explain xkcd - User contributions [en]

Talk:1402: Harpoons

2014-08-01T13:52:00Z

199.27.128.123:

I took the sentient space craft joke to be a reference to the movie "Dark Star".

Harpoon is a brand of rum. Did a bottle make it into space? [[Special:Contributions/108.162.219.196|108.162.219.196]] 12:55, 1 August 2014 (UTC)

Did this comic upload quite late in the day for anyone else? Is anyone else experiencing or did anyone else experience that "Latest Comic" is still going to 1401 as ix XKCD.com and XKCD.com/#

"This is obviously a joke, as sentient spacecraft cannot be created with current technology." Yeah, will need a citation on that... [[Special:Contributions/108.162.229.148|108.162.229.148]] 13:23, 1 August 2014 (UTC)

Talk:1308: Christmas Lights

2013-12-27T00:54:37Z

199.27.128.123:

I think the spectrum at the top of the tree is a specific star. The Sun. [[Special:Contributions/173.245.56.64|173.245.56.64]] 16:21, 26 December 2013 (UTC)

If I am reading the graphs right, except for the very top there is no blue lights.
[[User:Traisjames|From the guy with his eye on the sky.]] ([[User talk:Traisjames|talk]]) 06:41, 25 December 2013 (UTC)

Presumably the top is gold? [[Special:Contributions/173.245.52.211|173.245.52.211]] 07:47, 25 December 2013 (UTC)

Also the spike in the near IR of the large graph is likely to be a mercury line. I think fires would have a smoother curve of a black body.
[[Special:Contributions/199.27.128.122|199.27.128.122]] 06:47, 25 December 2013 (UTC)

Could someone make a coloured version?[[User:Guru-45|Guru-45]] ([[User talk:Guru-45|talk]]) 07:22, 25 December 2013 (UTC)

Also the light at the top of the tree seems to be emitting in the UV range. Perhaps it’s supposed to be a fluorescent lamp? [[Special:Contributions/108.162.245.7|108.162.245.7]] 07:30, 25 December 2013 (UTC)

I'm thinking it's a "white" LED. [[Special:Contributions/108.162.216.56|108.162.216.56]] 07:50, 25 December 2013 (UTC)

I think the one at the top matches the profile of a star...
[[Special:Contributions/141.101.99.211|141.101.99.211]] 08:18, 25 December 2013 (UTC)

The spike is not in the "near" infrared, this is water and/or carbondioxide line. {{unsigned ip|108.162.231.214}}

From a rough pixel-measurement and assuming a linear scale, the peak on the large spectrum is at around 800 nm. I'm not sure what to make from the peak, but infrared light is heat radiation, so it could be the representation of sharing warmth and love. 15:15, 25 December 2013 (UTC)

The top spectrum closely matches that of a cool-white LED. The strong peak in the blue, the broad peak from red to green, and the dip in the cyan range is a real give-away. Exactly like LEDs.[[User:ExternalMonolog|ExternalMonolog]] ([[User talk:ExternalMonolog|talk]]) 01:00, 26 December 2013 (UTC)ExternalMonolog

[http://i.imgur.com/hCbUpAl.png Here] is a "filled-in" version of the comic.[[User:Guru-45|Guru-45]] ([[User talk:Guru-45|talk]]) 17:06, 25 December 2013 (UTC)

:Very nice, Guru![[User:ExternalMonolog|ExternalMonolog]] ([[User talk:ExternalMonolog|talk]]) 01:35, 26 December 2013 (UTC)ExternalMonolog

I strongly disagree with the explanation's assertion that the peak in the large spectrum, the fire, is the 4.3µm CO2 emission listed in the source given. The peak in the source's spectrum is clearly outside of the near-infrared spectrum and it is just as clearly on the long wave side of the black-body peak in the chart. The comic doesn't even show these wavelengths at all. If, as it appears, that the chart in the comic is a semi-log plot, then the peak is roughly in the 1,000~1,200nm range.[[User:ExternalMonolog|ExternalMonolog]] ([[User talk:ExternalMonolog|talk]]) 01:20, 26 December 2013 (UTC)ExternalMonolog

;Misleading picture in link

The picture :

http://en.wikipedia.org/wiki/File:Flame_detection_spectrum.JPG

found in the link of the explanation is strongly misleading.

Visible radiation ( red to violet ) is 700 to 400 nm. The

example spectrum in the middle does not fit to this.

Maybe some guesswork here results from that link.

After some "metering" with a ruler on the screen my guess

for the spike in the fireplace spectum now is ca. 1.5 or 2.1 µm ,

being the first harmonic of either O-H or CO2 respectively. [[Special:Contributions/108.162.231.220|108.162.231.220]] 23:23, 26 December 2013 (UTC)

1297: Oort Cloud

2013-11-29T19:15:54Z

199.27.128.123: /* Explanation */

{{comic
| number = 1297
| date = November 29, 2013
| title = Oort Cloud
| image = oort_cloud.png
| titletext = ... I wanna try. Hang on, be right back.
}}

==Explanation==
{{incomplete|Not (yet) complete.}}
The {{w|Oort cloud}} is a cloud mostly composed of comets that makes up the outer region of our solar system, reaching out to roughly 50,000 [http://en.wikipedia.org/wiki/Astronomical_unit AU] or nearly one light-year from the sun. Gravitational forces from passing stars and the Milky Way sometimes perturb a comet enough to send it into the inner solar system. When the comet gets closer to the Sun (which is the “bright dot in the distance” here) it warms up and some of its body is lost as gas and dust, sometimes visible as a coma and perhaps a tail. If it gets close to the sun it may break up entirely.

The comet pictured here upon its return resembles the unusual asteroid/comet {{w|P/2013 P5}} which sported six comet-like tails. In that case they seem to have been generated partly by rapid spinning.

{{w|Comet ISON}} came from the Oort cloud and reached its closest approach to the sun ({{w|perihelion}}) on the day before this comic was published. The comet passed very close to the sun, at a distance of 1,860,000 kilometers or 1,150,000 miles. It was thus within one sun-diameter of the surface of the sun itself (diameter of sun = 1,391,000 km). The tail has changed its shape because the comet was partly broken up around the sun. The closest approach to Earth will be on December 27, 2013 but it's not clear if the comet will be visible by the naked eye.

This video shows an animation of the encounter at the sun: [http://stereo-ssc.nascom.nasa.gov/browse/2013/11/28/ahead_20131128_cor2_rdiff_512.mpg ISON 28.11.2013].

==Transcript==
:[Three asteroids float in space.]
:ISON: Have you noticed that bright dot in the distance?
:Asteroid: Yeah. What's the deal with it?

:ISON: Dunno. I'm gonna go check it out.

:[Pause while ISON checks it out off screen.]

:[Several million years later.]
:ISON (appears burnt): Wow. Do NOT go over there.
{{comic discussion}}
[[Category:Astronomy]]