1308: "Christmas Lights"

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Bassoon
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1308: "Christmas Lights"

Postby Bassoon » Wed Dec 25, 2013 5:31 am UTC

Image

Title Text wrote:Merry Christmas from xkcd!

curveofheaven
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Re: 1308: Christmas Lights

Postby curveofheaven » Wed Dec 25, 2013 5:34 am UTC

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!

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CatCube
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Re: 1308: "Christmas Lights"

Postby CatCube » Wed Dec 25, 2013 5:36 am UTC

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.

Bassoon
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Re: 1308: "Christmas Lights"

Postby Bassoon » Wed Dec 25, 2013 5:36 am UTC

It's the spectral content of each light source appearing in the comic. A neat little skit.

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Re: 1308: "Christmas Lights"

Postby curveofheaven » Wed Dec 25, 2013 5:38 am UTC

Wonderful! Well, that's a wrap, time for bed. Thanks for the confirmation of some thoughts.

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Re: 1308: "Christmas Lights"

Postby rhomboidal » Wed Dec 25, 2013 5:40 am UTC

I'm glowing inside, filled with Christmas spectrum.

Justme8800
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Re: 1308: "Christmas Lights"

Postby Justme8800 » Wed Dec 25, 2013 5:52 am UTC

I love this! Took me a second to connect "fireplace." The star's spectrum is kind of interesting, too.

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addams
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Re: 1308: "Christmas Lights"

Postby addams » Wed Dec 25, 2013 5:55 am UTC

Each spectrum can make a sound, like a bell.
http://www.youtube.com/watch?v=eQemvyyJ--g

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Re: 1308: "Christmas Lights"

Postby tarry » Wed Dec 25, 2013 5:56 am UTC

What's the peak in the infrared in the fire? Is it a wood or gas fire?

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StClair
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Re: 1308: "Christmas Lights"

Postby StClair » Wed Dec 25, 2013 6:07 am UTC

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?

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Re: 1308: "Christmas Lights"

Postby tarry » Wed Dec 25, 2013 6:13 am UTC

Tree lights are red and green. Star on top is probably white. Fire is reddish.

iabervon
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Re: 1308: "Christmas Lights"

Postby iabervon » Wed Dec 25, 2013 6:29 am UTC

The "white" LEDs in that star would never convince a mantis shrimp.

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Re: 1308: "Christmas Lights"

Postby flukiluke » Wed Dec 25, 2013 6:39 am UTC

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.

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Re: 1308: "Christmas Lights"

Postby J the Ninja » Wed Dec 25, 2013 6:52 am UTC

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
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Re: 1308: "Christmas Lights"

Postby iabervon » Wed Dec 25, 2013 8:17 am UTC

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).

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Re: 1308: "Christmas Lights"

Postby dtilque » Wed Dec 25, 2013 12:14 pm UTC

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.
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Flumble
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Re: 1308: "Christmas Lights"

Postby Flumble » Wed Dec 25, 2013 2:13 pm UTC

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. :)

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yellow103
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Re: 1308: "Christmas Lights"

Postby yellow103 » Wed Dec 25, 2013 2:30 pm UTC

The weather outside is frightfull,
but the spectrum inside is delightfull.

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Re: 1308: "Christmas Lights"

Postby stianhat » Wed Dec 25, 2013 4:16 pm UTC

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!

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Wnderer
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Re: 1308: "Christmas Lights"

Postby Wnderer » Wed Dec 25, 2013 10:00 pm UTC

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

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Re: 1308: "Christmas Lights"

Postby higgins2k » Wed Dec 25, 2013 11:31 pm UTC

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...)

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Re: 1308: "Christmas Lights"

Postby shorty0927 » Thu Dec 26, 2013 12:21 am UTC

You've already answered your own question. It IS infrared. Not any more complicated than that.

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Re: 1308: "Christmas Lights"

Postby JustDoug » Thu Dec 26, 2013 12:43 am UTC

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.

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Wnderer
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Re: 1308: "Christmas Lights"

Postby Wnderer » Thu Dec 26, 2013 12:59 am UTC

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

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Re: 1308: "Christmas Lights"

Postby cryptoengineer » Thu Dec 26, 2013 3:36 am UTC

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

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Re: 1308: "Christmas Lights"

Postby J the Ninja » Thu Dec 26, 2013 3:50 am UTC

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....
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Re: 1308: "Christmas Lights"

Postby mpatricke » Thu Dec 26, 2013 5:41 am UTC

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.)

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Re: 1308: "Christmas Lights"

Postby Sprocket » Thu Dec 26, 2013 6:41 am UTC

Ugh I hate those new bright blue-white christmas lights. I really like the slightly yellow ones much better.
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Re: 1308: "Christmas Lights"

Postby fruey » Thu Dec 26, 2013 9:13 am UTC

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?

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Flumble
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Re: 1308: "Christmas Lights"

Postby Flumble » Thu Dec 26, 2013 11:14 am UTC

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.

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Re: 1308: "Christmas Lights"

Postby medlii » Thu Dec 26, 2013 2:01 pm UTC

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...
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Re: 1308: "Christmas Lights"

Postby orbik » Thu Dec 26, 2013 2:11 pm UTC

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.

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Re: 1308: "Christmas Lights"

Postby cellocgw » Thu Dec 26, 2013 4:33 pm UTC

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.
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Re: 1308: "Christmas Lights"

Postby fruey » Thu Dec 26, 2013 5:04 pm UTC

Here ya go for an image of what it might look like
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LED Christmas tree

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Re: 1308: "Christmas Lights"

Postby Wnderer » Thu Dec 26, 2013 5:06 pm UTC

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.

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Re: 1308: "Christmas Lights"

Postby addams » Thu Dec 26, 2013 6:28 pm UTC

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.
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We are all in The Gutter.
Some of us see The Gutter.
Some of us see The Stars.
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Those that do not Know; Don't tell them.
They do terrible things to people that Tell Them.

jez12345
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Re: 1308: "Christmas Lights"

Postby jez12345 » Fri Dec 27, 2013 5:58 am UTC

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.

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Re: 1308: "Christmas Lights"

Postby dtilque » Fri Dec 27, 2013 8:09 am UTC

A thought just occured to me. This strip could have been cleverly titled Spectra of Christmas Present.
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Re: 1308: "Christmas Lights"

Postby TomTAC » Sat Dec 28, 2013 1:44 pm UTC

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".

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Re: 1308: "Christmas Lights"

Postby Nix_Seb » Mon Dec 30, 2013 10:33 am UTC

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.)



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