explain xkcd - User contributions [en]

Talk:2991: Beamsplitters

2024-11-19T01:00:37Z

172.68.225.192:

Pictures taken by telescope are filtered one colour at the time. If the filtered out colours could be diverted, those photons could be harvested without interfering with the scientific studies. Of course, it would still not be economically efficient. [[Special:Contributions/162.158.127.100|162.158.127.100]] 00:33, 28 September 2024 (UTC)
:Yes, a classic beam-splitter was the first color TV cameras. Three camera tubes (probably vidicons?) on the three outputs of two filtering beamsplitters. Later they did it all in one bottle; still later three chips on two beamsplitters. Color TV can be whacky. --[[User:PRR|PRR]] ([[User talk:PRR|talk]]) 01:35, 28 September 2024 (UTC)
The wavefunction explanation at the time the electron is generated is "wrong". The photovoltaic cell and the electron get entangled. See Wigner's Friend watching Schrödinger's Cat. Sebastian --[[Special:Contributions/172.68.110.188|172.68.110.188]] 16:19, 30 September 2024 (UTC)
: Please edit accordingly, with my thanks! [[Special:Contributions/172.68.22.8|172.68.22.8]] 16:31, 30 September 2024 (UTC)

[[lab.quantumflytrap.com]]

A difference of 5 magnitudes corresponds to a factor of 100 in brightness. The sun has magnitude -27, and Vega (by definition) is magnitude 0. This means that at Earth, the sun is 6e10 times brighter than Vega. Therefore a 10m diameter telescope (78.5 m^2) collects as much energy from Vega as a solar panel of size 1.23e-9 m^2, or a square 35 microns on a side. The brightest star, Sirius, is magnitude -1.46, which makes our 10m telescope equivalent to a square solar panel 70 microns on a side. (This calculation is a bit rough. To do it properly, we'd need to know the wavelength band which the solar panel can transform into electricity, and the magnitudes of the sun and star at that specific wavelength band.) [[Special:Contributions/198.41.236.144|198.41.236.144]] 03:08, 2 October 2024 (UTC)
:Suppose that telescope was aimed towards Vega on a sunny day with a clear sky, with a path that didn't intersect the sun. How much brighter is the sky itself, from scattered sunlight, than Vega? There are a lot of factors that would make a great deal of difference, but suppose we assume that the sun is directly overhead. [[User:BunsenH|BunsenH]] ([[User talk:BunsenH|talk]]) 19:42, 2 October 2024 (UTC)
::At first approximation, similar to a panel of the size of the aperture. Although the difference between the power landing on an 'end cap' panel and reaching down into a reciever down the length of the 'telescope tube' would be that the panel receives light from 2π steradians of sky (albeit only at top efficiency towards the perpendicular), whilst the better analogue might be a panel, the size of the barrel and ''down'' the barrel, set back where the primary mirror is so as to receiver (effectively, more or less) collimated light from the top end. Probably equal to a slightly overcast whole-sky (assuming it's a panel with good blue-absorption qualities and decent cross-spectrum sensitivity, rather than heavily reliant upon solar energy bands).
::The next question is whether the concentration of this viewport of the sky benefits from being concentrated via the lensing, but I suspect not. If anything, the localised heating might lower the efficiency, etc. [[Special:Contributions/172.69.195.103|172.69.195.103]] 21:42, 2 October 2024 (UTC)

Talk:2991: Beamsplitters

2024-11-19T01:00:12Z

172.68.225.192:

