Wikipedia:Reference desk/Archives/Science/2018 April 20

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April 20

Quantum immortals

Assume we discover people who have far outlived the normal human lifespan and/or who survive a series of normally fatal accidents/injuries seemingly against all odds-- like the subject of the quantum immortality thought experiment. Would such a discovery constitute empirical confirmation of the many-worlds interpretation of quantum physics? (This is not a request for debate; I want to know whether I'm misunderstanding the concept of quantum immortality.) 169.228.147.129 (talk) 03:13, 20 April 2018 (UTC)

No. The chance that you personally observe someone who survives some event that was extremely likely to kill him, is actually unaffected by whether the many-worlds interpretation is true. Consider: If this interpretation is false, and there is only one world, then the chance that someone survives as 1-in-a-zillion event is 1-in-a-zillion. Repeated experiments will tend toward this rate. If the many-worlds interpretation is true, and there are as many worlds as possible quantum states, then the chance that you wind up in a universe where someone has survived a 1-in-a-zillion event is... still 1-in-a-zillion. If the null and alternative hypothesis predict the same outcome for an experiment, then that experiment is incapable of falsifying either. Someguy1221 (talk) 04:01, 20 April 2018 (UTC)

Thank you, that clarifies things a lot. 169.228.147.129 (talk) 04:04, 20 April 2018 (UTC)

There's a reason why the various Interpretations of quantum mechanics are called interpretations and not theories: As noted by Someguy1221, they are not testable or falsifiable, and as such, do not occupy the same realm as formal theory. Some physicists even get annoyed by the existence of such interpretations, notably N. David Mermin's exhortation (often misattibuted to others such as Murray Gell-Mann or Richard Feynmann) to "Shut up and calculate!" --Jayron32 11:03, 20 April 2018 (UTC)

You can't diagnose quantum immortality in anyone but yourself; however, the concept suffers from some flaws from the perspective of anyone who has ever been knocked unconscious, since why aren't you in the world where you never lost consciousness...? Cf. atman; there is no quantum-based necessity for one single individual to survive to fulfill this many-worlds requirement, even if it is one. This is without even getting into speculations about the quantum nature of consciousness itself.... Wnt (talk) 00:07, 21 April 2018 (UTC)

(OP here) Wouldn't the same apply to sleep, too? Since going to sleep means a lapse in normal consciousness, under the quantum immortality interpretation we should all be subjectively experiencing constant insomnia. Same goes for anesthesia. 169.228.151.215 (talk) 03:22, 22 April 2018 (UTC)

The many-worlds interpretation does not imply quantum immortality anyway. So, besides the fact that quantum immortality would only be observable to the person him/herself, it wouldn't necessarily work even if the many-worlds interpretation were correct. In fact, the logic of quantum immortality as invoked in many-worlds can be turned on its head. Suppose I am 100 years old and being of that age is a-typical. I go to sleep and upon waking up, why would I then not find that I'm 25 years old living in some totally different place with no recollection of ever having lived till 100? It seems to me that this is a far more probable outcome given that there are far more 25 year-old copies of me than 100 year old ones. Count Iblis (talk) 03:50, 22 April 2018 (UTC)

Radiation-loving species

So, what's the deal with https://www.scientificamerican.com/article/radiation-helps-fungi-grow/ ? I haven't been able to find any articles about this fungus not from 2007. Have we discovered more of such radiation-loving species? Or is there some totally mundane explanation not involving radiation? 93.136.60.4 (talk) 03:34, 20 April 2018 (UTC)

I can't find any papers that reference new species beyond what was in the original paper, though I did find many recent papers about melanized fungi that are merely resistant to ionizing radiation, but that was suspected long before 2007. The phenomenon is still heavily studied, see [1]. But the interest seems to be in understanding the mechanism, rather than isolating new species. Or people have been trying to isolate new species, but they never report the attempts because they never succeed. Someguy1221 (talk) 03:55, 20 April 2018 (UTC)

