Wikipedia:Reference desk/Archives/Science/2016 November 4

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November 4

Physics: Black hole inside a larger black hole

I've read there could be black holes inside of black holes.

1.Smaller black holes evaporate faster than bigger black holes, according to Hawking. So if a black hole contains a smaller black hole, then the smaller one would seem likely to evaporate first(though I don't know for sure, maybe time passage is so messed up by gravity and general relativity that time goes slower for the one inside, so it ends up lasting longer), so what happens when the one inside does evaporate? Will this be in any way observable to us on the outside?(yes I've heard that in principle you can't get any information of what's happening inside, but I thought this could be an extreme case where that principle no longer holds or rather, gets modified, just as when something's going near the speed of light, newton's laws are modified.)

2. Could the craziness of black holes inside black holes cause the space or spacetime nearby it to be nonorientable topologically? thanks. 155.97.8.203 (talk) 00:56, 4 November 2016 (UTC)

A black hole merger has some weird predicted properties, like the area of the event horizons remains constant. But you're right that in a supermassive black hole, some say a person could fall in and not even notice it. (Others say a firewall (physics) or fuzzball (physics) intervenes, and what happens is something altogether more dramatic) If indeed nothing happened, you'd think that if you were orbiting a small black hole and fell past the horizon, you'd still be orbiting it after you fell in. But no matter what explosion happens if the small black hole decays, nothing should make it out past the supermassive black hole's event horizon, since nothing can. Wnt (talk) 01:10, 4 November 2016 (UTC)

The general governing principle here is the so-called no-hair theorem, which basically states that virtually nothing that happens inside a black hole is observable from outside it. John Archibald Wheeler expressed this idea by saying, "A black hole has no hair." Looie496 (talk) 15:09, 5 November 2016 (UTC)

"Nothing that happens inside a black hole is observable from outside it" is a defining property of a black hole, not a theorem. The no-hair theorem only holds in 3+1 dimensions, but event horizons shield the black hole interior from the exterior in any number of dimensions. -- BenRG (talk) 02:22, 7 November 2016 (UTC)

1. Nothing inside a black hole can escape to the outside; another black hole evaporating is not an exception to this. 2. I think there's nothing in general relativity that rules out nonorientable spacetimes (because general relativity says nothing about global properties of spacetime). For nonorientability to be interesting, though, you'd need an initially orientable space to evolve into a nonorientable space, and I don't know whether that's even geometrically possible, let alone physically possible.

In any case, a black hole inside another black hole is not that crazy. The interior of a black hole is much like any other region of spacetime. -- BenRG (talk) 02:22, 7 November 2016 (UTC)

The "black holes have no hair" thing seems like a rather oversimplified shorthand for "black holes have charge but not baryon number or weak isospin, rotation that affects the spacetime around them but not any vibration from exploding black holes inside of them". Actually it seems quite a mystery to me how people would know this. Wnt (talk) 23:09, 8 November 2016 (UTC)

@Wnt: We don't really know, of course, but well-established theories make predictions. The no-hair theorem says essentially that black holes (in 3+1 dimensions) don't preserve any information except what they're forced by conservation laws to preserve. Theory says that electric charge and angular momentum are conserved/preserved by everything, and black holes shouldn't be an exception. Baryon number is accidentally conserved in the Standard Model (see accidental symmetry) but there's no known reason to expect non-SM objects like black holes to conserve it. Weak isospin is nonconserved everywhere because of the background Higgs field (also, I'm not sure it's possible to formulate a conservation law for nonabelian gauge charges in the first place). Events inside the event horizon don't affect the exterior of the black hole by definition of "event horizon". The hole's measurable electric charge, angular momentum, and mass don't come from inside the event horizon but are fossilized fields the predate the formation of the event horizon. -- BenRG (talk) 20:12, 10 November 2016 (UTC)

@BenRG: Accidental symmetry is one of Wikipedia's very least developed articles - if you could do so, it would be great if you could expand it. Like ... what Lagrangian? And why do the number of terms depend on how hot it is? And... well, anyway, I don't know the topic, I can look it up but you'd do better at writing the article!

