4 ms·
> If I can see it, that means that it's radiating in all directions, not just into space That depends on what you mean by "see". If you paint a square on a whi
by powersnail 3y ago
> If I can see it, that means that it's radiating in all directions, not just into space
That depends on what you mean by "see". If you paint a square on a white paper with a magical paint that absorb 100% of the light, you can still see that there's a black square, because it's sitting on a contrasting background.
Even if the material is perfectly radiating everything to space, i.e., the roof sends no light to your eyes, it's still just a patch of blackness among normal things, and you can see the shape of it, just like a puddle on the road at night, as you walk with your back to the moon.