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1308: "Christmas Lights"

Posted: Wed Dec 25, 2013 5:31 am UTC
by Bassoon
Image

Title Text wrote:Merry Christmas from xkcd!

Re: 1308: Christmas Lights

Posted: Wed Dec 25, 2013 5:34 am UTC
by curveofheaven
Gonna be a little thick here, is this suggesting a relative light saturation for vague blobs of the comic? Is that what's going on?

Merry Christmas by the way!

Re: 1308: "Christmas Lights"

Posted: Wed Dec 25, 2013 5:36 am UTC
by CatCube
This was clever as hell. It took me a few minutes to figure out the large spectrum was from a fire, but I laughed when I got it.

Re: 1308: "Christmas Lights"

Posted: Wed Dec 25, 2013 5:36 am UTC
by Bassoon
It's the spectral content of each light source appearing in the comic. A neat little skit.

Re: 1308: "Christmas Lights"

Posted: Wed Dec 25, 2013 5:38 am UTC
by curveofheaven
Wonderful! Well, that's a wrap, time for bed. Thanks for the confirmation of some thoughts.

Re: 1308: "Christmas Lights"

Posted: Wed Dec 25, 2013 5:40 am UTC
by rhomboidal
I'm glowing inside, filled with Christmas spectrum.

Re: 1308: "Christmas Lights"

Posted: Wed Dec 25, 2013 5:52 am UTC
by Justme8800
I love this! Took me a second to connect "fireplace." The star's spectrum is kind of interesting, too.

Re: 1308: "Christmas Lights"

Posted: Wed Dec 25, 2013 5:55 am UTC
by addams
Each spectrum can make a sound, like a bell.
http://www.youtube.com/watch?v=eQemvyyJ--g

Merry Christmas, again.

Re: 1308: "Christmas Lights"

Posted: Wed Dec 25, 2013 5:56 am UTC
by tarry
What's the peak in the infrared in the fire? Is it a wood or gas fire?

Re: 1308: "Christmas Lights"

Posted: Wed Dec 25, 2013 6:07 am UTC
by StClair
CatCube wrote:This was clever as hell. It took me a few minutes to figure out the large spectrum was from a fire, but I laughed when I got it.

Ditto.

Anyone up to the task of deriving the color of each light from the spectrum?

Re: 1308: "Christmas Lights"

Posted: Wed Dec 25, 2013 6:13 am UTC
by tarry
Tree lights are red and green. Star on top is probably white. Fire is reddish.

Re: 1308: "Christmas Lights"

Posted: Wed Dec 25, 2013 6:29 am UTC
by iabervon
The "white" LEDs in that star would never convince a mantis shrimp.

Re: 1308: "Christmas Lights"

Posted: Wed Dec 25, 2013 6:39 am UTC
by flukiluke
Living in the Southern Hemisphere, it took a little while to get the idea of 'fire' for the big spectrum. The idea of fireplace at Christmas just doesn't 'click' to me.

Re: 1308: "Christmas Lights"

Posted: Wed Dec 25, 2013 6:52 am UTC
by J the Ninja
tarry wrote:Tree lights are red and green. Star on top is probably white. Fire is reddish.


Star is warm-white LEDs, it's a pretty distinctive spectrum: http://led-brdf.wikispaces.com/Introduction+to+LEDs

Re: 1308: "Christmas Lights"

Posted: Wed Dec 25, 2013 8:17 am UTC
by iabervon
J the Ninja wrote:
tarry wrote:Tree lights are red and green. Star on top is probably white. Fire is reddish.


Star is warm-white LEDs, it's a pretty distinctive spectrum: http://led-brdf.wikispaces.com/Introduction+to+LEDs


It's a cool white; the blue spike is more intense than the red-green bump (top spectrum from your link).

Re: 1308: "Christmas Lights"

Posted: Wed Dec 25, 2013 12:14 pm UTC
by dtilque
tarry wrote:What's the peak in the infrared in the fire? Is it a wood or gas fire?


Without looking it up (because I have no idea where to look it up) I'd guess that it's an emission line from either carbon dioxide or carbon monoxide.

Re: 1308: "Christmas Lights"

Posted: Wed Dec 25, 2013 2:13 pm UTC
by Flumble
CatCube wrote:It took me a few minutes to figure out the large spectrum was from a fire, but I laughed when I got it.