I get the idea of fossilized fields, but it seems like the idea might be a little too versatile. If I drop a black hole that is about to explode through an event horizon, could the fossilized field contain some kind of imprint of the future moment of the explosion that would have physical effects outside the hole? (I really doubt it, but I don't know that) Wnt (talk) 12:17, 11 November 2016 (UTC)

Hidden wire

Is it possible to locate a hidden wire inside a wall without having to tear it up (similar to how it's possible to find wall studs inside the drywall)? 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 00:57, 4 November 2016 (UTC)

If it is conducting electric current it should produce a magnetic field, so a magnetometer ought to do it. A metal detector might detect eddy currents in even a wire without current. You could look straight through the wall with a terahertz scanner - I remember reading a couple years ago that a "terahertz app" on a phone would be coming out any time [1][2][3] but find myself rather skeptical that mere peasants, the inferiors of cheap machines, will ever be allowed to have their grubby hands on that technology - anyone heard an update? Wnt (talk) 01:16, 4 November 2016 (UTC)

Can I buy any of these goodies at my local hardware store? 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 03:58, 4 November 2016 (UTC)

Ask for a stud finder that will also detect AC wires, like maybe one of these. Sjö (talk) 06:53, 4 November 2016 (UTC)

Thanks! This is even better -- it will find both the wall studs (to drill into) and the wires (to avoid)! So it's two for the price of one! 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 09:10, 4 November 2016 (UTC)

The sources you linked to don't describe a "terahertz app" which normally refers to simple software. It described the possibility of a cheap CMOS chip which functions as a transceiver of terahertz EM. This chip could potentially be integrated into a phone, or attached as an accessory (but on the later point, it could also and likely more easily be attached to a laptop or just be attached to a simple portable device with its own software etc, as some sources mention). You can't magically make a phone without such a chip and with no accessory function that way, and it isn't because of any major conspiracy. Nil Einne (talk) 08:04, 4 November 2016 (UTC)

True, that was a silly word to use. There are some political issues playing on my consciousness in regard to the tendency of surveillance tech to show up in phones yet be useless to the user, e.g. where people are spied on with GPS yet don't know where they are themselves. Wnt (talk) 11:17, 4 November 2016 (UTC)

I don't know what stud detectors are like, in fact this is the first time I've heard that term, but I've had a combined metal an voltage detector for years and always use before drilling any holes in the wall. The one I've got seems to be only good to a few inches in the wall so it might be worth checking for something better if you want to use it for anything big like bolts in an outside wall. Dmcq (talk) 08:40, 4 November 2016 (UTC)

Agreed, finding a wire that's not near the surface would be difficult, as closer metal objects, like nails and brackets, would give a much stronger return. StuRat (talk) 21:00, 4 November 2016 (UTC)

Our article on test lights (also known as voltage detectors) describes at length how this can be done if the wire is active and carries line voltage. These devices are generally available for a few bucks at your local hardware store. Looie496 (talk) 15:24, 5 November 2016 (UTC)

Belief perseverance

The article on Belief perseverance talks about people clinging to beliefs despite evidence to the contrary. I've been wondering if there is some good term for what I think of as the WMD effect where people were even more convinced that Saddam was hiding weapons and was even more evil and devious than they originally thought. Basically that the evidence against their belief makes them become quite extreme in their belief. I think there is the same effect with these Clinton emails - lots of people are now shouting kill the bitch as time goes on and successive inquiries come up with nothing of note. Is there a good reason why evidence against something should actually accentuate belief and is there an entry about it? Dmcq (talk) 09:00, 4 November 2016 (UTC)

• It sounds just like a particular form of confirmation bias. Tigraan^{Click here to contact me} 10:13, 4 November 2016 (UTC)

That didn't sound strong enough but I found a bit there which I think covers what I mean. Thanks. "The backfire effect is a name for the finding that, given evidence against their beliefs, people can reject the evidence and believe even more strongly". It has some references but says nothing much more about it that I can see. The link [4] has more about it and summarizes it as “When your deepest convictions are challenged by contradictory evidence, your beliefs get stronger.” It's pretty sad news if the Cinton hate business is part of some core belief. Dmcq (talk) 11:29, 4 November 2016 (UTC)

[5] is good too with lots of examples. Though I don't see how something like whether 0.9999... is 1 or not can be part of a core belief or deepest conviction. Certainly worth an article I think.. Dmcq (talk) 11:52, 4 November 2016 (UTC)

There seems to be another term for it as well 'motivated reasoning', see [6] which gives hope that there are ways to reason with people even when they are deeply committed to a point of view. However that seems to be more in common with 'belief perseverence' rather than the way contradictory data actually confirms the opposite in backfire effect. Dmcq (talk) 12:01, 4 November 2016 (UTC)

Trying to convince someone that their belief is wrong is typically a futile effort. It will be taken as a personal attack, and will only make them more defensive. The essence of it is "I'm right and you're wrong". All of us are guilty of it from time to time, and it generally doesn't work. ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:08, 4 November 2016 (UTC)

Jonathan Swift once wrote "Reasoning will never make a man correct an ill opinion, which by reasoning he never acquired..." which is often paraphrased as "You cannot reason a person out of a position he did not arrive at via reason." --Jayron32 15:19, 4 November 2016 (UTC)

cognitive dissonance. Count Iblis (talk) 18:14, 4 November 2016 (UTC)

Thanks for that. It does seem very strange. I didn't get a good idea of what might be behind it all, laziness in thinking does not explain why a person would be even more confirmed in their beliefs. I guess in Blair's case there might be a bit of him feeling he had to defeat any challenge. Dmcq (talk) 23:36, 5 November 2016 (UTC)

This logic often applies to a conspiracy theory:

1) P is "obviously true".

