Science desk
< April 2	<< Mar \| April \| May >>	April 4 >

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.

April 3

Lifetime of information as a function of temperature

See Timeline of the far future#Technological_projects. It gives a list of long-lived storage devices by their expected lifetime. If you investigate, what you find is that the expected lifetime of the storage device is always given as a function of temperature. See [1] for example. It states that the lifetime of the storage device is greater than $3.3\times 10^{17}$ seconds at room temperature.

My question is: How do you calculate the expected lifetime of a storage device as a function of temperature, in general? I tried to reproduce the calculation in that paper but I couldn't get the same answer (my every attempt was off by at least one or two orders of magnitude, and I really don't know what I should be doing). --49.184.160.10 (talk) 10:39, 3 April 2018 (UTC)[reply]

How do you know they did it right? ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:55, 3 April 2018 (UTC)[reply]

Consider the following data storage scheme: Carve ones and zeros into a block of pure water ice a few degrees above absolute zero. Will the data remain readable forever? No. The nature of water ice is that the atoms vibrate, and occasionally break loose from where they are attached to other atoms and re-bond somewhere else. This causes the surface of water ice to slowly morph, eventually erasing your ones and zeros. And the effect is a function of temperature; ice at 20 degrees above absolute zero will erase the ones and zeros faster than ice at 10 degrees above absolute zero will.

To do a proper calculation, you need to take into account the carving. Ones and zeros that are a kilometer tall will resist erasure longer than ones and zeros that are a micrometer tall.

All of the above is technically accurate, but essentially useless for calculating the life of the data. First, the morphing isn't the only thing that erodes the surface of water ice. There is also sublimation. In some environments (lots of UV light hitting the ice, ice is in a vacuum) the sublimation can be far faster. In darkness at a thousand atmospheres, not so much.

Now consider an experiment where a very patient researcher carves ones and zeros in some ice and tests the degradation over time as the temperature gets higher. There he is, happily documenting how the carved digits degrade slightly faster as he raises the temperature. Then he reaches zero degrees Celsius. Suddenly the erasure rate changes -- a lot -- and the earlier conclusion that ones and zeros that are a kilometer tall will resist erasure longer than ones and zeros that are a micrometer tall doesn't look so good. --Guy Macon (talk) 13:04, 3 April 2018 (UTC)[reply]

Thanks for your answer; yes, you can always measure it empirically. The expected life will probably be a complicated function of temperature, due to phase transitions for example. I probably need more background knowledge before I can calculate it theoretically. --49.184.160.10 (talk) 13:23, 3 April 2018 (UTC)[reply]

As the ice melts, it will gradually become less and less readable. At what point is the information lost?--49.184.160.10 (talk) 16:05, 3 April 2018 (UTC)[reply]

In the case of ones and zeros carved into a block of pure water ice, all information is lost when the temperature of the ice rises enough so that 100% of the ice turns to water. --Guy Macon (talk) 23:16, 3 April 2018 (UTC)[reply]

Sisters genetically more diverse than brothers?

Are sisters genetically more diverse than brothers? After all, the sister can get any of the two Xs from the mother, but the brothers have to get the only Y from the father.--Hofhof (talk) 13:59, 3 April 2018 (UTC)[reply]

Hint, a son can also have either of the two X chromosomes from the mother. Dragons flight (talk) 14:03, 3 April 2018 (UTC)[reply]

In fact, since (full) sisters always get the same X chromosome from their father, they share more DNA with each other on average than brothers do. - Lindert (talk) 14:28, 3 April 2018 (UTC)[reply]

This is likely based on a misconception that humans only have an X and then an X or Y chromosome. So, women have XX and men have XY - only. Humans have 23 pairs of chromosomes. One pair is XX or XY out of the 23. The other 22 pairs are not X or Y chromosomes in any way. Further, if you get an X chromosome from your father, he obviously got that X chromosome from his mother - your grandmother. That means that you do not, in any way, have the Y chromosome from your grandfather. That does NOT mean that you have no chromosomes from your grandfather. Out of the remaining 22 chromosomes, some of those could from from your grandmother or grandfather. It is statistically possible that all come from one or the other, but that isn't common. 209.149.113.5 (talk) 14:36, 3 April 2018 (UTC)[reply]