Pictures taken by telescope are filtered one colour at the time. If the filtered out colours could be diverted, those photons could be harvested without interfering with the scientific studies. Of course, it would still not be economically efficient. [[Special:Contributions/162.158.127.100|162.158.127.100]] 00:33, 28 September 2024 (UTC)
:Yes, a classic beam-splitter was the first color TV cameras. Three camera tubes (probably vidicons?) on the three outputs of two filtering beamsplitters. Later they did it all in one bottle; still later three chips on two beamsplitters. Color TV can be whacky. --[[User:PRR|PRR]] ([[User talk:PRR|talk]]) 01:35, 28 September 2024 (UTC)
The wavefunction explanation at the time the electron is generated is "wrong". The photovoltaic cell and the electron get entangled. See Wigner's Friend watching Schrödinger's Cat. Sebastian --[[Special:Contributions/172.68.110.188|172.68.110.188]] 16:19, 30 September 2024 (UTC)
: Please edit accordingly, with my thanks! [[Special:Contributions/172.68.22.8|172.68.22.8]] 16:31, 30 September 2024 (UTC)

[lab.quantumflytrap.com]

A difference of 5 magnitudes corresponds to a factor of 100 in brightness. The sun has magnitude -27, and Vega (by definition) is magnitude 0. This means that at Earth, the sun is 6e10 times brighter than Vega. Therefore a 10m diameter telescope (78.5 m^2) collects as much energy from Vega as a solar panel of size 1.23e-9 m^2, or a square 35 microns on a side. The brightest star, Sirius, is magnitude -1.46, which makes our 10m telescope equivalent to a square solar panel 70 microns on a side. (This calculation is a bit rough. To do it properly, we'd need to know the wavelength band which the solar panel can transform into electricity, and the magnitudes of the sun and star at that specific wavelength band.) [[Special:Contributions/198.41.236.144|198.41.236.144]] 03:08, 2 October 2024 (UTC)
:Suppose that telescope was aimed towards Vega on a sunny day with a clear sky, with a path that didn't intersect the sun. How much brighter is the sky itself, from scattered sunlight, than Vega? There are a lot of factors that would make a great deal of difference, but suppose we assume that the sun is directly overhead. [[User:BunsenH|BunsenH]] ([[User talk:BunsenH|talk]]) 19:42, 2 October 2024 (UTC)
::At first approximation, similar to a panel of the size of the aperture. Although the difference between the power landing on an 'end cap' panel and reaching down into a reciever down the length of the 'telescope tube' would be that the panel receives light from 2π steradians of sky (albeit only at top efficiency towards the perpendicular), whilst the better analogue might be a panel, the size of the barrel and ''down'' the barrel, set back where the primary mirror is so as to receiver (effectively, more or less) collimated light from the top end. Probably equal to a slightly overcast whole-sky (assuming it's a panel with good blue-absorption qualities and decent cross-spectrum sensitivity, rather than heavily reliant upon solar energy bands).
::The next question is whether the concentration of this viewport of the sky benefits from being concentrated via the lensing, but I suspect not. If anything, the localised heating might lower the efficiency, etc. [[Special:Contributions/172.69.195.103|172.69.195.103]] 21:42, 2 October 2024 (UTC)

404: Not Found

2024-11-14T04:16:45Z

172.68.225.192:

{{Quote|I have always been of the opinion that http://xkcd.com/404/ is an actual comic, if a slightly avant-garde one. I actually went out of my way to modify the 'random' button to include it, but that annoyed too many people—most of whom reasonably assumed it was a bug—and I eventually undid it.|[[Randall Munroe]], ''[https://web.archive.org/web/20190328010454/https://plus.google.com/111588569124648292310/posts/j6w9DkYApya Source]''}}

This was the first [[:Category:April fools' comics|April fools' comic]] released by [[Randall Munroe|Randall]]. The next became [[880: Headache]], released on Friday April 1, 2011. The [[403: Convincing Pickup Line|previous comic]] was released on Monday March 31, 2008, and the [[405: Journal 3|next comic]] was released on Wednesday April 2, 2008. This comic was released between the two, on Tuesday April 1st 2008.

