Editing 54: Science

{{comic
| number    = 54
| date      = January 18, 2006  <!-- The comic was released seven days earlier on LiveJournal than on xkcd.com (25/1 2006). We use the earliest possible day-->
| title     = Science
| before    = <big><big><span class="plainlinks">[https://web.archive.org/web/20060529063441/http://xkcd-drawings.livejournal.com/#:~:text=11%3A04%20pm-,Science,-Bonus%20points%20if LiveJournal title</span>]: '''Science'''</big></big>
| image     = science.jpg
| titletext = Bonus points if you can identify the science in question<br><br><span class="plainlinks">[https://web.archive.org/web/20060529063441/http://xkcd-drawings.livejournal.com/#:~:text=11%3A04%20pm-,Science,-Bonus%20points%20if LiveJournal caption</span>]: Bonus points if you can identify the science in question.
}}

==Explanation==
This was the forty-eighth comic originally posted to [[LiveJournal]]. The previous one was [[50: Penny Arcade]], and the next one was [[51: Malaria]]. It was among the [[:Category:Posted on LiveJournal after xkcd.com|last eleven comics]] posted both on LiveJournal and on [https://xkcd.com xkcd.com] after the new site was launched. This comic wasn't published on the same day across both sites, but most of them shared the same posting day. It was released on [https://xkcd.com xkcd.com] on January 25, 2006, seven days after originally being posted on LiveJournal. See the [[#Trivia|trivia section]] below.

The solid line represents the theoretical {{w|blackbody radiation|radiation for a blackbody}} at 2.73&nbsp;K according to {{w|Planck's Law}} (derived as early as 1900 by {{w|Max Planck}}). The formula, almost as written in the graph, can be found {{w|Black-body radiation#Planck's law of black-body radiation|here}}. The only changes are that on Wikipedia, the frequency ''f'' is represented by the Greek letter ''ν'' (nu) and the temperature ''T'' is included as an independent variable, so ''I''(''f'') becomes ''I''(''v'',''T''). However, ''I''(''v'',''T'') still represents the {{w|Radiance#Spectral radiance|spectral radiance}} (similar to energy density). In this formula, ''h'' is the Planck constant, ''c'' is the speed of light in a vacuum, and ''k'' is the Boltzmann constant. The frequency (''f'' or ''v'') along the ''x''-axis is measured in {{w|gigahertz}}. The curve peaks at 160.4&nbsp;GHz. There is no scale or unit on the {{w|energy density}} on the ''y''-axis.

The theory is that the blackbody in question was the universe at the point when it had cooled down enough {{w|Decoupling (cosmology)|to allow photons to escape}}, {{w|Chronology of the universe|0.38 million years}} into its {{w|Big Bang|13.8 billion years}} history. The photons that reach us today are the ones that have been travelling to us at lightspeed since then. As the light from astronomical objects suffers from {{w|redshift}} due to the expansion of the universe, and this shift becomes more pronounced with distance from the observer, this light displays in the infrared range.

The title text praises viewers who can identify where this equation and corresponding graph come from.

===T-shirt explanation===
This comic was made into a T-shirt but is no longer available. On the xkcd store, there was an explanation both for the title and for the graph in the comic:
<!-- DO NOT CORRECT This is a copy paste from xkcd with errors.-->
{{Quote|Science: We finally figured out that you could separate fact from superstition by a completely radical method: observation. You can try things, measure them, and see how they work! Bitches.|[https://web.archive.org/web/20140327062518/http://store.xkcd.com/products/science-works xkcd store]}}
<!-- DO NOT CORRECT -->
<!-- DO NOT CORRECT This is a copy paste from xkcd with errors.-->
{{Quote|The babydoll shirt is a slightly lighter green. The graph on the back of the shirt is data from the<!-- DO NOT CORRECT SPACING OR LINK This is a copy paste from xkcd with errors.-->[http://<!-- DO NOT CORRECT SPACING OR LINK This is a copy paste from xkcd with errors.-->en.wikipedia.org/wiki/COBE COBE mission]<!-- DO NOT CORRECT SPACING OR LINK This is a copy paste from xkcd with errors.--> which looked at the background microwave glow of the universe and found that it fit perfectly with the idea that the universe used to be really hot everywhere. This strongly reinforced the Big Bang theory and was one of the most dramatic examples of an experiment agreeing with a theory in history -- the data points fit perfectly, with error bars too small to draw on the graph. It's one of the most triumphant scientific results in history.|[https://web.archive.org/web/20140327062518/http://store.xkcd.com/products/science-works xkcd store]}}
<!-- DO NOT CORRECT -->

==Transcript==
:[A graph with a curve that begins at zero, then peaks at a given frequency, indicated via a thin vertical line, and then fades down towards zero. It is possible to see the data points, which fit the curve perfectly. The y-axis is labelled. Along the x-axis, the zero point and the frequency where the peak has its maximum are labelled and close to the arrow the unit of this axis is written.]
:y-axis: Energy Density
:Along the x-axis:
::0 
::160.4 
::GHz
:[Above the graph to the right is the following formula, with the last inner parentheses only included to make the formula clear, since in the drawing the fractions are written above and below horizontal lines:]
:I(f) = (2hf<sup>3</sup>/c<sup>2</sup>)(1/(e<sup>hf/kT</sup>-1))
:[Below the graph is written the following:]
:'''Science.'''
:It works, bitches.

==Trivia==
* For unknown reasons, on January 18, 2006, this comic was posted on LiveJournal on the same day that [[51: Malaria]] was released on [https://xkcd.com xkcd.com]. Three days later, on January 21, 2006, [[51: Malaria]] was posted on LiveJournal, thus forcing the next two comics ([[52: Secret Worlds]] and [[53: Hobby]]) to be released on [https://xkcd.com xkcd.com] two days before LiveJournal. Four days later, on January 25, 2006, this comic was finally posted on [https://xkcd.com xkcd.com], which fixed the date discrepancies and allowed the next comic, [[55: Useless]], to be published on the same day across both sites.
* This comic used to be available as a T-shirt at the [https://web.archive.org/web/20140327062518/http://store.xkcd.com/products/science-works xkcd store].

{{comic discussion}}

[[Category:Posted on LiveJournal| 48]]
[[Category:Posted on LiveJournal after xkcd.com]]
[[Category:Line graphs]]
[[Category:Analysis]]
[[Category:Math]]
[[Category:Physics]]
[[Category:Science]]
[[Category:Comics with lowercase text]]