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IceCube: In-ice Antarctic Telescope

Hi Casey, As the ultimate non-physicist, I must thank you for the wonderful explanations you gave on very technical subjects! Those are explanations I can use and understand :D I did  wonder, why is the glow from the cosmic background orange first? Also, thanks for the update on the Oden- sounds like quite a ride:) and that neat video of 24 hrs at the Pole. By now you may be home , so my best wishes for a restful holiday. Happy New Year, Lollie

Sat, 01/23/2010 - 21:08

Casey OHara

Hi Lollie,
Sorry for the delay in answering, I'm back home and a couple weeks into the Spring semester with my students! quite a transition from the south pole. 
Orange is my favorite color!  But this is a complex question so hopefully I can keep it short!  The reason why the big bang was originally "orange" has to do with temperatures.  To start with, consider, every star has a different surface temperature, which determines its color.  Hotter stars radiate higher frequencies and shorter wavelengths, which means closer to the blue end of the spectrum; cooler stars radiate lower frequencies and longer wavelengths, corresponding to redder colors.  Our sun is a "yellow" star - and hotter stars look more blue, and cooler stars look more red.
If you look out at the universe, you are looking back in time, since you are seeing the stars as they looked when the light left them.  When you look at the closest star, about 4 light years away, you see the light that left it 4 years ago and is just now reaching Earth.   Currently, the universe is mostly empty space, with a few clumps of matter (stars and such).  But when the big bang happened about 13.5 billion years ago, the universe expanded and went through stages of intense heat, until at one point in time it finally cooled enough that photons of light could pass through it and it became transparent. 
But before the universe became transparent, the average temperature matched stars of an orange color!  If you try to look any farther (in distance, which is also back in time) you hit this wall of opaque orange that you can't see through.  So that would make the universe appear "orange"!
To make it more confusing, since that time, the universe has expanded by a huge amount. This has "stretched" the orange wavelengths until they currently are no longer orange, or red, or even infrared.  This background radiation has been stretched so far that it now appears to be in the wavelength of microwaves.  So, scientists studying the big bang now use telescopes that are sensitive to microwave radiation. At the South Pole, the South Pole Telescope and the BICEP telescope both examine the cosmic microwave background radiation to study the universe after the big bang.
Hope this helps answer your question!
--Casey