The "{{w|HTTP 404|404 Not Found}}" error message is a HTTP standard response code to indicate that the browser was able to communicate with a given {{w|Server (computing)|server}}, but the server could not find what was requested. The error may also be used when a server does not wish to disclose whether it has the requested information. The website hosting server will typically generate a "404 Not Found" web page when a user attempts to follow a broken or dead link; hence the 404 error is one of the most recognizable errors encountered on the internet. (For example, a nonexistent page like https://xkcd.com/fooo will display an identical error message.) Randall deliberately skipped the comic number 404, so when people try to view it, they get a "404 Not Found" error instead. He has said that he considers 404 [https://web.archive.org/web/20190328010454/https://plus.google.com/111588569124648292310/posts/j6w9DkYApya an "actual comic"] and that for a time he made it possible to find it using the "random" button on [https://xkcd.com xkcd.com].

It might initially appear coincidental that the [[403: Convincing Pickup Line|comic 403]] was published just a day before April 1, 2008. However, Randall likely became aware of this possible correlation prior to that specific date, so he had an opportunity to influence the comic's release date. In May 2007 and in November 2007, Randall published the [[:Category:Choices|Choices series]] and the [[:Category:1337|1337 series]] respectively, each over five consecutive days, less than six months before April Fool's Day. This deliberate action shifted the release date of comic 403 from April 10, 2008, to March 31, 2008, when it was actually published. This alteration allowed for comic 404 to be posted on the April Fool's Day without abruptly disrupting the normal comic release schedule.

This comic was featured in [[1975: Right Click]] (in File > Open > C:\ > Bookmarks/ > Comics > comic num 404). Interestingly, the next comic, [[405: Journal 3]], includes the line "So, you found me after all." In [[1969: Not Available]], the error message 404 is referenced in the caption.

==Trivia==
The web comic Comic JK made [https://web.archive.org/web/20100925103935/http://comicjk.com/comic.php/404 a spoof of this comic] in the xkcd style.

[[Category:Design of xkcd.com]]

404: Not Found

2024-11-14T04:16:22Z

172.68.225.192:

==Explanation==
{{Quote|I have always been of the opinion that http://xkcd.com/404/ is an actual comic, if a slightly avant-garde one. I actually went out of my way to modify the 'random' button to include it, but that annoyed too many people—most of whom reasonably assumed it was a bug—and I eventually undid it.|[[Randall Munroe]], ''[https://web.archive.org/web/20190328010454/https://plus.google.com/111588569124648292310/posts/j6w9DkYApya Source]''}}

This was the first [[:Category:April fools' comics|April fools' comic]] released by [[Randall Munroe|Randall]]. The next became [[880: Headache]], released on Friday April 1, 2011. The [[403: Convincing Pickup Line|previous comic]] was released on Monday March 31, 2008, and the [[405: Journal 3|next comic]] was released on Wednesday April 2, 2008. This comic was released between the two, on Tuesday April 1st 2008.

The "{{w|HTTP 404|404 Not Found}}" error message is a HTTP standard response code to indicate that the browser was able to communicate with a given {{w|Server (computing)|server}}, but the server could not find what was requested. The error may also be used when a server does not wish to disclose whether it has the requested information. The website hosting server will typically generate a "404 Not Found" web page when a user attempts to follow a broken or dead link; hence the 404 error is one of the most recognizable errors encountered on the internet. (For example, a nonexistent page like https://xkcd.com/fooo will display an identical error message.) Randall deliberately skipped the comic number 404, so when people try to view it, they get a "404 Not Found" error instead. He has said that he considers 404 [https://web.archive.org/web/20190328010454/https://plus.google.com/111588569124648292310/posts/j6w9DkYApya an "actual comic"] and that for a time he made it possible to find it using the "random" button on [https://xkcd.com xkcd.com].

It might initially appear coincidental that the [[403: Convincing Pickup Line|comic 403]] was published just a day before April 1, 2008. However, Randall likely became aware of this possible correlation prior to that specific date, so he had an opportunity to influence the comic's release date. In May 2007 and in November 2007, Randall published the [[:Category:Choices|Choices series]] and the [[:Category:1337|1337 series]] respectively, each over five consecutive days, less than six months before April Fool's Day. This deliberate action shifted the release date of comic 403 from April 10, 2008, to March 31, 2008, when it was actually published. This alteration allowed for comic 404 to be posted on the April Fool's Day without abruptly disrupting the normal comic release schedule.

