select str2ipv4(i) from tmp'
time sqlite3 $t 'drop table tmp'
time sqlite3 $t 'create index ti on t(i)'
This reduces us to 2 million IP rows from the total possible 16 million IPs.
OK now just counting hits on fixed windows has way too many results:
sqlite3 208-up-uniq.sqlite "\
SELECT * FROM (
  SELECT min(i), COUNT(*) OVER (
    ORDER BY i RANGE BETWEEN 15 PRECEDING AND 15 FOLLOWING
  ) as c FROM t
) WHERE c > 20 and c < 30
"
Let's try instead consecutive ranges of length exactly 31 instead then:
sqlite3 208-up-uniq.sqlite <<EOF
SELECT f, t - f as c FROM (
  SELECT min(i) as f, max(i) as t
  FROM (SELECT i, ROW_NUMBER() OVER (ORDER BY i) - i as grp FROM t)
  GROUP BY grp
  ORDER BY i
) where c = 31
EOF
271. Hmm. A bit more than we'd like...
Another route is to also count the ups:
n=208
time awk '$3=="up"{ print $1 }' $n | uniq -c | sed -r 's/^ +//;s/ /,/' | tee $n-up-uniq-cnt
t=$n-up-uniq-cnt.sqlite
rm -f $t
time sqlite3 $t 'create table tmp(cnt text, i text)'
time sqlite3 $t ".import --csv $n-up-uniq-cnt tmp"
time sqlite3 $t 'create table t (cnt integer, i integer)'
time sqlite3 $t '.load ./ip' 'insert into t select cnt as integer, str2ipv4(i) from tmp'
time sqlite3 $t 'drop table tmp'
time sqlite3 $t 'create index ti on t(i)'
Let's see how many consecutives with counts:
sqlite3 208-up-uniq-cnt.sqlite <<EOF
SELECT f, t - f as c FROM (
  SELECT min(i) as f, max(i) as t
  FROM (SELECT i, ROW_NUMBER() OVER (ORDER BY i) - i as grp FROM t WHERE cnt >= 3)
  GROUP BY grp
  ORDER BY i
) where c > 28 and c < 32
EOF
Let's check on 66:
grep -e '66.45.179' -e '66.45.179' 66
not representative at all... e.g. several convfirmed hits are down:
66.45.179.215   1335305700      down    no-response
66.45.179.215   1337579100      down    no-response
66.45.179.215   1338765300      down    no-response
66.45.179.215   1340271900      down    no-response
66.45.179.215   1346813100      down    no-response
Cloud computing market share Updated +Created
Figure 1.
Cloud Computing market share in Q2 2022 by statista.com
. Source.
Galactic algorithm Updated +Created
Hadron Updated +Created
Monophyly Updated +Created
Basically the same as clade.
Sometimes you can debug software by staring at the code for long enough Updated +Created
Once upon a time, when Ciro Santilli had a job, he had a programming problem.
A senior developer came over, and rather than trying to run and modify the code like an idiot, which is what Ciro Santilli usually does (see also experimentalism remarks at Section "Ciro Santilli's bad old event memory"), he just stared at the code for about 10 minutes.
We knew that the problem was likely in a particular function, but it was really hard to see why things were going wrong.
After the 10 minutes of examining every line in minute detail, he said:
I think this function call has such or such weird edge case
and truly, that was the cause.
Text-based user interface Updated +Created
The perfect Middle Way between command-line interfaces and GUIs. A thing of great beauty.

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