2) Organization Q should therefore acknowledge the truth of P.

3) Therefore, the fact that organization Q did not do so indicates that they must be in on the conspiracy, and the conspiracy is even bigger than we thought.

Note that the only flaw in the logic is the false assertion that P is obviously true. In a case where P really is obviously true, like Galileo's assertion that the Earth revolved around the Sun (obvious to anyone who studied it), this logic does prove that there was a conspiracy to hide the truth. StuRat (talk) 21:02, 4 November 2016 (UTC)

That logic stream is a good example of what a math teacher once told us: "If you start with incorrect assumptions, you're liable to get 'interesting' results." ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:17, 5 November 2016 (UTC)

Another way to state that mathematically is that extrapolation greatly magnifies any slight errors in the initial conditions. StuRat (talk) 00:43, 5 November 2016 (UTC)

The original assumption is not what is really wrong with that argument. The real problem is what I was asking about which is part 3. Yes it is possible that one should assign a higher probability of the organization being part of a conspiracy - but one should also reduce one's confidence in the original assumption. Increasing the probability should only be done if one starts with the assumption that statements by the organisation are evidence of the contrary or have other good independent evidence of that rather than just coming to that conclusion because they disagree with the original assumption. Dmcq (talk) 17:24, 7 November 2016 (UTC)

In the case of Hillary's emails, the problem is worse because there is a grain of truth there. If the birther nonsense can survive for years without any facts to back it up, you can see how something which is partially true is far harder to dismiss. StuRat (talk) 21:35, 4 November 2016 (UTC)

What we really need to examine is why so many people are so absolutely certain of something completely untrue, in the first place (my #1). IMHO, it mainly has to do with the system we use to determine what is true, where the more times we hear an assertion P, and the fewer times we hear ~P, the more confidant we are that P is true. The abolition of the US Fairness Doctrine, which formerly required equal time for the opposing POV by US broadcasters, has led to this polarization. While we used to hear both sides of every issue, now we just listen to whatever broadcaster fits our preconceptions the closest, which means we barely hear the opposing POV, and when we do, it's so out of line with what we hear all the time, that we assume it's a lie and/or conspiracy. StuRat (talk) 21:02, 8 November 2016 (UTC)

Full meaning of:" 66.038 ± 0.025/0.049 Ma " in Science (journal)

Hello women and men! We are having problems in the equivalent of this reference desk in French (we call it "The Oracle"), here [7] and more specifiquely here [8]. No need to read French; the problem is how to understand several figures in this paper [9], coming from Science Magazine about the date of the Cretaceous–Paleogene extinction event. Several figures as "66.032 ± 0.058/0.072 Ma" or "66.038 ± 0.025/0.049 Ma" (6 series of such figures) are written.
For example: concerning "66.038 ± 0.025/0.049", somebody proposed the following explanation, standard deviation = sigma = 0.025 thus probability(m-1.96*sigma < age < m+1.96*sigma) = (66.038-0.049 < age < 66.038+0.049) = 95% because 1.96*25 = 49 (these 1.96 and 95% are known figures coming from [10]).
But this explanation does not fit for "66.032 ± 0.058/0.072" because 0.058*1.96≈0.114≠0.072
SOS. Who can rescue our French team? I never was a scientist, but I can understand some things about statistics and about Radiometric dating. Thank you a lot for the time you took reading this question.--Jojodesbatignoles (talk) 17:56, 4 November 2016 (UTC)

This detail of notation will be buried somewhere in Science's Information for Authors. Hopefully we can narrow down to a more specific publication-requirement.

Nimur (talk) 18:00, 4 November 2016 (UTC)

There are two relevant footnotes in the article:

9. Uncertainties here and throughout are stated at the 68% confidence level.

11. Uncertainties given as TX/Y refer to values excluding (X) and including (Y) systematic sources as defined in the supplementary materials.

