Wikipedia:Reference desk/Archives/Science/2018 June 1

= June 1 =

Unknown Soviet Helicopter
Which model is this helicopter? Is seems not to be a Mil Mi-8.

--Doroletho (talk) 12:03, 1 June 2018 (UTC)
 * (ec) Yes, it's an Mil Mi-4 with Aeroflot marking, here's a better picture, also called "Trumpeter", and here's a model of it. DroneB (talk) 12:35, 1 June 2018 (UTC)

"Minimize sun exposure between 10 a.m. and 4 p.m."
This is an EPA recommendation: https://www.epa.gov/sunsafety/uv-index-scale-1 Assuming they meant 12 as midday, why is it asymmetric? I've seen research suggesting that our bodies can repair DNA damage more effectively in the morning, but they seem to take this as a fact. Is it a fact that the pm sun is more dangerous than the am sun? --Doroletho (talk) 12:17, 1 June 2018 (UTC)
 * No, it is because real (solar) noon is typically closer to 1 PM in the summer (because of daylight saving time), than to 12:00. However, this varies with location and time zone, so it is not entirely accurate for everyone. - Lindert (talk) 12:26, 1 June 2018 (UTC)
 * Yes, Arizona, for example, has no DST, but plenty of sun. OK, so they chose the easier to understand, but kinda wrong way of expressing 'avoid the sun 3 hours before or after solar noon'. I wonder if they have a style guide explicitly dealing with this. Expressing ideas in this form can lead to misunderstandings. It reminds me of the message at the beginning of the AIDS epidemics, in the 90s. They could have said the "HIV is contagious through blood and semen", but chose the 'through bodily fluids' form instead to avoid shocking people. Even well-educated were then afraid of sweat and saliva of HIV+ patients.  --Doroletho (talk) 13:35, 1 June 2018 (UTC)
 * Actually, any amount of exposure to the sun can have detrimental effects. The higher the UV index, the higher the risk. The closer to high noon, the higher the UV index. Hofhof (talk) 16:04, 1 June 2018 (UTC)
 * That depends on your skin-type. If you have the skin-type people in Northern Scandinavia have but you live at a place where the indigenous people are as black as coal, you shouldn't be surprised that your skin can't tolerate being exposed to the Sun at Noon. Count Iblis (talk) 13:05, 2 June 2018 (UTC)


 * In any case if the 3-hour approximation is appropriate for one latitude, it won't be ideal for another. It really is just a rough idea. --76.69.118.94 (talk) 21:55, 1 June 2018 (UTC)
 * And of course not every city or state lies dead center in its nominal time zone, and solar noon doesn't happen at the same time every day. For example, in Phoenix solar noon is actually around 12:30 anyway (at least during the summer months) not the 12:00 you'd expect from its time zone.  In any case, as Jayron32 notes below, it works well as a rule of thumb; it's not meant to be a bright-line law.  The Sun doesn't turn its UV emission on at 9 am sharp (solar time) every morning. TenOfAllTrades(talk) 13:25, 2 June 2018 (UTC)


 * "the beginning of the AIDS epidemics, in the 90s" — is that a typo or what? —Tamfang (talk) 22:41, 3 June 2018 (UTC)
 * The article HIV/AIDS in the United States mentions 1981 as a year when it started to really get the public's attention, and a number of public figures had died from it by the mid-1980s. ←Baseball Bugs What's up, Doc? carrots→ 22:48, 3 June 2018 (UTC)
 * Yes, that's obviously not the 90s, but the 80s: the "outbreak in the early 1980s of the virus that causes AIDS.", when " public officials, ... failed to communicate this information in ways most people understand. " "At the onset of the AIDS epidemic, officials and journalists spoke of “bodily fluids” to avoid using words like penis, vagina and sperm." "Ambiguity was costly. People avoided restaurants where waiters were perceived to be gay". Extracted from the NYTimes article "Epidemics of Confusion . --Doroletho (talk) 12:44, 4 June 2018 (UTC)
 * There's never been a taboo against talking about blood. ←Baseball Bugs What's up, Doc? carrots→ 18:05, 4 June 2018 (UTC)
 * It is interesting (if off-topic) to note that the first AIDS death in the U.S. (of Robert Rayford) was a few months before the Stonewall Riot. Wnt (talk) 02:33, 5 June 2018 (UTC)


 * See false precision. You aren't supposed to time the matter with an atomic clock and race through the door at the exact moment those hours strike.  It's just a reminder to limit sun exposure when it is highest in the sky.  -- Jayron 32 02:14, 2 June 2018 (UTC)
 * Of course, if you're writing a movie, a TV show, or a suspense novel, it's a different matter. Then if your hero gets out of the sun at 9:59:59 am he's perfectly unharmed, otherwise he's doomed to die. --76.69.118.94 (talk) 11:35, 2 June 2018 (UTC)