At first I thought it was the heart-warmth. :)

Re: 1308: "Christmas Lights"

Posted: Wed Dec 25, 2013 2:30 pm UTC
by yellow103
The weather outside is frightfull,
but the spectrum inside is delightfull.

Re: 1308: "Christmas Lights"

Posted: Wed Dec 25, 2013 4:16 pm UTC
by stianhat
dtilque wrote:Without looking it up (because I have no idea where to look it up) I'd guess that it's an emission line from either carbon dioxide or carbon monoxide.


Since we are guessing, I'd guess it to be an electron on the oxygen atom of an oxygen molecule (involved inreactions CO/CO2) going from singlet to back to triplet. That has a peak at near-infrared (1270 says wikipedia)

Merry christmas!

Re: 1308: "Christmas Lights"

Posted: Wed Dec 25, 2013 10:00 pm UTC
by Wnderer
stianhat wrote:
dtilque wrote:Without looking it up (because I have no idea where to look it up) I'd guess that it's an emission line from either carbon dioxide or carbon monoxide.


Since we are guessing, I'd guess it to be an electron on the oxygen atom of an oxygen molecule (involved inreactions CO/CO2) going from singlet to back to triplet. That has a peak at near-infrared (1270 says wikipedia)

Merry christmas!


I think it's hydrogen.

739px-LymanSeries.svg.png


I recall from high school chemistry sticking a glass tube into a candle flame and burning the hydrogen on the other end. I think wood works the same. I think you need a heated gas to produce the spectral line and I think that gas is wood gas.

http://en.wikipedia.org/wiki/Wood_gas

Re: 1308: "Christmas Lights"

Posted: Wed Dec 25, 2013 11:31 pm UTC
by higgins2k
Wnderer wrote:I think it's hydrogen.

The hydrogen emission lines in your picture are in the ultraviolet, with wavelengths between 900 and 1300 Angstroms. Visible light is between 4000ish Angstroms (purple) and 7000ish (red).

The emission peak we see in Mr. Munroe's fireplace is well into the infrared, somewhere beyond 10,000 Angstroms or 1000 nanometers. So no, I don't think it's hydrogen. (Not that I know what the correct answer is...)

Re: 1308: "Christmas Lights"

Posted: Thu Dec 26, 2013 12:21 am UTC
by shorty0927
You've already answered your own question. It IS infrared. Not any more complicated than that.

Re: 1308: "Christmas Lights"

Posted: Thu Dec 26, 2013 12:43 am UTC
by JustDoug
higgins2k wrote:
Wnderer wrote:I think it's hydrogen.

The hydrogen emission lines in your picture are in the ultraviolet, with wavelengths between 900 and 1300 Angstroms. Visible light is between 4000ish Angstroms (purple) and 7000ish (red).

The emission peak we see in Mr. Munroe's fireplace is well into the infrared, somewhere beyond 10,000 Angstroms or 1000 nanometers. So no, I don't think it's hydrogen. (Not that I know what the correct answer is...)


That's because it's not really a fireplace we're seeing, but the red-shifted tailights of Santa's receding sleigh.

Re: 1308: "Christmas Lights"

Posted: Thu Dec 26, 2013 12:59 am UTC
by Wnderer
higgins2k wrote:
Wnderer wrote:I think it's hydrogen.

The hydrogen emission lines in your picture are in the ultraviolet, with wavelengths between 900 and 1300 Angstroms. Visible light is between 4000ish Angstroms (purple) and 7000ish (red).

The emission peak we see in Mr. Munroe's fireplace is well into the infrared, somewhere beyond 10,000 Angstroms or 1000 nanometers. So no, I don't think it's hydrogen. (Not that I know what the correct answer is...)


You're right. I looked at that graph and mistakenly read nanometers.

EDIT: On the Wikipedia page all the graphs and tables are in nanometers except that one. :roll:
http://en.wikipedia.org/wiki/Hydrogen_spectral_series

Re: 1308: "Christmas Lights"

Posted: Thu Dec 26, 2013 3:36 am UTC
by cryptoengineer
Wnderer wrote:
higgins2k wrote:
Wnderer wrote:I think it's hydrogen.

