Wikipedia:Reference desk/Archives/Science/2018 November 5

= November 5 =

"Flashing" bright colors
Recently I saw somewhere a bright blue (cyan) color that was so saturated that it appeared to be flashing at the edges, although it obviously wasn't, and I realized I haven't seen this in ages. My friends and I used to see this a lot when we were kids in the 90s, but my mom doesn't remember ever seeing anything like this. Did this happen because we were kids or did it go away because today faded colors are more fashionable? What's the scientific name for this? Tanagra212 (talk) 00:26, 5 November 2018 (UTC)


 * I saw something like that when I was younger, though it was more as though the intense colour stood proud of the background rather than flashing. According to our Ultraviolet article, "Under some conditions, children and young adults can see ultraviolet down to wavelengths of about 310 nm". I suspect something like that may be what was going on.--Shantavira|feed me 09:46, 5 November 2018 (UTC)


 * Unfortunately you didnt write where you saw bright (saturated?) Blue in your youth. Blue is special since there are almost no natural blue pigments. Most blue color in nature is not a result of microscopic pigments, like all the other colors as well as black and white (which dont count as color) but of socalled light refraction! This allows a special surprise if you add a transparent fluid as the pigments colors still work but the refraction stops and the blue vanishes.
 * See this nice educational video on youtube for the visual demonstration: https://www.youtube.com/watch?v=3g246c6Bv58 (youtube 8:26) --Kharon (talk) 13:00, 5 November 2018 (UTC)


 * Shantavira, this seems a lot like what used to happen to me. Flashing is not the right word, it was more if you were looking in that direction but not right at the object, it seemed to kind of momentarily pulse in stronger color at the edges and sort of "assert itself" in your visual field, a bit like impossible colors. It wasn't only blue it could be any color so long as it was strongly saturated/non-gray. I remember green, red, yellow, even be ultramarine blue, although it had to be saturated, not just bright. I definitely don't remember it ever happening with white, for example. Tanagra212 (talk) 03:32, 6 November 2018 (UTC)


 * I can comment that I've seen this effect with red hues, for example with a certain very brightly red flower, but alas I've never seen reference to the science behind it. Wnt (talk) 09:17, 6 November 2018 (UTC)


 * Yes, as with others commenting above, I can confirm that it's happened to me, but I was never able to figure out an explanation. I don't experience it very often now, but I'm not sure if it's because I'm older and have weaker eyes or if it's just that I'm not exposed to flat vibrant primary colours like I used to be. I used to get it with say, red block printing on bright blue background, such as you might see on the cover of a colouring book. The letters would seem to "pop" slightly and shimmer at the edges. It's probably to do with the high contrast, but I never experienced it with other colour combinations. Matt Deres (talk) 18:57, 6 November 2018 (UTC)


 * Yes, that sounds exactly like it. I was a little worried I'd never experience this again, since I couldn't find anyone over 30 who remembered something like this. FWIW I also have some problems with eyesight and usually have to wear strong sunglasses whenever I'm outside in daylight. Tanagra212 (talk) 22:35, 6 November 2018 (UTC)


 * Well, I'm significantly over thirty and also have eye problems (myopia), but I think this is likely a simple optical illusion of some kind rather than an artifact of our vision problems. My eyesight was much better as a child and I certainly saw it then. Perhaps related to the effect seen here, where the black/white contrast creates the illusion of movement. Matt Deres (talk) 15:51, 7 November 2018 (UTC)  Revolving_circles.svg.

Supergroups of eukaryotes
How many supergroups of eukaryotes are there? — Preceding unsigned comment added by Heegoop (talk • contribs) 01:43 5 November (UTC)


 * This reference taken from our eukaryote article should tell you what you want to know. Mikenorton (talk) 09:24, 5 November 2018 (UTC)

Are gravitational waves real?
The article leaves no doubt that gravitational waves as "disturbances of spacetime" are real, at least since they have been discovered experimentally (by measurement). I admit that the LIGO experiment has measured real effects; but did these effects say to the experimenter "Hello, here we are, and we are disturbances of spacetime"? I doubt this. Rather the identification of the measured effects as demonstrating the existence of "gravitational waves in the sense of Einstein's general relativity" evidently requires to presuppose Einstein's theory which predicts the existence of spacetime and of these waves as disturbances of it. Without the presupposed ART nobody would ever have understood some unidentified waves in this very sense. The suspicion then is well-founded that the identification results from a logical mistake, say of begging the question, and therefore is unjustified. Ed Dellian2003:D2:9703:5941:A81D:7A1B:AD26:ABD0 (talk) 11:39, 5 November 2018 (UTC)


 * FWIW - seems the following earlier post (see copy below) may (or may not) be relevant to the discussion:



Copied from Talk:First observation of gravitational waves

-- Danish physicists doubt 1st GW detection - worth noting or not? --

FWIW - seems a team of Danish physicists at the Niels Bohr Institute have raised doubts about the first detection of a gravitational wave - this concern was added to the main article, but later reverted by another editor.

