Radiation

[desperance]

Umm - thinks - is it possible to radiate in one direction only, or only in a few? Or is 'radiate in all directions' an absolute tautology, in all circumstances? Answer on one side of the interweb only...

Comments

[adrian-turtle.livejournal.com]

Radiation is usually isotropic, but a radiation source can be partly shielded so it only radiates on one side. (Think of a charcoal grill. Light and heat radiate up and sideways, but the base of the grill mostly prevents it from going down.) An individual piece of charcoal may be radiating in all directions, but a person looking at the whole grill from across the yard would not perceive it on that scale.

[desperance.livejournal.com]

Clear as unshielded glass, thank you - and a new word, too (isotropic - I have almost no scientific vocabulary at all. And yet I aspire to write SF. That's 'aspire' in the standing-at-the-bottom-of-the-mountain, gazing-up-in-awe-and-wonder sort of sense...).

[adrian-turtle.livejournal.com]

"Isotropic" is a great word, if you're just starting to build your scientific vocabulary. It means something is the same in all directions. If there is more in one direction than others, it is "anisotropic." If you're looking from a distance, the way we look at stars, radiation is isotropic. But if we were close enough, there might be enough anisotropy to matter, like with the grill example.