# Thread: Errors in Death from the Skies

1. If you think people are being rude, report it.

2. 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.

3. 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.

4. Newbie
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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.

5. 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...

6. 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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