Umbra

Umbra (pronounced uhm-bruh)

(1) Shade; shadow, now restricted mostly to literary use.

(2) The invariable or characteristic accompaniment or companion of a person or thing.

(3) In astronomy, the complete or perfect shadow of an opaque body, as a planet, where the direct light from the source of illumination is completely cut off.

(4) In astronomy, the dark central portion of a sunspot.

(5) A phantom or shadowy apparition, as of someone or something not physically present; ghost; spectral image.

(6) An uninvited guest brought along by one who was invited (archaic).

(7) The fully shaded inner region of a shadow cast by an opaque object.

(8) One of the family Umbridae of mudminnows; a sciaenoid fish, the umbrine.

(9) In typography, a sans-serif display typeface released in 1935 as a variation of the earlier Tempo.  Similar to many contemporary art deco designs, it's constructed with a shadow effect, the letter shapes built as negative space and defined by a black dimensional shadow.

1590s: From the Latin umbra (literally “shade”; shadow), a doublet of umber and of uncertain origin.  If it was from the Old Latin omra, source may have been the primitive Indo-European hzmrup-, related to the Ancient Greek ἀμαυρός (amaurós) (dark) and “rot” & “rotten” in the Luwian hieroglyphic.  Etymologists also note the Hittite Maraššantiya (their name for the Kızılırmak River), and this Indo-European source is said to be a possible borrowing from a Semitic root ḥ-m-r (be red), linked to the Arabic ح م ر‎ (ḥ m r).  All agree there is a connection with the Lithuanian unksna.  The adjectives are umbral & umbrageous and the noun plurals are umbras & umbrae.

The early meaning was that of a “phantom or ghost," a figurative use drawn from the Latin umbra (shade, shadow), which gave rise to the later umbrage (A feeling of anger or annoyance caused by something offensive or (now rarely) a feeling of doubt, from the Middle French ombrage (umbrage), from the Old French ombrage, from the Latin umbrāticus (in the shade), from umbra (shadow, shade)).  The astronomical sense of a "shadow cast by the earth or moon during an eclipse" was first used during the 1670s.  The meaning "an uninvited guest accompanying an invited one" is from 1690s and was an invention in English, from a secondary sense used in Ancient Rome.

The related noun umber (brown earthy pigment) is from the 1560s, from the French ombre (in terre d'ombre), or the Italian ombra (in terra di ombra), both from the Latin umbra (shade, shadow) or otherwise from Umbra, the feminine form of Umber "of or belonging to Umbria, the region in central Italy from where the coloring material was first discovered.  Burnt umber, specially prepared and redder in color, is attested from circa 1650 and distinguished from raw umber, both well-known to artists of the era.

It’s the cosmic coincidence of the relationship between the diameter of the Moon and its distance from the Sun which makes solar eclipses such a spectacular sight from planet earth.  On other planets, where the relationship is different, solar eclipses may not be as enchanting.  A solar eclipse happens sometimes as the Moon moves between the Sun and Earth, the Moon blocking the light of the Sun from reaching Earth.  Astronomers classify solar eclipses into three types:

(1) A total solar eclipse which is visible from a small area on Earth.  Those who see a total eclipse are those standing in the center of the Moon's shadow when it hits Earth. The sky becomes very dark, as if it were night. A total eclipse occurs only when the Sun, Moon and Earth are in a direct line.

(2) A partial solar eclipse happens when the Sun, Moon and Earth are not exactly aligned, the sun appearing to have a dark shadow on a small part of its surface.

(3) In an annular solar eclipse, the Moon seems further because the annular happens when the Moon is farthest from Earth and thus does not block the entire view of the Sun, instead looking like a dark disk on top of a larger Sun-colored disk.

A solar total eclipse.

Solar eclipses are not rare, visible around every eighteen months somewhere on Earth although the viewing spot is always relatively small.  Unlike lunar eclipses, solar eclipses last only a few minutes.  The umbra is the darkest part of a shadow, especially the cone-shaped region of full shadow cast by Earth, the Moon, or another body during an eclipse. In a full lunar eclipse, which generally lasts for one or two hours, the entire disk of the Moon is darkened as it passes through the umbra. During this period the Moon takes on a faint reddish glow due to illumination by a small amount of sunlight that is refracted through the Earth's atmosphere and bent toward the darkened Moon; the reddish tint is caused by the filtering out of blue wavelengths as the sunlight passes through the Earth's atmosphere, leaving only the longer wavelengths on the red end of the spectrum.

The umbra is the innermost and darkest part of a shadow, the area in which the light source is entirely obscured by the occluding body and if standing in this space, the viewer will experience a total eclipse.  Viewed in the abstract, the Sun, Moon & Earth all being (almost) spherical, umbra forms a right circular cone and, if viewed from the cone's apex, the two bodies will seem the same size.  The penumbra, from the Latin paene (almost, nearly) is the region in which only some of the light source is obscured by the occluding body so the viewer standing in the experiences a partial eclipse.  The antumbra, from the Latin ante (before) is the region from which the occluding body appears entirely within the disc of the light source.  The viewer standing in this apace experiences an annular eclipse, which manifests as a bright ring visible around the eclipsing body.  If the viewer is able to move closer to the light source, the apparent size of the occluding body increases until it causes a full umbra.

An umbraphile (shadow lover) is a person with much interest in eclipses, often making extraordinary efforts to travel to see them.  The construct is umbra +‎ phile.  Phile is from the Latin -phila, from the Ancient Greek φίλος (phílos) (dear, beloved) and from the same source is -phil, a word-forming element meaning "one that loves, likes, or is attracted to," via the French -phile and the Medieval Latin -philus in this sense, from the Ancient Greek -philos, a common suffix in personal names (such as Theophilos), from philos (loving, friendly, dear; related, own) and related to philein (to love) which is of unknown origin.  One authoritative etymologist suggests the original meaning was "own; accompanying" rather than "beloved."

Umbraphilia emerged as a niche in nineteenth century high-end tourism, gentlemen scientists and society figures sailing around the world to observe and sometimes report their findings.  The longest known observation of a solar eclipse was that undertaken on 30 June 1973 when a group travelled on board the Concorde, enjoying seventy-four minutes of totality.