54: Science

< Prev Comic #54 (January 18, 2006) Next >

Science

Title text: Bonus point if you can identify the science in question

Explanation

The graph shows the relationship between energy density and frequency for two sources: the solid line represents the theoretical Blackbody Radiation, and the dots represent measurements of the Cosmic Background Radiation. The equation is Planck's Law, derived in 1900 by Max Planck for the energy density of blackbody radiation.

This comic shows the very close match between theory and prediction, showing that the Cosmic Background Radiation looks exactly like a blackbody at 2.73 K, which is what we would expect if the CMB is the result of the light of the Big Bang cooled by the expansion of the universe.

Transcript

[Graph of cosmic microwave background radiation: Y axis is energy density, X axis is frequency in GHz. Energy density peaks at 160.4 GHz.]

I(f) = ((2hf^3)/(c^2))*(1/(e^(hf/kT)-1))

SCIENCE.

It works, bitches.

Trivia

• This is the 48th comic originally posted to livejournal. The previous comic was 50: Penny Arcade, the next is 51: Malaria.
• This comic is available on a t-shirt at the xkcd store.

 add a comment!

Discussion

It's also commonly called "Microwave Background Radiation" because where the radiation peaks at 160.4 GHz is in the microwave range of the electromagnetic spectrum. --Dangerkeith3000 (talk) 18:02, 13 March 2013 (UTC)