The only chromosome you're particularly likely to get from a grandfather would be the Y chromosome from your paternal grandfather. The Pseudoautosomal regions (and mutation rates) are small enough that you could perhaps still call it your paternal grandfather's Y chromosome. You don't generally inherit any other chromosome from any grandfather, you inherit parts of their chromosomes. Actually the only other chromosome you could say you're likely to get from anyone would be for females who inherit their father's X chromosome (in this case, even more clearly so given the vastly differing sizes). Chromosomal crossover means any other chromosome is generally a mishmash of the two chromosomes from whichever parent, and the further back you go, even more of a mishmash. To be fair, there are occasions when crossing over does not occur, however this can also often result in bad things. Also it doesn't happen very often with male gametes. (So if we're talking about grandfathers, all chromosomes are likely to have had at least one cross over. I don't think we're talking about a nil chance and I'm sure it's also possible one of the autosomes the crossover was small enough that you could still say it's largely the same as one of the grandfathers autosomes. But still, I'm not convinced it's generally particularly useful to think of inheritance as happening on a whole chromosome level outside of the sex chromosones.) See Nondisjunction#Sex-specific differences in meiosis and the linked source [2]. BTW, how chromosomes are inherit has been discussed many times on the RD before. See Wikipedia:Reference desk/Archives/Science/2017 September 9#Genetics questions for one such discussion. Nil Einne (talk) 15:38, 3 April 2018 (UTC)[reply]

Correct. I simply felt it necessary at this point to use the simplistic model used in grade schools when they track genetic traits in flies or mice. 209.149.113.5 (talk) 17:13, 3 April 2018 (UTC)[reply]

Also, the X and Y chomosome do not have the same number of genes. The following are some gene count estimates:

X CHROMOSOME:

Estimated by	Protein-coding genes	Non-coding RNA genes	Pseudogenes
CCDS	804	-	-
HGNC	825	260	606
Ensembl	841	639	871
UniProt	839	-	-
NCBI	874	494	879

Y CHROMOSOME:

Estimated by	Protein-coding genes	Non-coding RNA genes	Pseudogenes
CCDS	63	-	-
HGNC	45	55	381
Ensembl	63	109	392
UniProt	47	-	-
NCBI	73	122	400

--Guy Macon (talk) 19:37, 3 April 2018 (UTC)[reply]

For those interested in the biology behind it, this is for the obvious reason that only biological males have a Y chromosome, so it can't contain any genes essential for life. Hence, selective pressure drives the Y chromosome to get smaller over time. In some species it consists of just the single gene TDF/SRY, which is what initiates development of the male phenotype in embryos. Eventually it disappears entirely and is replaced by some other sex-determining mechanism, which has happened in a few species, as stated in the Y chromosome article. --47.146.60.177 (talk) 06:09, 4 April 2018 (UTC)[reply]

Non-oceanic tides

Why are there no tides except in the ocean and connected waters? I've found reasonable pop-sci explanations, e.g. [3] and [4] and [5] (so I don't need to be told the answer to my question), but no reliable sources for expanding the tide article. Nyttend backup (talk) 14:47, 3 April 2018 (UTC)[reply]

Extended content

Some large lakes have small, barely measurable diurnal tides like oceans; this article notes that gravitational tides on the Great Lakes are about 5 cm; which is often masked by other effects. --Jayron 32 14:54, 3 April 2018 (UTC)[reply]

This article and this article notes that the tides are proportional to the volume of the body of water itself; since the oceans are vastly larger, they have vastly larger tides; smaller bodies of water probably have calculable tidal effects which are entirely overrun by other effects; which is to say they do have tides, but you'll never notice or measure it. --Jayron 32 14:57, 3 April 2018 (UTC)[reply]

Notice also that tides in the Mediterranean are not much larger ([6] says about 10cm, when the surface of the Mediterranean Sea is about ten times as large as that of the Great Lakes combined, and its depth is larger), so I am not sure that "proportional to the volume" is a really good thumb rule. The resonance phenomena (cf. theory of tides) are a bit complex. Tigraan^{Click here to contact me} 16:56, 3 April 2018 (UTC)[reply]

Maybe not a linear proportion, but the larger the body of water, the larger the tides, pusuant to various other effects, such as the shape of the body of water and its specific location on the sphere of the earth, all of which also have effects. None of this stuff is independent of all other factors. There's a WHOLE lot of things going into determining the intensity of the tides, and the size of the body of water is but one of them; the point is that even the largest lakes in the world are miniscule compared to the World Ocean. --Jayron 32 17:41, 3 April 2018 (UTC)[reply]