That's a little too technical for me. So they're not really thriving in radiation, they'll just survive in a low-medium radiation environment, and high enough radiation will wipe them out just like other known lifeforms? 93.136.96.61 (talk) 18:06, 20 April 2018 (UTC)

They're thriving in the sense that a little bit of radiation makes them grow faster. But yes, a lot of radiation, and they still die. Though for these little guys, "a lot" is way more than what ordinary organisms could tolerate. Someguy1221 (talk) 19:03, 21 April 2018 (UTC)

On measuring weight via force

When I stand on my analog bathroom scale and remain still, the scale displays a steady weight. If I move my arms up and down while standing on the scale, the scale displays a variable weight. Reddit explains this is because the bathroom scale is actually measuring force not mass.

My question is if I found a balance scale big enough to stand on, did so, and had kilogram weights used to balance balance the scale would any arm movement impact the balance?

Similarly, is there an approach for determining the mass of a person that is immune to these perturbations?

Thanks in advance. I find this reference desk a delightful source of information and knowledge. I enjoy all the great information and discussion that takes place here.

128.229.4.2 (talk) 12:47, 20 April 2018 (UTC)

• I am not aware of any mass determination method that does not involve measuring a force (be it the inert or gravitational mass). Any such method is bound to be fooled by weight-swinging, as adequately explained by the redditors. I do not understand the first question. Tigraan^{Click here to contact me} 13:07, 20 April 2018 (UTC)

Ok, thanks Tigraan. To clarify the first question, my bathroom scale looks like this, and by balance scale I'm talking about a scale like this. I didnt know if differences between the two scales might change things. 128.229.4.2 (talk) 13:25, 20 April 2018 (UTC)

Both of these operate by measuring the force of gravity on an object, by countering that force against another force. In the case of the bathroom scale, the opposing force is the force of a spring, governed by Hooke's law; the roughly linear response to compressing a spring allows one to make a simple bathroom scale; double the force, double the compression, turn the dial twice as far. But it's still using force. The second scale, the balance-type scale, takes advantage of torque, in this case if the cross arms are equal length from center to the pan, then equal forces on the pans will exactly balance, because the opposing torques will cancel out. This is still using the force of gravity; just using it twice. Any time you introduce an outside force to the system (such as waving your arms around), you're going to throw it off, since no scale can tell the difference between force of gravity and other forces. They're all just force-measuring devices. --Jayron32 13:42, 20 April 2018 (UTC)

Cool! Thanks Jayron32! 128.229.4.2 (talk) 14:09, 20 April 2018 (UTC)

Not exactly a different principle, but the way to correct for these pertubations is simply measuring the average force over time. If you integrate the force on a scale over 30 seconds, you can swing your arms all you want, but as long as you don't step off the scale, the scale can still calculate your mass very accurately (even a 10 seconds measurement is pretty good). - Lindert (talk) 14:40, 20 April 2018 (UTC)

As Lindert notes, random arm waving would be a classic example of noise; which can be reduced by common noise reduction techniques; all of which rely on averaging a bunch of measurments over a long period of time; over time the signal to noise ratio generally improves with a greater sampling rate. --Jayron32 16:05, 20 April 2018 (UTC)

Yes there is a way to measure mass that will be somewhat immune to arm waving. Suspend a large mass on a string. Measure its position. Now move closer to it. Measure its position again. Wave your arms. No effect. The gravitational force between you and the sphere is not much affected by you waving your arms in the plane tangential to the line joining you and the sphere. There are many other problems of course. Greglocock (talk) 17:47, 20 April 2018 (UTC)

The waving of your arms is likely to generate sufficient air currents to perturb the position of the sphere several orders of magnitude greater than the movement due to gravitational attraction to you. --Jayron32 17:55, 20 April 2018 (UTC)

I like this idea. Indeed there are problems, as Jayron expands, but I liked it nonetheless. I was thinking in this sort of direction as well. Not gravitation, but I was thinking that if mass is equal to density x volume, volume here could be gathered by water displacement. Finding the density of a person might be more complex? Or might just involve a tool(s) I'm not familiar with. 128.229.4.2 (talk) 19:19, 20 April 2018 (UTC)

Is it known if retargeting ICBMs would take longer if you want an explosion near the maximum possible altitude?

