Transversal time dilation Updated 2025-07-16
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Light watch transverse to direction of motion. This case is interesting because it separates length contraction from time dilation completely.
Of course, as usual in special relativity, calling something "time dilation" leads us to mind boggling ideas of "symmetry breaking": if both frames have a light watch, how can both possibly observe the other to be time dilated?
And the answer to this, is the usual: in special relativity time and space are interwoven in a fucked up way, everything is just a spacetime event.
In this case, there are three spacetime events of interest: both clocks start at same position, your beam hits up at x=0, moving frame hits up at x>0.
Those two mentioned events are spacelike-separated events, and therefore even though they seem simultaneous to you, they are not going to be simultaneous to the moving observer!
If little clock one meter away from you tells you that at the time of some event (your light beam hit up) the moving light watch was only 50% up, this is just a number given by your one meter away watch!
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Sitare Foundation Updated 2025-07-16
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Common Crawl Updated 2025-07-16
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Amazing project, that basically makes a more searchable Wayback Machine.
A bit hard to use their data though, partly due to size, but also lack of free to use querrying mechanisms, and how obtuse Amazon S3 is to use.
Notably, aws-cli with an account is the only reliable way, everything else is way too broken, e.g. trying the to check the an index index.commoncrawl.org/CC-MAIN-2023-06/ very often 500s.
But still, their projct is amazing.
The only out-of-the-box search they seem to have is: urlsearch.commoncrawl.org/ for domains/URLs. It is good, but there could be so much more... notably IPs.
Also could should document the data shape a bit better.
To explore the data, after login:
aws s3 ls s3://commoncrawl/crawl-data/CC-MAIN-2013-20/
Copy the toplevel directory only:
aws s3 cp s3://commoncrawl/crawl-data/CC-MAIN-2013-20/ . --recursive --exclude "*/*"
Copy some wet/wat files:
aws s3 cp s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368696381249/wat/CC-MAIN-20130516092621-00000-ip-10-60-113-184.ec2.internal.warc.wat.gz .
aws s3 sync s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368696381249/wet/CC-MAIN-20130516092621-00000-ip-10-60-113-184.ec2.internal.warc.wet.gz .
Directory structrure:
  • cc-index.paths.gz (1K)
  • cc-index-table.paths.gz (1K)
  • segment.paths.gz (1.7K) Sample lines:
    crawl-data/CC-MAIN-2013-20/segments/1368696381249/
crawl-data/CC-MAIN-2013-20/segments/1368696381630/
  • index.html (2.3K)
  • wat.paths.gz (98K) Sample lines:
    crawl-data/CC-MAIN-2013-20/segments/1368696381249/wat/CC-MAIN-20130516092621-00000-ip-10-60-113-184.ec2.internal.warc.wat.gz
crawl-data/CC-MAIN-2013-20/segments/1368696381249/wat/CC-MAIN-20130516092621-00001-ip-10-60-113-184.ec2.internal.warc.wat.gz
  • wet.paths.gz (98K) Sample lines:
    crawl-data/CC-MAIN-2013-20/segments/1368696381249/wet/CC-MAIN-20130516092621-00000-ip-10-60-113-184.ec2.internal.warc.wet.gz
crawl-data/CC-MAIN-2013-20/segments/1368696381249/wet/CC-MAIN-20130516092621-00001-ip-10-60-113-184.ec2.internal.warc.wet.gz
  • warc.paths.gz (99K)
    crawl-data/CC-MAIN-2013-20/segments/1368696381249/warc/CC-MAIN-20130516092621-00000-ip-10-60-113-184.ec2.internal.warc.gz
crawl-data/CC-MAIN-2013-20/segments/1368696381249/warc/CC-MAIN-20130516092621-00001-ip-10-60-113-184.ec2.internal.warc.gz
  • segments: directgory with actual data
    • 1368696381249: one of many segments, any meaning of name?
      • CC-MAIN-20130516092621-00000-ip-10-60-113-184.ec2.internal.warc.wet.gz (142M, 334M unzipped)
        A tiny bit of metadata, and then plaintext content from the website, e.g. the second one:
        WARC/1.0
WARC-Type: conversion
WARC-Target-URI: http://004eeb5.netsolhost.com/stephensilver.htm
WARC-Date: 2013-05-18T08:11:02Z
WARC-Record-ID: <urn:uuid:773b31ba-ddc6-47a5-ae24-d08141b9944d>
WARC-Refers-To: <urn:uuid:4b1bdbff-4926-4ced-86f6-072f5bb3837a>
WARC-Block-Digest: sha1:LQFSCR2LIJQYMPTXRHWU7HAPQTVSYS3A
Content-Type: text/plain
Content-Length: 12046