Any solid sources for this question? Once again, I'm looking for solid sources, not pop-sci pages that answer the question; I already knew the answer before I came here. Nyttend (talk) 21:54, 3 April 2018 (UTC)[reply]

Hmm, maybe [7] or the sources it cites? I got it from [8] if you're wondering. --47.146.60.177 (talk) 06:16, 4 April 2018 (UTC)[reply]

Excuse me, your question was "Why are there no tides except in the ocean and connected waters". I wonder what answer you already knew, because that "there are not tides except in the oceans" is simply not true. Tides are known in smaller Seas like the Mediterranean (where they are not dependent on its connection with the Atlantic) and in the ground also, e.g. I understand in Jugoslavia there are caves where water seems to sink and rise periodically because the whole mountain is rising resp. sinking. And it is known that the large CERN ring in Geneva is affected by the tides of the ground it is carved in, so that the controlling power must be increased and reduced according to the position of the Moon. 194.174.76.21 (talk) 18:05, 5 April 2018 (UTC) Marco Pagliero Berlin[reply]

Dental floss mole removal

Is there any scientific analysis or experiment about the dental floss mole remover method? That is, tie the mole by the base until it dies. Or is it so obviously wrong that no testing is necessary? All the material I find is dubious at best. — Preceding unsigned comment added by 31.177.97.108 (talk) 14:50, 3 April 2018 (UTC)[reply]

I'm afraid that we cannot recommend any medical advice. You'll have to ask a medical professional. --Jayron 32 14:52, 3 April 2018 (UTC)[reply]

I assume it's right to point to sources like Safety & efficacy of agents used for home mole removal.--Hofhof (talk) 16:18, 3 April 2018 (UTC)[reply]

Yes of course, thank you. Full text of that article can be requested from the authors here [9], first page is readable here [10]. SemanticMantis (talk) 16:36, 3 April 2018 (UTC)[reply]

Please read questions before responding: this wasn't asking for advice at all. Nyttend backup (talk) 16:19, 3 April 2018 (UTC)[reply]

Asking how to remove a growth qualifies as a request for medical advice. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:37, 3 April 2018 (UTC)[reply]

It didn't ask how. It explained how. It asked if the described method has scientific analysis. 209.149.113.5 (talk) 17:15, 3 April 2018 (UTC)[reply]

The original question is a request for medical advice. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:19, 3 April 2018 (UTC)[reply]

I haven't read it as asking for advice. It can perfectly be answered with sources, without considering whether the OP is planning to do it or not, or even suffering from this. Hofhof (talk) 17:22, 3 April 2018 (UTC)[reply]

He's asking if it's safe to use a particular method to remove a growth. That's a request for medical advice. No one here is qualified to answer the specific question, regardless of alleged sources. He would need to see his dermatologist. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:26, 3 April 2018 (UTC)[reply]

Evaluating which sources of information to provide, and choosing specific ones, and recommending he read them is tantamount to telling him how to medically treat himself. That's not what we do here. If he wants to know how to treat his medical condition, he can either randomly find his own websites or see a doctor. Either way, we shouldn't be involved in recommending courses of treatment by linking to them. --Jayron 32 17:39, 3 April 2018 (UTC)[reply]

Isn't that comparable to what you wrote here: Wikipedia:Reference_desk/Archives/Science/2018_March_13#Vitamin_K — Preceding unsigned comment added by Hofhof (talk • contribs) 17:48, 3 April 2018 (UTC)[reply]

No.--Jayron 32 03:28, 4 April 2018 (UTC)[reply]

Is there any scientific analysis or experiment about ...[a] method? -- I cannot imagine a more clearly written request for references. The idea that anyone trained in science or reference librarianship would think that this is a question seeking medical advice boggles the mind. Oh well. SemanticMantis (talk) 16:56, 4 April 2018 (UTC)[reply]

Can we remove a rabbit in this way? — Preceding unsigned comment added by 213.205.242.246 (talk) 23:58, 3 April 2018 (UTC)[reply]

Ask your veterinarian. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:14, 4 April 2018 (UTC)[reply]