They can reach about 8 kilometres per second so the maximum possible altitude is very high. Sagittarian Milky Way (talk) 16:16, 20 April 2018 (UTC)

Question does not make sense. One does not want the warhead to go off at max altitude. It diminishes the destructive power at ground level. Re-targeting would take time because ICBM's are pre-targeted (mostly). The ICBM's also have accelerometers etc to ensure that they don't go off prematurely in the event of a bad launch, which could amount to a home goal. The launch teams as far as I know have no way of overriding these safety precautions to allow the warhead to go off at max apogee. If some editor knows better, you can bet that they will correct me in the next post. Aspro (talk) 18:44, 20 April 2018 (UTC)

Well, it depends on what you're trying to achieve. If you want to kill the most people, then you want a burst at some modest altitude. But if your goal is maximum disruption for fewest deaths, then maybe you're going for a nuclear electromagnetic pulse, which could indeed mean you want to detonate at a high altitude (though as 209 says below, still not "maximum" altitude). --Trovatore (talk) 03:03, 21 April 2018 (UTC)

Further, there is no "maximum possible altitude" for "ICBM." There are many different types of ICBM missiles. They are designed and fueled to just barely make it into orbit and then follow a ballistic path back to Earth. Smaller ones don't make it to orbit at all. Larger ones not only have the ability to make it into orbit, they are used without warheads to put things into orbit. So, they can obviously reach an escape velocity for an undetermined maximum altitude as it floats off through space. 209.149.113.5 (talk) 18:54, 20 April 2018 (UTC)

Presumably the interest regards targeting aliens, asteroids, uppity space prison inmates, etc. Then escape velocity is over 11 km/s which means the things as described are tragically unsuited for many purposes. And with so much fuel devoted to climbing it seems inevitable that retargeting must suffer for a lack of reserve. Wnt (talk) 00:04, 21 April 2018 (UTC)

• Back during the days of MAD, all of the possible strategic targets were known in advance and the appropriate parameters were precomputed for each target, so retargeting was a matter of setting these precomputed parameters for the new target. Because the time of flight for an ICBM is quite long, setting a new target in real time makes no sense as the target will have moved. The situation for IRBMs and theater ballistic missiles is a bit different. -Arch dude (talk) 02:51, 21 April 2018 (UTC)

Neither Peak nickel nor Peak lithium article?

Given the apparent development of the vehicle fleet towards electric vehicles, wouldn't that lead to depletion of possible battery components like lithium or nickel? Or is our back covered for so many decades that's not worth worrying? According to the links in the peak oil article, lots of materials have a peak that can be allegedly calculated. Aren't concepts like 'peak nickel' or 'peak lithium' notable? --Hofhof (talk) 18:30, 20 April 2018 (UTC)

The general agreement among reliable sources seems to be that "peak lithium" is not a thing. --Jayron32 18:42, 20 April 2018 (UTC)

yes, but even if people claim it won't happen, doesn't that make the concept notable, since people are discussing it? --Hofhof (talk) 18:52, 20 April 2018 (UTC)

Unlike oil or other hydrocarbons, nickel and lithium are elements. The quantity of nickel, lithium, or any other pure element on earth is likely to stay constant, isn't it? ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:06, 20 April 2018 (UTC)

However the economically recoverable amount may not. See peak phosphorus, for example. Also we are currently burning quickly through our conveniently obtainable helium, which is currently massively underpriced due to the sell-down of the National Helium Reserve. --Trovatore (talk) 20:14, 20 April 2018 (UTC)

Then, what's all the fuss about Peak copper?Hofhof (talk) 20:27, 20 April 2018 (UTC)

Lithium#Reserves has some relevant comments, and Nickel#World production could be expanded to do the same for Nickel. Klbrain (talk) 21:54, 20 April 2018 (UTC)