QUESTION: Are the doubts about the first detection of a gravitational wave worth noting (see possible edit addition below) in the main article - or not? Perhaps for an "historical reason", if for no other reason?

Comments Welcome from other editors.



[Possible Edit Addition]

--- Doubts of detection --- In October 2018, doubts about the first detection of a gravitational wave have been raised by a team of physicists at the Niels Bohr Institute in Copenhagen, Denmark, who consider the original gravitational wave signal detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) an "illusion." However, LIGO Executive Director David Reitze of Caltech noted in response, "Their analysis has been looked at by many people who have all concluded there is absolutely no validity to their claims."

In any case - Enjoy! :) Drbogdan (talk) 13:59, 2 November 2018 (UTC)


 * Hope this helps in some way - iac - Enjoy! :) Drbogdan (talk) 15:52, 5 November 2018 (UTC)


 * We discussed this topic in September.
 * Here's a link to the 2017 Nobel Lecture for the Prize in Physics in which the principal invesigator explains this research.
 * Everyone is entitled to draw their own conclusions, but many very smart scientists have reviewed the LIGO work. The LIGO data analysis is published and took a lot of details into consideration, and if anyone wants to quibble over it, they ought to spend a few months studying those details.  Otherwise, there's no real reason to pay attention to the quibbling.  Nimur (talk) 15:59, 5 November 2018 (UTC)


 * Science works by proposing a theory, then testing it to see if it accurately predicts reality. If it does, then we accept the theory as "real" unless and until a better theory comes along.  The predictions of general relativity seem to have been adequately confirmed to the satisfaction of most scientists, so they treat gravitational waves as a "real" phenomenon. I suppose if someone comes up with a better theory that accurately predicts the observed effects, then science might reconsider, but I can't see that happening in the near future.   Dbfirs  16:17, 5 November 2018 (UTC)


 * This seems like a perfect example of how the scientific method works. A theory is proposed (General Relativity). We work out predictions of what effects would be observable if the theory were correct (periodic stretching of spacetime by gravitational waves). We conduct an experiment to look for the effects, and we find exactly what is predicted by the theory. No, this doesn't "prove" that gravitational waves are real, because "proof" is a concept in mathematics -- nothing in science is ever "proven". But it does offer more support for that theory, and a new constraint to any alternative theory -- such a theory now must predict these new observations and explain what causes them if it is not gravitational waves. CodeTalker (talk) 16:23, 5 November 2018 (UTC)
 * Just to clarify, things in science are never proven. They are supported.  But they can be disproven, see Karl Popper and falsifiability.  Science is a pursuit that narrows down possibilities.  It does not create singular answers, just better answers than what we had before.  -- Jayron 32 16:25, 5 November 2018 (UTC)
 * Indeed. If the opponents of science were actually very good at their job, they'd stop trying to disparage science using fruitless efforts to discredit it; and start attacking the more subjective elements: does the scientific work yield practical useful results that help improve people's lives?  Does the scientific result yield an actionable policy-choice that we would otherwise have overlooked?
 * But such critiques would require intelligence, and members of the anti-science community are soundly lacking in such matters; so, they instead attempt an all-out, full-frontal assault on the science itself. Frustratingly, their methods are entirely unconvincing to intelligent people; but we often forget that their methods are extremely effectively convincing to unintelligent people.
 * Half a century ago - before we had this omnipresent global telecommunications network - the uneducated masses would, at best, get their science news from a local high school science teacher. Today, thanks to the internet, the uneducated masses can ignore their science teacher, and ignore free access to primary resources like the Nobel laureate lecture; and instead, they get their science news via Twitter and Facebook.  We have dramatically regressed, and I fear we are in an information-era "dark age."
 * Nimur (talk) 16:31, 5 November 2018 (UTC)


