Wikipedia:Reference desk/Archives/Science/2016 June 28

Science desk
< June 27	<< May | June | Jul >>	June 29 >

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

June 28

Mechanism of desquamation

When you experience a severe sunburn, it's not a surprise to experience desquamation a few days later. What causes the skin to start peeling? Or in other words, what causes the old skin to start peeling at a specific time/day, as opposed to some hours earlier or later? Is it merely that the new skin reaches a threshold of viability (and if so, what is it), or is there some other trigger? Nyttend (talk) 01:30, 28 June 2016 (UTC)

I'll hypothesize that the mechanism is the same as what causes individual dead skin cells to be shed normally, constantly, 24 hours per day, as individual skin cells reach their end of useful life and dry out.

When you get sunburned, a whole layer of skin cells die off all at once, so they shed in quantities sufficient for connected dead cells to peel off together.

I've never personally noticed that my sunburn starts peeling at a specific time or day. The process of peeling starts in small spots at any time of day, and spreads to larger areas over the next few days. The more badly burned areas start peeling first. ~Amatulić (talk) 05:01, 28 June 2016 (UTC)

I am curious as to the principle behind Foot Peeling Liquid.[1][2][3][4] Is it the same principle that is behind sunburn peeling? --Guy Macon (talk) 08:31, 28 June 2016 (UTC)

Alpha hydroxy acids, perhaps? Or something else: we have a chemical peel article which goes into other possibilities. -- The Anome (talk) 09:51, 28 June 2016 (UTC)

Law of Science or thaumaturgy

Recently I saw on internet a very amazing phenomenon. It was a simple LCD calculator we all use now and then. A powerful rare-earth magnet was brought near it (keeping just a few millimeters from the screen), and the showman/physicist pressed seven or eight buttons to bring a random value to the screen (though quite notably he didn't touch the calculator's memory button). Then he took the magnet away and pressed the "clearscreen" button, making screen empty except for a zero. The machine was switched off and on again. The inevitable zero reappeared. Then he brought the magnet near the LCD again, and lo....the random value of 7 or 8 digits reincarnated out of the blue !

Of course I tried it several times and failed each. Almost skeptical though, a little doubt lingers - may be I missed something, somewhere ? (Afterall I can't fly a kite or play the piano - but that doesn't mean that those pastimes are impossible ! )

Was it a sleight of hand or like Nitinol memory wire strong magnet too has a memory.  Jon Ascton  (talk) 10:43, 28 June 2016 (UTC)

You said you "saw on internet" - so you saw a video. Sadly, a very large percentage of those things are faked. Point us to where you saw it - and maybe we can point out how it was done. For sure it isn't real - it's just a matter of how it's not real. SteveBaker (talk) 16:57, 28 June 2016 (UTC)

My guess is the calculator had some kind of undo button ... made with something metallic. :) Wnt (talk) 17:27, 28 June 2016 (UTC)

Was it this video ? AllBestFaith (talk) 22:58, 29 June 2016 (UTC)

As one of the comments on the video points out - 55 seconds into the video, the calculator clears the display to 0 a fraction of a second BEFORE the guy presses the 'C' button. It's clearly fake - but how? If I were setting out to do that, I'd dismantle the calculator and solder some thin wires to a few of the pads on the underside of the keyboard - then thread those through a hole in the table under the calculator and attach a push button switch to each one. It would be easy to use the memory store/recall functions to achieve the effects demonstrated - so perhaps only a couple of buttons would need to be rigged up that way. SteveBaker (talk) 05:56, 30 June 2016 (UTC)

List of video editing software. WP:NOTHOWTO. AllBestFaith (talk) 13:20, 30 June 2016 (UTC)

If it is that video, it was done by pasting a still frame of the saved value over the display. You can see the whole boundary of the display jump at the beginning and end, and there are frozen JPEG/MPEG compression artifacts on the display in between. This first happens at 0:21–0:25 and next at 0:51–0:56. A competent special effects person could have made a much more convincing effect with motion-tracking software. Watch this video (about 3 minutes; the interesting part starts around 1:00) and see if you're still impressed by the calculator. -- BenRG (talk) 22:07, 30 June 2016 (UTC)

Human breathing in past geological periods

Per Jurassic for example, "Mean atmospheric O₂ content over period duration" was "c. 26 vol % (130 % of modern level)" and "mean atmospheric CO₂ content over period duration" was "c. 1950 ppm (7 times pre-industrial level)". In theory, would such levels be dangerous for human to breathe and would a human sense some differences compared to modern everyday air? Brandmeister^talk 17:18, 28 June 2016 (UTC)

The reference can be found here Hypercapnia#Tolerance. It says that below 1% atmospheric CO^2 there is no detectable limitation over a lifetime. Unless I'm mistaken you still need 5 times 1950ppm to get 1%. I'm fairly certain 26% oxygen vs 21% is also not noticeable, but I don't' have a source.Vespine (talk) 00:32, 29 June 2016 (UTC)

As to the oxygen level, hyperoxia doesn't say mentions medical usage at 28% while oxygen toxicity talks about effects at concentrations significantly above that, which at leasts suggests that breathing 26% full-time should be safe, but is hardly conclusive. --69.159.9.187 (talk) 03:11, 29 June 2016 (UTC)

There was a study from a few years ago that claimed that short exposure (hours) at 1000 ppm of CO2 had a discernible minor impact of mental acuity, while 2500 ppm had a much more dramatic effect. [5] Dragons flight (talk) 05:39, 1 July 2016 (UTC)

Leiobunum free online species key

Hello! I recently found a harvestman (genus: probably Leiobunum) which I'm having trouble identifying. Is there any free (this is important; I know there is a ton you can buy!) online species key for Leiobunum? There probably isn't, seeing as harvestmen (or invertebrates as a whole!) are of little public interest (why?!). I'd like to post a picture of her but I have no good camera that will provide details of the characteristic features ):. Thanks for reading, Megaraptor12345 (talk) 17:31, 28 June 2016 (UTC)

Help us help you: Leiobunum is cosmopolitan, where in the world did you collect this critter? E.g. here's [6] a decent-looking key for NZ but that won't help if you're in central Europe. SemanticMantis (talk) 17:51, 28 June 2016 (UTC)

Ah yes, how stupid of me. I found it in Ireland. But I have a written key to the British species, and I can't identify it with that (and I am quite experienced in arthropod identification), so I need one for Europe, or just northern continental Europe at least. Thanks, Megaraptor12345 (talk) 21:06, 28 June 2016 (UTC)

Ok, sorry I can't find a good key for Ireland. Have you seen this [7] page for Nottinghamshire? It is not a key but has very good pics and descriptions for several Leiobunum. Sadly, you are probably the best person at harvestman ID reading this. You might in the future try asking for IDs and keys on reddit - both WhatsThisBug [8] and Entomology [9] have fairly large and skilled communities that are focused on arthropod stuff. SemanticMantis (talk) 15:38, 29 June 2016 (UTC)