Stephen Silver is a journalist and editor who specializes in the areas of politics, pop culture, film and sports. He works as an editor with the North American Publishing Co. and as a film critic with The Trend, a local newspaper in the Philadelphia area.
        No IP unfortunately.
      • CC-MAIN-20130516092621-00000-ip-10-60-113-184.ec2.internal.warc.wat.gz (329M, 1.4G unzipped)
        A lot of JSON metadata and no contents as desired. Contains IP! Some entries however are humongous with a ton of useless data, that's what bloats these so much:
        WARC/1.0
WARC-Type: metadata
WARC-Target-URI: CC-MAIN-20130516092621-00000-ip-10-60-113-184.ec2.internal.warc.gz
WARC-Date: 2013-11-22T14:51:12Z
WARC-Record-ID: <urn:uuid:ec54e493-8965-41be-b344-07596cc30b3a>
WARC-Refers-To: <urn:uuid:cfeff436-7c4c-4119-aaa4-ec2ce27ad3e1>
Content-Type: application/json
Content-Length: 1180

{"Envelope":{"Format":"WARC","WARC-Header-Length":"274","Block-Digest":"sha1:JCZOI4V3UOTXGIRLFMPLW4J2WPLAKGVR","Actual-Content-Length":"372","WARC-Header-Metadata":{"WARC-Type":"warcinfo","WARC-Filename":"CC-MAIN-20130516092621-00000-ip-10-60-113-184.ec2.internal.warc.gz","WARC-Date":"2013-11-22T14:51:12Z","Content-Length":"372","WARC-Record-ID":"<urn:uuid:cfeff436-7c4c-4119-aaa4-ec2ce27ad3e1>","Content-Type":"application/warc-fields"},"Payload-Metadata":{"Trailing-Slop-Length":"0","Actual-Content-Type":"application/warc-fields","Actual-Content-Length":"372","Headers-Corrupt":true,"WARC-Info-Metadata":{"robots":"classic","software":"Nutch 1.6 (CC)/CC WarcExport 1.0","description":"Wide crawl of the web with URLs provided by Blekko for Spring 2013","hostname":"ip-10-60-113-184.ec2.internal","format":"WARC File Format 1.0","isPartOf":"CC-MAIN-2013-20","operator":"CommonCrawl Admin","publisher":"CommonCrawl"}}},"Container":{"Compressed":true,"Gzip-Metadata":{"Footer-Length":"8","Deflate-Length":"453","Header-Length":"10","Inflated-CRC":"866052549","Inflated-Length":"650"},"Offset":"0","Filename":"CC-MAIN-20130516092621-00000-ip-10-60-113-184.ec2.internal.warc.gz"}}

WARC/1.0
WARC-Type: metadata
WARC-Target-URI: http://%20jwashington@ap.org/Content/Press-Release/2012/How-AP-reported-in-all-formats-from-tornado-stricken-regions
WARC-Date: 2013-05-18T05:48:54Z
WARC-Record-ID: <urn:uuid:d519658f-7a63-46c1-849b-4cd92332ddb8>
WARC-Refers-To: <urn:uuid:cefd363b-1fec-4590-8305-4c6fab2e095f>
Content-Type: application/json
Content-Length: 1501

{"Envelope":{"Format":"WARC","WARC-Header-Length":"433","Block-Digest":"sha1:B2B6JDSGWCUQIIUGV54SXEE25RX4SANS","Actual-Content-Length":"302","WARC-Header-Metadata":{"WARC-Type":"request","WARC-Date":"2013-05-18T05:48:54Z","WARC-Warcinfo-ID":"<urn:uuid:cfeff436-7c4c-4119-aaa4-ec2ce27ad3e1>","Content-Length":"302","WARC-Record-ID":"<urn:uuid:cefd363b-1fec-4590-8305-4c6fab2e095f>","WARC-Target-URI":"http://%20jwashington@ap.org/Content/Press-Release/2012/How-AP-reported-in-all-formats-from-tornado-stricken-regions","WARC-IP-Address":"165.1.125.44","Content-Type":"application/http; msgtype=request"},"Payload-Metadata":{"Trailing-Slop-Length":"4","HTTP-Request-Metadata":{"Headers":{"Accept-Language":"en-us,en-gb,en;q=0.7,*;q=0.3","Host":"ap.org","Accept-Encoding":"x-gzip, gzip, deflate","User-Agent":"CCBot/2.0","Accept":"text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8"},"Headers-Length":"300","Entity-Length":"0","Entity-Trailing-Slop-Bytes":"0","Request-Message":{"Method":"GET","Version":"HTTP/1.0","Path":"/Content/Press-Release/2012/How-AP-reported-in-all-formats-from-tornado-stricken-regions"},"Entity-Digest":"sha1:3I42H3S6NNFQ2MSVX7XZKYAYSCX5QBYJ"},"Actual-Content-Type":"application/http; msgtype=request"}},"Container":{"Compressed":true,"Gzip-Metadata":{"Footer-Length":"8","Deflate-Length":"455","Header-Length":"10","Inflated-CRC":"453539965","Inflated-Length":"739"},"Offset":"453","Filename":"CC-MAIN-20130516092621-00000-ip-10-60-113-184.ec2.internal.warc.gz"}}
        Let's beautify one of them to see it better:
        
