Comment by chr15m

Thanks for pointing out those follow ups. Interesting stuff!

> correct and uncontraversial

From the original quote it is clear he was referring to the idea of aliens being detectable by infrared because they will absorb all of their sun's energy. Later in the same paragraph he says:

> Unfortunately I went on to speculate about possible ways of building a shell, for example by using the mass of Jupiter... > These remarks about building a shell were only order-of-magnitude estimates, but were misunderstood by journalists and science-fiction writers as describing real objects. The essential idea of an advanced civilization emitting infrared radiation was already published by Olaf Stapledon in his science fiction novel Star Maker in 1937.

So the Dyson Sphere is a rhetorical vehicle to make an order-of-magnitude estimate, not a description of a thing that he thought could physically exist.

Full quote from the video cited before "the idea was a good one":

> science fiction writers got hold of this phrase and imagined it then to be a spherical rigid object. And the aliens would be living on some kind of artificial shell. a rigid structure surrounding a star. which wasn't exactly what I had in mind, but then in any case, that's become then a favorite object of science fiction writers. They call it the Dyson sphere, which was a name I don't altogether approve of, but anyway, I mean that's I'm stuck with it. But the idea was a good one.

Again he explicitly says this "wasn't exactly what I had in mind." This one hedges a bit more and could be interpreted as his saying the idea of a Dyson Sphere is a good one. He may have meant that in the sense of it being a good science fiction idea though, and he subsequently goes on to talk about that.

The Dyson Sphere is good for order-of-magnitude calculations about hypothetical aliens, and also for selling vapourware to the types of people who uncritically think that vapourware is real.