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The The Magician's Nephew is about red giants, or at least the expanding phase of a star like the sun. It's from the 1950s, and C. S. Lewis wrote science fictio

by Vecr 3y ago

The The Magician's Nephew is about red giants, or at least the expanding phase of a star like the sun. It's from the 1950s, and C. S. Lewis wrote science fiction earlier.

gwern 3y ago
No, I think OP makes a good case that Lewis did not mean an expanding red giant in _Magician's Nephew_, even if he could have used the most recent science at the time to choose to do so: "“So big, so red, and so cold.” “It has always been so,” said Jadis. “At least, for hundreds of thousands of years. Have you a different sort of sun in your world?”" A red giant expanding to the point of taking up much of the sky would not be 'cold', nor would it 'always been so...for hundreds of thousands of years'. (It would be hot, the world heating up at that close an approach, and the expansion quite visible on the order of millions of years rather than totally static and unchanging.) That only is consistent with the cooled-down prior version.
- Vecr 3y ago
  How would it appear large in the sky though? Gravitational waves are out, maybe solar wind and light pressure were supposed to be keeping the planet orbiting higher? Or is the point that the planet was always close, but only cooled down enough for life after the star started cooling down?
  - gwern 3y ago
    > Initial estimates put the sun’s lifespan at around 20 million years. It could hardly be much younger than that, so its lifetime appeared to be mostly over. Soon it would burn out. What about the earth? It would freeze over, its orbit would decay, and it would draw closer to the husk of the sun, becoming tidally locked. Ultimately, it would fall into the remains of the sun and be destroyed, but not until long after all life went extinct.
    - Vecr 3y ago
      Yeah, that's in the article. I should look at the emissions curve for various stages of red giant stars. Maybe it's a late phase red giant, and the planet was always far away? It would need increased emissions and then they would have to start going down again. It is kind of suspicious for life to start on a planet only after the star starts expanding into a red giant, but it might be a similar handwave to the characters being human like.

by Vecr 3y ago

The The Magician's Nephew is about red giants, or at least the expanding phase of a star like the sun. It's from the 1950s, and C. S. Lewis wrote science fiction earlier.

gwern 3y ago

No, I think OP makes a good case that Lewis did not mean an expanding red giant in _Magician's Nephew_, even if he could have used the most recent science at the time to choose to do so: "“So big, so red, and so cold.” “It has always been so,” said Jadis. “At least, for hundreds of thousands of years. Have you a different sort of sun in your world?”" A red giant expanding to the point of taking up much of the sky would not be 'cold', nor would it 'always been so...for hundreds of thousands of years'. (It would be hot, the world heating up at that close an approach, and the expansion quite visible on the order of millions of years rather than totally static and unchanging.) That only is consistent with the cooled-down prior version.

Vecr 3y ago
How would it appear large in the sky though? Gravitational waves are out, maybe solar wind and light pressure were supposed to be keeping the planet orbiting higher? Or is the point that the planet was always close, but only cooled down enough for life after the star started cooling down?
- gwern 3y ago
  > Initial estimates put the sun’s lifespan at around 20 million years. It could hardly be much younger than that, so its lifetime appeared to be mostly over. Soon it would burn out. What about the earth? It would freeze over, its orbit would decay, and it would draw closer to the husk of the sun, becoming tidally locked. Ultimately, it would fall into the remains of the sun and be destroyed, but not until long after all life went extinct.
  - Vecr 3y ago
    Yeah, that's in the article. I should look at the emissions curve for various stages of red giant stars. Maybe it's a late phase red giant, and the planet was always far away? It would need increased emissions and then they would have to start going down again. It is kind of suspicious for life to start on a planet only after the star starts expanding into a red giant, but it might be a similar handwave to the characters being human like.