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(15 replies)

UV-radiation hazardous POWER

No.13420239 ViewReplyOriginalReport
Hello everyone. There is a LOT of controversy surrounding UV-radiation power that is considered hazardous, so I decided to estimate it myself based on assumption: people do not get a hazardous level of UV light during 10 minute outdoor July-month walking in middle Europe.
Let's go.
https://www.ncbi.nlm.nih.gov/books/NBK401584/
In that paper we have estimation of 5% of sun light power at ocean level (below atmosphere) is UV light.
See picture in next post from EU PHOTOVOLTAIC GEOGRAPHICAL INFORMATION SYSTEM where we have daily irradiance of 672 W/m2 somewhere in Poland at 11:00 o'clock.
Okay, so we got UV part equal 0.05 * 672 = 33.6 W/m2
Now let's consider human body open parts as 20% of all body surface area which is approx. 1.90 m2 according to Mosteller RD. Simplified calculation of body-surface area. N Engl J Med 1987;317:1098 and divide it by two because we have sun lighting from one direction, not everywhere.
So we got 0.2 * 1.9 * 0.5 = 0.19 m2.
So power of UV-radiation exposure is 33.6 * 0.19 = 6.4 W.
BUT take a look at datasheet of typical UV LED https://www.mouser.fr/datasheet/2/50/UV3TZ-XXX-XX-881014.pdf
so here we have 10mW and in general you can find something from 1 mW to 100 mW, but them almost by any resource (including manufacturers) named dangerous (cancer-inducing, wear protection and so on).
Also I have an mercury lamp which is highly dangerous according to its manual, it has 1 W/m2 power.
Energy of Sun MUCH greater and someone is really wrong here, maybe me? Appreciate your answer.
P.S.: I have a clue: maybe it is our eyes are much more susceptible for UV-radiation than skin and all of that based on danger for eye vision, but on the contrary we have a lot of reflecting surfaces on sunny day which may return us to a problem in numbers I have here.
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(28 replies)

????

No.13421272 ViewReplyOriginalReport
>Multiplication is NOT repeated addition
>Exponentiation is NOT repeated multiplication
>Modulus is NOT the remainder function
So what are they then?
>inb4 some faggot copes by using math jargon like "fields" or some shit.
Explain it simply. You should be able to do that if you really understand it, right Anon?
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(23 replies)
No.13420813 ViewReplyOriginalReport
The set of ordinal numbers has the important property of being well ordered, which means that every subset has a minimum element. This is unlike the integers or the positive real numbers, where any element has another that comes before it.
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(16 replies)
No.13418458 ViewReplyOriginalReport
Did any of you ever do a line of coke before an oral exam? How did it go?
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(229 replies)

/mg/ - maths general

No.13389731 ViewReplyLast 50OriginalReport
Formerly >>13358185

Kuranishi edition.

Talk maths.
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(22 replies)

Gambler Fallacy Paradox

No.13421440 ViewReplyOriginalReport
The following does not seem to square with the gamblers fallacy bias.

Lets take a roulette wheel (50-50 red black only, ignoring green)

True
>4 R in a row is less likely than 3 R in a row

So given that it is less likely, and there are only two options, why isnt it more likely to be black on the fourth spin?
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(17 replies)

Wolfram's new science

No.13417070 ViewReplyOriginalReport
Stephen Wolfram and his "new kind of science" which is redoing all physics based on better math and cellular automata theory. Discuss. He sounds too smart to be a total whackjob about it. Tell me more about it if you know. Pseud or onto something? I didn't understand a jack shit about what he was talking about on that podcast because I'm not physicist nor advanced math man.
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(75 replies)
No.13410722 ViewReplyLast 50OriginalReport
https://www.youtube.com/watch?v=YBf2PU_Bvog
How right is he here? [6 minute video]
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(22 replies)
No.13421175 ViewReplyOriginalReport
This might be a stupid question and is very hypothetical but if you would travel to the past would your past self have a consciousness? Sounds weird at first but it's strange.
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(784 replies)

/sfg/ - Space Flight General

No.13417764 ViewReplyLast 50OriginalReport
Blue Balls no more edition
Previous: >>13413263

5:30 AM Central time Wednesday: SpaceX Crew Dragon Relocates
https://www.youtube.com/watch?v=kouNcNlfprQ

8:30 AM Central time Wednesday: Nauka launches on a Proton-M
https://www.youtube.com/watch?v=t-V-hgTPZBs
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