Kitworks

I heard it recently on a podcast, I think, or possibly on NPR, but I can't for the life of me remember where and it is impossible to find on Google because of all the videos of giant hornets. Any help would be hugely appreciated!

If we were sufficiently motivated, could we constantly rejuvenate a star by pumping matter out of it, and then resupplying it with fresh hydrogen, always keeping the two processes in balance to maintain roughly constant mass/elemental composition?

Obviously it would be very expensive and impractical, but I could imagine us doing it for our Sun for sentimental reasons.

If you had two spaceships, each traveling at a constant speed greater than half the speed of light directly towards each other, what would they see?

I'm pretty sure they would each have the same view, as their frames of reference are mirrored images of each other.

Also can work out that, even though they would be approaching each other at a combined velocity greater than light speed, it would look different than actual super-luminal travel, since you would still see the other ship's approach (as the others aren't out-pacing their light emissions).

I've got some other hunches but they're probably wrong so I'll wrap it up - interested to hear what I'm missing (since I know I broke my brain

I understand that many ancient Greek philosophers thought that vision relied on rays cast from our eyes onto an object, and then returned to the eye, which I can see as a not totally unreasonable idea. (After all, we now do exactly that for sonar, radar, lidar...)

My question is - what did they think lamps were doing? Obviously, even if vision worked as they thought, it was contingent on some source of illumination. Put a person in a totally dark room and they can't see anything. So what was their understanding of what lamps, fires, the sun, etc. were doing to objects?

(I feel like this is the biggest reason we look back and go, "Duh, greeks, how dumb are you?" so I feel like there must ha