The hydrogen emission lines in your picture are in the ultraviolet, with wavelengths between 900 and 1300 Angstroms. Visible light is between 4000ish Angstroms (purple) and 7000ish (red).

The emission peak we see in Mr. Munroe's fireplace is well into the infrared, somewhere beyond 10,000 Angstroms or 1000 nanometers. So no, I don't think it's hydrogen. (Not that I know what the correct answer is...)


You're right. I looked at that graph and mistakenly read nanometers.

EDIT: On the Wikipedia page all the graphs and tables are in nanometers except that one. :roll:
http://en.wikipedia.org/wiki/Hydrogen_spectral_series


I don't know where Munro got his fire spectrum; it seems very idealized. Googling for for 'infrared spectrum of a wood fire' gives a lot of spectra, none as simple as his. Wikipedia has this. Even accounting for the fact that the spectrum is flipped in direction compared to Munro's, its not a good match, but the big spike is probably CO2.

ce

Re: 1308: "Christmas Lights"

Posted: Thu Dec 26, 2013 3:50 am UTC
by J the Ninja
iabervon wrote:
J the Ninja wrote:
tarry wrote:Tree lights are red and green. Star on top is probably white. Fire is reddish.


Star is warm-white LEDs, it's a pretty distinctive spectrum: http://led-brdf.wikispaces.com/Introduction+to+LEDs


It's a cool white; the blue spike is more intense than the red-green bump (top spectrum from your link).



Arrgh. You're right. So used to spectrum graphs with red on the left....

Re: 1308: "Christmas Lights"

Posted: Thu Dec 26, 2013 5:41 am UTC
by mpatricke
Flumble wrote:At first I thought it was the heart-warmth. :)


I like that :-)

BUt I thought it was the whole of the E-M spectrum, with a spike in the TV transmission band.

(Newbie here, apologies if the formatting's stuffed.)

Re: 1308: "Christmas Lights"

Posted: Thu Dec 26, 2013 6:41 am UTC
by Sprocket
Ugh I hate those new bright blue-white christmas lights. I really like the slightly yellow ones much better.

Re: 1308: "Christmas Lights"

Posted: Thu Dec 26, 2013 9:13 am UTC
by fruey
I've created an image of the fire & tree as it might look, but I can't post images on here. Links to Dropbox get flagged as spam. Anyone help?

Re: 1308: "Christmas Lights"

Posted: Thu Dec 26, 2013 11:14 am UTC
by Flumble
mpatricke wrote:BUt I thought it was the whole of the E-M spectrum, with a spike in the TV transmission band.

Hahah, they'd better not be watching one of those loathed christmas films.

Re: 1308: "Christmas Lights"

Posted: Thu Dec 26, 2013 2:01 pm UTC
by medlii
StClair wrote:
CatCube wrote:This was clever as hell. It took me a few minutes to figure out the large spectrum was from a fire, but I laughed when I got it.

Ditto.

Anyone up to the task of deriving the color of each light from the spectrum?


This the best I can do for the tree using MS Paint without a mouse...

Re: 1308: "Christmas Lights"

Posted: Thu Dec 26, 2013 2:11 pm UTC
by orbik
cryptoengineer wrote:I don't know where Munro got his fire spectrum; it seems very idealized. Googling for for 'infrared spectrum of a wood fire' gives a lot of spectra, none as simple as his. Wikipedia has this. Even accounting for the fact that the spectrum is flipped in direction compared to Munro's, its not a good match, but the big spike is probably CO2.

ce


I was wondering about this too, and some googling revealed that the spike must be 4.3 µm from CO2.
http://www.patol.org/com_files/spectrum.jpg
But then the blackbody spectrum can't be right. The intensity keeps increasing well beyond the CO2 spike, which according to the graph above, suggests a flame temperature of less than 200°C. Too low to burn normal wood.

EDIT:
Yeah, I just realized it's not just the flame but the whole fireplace, the majority of which must be cool enough to increase the lower IR intensity. Randall was probably right after all.