 * I think there are several connected questions here:
 * Do gravitational waves exist ? Yes. Even before LIGO came on line, consensus was that gravitational waves definitely existed. Big questions were did we have the technology to detect them directly and how closely would their attributes match the detailed predictions of GR.
 * Does a single LIGO observation constitute detection of gravitational waves ? Probably. However, the low signal-to-noise ratio in raw LIGO data, the amount of processing and interpretation required to extract a meaningful signal, and the fact that detection involves statistical matching to a library of expected signal templates all introduce some room for doubt. This week's New Scientist has a lead article making these points.
 * Does the accumulated body of LIGO and Virgo observations and other data constitute detection of gravitational waves ? Yes. Simultaneous detection by more than two interferometers plus the associated gamma ray burst that was observed with GW170817 reduce the chances of mistaking noise for a real event to an insignificant level. Gandalf61 (talk) 17:03, 5 November 2018 (UTC)


 * AFAiK, besides GRB 170817A, seems AT 2017gfo, an astronomical transient, was also detected around the same time as GW170817 - making the GW detection, in this instance, even more "real" and/or "likely", I would think - iac - Enjoy! :) Drbogdan (talk) 17:27, 5 November 2018 (UTC)


 * Reading that gravitational waves (GW) exist, because even before LIGO "consensus was that gravitational waves definitely existed", I feel that this argument is circular: GW exists, because a majority believes that they exist. I also wonder what this consensus is based on. Is it GR? But, does it make sense to theoretically presuppose the existence of something that should be mesured first in order to establish its existence? Above it has been said that "This seems like a perfect example of how the scientific method works. A theory is proposed (General Relativity). We work out predictions of what effects would be observable if the theory were correct (periodic stretching of spacetime by gravitational waves). We conduct an experiment to look for the effects, and we find exactly what is predicted by the theory". Should this be true, the scientific method would always be "begging the question", logically circular, that is, or tautological, and therefore worthless. In the case of gravitational waves the logical circularity is evident for me. It is clear that "to find what is predicted by the theory" means to tacitly use the unproven (!) theory as the true standard for determining what there has been measured. As I said it before: Without GR nobody would ever identify a measured wave as a "gravitational wave stretching spacetime". What is "spacetime"? What is a "gravitational wave"? Well, it is what we by presupposing GR believe it to be. Isn't the circularity of this reasoning evident? Ed Dellian2003:D2:9703:5994:1023:178C:E142:6D5B (talk) 18:48, 6 November 2018 (UTC)


 * If someone comes up with a better theory that explains the observations, then the old theory will be relegated to history, as with Phlogiston, but unless that happens, the majority of scientists just follow the scientific method. In this case, the theory and the predictions came first, and the observations confirmed the predictions, thereby persuading scientists that the theory is useful. How is this "begging the question"?  Gravitational waves are just one of the predictions that have confirmed the theory.  Taken alone, I agree that they would not currently be adequate.   We have an article on spacetime.   <i style="color: blue;">D</i><i style="color: #0cf;">b</i><i style="color: #4fc;">f</i><i style="color: #6f6;">i</i><i style="color: #4e4;">r</i><i style="color: #4a4">s</i>  22:08, 6 November 2018 (UTC)
 * I think you're talking about the idea that "observations are theory-laden", which is true, but not a problem specific to gravitational waves. It's a fundamental issue in empirical epistemology generally.  Unless you're going to go all the way to radical skepticism, which is not really that useful, you have to come to terms with it somehow, and you might as well apply that accommodation, whatever it is, to the LIGO experiments. --Trovatore (talk) 23:02, 6 November 2018 (UTC)


 * See also here. Count Iblis (talk) 16:52, 7 November 2018 (UTC)

FWIW - Seems, more recently, in December 2018, a relevant report was published in Quanta Magazine - in any case - Enjoy! :) Drbogdan (talk) 14:05, 2 January 2019 (UTC)

"How many years older will you be 1.00 gigasecond from now? (Assume a 365-day year.) ."
This is a homework problem (obviously).

I tried:

1 year = 365 * 24 * 3600 (days, hours, seconds) = 31536000 Gigasec: 1,000,000,000 So, 1 years has 31,536,000,000,000,000 gigaseconds. I thought: 1/31,536,000,000,000,000 years older.

But the answer in the book: 31.7 y.

