During a lunar eclipse, the surface temperature on the moon drops by about 150 to 250 degrees Celsius in a few minutes. The whole "day" side of the moon—an immense region about seven million square miles in area—is plunged into darkness. For anyone on (that half of) the moon “outdoors”, it would be impossible to miss: one would not even have to look at the sky to see the sun being blotted out by the earth; one could tell from the surrounding light and the temperature. The moon is physically affected in a significant way. Even if someone on the moon did not care about the earth, they would care about the time of the lunar eclipse. All this lines up somewhat (at least matches the timeline) with our apparent perception from earth.

During a solar eclipse, someone on the sun would hardly notice. The surface temperature does not change; the brightness does not change; the earth is about a 100 million miles away and occupies less than 10^-7% of the sun's sky (18 arc seconds; compare with the ~30 arc minutes that the sun or moon occupy in earth's sky). An observer on the sun would need to have very good optical instruments to take note of the entire earth in the first place; let alone the patch of earth a few miles across that is experiencing a total solar eclipse. Unless they were looking for it, they would not be aware of (what the earthlings call) a solar eclipse taking place.

(During a solar eclipse, we people on the earth do notice. The sun is hugely significant to the earth physically even though the earth is barely significant to the sun; the temperature can fall by maybe 15 degrees Celsius; people in the affected area of earth are plunged into darkness, etc.)

As a physically significant phenomenon, what's real during a solar eclipse (in somewhat the same way as a lunar eclipse) is happening on earth; if we called it a terrestrial eclipse it would be fairly real, but is the sun significantly affected? I'd say not really.

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Now, as this is my last post, there are a few philosophical issues this conversation has brought up:

- One is a question of ontology: What is "real"? I think people can differ in the level of how physical/material their ontology is; certainly everyone would agree about a visual spectacle taking place, but some would consider more "physical" phenomena more real (as in my earlier remark about whether shadows are “real”), and a brightness-and-temperature difference over half the entire moon is surely a physically more significant event (to the moon) than some faraway object casting a shadow on another faraway object would be to the sun.

- The second is a question of semantics: What connotations does the word "eclipse" carry? To some people, it carries connotations (e.g. "X-adj eclipse"="X experiencing a seizure") such that, for instance, a "solar eclipse"="sun being darkened" is only appearance not reality, while "lunar eclipse"="moon being darkened" is both appearance and reality.

- The third is a question of interpretation/hermeneutics. When I read something, I'm trying to see: "Is there some interpretation under which what I'm reading is correct?" The question of "Is there some interpretation under which the author of the above email is wrong, and solar eclipses are similar to lunar eclipses?" is not very interesting; of course the answer is yes, and in my earlier comments I've mentioned at least three interpretations under which the author is wrong. Certainly, it's not the language I'd use: before reading the post I'd never have described lunar eclipses as real and solar eclipses as virtual, and I probably still won't. Maintaining that the author is wrong does not challenge my perspective or contribute anything new to my life. I feel secure in my understanding of eclipses, and if someone has a different perspective, it does not feel like my perspective is being questioned; it's just an opportunity. On the other hand, "Is there an interpretation under which the author is right?" (the principle of charity) is more interesting, and having newly experienced this perspective I've been defending an answer of "yes": yes, not only is there a combination of connotations of "solar eclipse" and "real" under which a so-called solar eclipse is not a "solar-ly" significant event (thus not "real" in that sense), but also it's quite a fresh way of looking at things and appreciating how, even though both appear the same to us, one (which we call a "sun-seizure") is an event of significance only to us puny humans on earth and the sun is unaffected, while the other is truly, improbably, a case where the earth (our home!) has an unmissable effect on the moon, a case where our visual perception, of the moon falling into shadow, is actually correct, something contrary to our perception being so frequently wrong in the astronomical domain where for instance the sun and moon and stars appear to rotate around us every day and night but reality is different.