There's nothing stopping the OP from either creating those articles or creating redirects to portions of other articles. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:56, 20 April 2018 (UTC)

See [2] and original article [3]. The difference between batteries and fossil fuels is that you consume energy in fossil fuels, but you merely need to use elements in batteries, which means that there are endless ingenious variations possible. Wnt (talk) 00:01, 21 April 2018 (UTC)

But batteries, even the rechargeable ones, do not live forever and are never completely recycled, so we do actually "consume" the constituent materials, not just "use" them. I think the question, how long can our reserves of nickel and lithium last if we massively build electric cars is not completely meaningless. The same question has been asked formerly relating to neodymium in wind generators, I think 194.174.76.21 (talk) 14:23, 24 April 2018 (UTC) Marco Pagliero Berlin

Are depressed people more likely to drink alcohol, or does heavy alcohol consumption make people more likely to be depressed?

In other words, does depression make people more likely to drink alcohol? Or does drinking alcohol (a depressant) make a person more depressed? Also, if a depressed person takes a stimulant, like caffeine, can that treat the person's depression? SSS (talk) 22:44, 20 April 2018 (UTC)

Both. Depression is not a condition. Depression is a wide range of conditions with many different causes. Alcohol doesn't have one effect. Alcohol has many different effects for many different people. — Preceding unsigned comment added by 2600:1004:B158:83F3:4A0:F30A:43F7:3114 (talk) 23:00, 20 April 2018 (UTC)

Do you have any references? SSS (talk) 23:16, 20 April 2018 (UTC)

You could start with Depression (mood)#Factors and Alcoholism#Causes. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:38, 20 April 2018 (UTC)

Does personality (in normal people) has to do something with genetics?

How much genetics influence on our personality? Do we expected to be like our father or mother or their relatives based on the genetics? If we look at dogs, then almost everyone knows that there are dog races more calm as well as less calm, and it strengthens my assumption that there is a relation between personality and genetics. But I'm not sure what accepted widely about it in science world and I'd like to know about it. 93.126.116.89 (talk) 22:51, 20 April 2018 (UTC)

See nature versus nurture. 2600:1004:B158:83F3:4A0:F30A:43F7:3114 (talk) 23:03, 20 April 2018 (UTC)

There is some evidence that personality may also be affected by the gut microbiome see:[4][5]. Richerman (talk) 23:18, 20 April 2018 (UTC)

Even identical twins tend to have distinguishable personalities. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:36, 20 April 2018 (UTC)

Even the inseparable ones tend to not share wives for instance. Non-identical lives, non-identical humans. Sagittarian Milky Way (talk) 02:18, 21 April 2018 (UTC)

Well, the original Siamese Twins "almost" did. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:44, 22 April 2018 (UTC)

It's worth noting that the DNA of identical twins isn't necessarily strictly identical. Different copy number variants have been found, for example, in identical twins. - Nunh-huh 03:44, 22 April 2018 (UTC)

“Most children resemble the brother of the mother.”

Is there any scientific support to the written in the Babylonian Talmud Baba Batra (110a)? There are two translations to the text that was written originally in Aramic language: 1st translation: “Most children resemble the brother of the mother.” or the 2nd translation: “sons usually inherit the traits of their mother's brothers” (The Encyclopædia of Sexual Behaviour, Volume 2 p.583). Is there any scientific support this claim? 93.126.116.89 (talk) 23:37, 20 April 2018 (UTC)

Anecdotally, I can tell you that I am a lot like my father in both personality and appearance, and nothing like my mother's brothers. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:40, 20 April 2018 (UTC)

It's written there "most" so it can be 51% and more, you can be from that minority, that's why I don't look at in a personal examples). 93.126.116.89 (talk) 00:17, 21 April 2018 (UTC)

"Most" would need to be a lot more than a bare minimum majority. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:31, 21 April 2018 (UTC)