How come?--Doroletho (talk) 17:59, 5 November 2018 (UTC)
 * No, 1 year has 31,436,000/1,000,000,000 gigaseconds. A gigasecond is really big, so there are less of them in a year than there are seconds.  Which means you need to DIVIDE by the conversion factor, since you want to make the NUMBER of gigaseconds smaller than the NUMBER of seconds.  -- Jayron <b style="color:#090">32</b> 18:09, 5 November 2018 (UTC)


 * I read the question as "How much older will you be when 1,000,000,000 seconds have passed?". † dismas †|(talk) 18:10, 5 November 2018 (UTC)


 * Just a quick note, the OP removed the question a few minutes after answering it as they resolved it themselves. [//en.wikipedia.org/w/index.php?title=Wikipedia:Reference_desk/Science&diff=867433320&oldid=867433167] It was added back by Jayron32 [//en.wikipedia.org/w/index.php?title=Wikipedia:Reference_desk/Science&diff=867433502&oldid=867433320], possibily by accident in an EC. I do think the responses are a good read for the OP if they're still checking this question since they may help to think in a way to immediately notice when you've done something wrong. Nil Einne (talk) 18:27, 5 November 2018 (UTC)


 * I am just out the door and don't have time to check the numbers, but the following is often claimed:
 * A billion seconds ago it was 1959.
 * A billion minutes ago Jesus was alive
 * A billion hours ago our ancestors were living in the Stone Age
 * A billion days ago no-one walked on the earth on two feet
 * A billion dollars ago was only 8 hours and 20 minutes at the current rate of government spending
 * If nobody checks the numbers before then, I will do it later. --Guy Macon (talk) 21:03, 5 November 2018 (UTC)


 * I'm guessing that's just one particular government. Martinevans123 (talk) 21:30, 5 November 2018 (UTC)


 * For the first four, I make it
 * A billion seconds ago it was 1987
 * A billion minutes ago its was AD 117, so well after Jesus
 * A billion hours ago it was the Middle Paleolithic, so yes it was part of the stone age
 * A billion days ago it was near the end of the Pliocene ~2.7 million years ago (mya) - the earliest evidence of bipedal hominins is about 3.6 mya, so that's not true, depending on exactly what that statement means. Mikenorton (talk) 22:09, 5 November 2018 (UTC)
 * Just imagine how much worse it would be if we didn't have the Republicans running the government and cutting spending. ←Baseball Bugs What's up, Doc? carrots→ 22:11, 5 November 2018 (UTC)
 * Ah yes, the good old Republicans... thank goodness for the Donald. Martinevans123 (talk) 22:26, 5 November 2018 (UTC)
 * Since we're on the topic of Fermi problems, I'd like to comment that discussions of the Federal budget in the United States aren't particularly meaningful if you aren't very good at thinking about the relative sizes of large numbers.
 * For example, you might choose to normalize the budget per capita, dividing by the number of citizens. So, if the expected budget deficit is the quite large-sounding number of $782 billion in Fiscal Year 2018, we can divide that by the estimated current population of the United States, a quite large-sounding number near 330 million people.  (...Wasn't it just this morning that we were discussing the ratios of quantities trending toward infinities?)
 * So this means that we're accruing a debt of about six dollars per citizen per day; or, an average of six dollars of economic activity is contributed toward my wellbeing each day, at the potential future taxpayers' expense. I'm pretty comfortable with that: really, almost three of those dollars is being spent on paying for benefits for the elderly and the sick.  I can spare a few dollars a day to help the old and the ill in my country, even if fifty cents is regrettably wasted on nuclear brinksmanship.
 * I think a lot of politicians - especially people who pretend to be "conservative" by abusing that word beyond recognition - use scare-mongering and mathematical ineptitude to make these types of budget numbers sound really frightening, but they never present even an elementary analysis of why the numbers carry any particular value; nor do they even remotely attempt to discuss the practical consequences of these budget choices.
 * Let's encourage our readers to use quantitative and analytical skills, instead of just shouting about large numbers that end in "-illion" as if those numbers intrinsically mean anything.
 * Nimur (talk) 00:58, 6 November 2018 (UTC)


 * What would be interesting would be to calculate how much you are paying for benefits that people received 25, 50, and 100 years ago. Also interesting would be an estimate of how much the benefits you are receiving will cost each person 25, 50 and 100 years from now, given some reasonable assumptions about population growth/loss and whether the population will skew older, as it has in Japan. --Guy Macon (talk) 17:47, 7 November 2018 (UTC)
 * Of course also taking into account inflation, purchasing power, and the like. -- Jayron <b style="color:#090">32</b> 17:52, 7 November 2018 (UTC)


 * One way to help this is to pay Treasury bondholders on time and not have government shutdowns. Or get close enough for the credit rating to drop from AAA stable outlook. Sagittarian Milky Way (talk) 19:08, 8 November 2018 (UTC)