This comic was featured in [[1975: Right Click]] (in File > Open > C:\ > Bookmarks/ > Comics > comic num 404). Interestingly, the next comic, [[405: Journal 3]], includes the line "So, you found me after all." In [[1969: Not Available]], the error message 404 is referenced in the caption.

==Trivia==
The web comic Comic JK made [https://web.archive.org/web/20100925103935/http://comicjk.com/comic.php/404 a spoof of this comic] in the xkcd style.

[[Category:Design of xkcd.com]]

404: Not Found

2024-11-14T04:15:00Z

172.68.225.192:

{{comic
| number = 404
| date = April 1, 2008
| title = Not Found
| before = <br><big><big><big><big><big>'''404 Not Found'''<br><br></big></big></big></big><hr>nginx</big>
}}

==Explanation==
{{Quote|I have always been of the opinion that http://xkcd.com/404/ is an actual comic, if a slightly avant-garde one. I actually went out of my way to modify the 'random' button to include it, but that annoyed too many people—most of whom reasonably assumed it was a bug—and I eventually undid it.|[[Randall Munroe]], ''[https://web.archive.org/web/20190328010454/https://plus.google.com/111588569124648292310/posts/j6w9DkYApya Source]''}}

This was the first [[:Category:April fools' comics|April fools' comic]] released by [[Randall Munroe|Randall]]. The next became [[880: Headache]], released on Friday April 1, 2011. The [[403: Convincing Pickup Line|previous comic]] was released on Monday March 31, 2008, and the [[405: Journal 3|next comic]] was released on Wednesday April 2, 2008. This comic was released between the two, on Tuesday April 1st 2008.

The "{{w|HTTP 404|404 Not Found}}" error message is a HTTP standard response code to indicate that the browser was able to communicate with a given {{w|Server (computing)|server}}, but the server could not find what was requested. The error may also be used when a server does not wish to disclose whether it has the requested information. The website hosting server will typically generate a "404 Not Found" web page when a user attempts to follow a broken or dead link; hence the 404 error is one of the most recognizable errors encountered on the internet. (For example, a nonexistent page like https://xkcd.com/fooo will display an identical error message.) Randall deliberately skipped the comic number 404, so when people try to view it, they get a "404 Not Found" error instead. He has said that he considers 404 [https://web.archive.org/web/20190328010454/https://plus.google.com/111588569124648292310/posts/j6w9DkYApya an "actual comic"] and that for a time he made it possible to find it using the "random" button on [https://xkcd.com xkcd.com].

It might initially appear coincidental that the [[403: Convincing Pickup Line|comic 403]] was published just a day before April 1, 2008. However, Randall likely became aware of this possible correlation prior to that specific date, so he had an opportunity to influence the comic's release date. In May 2007 and in November 2007, Randall published the [[:Category:Choices|Choices series]] and the [[:Category:1337|1337 series]] respectively, each over five consecutive days, less than six months before April Fool's Day. This deliberate action shifted the release date of comic 403 from April 10, 2008, to March 31, 2008, when it was actually published. This alteration allowed for comic 404 to be posted on the April Fool's Day without abruptly disrupting the normal comic release schedule.

This comic was featured in [[1975: Right Click]] (in File > Open > C:\ > Bookmarks/ > Comics > comic num 404). Interestingly, the next comic, [[405: Journal 3]], includes the line "So, you found me after all." In [[1969: Not Available]], the error message 404 is referenced in the caption.

==Transcript==
:[Instead of the regular xkcd site layout, just a white page that states on top center:]
:404 Not Found

==Trivia==
The web comic Comic JK made [https://web.archive.org/web/20100925103935/http://comicjk.com/comic.php/404 a spoof of this comic] in the xkcd style.
{{comic discussion}}

[[Category:April fools' comics]]
[[Category:No title text]] 
[[Category:Comics with lowercase text]]