# Errors in Death from the Skies

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• 2009-May-06, 05:09 PM
Gillianren
If you think people are being rude, report it.
• 2009-May-06, 07:37 PM
dirty_g
same for you. The point it its not rude enough to report is it. Being sarcastic or snarky you can get away with. Being outright nasty you cannot.
• 2009-Aug-25, 03:31 PM
hhEb09'1
• 2009-Aug-25, 05:04 PM
Spoons
hhEb09'1 - Did Phil ever end up getting on to Colbert? If so I must have missed it. If not, we must petition for this! 2 stars on one show - a binary episode.
• 2011-May-26, 05:49 AM
Ze_Kraggash
Quote:

Originally Posted by hhEb09'1
Page 205, DFTS; describes the red giant Sun swollen to 100 times its present radius. It mentions that the gravity at the surface will be less than 1 percent of Earth gravity.The square inches are measured at the current radius, I guess, before and after. By the time it gets to the surface of the red giant, the radiation per square inch will be 1/10,000 of that, right? But, wouldn't luminosity be related to the surface?

If the Sun is 100 times bigger, it area will be 100 x 100 = 10,000 times bigger than today. However, on page 204 it says the luminosity will be 2,400 times as great. That means each square inch will be (2,400)/(10,000) or roughly 1/4 as luminous as today.
• 2011-May-29, 04:55 AM
grapes
Quote:

Originally Posted by Ze_Kraggash
If the Sun is 100 times bigger, it area will be 100 x 100 = 10,000 times bigger than today. However, on page 204 it says the luminosity will be 2,400 times as great. That means each square inch will be (2,400)/(10,000) or roughly 1/4 as luminous as today.

Yes, I think that was the point I was trying to make. I'll have to go back to the book to remember the context...
• 2011-May-30, 12:27 AM
Tobin Dax
Remember that Luminosity per square inch varies with temperature to the fourth power, following the Stefan-Boltzmann law. The red giant sun will have a cooler surface temperature than its current temperature, and so the luminosity per square inch will be less then than it is now.
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