Twenty-odd years ago I had an annoying case of recurrent appendicitis, which had come and gone for twenty-odd years. This thread oddly suggests that one might ask about the wisdom of using dental floss to remove a mole, which would be like using a steak knife to stab the lower right abdomen, then put a strangulation knot of dental floss around the inflamed appendix. The surgeon eventually removed the problem organ. The nurse did an enema before the operation,and laughed when I related a story from a professor. The prof had said that a hospital patient was not allowed to consume any food by mouth. But he craved some cocoa. He persuaded a nurse to buy him some hot Cocoa from the vending machine and to administer it to him via enema. She did so and he started to writhe in pain. She said “Is it too hot?” Whereupon he replied “No, it’s too sweet!”Edison (talk) 06:03, 4 April 2018 (UTC)[reply]

I see once again people have become deeply bogged down in the debate of whether it is ethically acceptable to discuss scientific papers. On a somewhat related (well, not really) note I should highlight this highly esteemed publication which warns that companies that tell you your own genome are giving largely false data since a third-party site might say some of your genes are "variants" but their list disagrees with the authors' better list. Nobody complains that the genetic data sent out over the internet is all vacuumed up by the NSA, because you might be dissidents and they might need your P450 profile to develop custom toxins to eliminate you and your family. Nobody complains that endless idiotic advertisements encourage the proles to petition these novelty companies to upload their genomes to tell them whether they ought to wear lederhosen or a kilt, because the companies are inherently better than they are and are in the proper position to make that determination. But if they can use that data to find out about themselves and do something, then this is wrong, because they should have to hand over every penny they have in order to find out anything medical about themselves, then be thrown out on the street and denied treatment, or left with 16th-century pain relief waiting to die if they have lingering insurance. Even the human genes in the proles' bodies were counted as property until an obstructionist supreme court made a hindrance. Medical ethics, succinctly put, is that anything that stands between a Doctor and his Profit is wrong -- and his profit is rightly the whole world. Wnt (talk) 07:04, 4 April 2018 (UTC)[reply]

I congratulate you for putting that lengthy joke in small print. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:47, 4 April 2018 (UTC)[reply]

Easter chocolate

Is it best to eat the Easter chocolate one has been given a little at a time over a long period? Or is it better to pig it all down at once so ones overwhelmed digestive system only has time to absorb a small amount of it? SpinningSpark 15:18, 3 April 2018 (UTC)[reply]

What's the basis of your premise? ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:37, 3 April 2018 (UTC)[reply]

This question seems to ask for medical advice. "Best" probably means whether or not it's medically advisable to do something. 140.254.70.33 (talk) 17:29, 3 April 2018 (UTC)[reply]

The OP's premise is that eating it faster would somehow result in fewer calories being absorbed. I question that premise. He's using "better" to mean "less fattening". But you're right, asking a doctor would be the best course, since we don't know what medical conditions the OP might have which could trigger specific results. So "best" might equate to not eating any of it, just throwing it away. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:34, 3 April 2018 (UTC)[reply]

This might have been asking for medical advice, but it no longer is since I have now eaten it and it's too late to act on any answers I might get. SpinningSpark 17:39, 3 April 2018 (UTC)[reply]

If you get sick from it, don't ask for further advice here, go see your doctor. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:51, 3 April 2018 (UTC)[reply]

I suggest you enjoy Easter eggs before the best before date on the box. You could leave them to your ancestors and they might make some money - 170 year old Easter egg --TrogWoolley (talk) 22:11, 3 April 2018 (UTC)[reply]

Or better yet, your descendants. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:17, 3 April 2018 (UTC)[reply]

In second grade, countless decades ago, in.some inane contest I won an enormous chocolate bunny at Easter time. I carried it home on the school bus. I showed it to my family and gave them broken off bits. But I ate most of it myself at one or two goes. I reckon it one of the top ten highlites of my life. I recommend immediate consumption. Caution: the thing was fake, since it was a hollow shell and thus afforded scarcely a tenth of the chocolate bliss it suggested. Edison (talk) 05:36, 4 April 2018 (UTC)[reply]

Everybody knows that if you consume food on a holiday, you don't have to feel guilty about your diet. This is the entire premise of American Thanksgiving.

So obviously, you need to eat all your Easter chocolate on Easter. ApLundell (talk) 16:36, 4 April 2018 (UTC)[reply]

Also, if you eat in the dark, the fat cells don't see the food coming^{[Citation Needed]} and don't know to expand. --Guy Macon (talk) 16:47, 4 April 2018 (UTC)[reply]

That was kind of the premise in "Junk Food Junkie". ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:51, 4 April 2018 (UTC)[reply]