Jyrki wrote:Some folks were worried about a supernova blinding us as a consequence of a near point-like like source capable of 'turning night into a day' must have awfully high luminosity. Does that wash?
Well, the brightest & closest known supernova was
Vela 12,000 years ago which was supposedly as bright as a full moon.
Betelgeuse is twice as close as
Vela so it might be as bright as 4 full moons
which would certainly make for a bright night but not a particularly bright day.
And a supernova would be a
twinkling near point-like like source
with it's dangerous UV-C radiation absorbed out by our ozone layer.
Richard Feynman was able to watch the Trinity A-bomb blast with his naked eye
by using just the windshield of a Jeep for UV-C radiation protection
and his natural "blink reflex" to visible light for the rest.
Now there might be a few folks willing to simply stare at such a supernova
for extended periods...but they should read about
Joseph Plateau
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http://en.wikipedia.org/wiki/Laser_safety wrote:
<<The coherence, the low divergence angle of laser light and the focusing mechanism of the eye means that laser light can be concentrated into an extremely small spot on the retina. A transient increase of only 10 °C can destroy retinal photoreceptors. Sufficiently powerful visible to near infrared laser radiation (400-1400 nm) will penetrate the eyeball and may cause heating of the retina, whereas exposure to laser radiation with wavelengths less than 400 nm and greater than 1400 nm are largely absorbed by the cornea and lens, leading to the development of cataracts or burn injuries. Infrared lasers are particularly hazardous, since the body's protective "blink reflex" response is triggered only by visible light.>>
[quote="Jyrki"]Some folks were worried about a supernova blinding us as a consequence of a near point-like like source capable of 'turning night into a day' must have awfully high luminosity. Does that wash? [/quote]
Well, the brightest & closest known supernova was [url=http://en.wikipedia.org/wiki/Vela_Supernova_Remnant][b]Vela[/b][/url] 12,000 years ago which was supposedly as bright as a full moon.
Betelgeuse is twice as close as [url=http://en.wikipedia.org/wiki/Vela_Supernova_Remnant][b]Vela[/b][/url] so it might be as bright as 4 full moons
which would certainly make for a bright night but not a particularly bright day.
And a supernova would be a [b]twinkling[/b] near point-like like source
with it's dangerous UV-C radiation absorbed out by our ozone layer.
Richard Feynman was able to watch the Trinity A-bomb blast with his naked eye
by using just the windshield of a Jeep for UV-C radiation protection
and his natural "blink reflex" to visible light for the rest.
Now there might be a few folks willing to simply stare at such a supernova
for extended periods...but they should read about [url=http://en.wikipedia.org/wiki/Joseph_Plateau][b]Joseph Plateau [/b][/url]
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[quote=" http://en.wikipedia.org/wiki/Laser_safety"]
<<The coherence, the low divergence angle of laser light and the focusing mechanism of the eye means that laser light can be concentrated into an extremely small spot on the retina. A transient increase of only 10 °C can destroy retinal photoreceptors. Sufficiently powerful visible to near infrared laser radiation (400-1400 nm) will penetrate the eyeball and may cause heating of the retina, whereas exposure to laser radiation with wavelengths less than 400 nm and greater than 1400 nm are largely absorbed by the cornea and lens, leading to the development of cataracts or burn injuries. Infrared lasers are particularly hazardous, since the body's protective "blink reflex" response is triggered only by visible light.>>[/quote]