{
  "Envelope": {
    "Format": "WARC",
    "WARC-Header-Length": "274",
    "Block-Digest": "sha1:JCZOI4V3UOTXGIRLFMPLW4J2WPLAKGVR",
    "Actual-Content-Length": "372",
    "WARC-Header-Metadata": {
      "WARC-Type": "warcinfo",
      "WARC-Filename": "CC-MAIN-20130516092621-00000-ip-10-60-113-184.ec2.internal.warc.gz",
      "WARC-Date": "2013-11-22T14:51:12Z",
      "Content-Length": "372",
      "WARC-Record-ID": "<urn:uuid:cfeff436-7c4c-4119-aaa4-ec2ce27ad3e1>",
      "Content-Type": "application/warc-fields"
    },
    "Payload-Metadata": {
      "Trailing-Slop-Length": "0",
      "Actual-Content-Type": "application/warc-fields",
      "Actual-Content-Length": "372",
      "Headers-Corrupt": true,
      "WARC-Info-Metadata": {
        "robots": "classic",
        "software": "Nutch 1.6 (CC)/CC WarcExport 1.0",
        "description": "Wide crawl of the web with URLs provided by Blekko for Spring 2013",
        "hostname": "ip-10-60-113-184.ec2.internal",
        "format": "WARC File Format 1.0",
        "isPartOf": "CC-MAIN-2013-20",
        "operator": "CommonCrawl Admin",
        "publisher": "CommonCrawl"
      }
    }
  },
  "Container": {
    "Compressed": true,
    "Gzip-Metadata": {
      "Footer-Length": "8",
      "Deflate-Length": "453",
      "Header-Length": "10",
      "Inflated-CRC": "866052549",
      "Inflated-Length": "650"
    },
    "Offset": "0",
    "Filename": "CC-MAIN-20130516092621-00000-ip-10-60-113-184.ec2.internal.warc.gz"
  }
}
        Fuck no IP addresses either. But other entries do have it, why not this one?
        The reason these can be huge is the HTML-Metadata section which contain all outlinks! gist.github.com/Smerity/e750f0ef0ab9aa366558#file-bbc-pretty-wat-L34
      • CC-MAIN-20130516092621-00000-ip-10-60-113-184.ec2.internal.warc.gz ()
        Obtain:
        aws s3 cp s3://commoncrawl/crawl-data/CC-MAIN-2013-20/segments/1368696381249/warc/CC-MAIN-20130516092621-00000-ip-10-60-113-184.ec2.internal.warc.gz .
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Computational problem Updated 2025-07-16
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Fandom (website) Updated 2025-07-16
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Puzzle Updated 2025-07-16
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Yitang Zhang's theorem Updated 2025-07-16
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There are infinitely many primes with a neighbor not further apart than 70 million. This was the first such finite bound to be proven, and therefore a major breakthrough.
This implies that for at least one value (or more) below 70 million there are infinitely many repetitions, but we don't know which e.g. we could have infinitely many:
(1)
or infinitely many:
(2)
or infinitely many:
(3)
or infinitely many:
(4)
but we don't know which of those.
The Prime k-tuple conjecture conjectures that it is all of them.
Also, if 70 million could be reduced down to 2, we would have a proof of the Twin prime conjecture, but this method would only work for (k, k + 2).
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Computer manufacturer Updated 2025-07-16
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This section is about companies that integrate parts and software from various other companies to make up fully working computer systems.
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Computer science course of the University of Oxford Updated 2025-07-16
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Course lists: www.cs.ox.ac.uk/teaching/courses/ True to form, courses appear to have identifiers, e.g. qi for the Quantum Information course of the University of Oxford rather than more arbitrary A1/A2/A3, B1/B2/B3, naming convention used by the Mathematics course of the University of Oxford and the Physics course of the University of Oxford, and URLs can either have years or not:
The "course materials" section of each course leads to courses.cs.ox.ac.uk/ which is paywalled by IP (accessible via Eduroam): TODO which system does it use? Some courses place their materials directly on "www.cs.ox.ac.uk", and when that is the case they are publicly accessible. So it is very much hit and miss. E.g. www.cs.ox.ac.uk/teaching/courses/2022-2023/quantum/index.html from Quantum Processes and Computation course of the University of Oxford has the assignments such as www.cs.ox.ac.uk/people/aleks.kissinger/courses/qpc2022/assignment1.pdf publicly visible, but e.g. www.cs.ox.ac.uk/teaching/courses/2022-2023/modelsofcomputation/ has nothing.
Handbook:
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Condenser microphone Updated 2025-07-16
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Cuisine by region Updated 2025-07-16
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Cycling lobbying entity Updated 2025-07-16
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Data breach Updated 2025-07-16
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List of fighting game Updated 2025-07-16
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Sci-Inspi (YouTube channel) Updated 2025-07-16
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The channel is also notable for the fact that the author makes his own music.
Video 1.
Behind the Scenes by Sci-Inspi (2020)
Source. His name is Manuael, aka Manu, and he is the chemistry lab technician at a community college.
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Scilab Updated 2025-07-16
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Secret society Updated 2025-07-16
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Bone Updated 2025-07-16
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Continent Updated 2025-07-16
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Delft OpenCourseWare Updated 2025-07-16
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They have a lot of stuff, well done.
CC BY-NC-SA by default unfortunately, but what can you do...
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