Re: 1308: "Christmas Lights"

Posted: Thu Dec 26, 2013 4:33 pm UTC
by cellocgw
orbik wrote:I was wondering about this too, and some googling revealed that the spike must be 4.3 µm from CO2.
http://www.patol.org/com_files/spectrum.jpg
But then the blackbody spectrum can't be right. The intensity keeps increasing well beyond the CO2 spike, which according to the graph above, suggests a flame temperature of less than 200°C. Too low to burn normal wood.

EDIT:
Yeah, I just realized it's not just the flame but the whole fireplace, the majority of which must be cool enough to increase the lower IR intensity. Randall was probably right after all.


Or maybe the fire's behind a glass door panel, and the spike is a transmission line of the glass. <-- I completely made that up.
The spike is due to a molpy going up in a puff of smoke.

Re: 1308: "Christmas Lights"

Posted: Thu Dec 26, 2013 5:04 pm UTC
by fruey
Here ya go for an image of what it might look like

Re: 1308: "Christmas Lights"

Posted: Thu Dec 26, 2013 5:06 pm UTC
by Wnderer
orbik wrote:
cryptoengineer wrote:I don't know where Munro got his fire spectrum; it seems very idealized. Googling for for 'infrared spectrum of a wood fire' gives a lot of spectra, none as simple as his. Wikipedia has this. Even accounting for the fact that the spectrum is flipped in direction compared to Munro's, its not a good match, but the big spike is probably CO2.

ce


I was wondering about this too, and some googling revealed that the spike must be 4.3 µm from CO2.
http://www.patol.org/com_files/spectrum.jpg
But then the blackbody spectrum can't be right. The intensity keeps increasing well beyond the CO2 spike, which according to the graph above, suggests a flame temperature of less than 200°C. Too low to burn normal wood.

EDIT:
Yeah, I just realized it's not just the flame but the whole fireplace, the majority of which must be cool enough to increase the lower IR intensity. Randall was probably right after all.

If we're looking at the whole fireplace, CO2 makes sense. There is a lot of hot C02 gas in there to make the spectral lines and I have built CO2 detectors that work by detecting absorption in the infrared, so there is definitely a band in there somewhere.

Re: 1308: "Christmas Lights"

Posted: Thu Dec 26, 2013 6:28 pm UTC
by addams
medlii wrote:
StClair wrote:
CatCube wrote:This was clever as hell. It took me a few minutes to figure out the large spectrum was from a fire, but I laughed when I got it.

Ditto.

Anyone up to the task of deriving the color of each light from the spectrum?


This the best I can do for the tree using MS Paint without a mouse...

That is good.
Can you do the Fire?

oops. It has been done.
excuse.

Re: 1308: "Christmas Lights"

Posted: Fri Dec 27, 2013 5:58 am UTC
by jez12345
Never posted here before, but that peak in the fire spectrum is stopping me from working :?
If you estimate the wavelength scale based on the colors (can't seem to attach my version sorry) it looks like the spectrum is linear in wavelength or pretty close. The peak is at maybe 900nm +/- 100nm. Which means not CO2. It might be water vapour, there's an overtone band at about 950nm. I'm surprised that it would be an emission (positive) peak instead of absorption though. Argh.

Re: 1308: "Christmas Lights"

Posted: Fri Dec 27, 2013 8:09 am UTC
by dtilque
A thought just occured to me. This strip could have been cleverly titled Spectra of Christmas Present.

Re: 1308: "Christmas Lights"

Posted: Sat Dec 28, 2013 1:44 pm UTC
by TomTAC
flukiluke wrote:Living in the Southern Hemisphere, it took a little while to get the idea of 'fire' for the big spectrum. The idea of fireplace at Christmas just doesn't 'click' to me.


Then you're excused.

My brother-in-law's family in South America sent a video of their Christmas once. The most memorable scene was people in shorts and tanktops watching fireworks at night. I guess one could call the fireworks "Christmas Lights".

Re: 1308: "Christmas Lights"

Posted: Mon Dec 30, 2013 10:33 am UTC
by Nix_Seb
mpatricke wrote:
Flumble wrote:At first I thought it was the heart-warmth. :)


I like that :-)

BUt I thought it was the whole of the E-M spectrum, with a spike in the TV transmission band.

(Newbie here, apologies if the formatting's stuffed.)



I'm not going to lie, my instant thought was they were listening to the radio, but then I always do rush to a conclusion before then looking closely.