Footnote 9 seems self-explanatory to me; 68% corresponds to 1 standard deviation if the values have a normal distribution. I did not read the supplementary materials, but an example of random vs. systematic errors would be making measurements with a tape measure. Some of the (most likely) random errors in making measurements would be reading values when the length of an object falls between divisions, deciding where an object begins and ends when the shape is irregular, etc. A systematic error would be a tape measure that is 0.1 % too short, or not supporting the tape measure all along its length while using it, and failing to account for the sag. So the authors of this paper were able to identify certain error sources as systematic, and provided uncertainties with just the random errors, and with the combined random and systematic errors. Jc3s5h (talk) 18:16, 4 November 2016 (UTC)

See Experimental uncertainty analysis for our (very detailed) article on the subject. Measurement uncertainty is perhaps more accessible to the general reader. Tevildo (talk) 21:04, 4 November 2016 (UTC)

The supplemental materials include the following explanation: "For some of the age comparisons made herein, contributions from sources of systematic uncertainty (i.e., uncertainties in 40Ar/40K of the standard and 40K decay constants) are neglected and only analytical uncertainties in isotope measurements of samples and standards are included. These uncertainties are referred to herein as “analytical uncertainties”. For the purposes of this study analytical uncertainties include contributions from uncertainties in the interference corrections because these interference corrections have variable effects due to the variable chemistry of the samples considered. Where not otherwise distinguished, uncertainties are stated as X ±Y/Z, where Y is the analytical uncertainty as defined above, and Z is the full uncertainty considering both analytical and systematic sources of uncertainty." John M Baker (talk) 20:13, 7 November 2016 (UTC)

And now I see that someone on French Wikipedia had already tracked down and posted the explanation. Well, the above may still be of interest for those playing along at home. John M Baker (talk) 20:31, 7 November 2016 (UTC)

Transitional epithelium and urothelium

What is the precise relationship between the terms transitional epithelium and urothelium? My current hypothesis is that they are effectively synonyms, since both terms describe the epithelial lining of the renal pelvis, the ureters, the bladder, and (the proximal parts of) the urethra. But since "transitional epithelium" describes the morphology of the epithelium, and "urothelium" describes the location of it, it would also make sense to say that "transitional epithelium" is a hypernym of "urothelium".

But if the terms are really synonyms, why do Wikipedia have two separate articles on them?

What do you say? --Andreas Rejbrand (talk) 21:00, 4 November 2016 (UTC)

The article says the latter is a subset of the former. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:14, 5 November 2016 (UTC)

Presumably a proper subset, or they could indeed be identical. StuRat (talk) 01:12, 5 November 2016 (UTC)

So the difference is the transitional epithelium found in prostatic ducts, which cannot be described as urothelium? Any sources? --Andreas Rejbrand (talk) 12:21, 5 November 2016 (UTC)

According to Pawlina, Wojciech (2015). Histology: A Text and Atlas (With Correlated Cell and Molecular Biology) (Seventh, International Edition). Wolters Kluwer. China (2015). ISBN 978-1-4698-8931-3, the terms are synonyms. --Andreas Rejbrand (talk) 23:18, 6 November 2016 (UTC)

Is this static electricity?

In m room I have two short walls that protrude part way across. The first is shorter than the second and has no electrical in it. The second has a regular light switch. If I touch the light switch first I get the usual static electricity, the blue spark, crack sound and minor shock, that is common in dry houses in winter. If I put the palm of my hand flat on the first wall I get a greenish glow around it, no noise and no shock. However, this only works when I get out of bed and never if I walk into the room from the corridor. What am I seeing? Is it just a different form of static? Could it be caused by the paint on the wall? The bed and door are next to each other so it's not caused by walking. I tried with and without socks, changed the blanket and sheets but that doesn't make any difference and I get a kick out seeing the glow. CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 22:54, 4 November 2016 (UTC)

You should probably mention the climate in the room. If you are still in Cambridge Bay I am guessing the humidity is very low now, unless you have a humidifier. That affects static electricity. Could the green glow be many tiny sparks ? The getting out of bed part does make me think that you collect static electricity when you drag yourself past the blankets.

Also see St. Elmo's fire. Not that it's what you are experiencing, but it may be a related form of corona discharge. And check out Kirlian_photography, a way to photograph coronal discharges. StuRat (talk) 00:28, 5 November 2016 (UTC)

I suspect that the paint on the wall contains something electroluminescent. Looie496 (talk) 14:58, 5 November 2016 (UTC)

Thanks both. I need to try and get a picture of it. CambridgeBayWeather, Uqaqtuq (talk), Sunasuttuq 04:32, 6 November 2016 (UTC)