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I once heard of a strange phenomenon, but now cannot find anything about it on the Internet. I might be looking for the wrong keywords or misremember some relevant aspect. So maybe someone here can help me out and point me in the right direction.

The described phenomenon goes like this, as I remember it:

During the course of the scientific research, people found out more and more about the objects surrounding us. Moon, Sun, planets, other stars, other galaxies, etc. But each time (more or less) a little later (after a new discovery was getting an established fact) it showed that the closest object of this kind to Earth was rather an exception among its peers. For instance, the closest other galaxy is blue-shifted. Or that the closest Pulsar is somehow an exception among its peers.

It might be that the rule was not about the closest but about the first found object of a kind.

I think I remember Prof Harald Lesch (a German physicist lecturing on TV in a popular format called "Alpha Centauri") mentioning this peculiar phenomenon and fleshing it out with some examples, but now I'm not able to find the clip.

I understand the point about closing this question, but maybe leave it open for some weeks (or months), just in case somebody drops by who has something to contribute. After a grace period the non-reaction can be counted as a vote for "isn't common knowledge". Without such a grace period closing the question can only be based on "I don't know such a thing" (which should not be enough).

The concrete questions (because that was asked for, so it seemed to be unclear to some people) are:

  • Is such a phenomenon known?
  • Is there a source describing it?
  • Is there a name to it?
  • What are examples of such objects?
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  • $\begingroup$ The closest phrase I can think of is "observation bias" (we think everything is similar to what we personally experience), but I'm not sure that applies here. $\endgroup$ – barrycarter Jul 30 '17 at 13:37
  • $\begingroup$ History of Science and Math Stackexchange hsm.stackexchange.com might be a good, even better place to ask this if you think it might have an historical aspect to it. $\endgroup$ – uhoh Jul 30 '17 at 15:53
  • $\begingroup$ So what is exceptional about Proxima Centauri? $\endgroup$ – Rob Jeffries Aug 21 '18 at 7:17
  • $\begingroup$ @RobJeffries Two answers: ① Proxima Centauri (α Cen C) is the smallest of a trinary star system, a far-out-lying companion of an otherwise standard binary star system (composed of α Cen A and α Cen B). If nothing else, its orbital period of half a million years around its two siblings in the trinary system make it special. But okay, if you think all this isn't very special, then: ② Maybe not all nearest objects. Our closest star (Sol) doesn't seem to be very special, for instance. But many nearest examples of different object kinds. $\endgroup$ – Alfe Aug 22 '18 at 12:13
  • $\begingroup$ An orbit of 0.5 million years for a multiple system is well beyond the median, but it is not "exceptional" - and not really more exceptional than the Sun which is among the top 10% of stars by mass in our Galaxy. The nearest star to us is an absolutely typical star - about 0.25 solar masses, half the age of the Galaxy, and part of a multiple system. Neither is it odd that the closest large (there are closer, smaller objects, which again, is what you would expectl) galaxy is moving towards us - that's gravity. $\endgroup$ – Rob Jeffries Aug 22 '18 at 13:10
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I have not heard of any idea that the nearest object is exceptional in any significant way, and in the case of the nearest pulsar, nearest star, nearest (large) galaxy etc. the properties are usually typical of the underlying population, though perhaps not the observed population because of biases and selection effects.

Take Proxima Centauri as an example. It is unlike any star that can be observed with the naked eye. However, it is a very good example of a "modal" star - much less massive than the Sun, about half the age of the Galaxy and a member of a multiple system. The reason for the discrepancy is of course that stars have a wide range of luminosities and distances; in a "flux-limited" survey, we always pick out the brightest sources, which tend to be the most luminous sources at large distances, where our survey volume is largest.

So, it is true that nearby objects are different to the observed population.

The same may apply whenever some unusual chacteristic makes a type of object more likely to be detected. There is certainly a phenomenon in astronomy where the prototype of a class of objects (usually the first discovered) turns out to be atypical of the class as a whole.

As an example we could consider RS CVn binaries, named after the object RS CVn, which is a close binary system containing an evolved (subgiant) component, and exhibiting extreme levels of magnetic activity (star spots, coronal X-ray emission).

It was initially believed that the presence of an evolved component was a defining feature of the class. However, over the years it has become apparent that there are many more examples of close, magnetically active binaries with main sequence components. The prototype is atypical in having an evolved component - the explanation is that, although short-lived and rarer, evolved magnetically active stars are much more luminous and easier to find/study.

As a final word on this, there is a set of nearby/nearest objects, including the Sun and Moon, that are somewhat unusual. The Sun is more massive than 90+% of stars in the Galaxy; no other planets in our solar system have a moon that is so (relatively) large. An explanation for these things may lie with the anthropic principle, which argues that we would not observe any circumstance that would preclude the development of intelligent life on Earth or, to turn that around, we are more likely to find ourselves in a situation that is favourable for the development of intelligent life on Earth.

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  • $\begingroup$ Thank you for your detailed answer! Indeed I'm not so sure anymore if what I think I remember was about the closest objects or the first found examples of a kind of object. I'm pretty sure though that the list of examples also contained rather far away stuff without any obvious influence on us, so the anthropic principle should not account for all of them. The object being more obvious than its peers in kind sounds like a good explanation though. Anyway, I wasn't looking for an explanation (though nice to have!) but a link to a reference ... $\endgroup$ – Alfe Aug 22 '18 at 23:14
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One thing to keep in mind is that Earth isn't really all that special from the rest of the universe.

I don't believe the phenomenon exists, since that would really put Earth in a "special" position, and that's not really correct. If it did exist, then it'll probably be famous or well known.

I've never watched these "alpha centauri" videos before, and they seem to not be in english, but based off of my background knowledge, I do not recall any phenomenon of the sort.

Obviously, there are some exceptions to the "every galaxy has a red shift" rule, such as...

  • The Andromeda Galaxy has a blue shift because it is moving towards us, and on a collision course.
  • I saw this article (here) that stated that a galaxy named M98 that is nearly traveling as fast as the Andromeda Galaxy, even though it isn't even close to us (50 million ly) and isn't on a collision course.

Besides these few exceptions I doubt that there really isn't any phenomenon. Not to mention that only galaxies are affected by the redshift-blueshift thing - not individual stars.

Hope that helps!

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  • $\begingroup$ Well, Earth surely is special in one aspect: It carries us. We don't really know and understand which aspects are relevant to achieve this feature, and science is trying to find out. It is not valid to use the hypothesis "we aren't special" apriori to explain why something cannot be there; it might be the result of observations, though. I (think I) remember hearing of observations which appear to contradict this hypothesis; but not really of course. I don't see how the fact that the closest black hole is special makes us special. $\endgroup$ – Alfe Aug 22 '18 at 12:51
  • $\begingroup$ My point is, because we aren't "special", that doesn't mean that objects closest to us should be moving towards us, because then we would affecting the universe in a different way than ALL the planets. $\endgroup$ – MystaryPi Aug 22 '18 at 17:44
  • $\begingroup$ There is also no evidence of the objects close to us being blue shifted. Anyway, as I stated in my answer, individual objects cannot be shifted - only galaxies. $\endgroup$ – MystaryPi Aug 22 '18 at 17:45
  • $\begingroup$ I'm sorry if I somehow overstressed the example of something close being blueshifted. That was just one example for an object being special in any way. I never intended to say that everything close was blueshifted. $\endgroup$ – Alfe Aug 22 '18 at 23:00

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