Henry Spencer wrote:

In article ,
Bruce Palmer wrote:

On some afternoons, depending on clouds and atmospheric dust, the sun
looks like a giant orange ball that you can actually look at without eye
damage as it sets...


A note of caution: safely low visible-light intensity doesn't necessarily
equate to safely low UV and IR intensity (especially the latter, which has
a tendency to penetrate clouds etc. better than visible light). Your eye
is not a reliable guide to what's eye-safe.

(I'll admit to having yielded to the temptation to look in such situations,
especially when there were naked-eye sunspot groups visible... but only in
brief glances, never looking steadily.)

Interesting. I hadn't thought of that. Luckily I can't ever
remembering actually staring at it that way for more than a short while.

Nevertheless, as you move away from the sun, beyond 1 AU, there must be
a point at which the intensity of harmful radiation falls below the
level that will damage your eyes. I'm going to try to find an
ophthamologist (sp?) who might be able to tell me the level of radiation
(at whatever wavelength) considered "safe". From there it should be
simple to derive a distance from the sun. I realize that the "safe"
distance in an ocular sense might not be "safe" in terms of other
energized particles that could cause radiation damage of other sorts.

I was watching a hockey game the other night and one of the opposing
team members' last name was Van Allen. At one point I yelled at the TV
"How's your radiation belt?" and got the most peculiar glance from my
wife. She sort of laughed. I thought it was funny. Guess you had to
be there.

--
bp
Proud Member of the Human O-Ring Society Since 2003