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star talk radio, a bit on darkness

Anyone else listen to the star talk radio podcasts that neil degrasse tyson hosts? It's pretty awesome.

This last episode he kinda got me with something. A listener wrote in to ask, "If there are so many billions of stars shining light down on us, why is the sky so dark?"

His response? It's not dark. The problem is that there's only a tiny portion of the electromagnetic spectrum that we process visually: red to violet. Wavelengths between 380 nm and 760 nm.

If we could see more of the spectrum, there would never be darkness. Radio telescopes see a universe that's lit up everywhere you look, any time of day. They talked about this on the show and sorta got into a side discussion about Geordi's visor in Star Trek... but the point is, it's never dark here. We just had to scale our vision back or else we wouldn't be able to handle it all.

Comments

( 4 comments — Leave a comment )
browngirl
Oct. 20th, 2013 10:49 pm (UTC)
*takes notes*
naath
Oct. 21st, 2013 09:17 am (UTC)
http://en.wikipedia.org/wiki/Olbers%27_paradox

It is dark; and the reason that there isn't that much light here is mostly because the universe is expanding (and the speed of light is finite).
astrogeek01
Oct. 21st, 2013 02:52 pm (UTC)
And dust. Lots and lots of dust.

But he's right of course, that's just in the visible. Redshifted light (into IR and radio) would make the sky very bright in those wavelengths.
aposteriori
Oct. 27th, 2013 12:27 pm (UTC)
There was a great video for this on Minute Physics a while back :)

http://www.youtube.com/watch?v=gxJ4M7tyLRE&list=TLVxfZZz5rA0yt5xFd0P8bN0LZYZJJ84vE
( 4 comments — Leave a comment )

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