Radiation Mass Density
Most recent answer: 04/20/2017
- Stefanescu Marian (age 20)
Cluj Napoca, Romania
Your calculation can be greatly simplified, reducing the number of places that errors can creep in, e.g. in converting 100 billion to exponential form. Take one star and ask whether in its lifetime the radiation emitted has mass comparable to the star's mass. Take your power output of the Sun, 4*1026 W times the total lifetime of a star like that, around 1018 s, to get around 4*1044 J radiant energy. That's 4*1027 kg. As you say, that's a little more than 1/1000 of the Sun's mass. The point of doing the calculation this way is that you see right off that changing the number of stars doesn't change that ratio. It will come out different for different types of stars, but you'll still end up with most of the energy as star rest energy, not radiation.
In the long run as things clump into black holes and then (we believe) evaporate via Hawking radiation stars will turn into a thin radiation soup, but that's a much, much slower process.
Mike W.
(published on 04/20/2017)