Brothers and sisters share 50% of their genes, as do mothers and sons, so the resemblance is 25%. That said, (a) a gene might not affect a woman in the same way, (b) social prejudices may not permit recognition if it does, and (c), most interestingly, there are some sex-linked traits on the X chromosome. So suppose a male grandchild suffers a trait with X-linked recessive inheritance like hemophilia A. Then his mother must be a carrier; in all likelihood she does not have the disease because she has another X chromosome. She in turn inherited that gene either from her mother (who would appear unaffected) or else from her father (who would be affected). As we know she must be a woman, she necessarily inherited one X from each of her parents so the odds of either being a carrier/affected should be the same. If her father was affected, her brother (the child's uncle) cannot have inherited the gene from him; but if her mother was a carrier, then her brother had a 50% chance of being affected depending on which X he received. Well... that means the grandfather and uncle each had 25% overall chance of being hemophiliacs, given that the child has the trait. Which gets us nowhere new. But ... if we suppose the condition is something fatal (and hemophilia may be) then the grandfather was less likely to have had it because then he might have died and not passed the condition on if he had. If it is truly lethal we know it hasn't reared its ugly head in the child's direct line of descent, and only uncles could have had it. It is, therefore, at least conceivable that someone with a particular interest might have penned this verse, but I can't tell you. Oh, and note that Tay-Sachs disease is not on the X, so that's not it. Wnt (talk) 23:56, 20 April 2018 (UTC)

Thank you for your answer. But I'm not sure that I understood it well. Do you want to say that the statement that I brought from the Talmud isn't correct based on the science nowadays? 93.126.116.89 (talk) 23:03, 22 April 2018 (UTC)

Well, to recap...

• For most genetic traits, a child will resemble its first degree relatives most (50%), and second degree relatives 25%.
• For X-linked recessive traits, a male child will not resemble his mother (who is unaffected), but would match his brothers most (50%). If the trait is harmless, he will resemble his mother's father and mother's brother equally (25%).
• However, if the trait is quickly fatal, the mother's father did not have it, so the mother's mother is a carrier and the mother's brother had a 50% chance of being affected.

I have not looked at the text from the Talmud in context to understand what situation they have in mind. If it is a general statement about all children and all traits to be read at face value it's pretty much wrong. But if the authors could be assumed to have excluded brothers and fathers "because everyone knows they're more alike", then maybe he was saying that the mother's brother is more similar than the father's brother. And that statement actually is true; the point is, the father's brother shares only a Y chromosome with the boy in question, which has very few genes, while the mother's brother shares 25% to 50% of an X that is quite long and shares many genes that are present as a haploid genome. I haven't looked into whether that is a valid interpretation or not. Wnt (talk) 10:24, 24 April 2018 (UTC)

Does that actually work out? Both the mother and father will have half a chance of having the same Y gene as a brother, but the father is sure of having the same X gene. Dmcq (talk) 16:16, 24 April 2018 (UTC)

@Dmcq: Nay, a man is sure to receive the X from the same woman as his brother, but that woman has two X chromosomes, so it's 50% chance of either. But his brother is sure to have the same Y, because the father only has one. The mother will not have a Y. Wnt (talk) 11:48, 26 April 2018 (UTC)

Sorry mixed up X and Y, and I was mistaken anyway. Dmcq (talk) 12:08, 26 April 2018 (UTC)

So is it saying that in the case of children of a mother who has a brother, and lets ignore the case where she has more than one brother, the children will look like a man - and in fact a particular man, the brother? That sounds rather iffy. Perhaps they are saying they will look like the brother bbut not as he hhas grown to as a man? And if they are brother and sister would they not both resemble an uncle? But the sister even so would less resemble the children than her brother? This is getting beyond iffy. Why don't you apply for a grant to check it out from some crowd like the Discovery Institute :-) Dmcq (talk) 10:38, 24 April 2018 (UTC)

@Dmcq: See the comment directly above. I think there may be a way that this statement makes sense, at least if you interpret it ... talmudically. ;) It is hard to know what assumptions influence the meaning of a sentence from ages past. Wnt (talk) 12:12, 24 April 2018 (UTC)