Question is in the title. Why do they happen?
Here’s the wikipedialink, for those of us who don’t know what the hell you’re talking about, like me.
And I was going to say “Sainthood” or “painters”…
Partly, the shadows of objects you’re looking at are hidden behind the objects themselves, because the light source is shining in the exact direction you’re looking.
How is that pronounced in English / American?
Heelygansheen?
High-lig-en-shine.
Danke!
¡De nada!
For reference:
The ‘ei’ combination is pronounced as in ‘high’.
The ‘ie’ combination is pronounced ‘ee’.
The ‘eu’ combination is pronounced ‘oy’.
'G’s make a hard ‘g’ sound, as in ‘get’. (So ‘Eugene’ would be pronounced ‘Oygen’.)
‘W’ makes a ‘v’ sound. (The letter is called ‘vay’.)
‘V’ makes an ‘f’ sound. (The letter is called ‘fau’.)
‘Z’ makes a ‘ts’ sound. (The letter is called ‘tset’.)
A double-s, sometimes depicted as ß (called ‘Eszett’) depending on position, makes an ‘s’ sound.
A single ‘s’ makes a ‘z’ sound.
Umlauts (ä, ë, ö, ü) are a little tricky in English. The best approximation I can do is to shape my mount for a given letter, and to vocalise ‘eh’.
Thanks! But you missed “oe”.
No one I know in the New York City area (myself included) knows the proper pronunciation of “Goethals Bridge”. I mean, we all know how New Yorkers pronounce it (Ga-thilz, “a” as in “far”), but no one knows if that is correct, and in fact, we’re all pretty confident that it’s wrong. Not that we care – at least, not any more than we care about the pronunciation of Houston Street (“How-stun”). But we’re curious.
Oh — We are intelligent enough to know that the “oe” in “Goethals Bridge” would be pronounced that same as in “Goethe”. Except we’re clueless about him too.
I didn’t, but it’s hidden. 
I would write ‘oe’ as ‘ö’, ‘ae’ as ‘ä’, and ‘ue’ as ‘ü’. (I can’t think of any words with ‘ë’ at the moment. But it’s been many years since I spoke German.)
One could argue that in English, there’s no objectively right or wrong way to pronounce a proper name.
Indeed, in England itself, a pretty high percentage of place names are pronounced in a way that defies logic.
I thought the “ig” sound in German was a soft gutteral “g,” such as the word “pfennig.”
Americans say “Fenning,” but IIRC, the correct pronunciation is more like “Fennich” with the “ch” sound made very softly in the throat.
~VOW
I forgot about enging 'g’s.
Actually, you voice the “P” : “Pfennig”. It also depends on the dialect/ accent: in some regions, it’s more like Pfennich, in others, it close to Pfenning.
I apologize. Americans would say “Fenning,” a German would say, “PFennich,” with the soft gutteral “ch” sound.
We lived for a while in a tiny town called Feucht. I never could get the gutteral sound correct in the middle of the word. Americans would just call the town “Foit.” I at least tried to get some back-of-the-throat gargle in the word.
As the spouse of an American GI, I felt if I were living in Germany, I should at least TRY to speak the language. Most Germans know a bit of English, and they all seemed appreciative of my efforts to try to speak German (however badly I butchered the language).
~VOW
Slight hijack: What causes Heiligenscheins? 
I wasn’t quite right. The effect in question is similar to the retroreflectve effect of cats eyes (both kinds) and Scothbrite material. The refractive and reflective properties of droplets of water tend to reflect light rays back toward their source.
The shadow effect I described is a separate phenomenon, but often seen together. The photo on the Wikipedia article displays both together.
Sorry I couldn’t come in before – I don’t have access during the day anymore.
Mangetout is right (the second time), but his explanation might not be entirely clear. What happens in heiligenschein is this:
The water droplets are very nearly spherical and stand a little away from the surface of the grass, being suspended on small fibers. (Sometimes the droplets are on the grass directly, but the more impressive effect is when the drops are not toucjhing). The droplets act like lenses, focusing the light from the sun onto the grass itself. The distance probably won’t be correct, but that doesn’t matter – what’s important is that the droplet causes a concentration of the light into a small spot on the grass, even if it might not be a perfect focal spot.
The grass then scatters the light in all directions. Those rays that approximately retrace their path through the drop end up being nearly collimated back the way they came. It’s not perfect, since it’s not a focal spot, it’s likely at the wrong distance, and many of the rays will only be in approximately the right direction afterwards. What’s impoprtant is that an awful lot of the light will be returning along the opposite direction, towards the sun, confined to a relaytively narrow angle.
So if you are standing between the sun and the dew-covered grass, and you look around your shadow, you se a “halo” of bright light around your shadow. That’s heiligenschein.
It is indeed the way many retroreflectors work – particularly the white reflective paint that consists of white paint with tiny glass beads embedded in it. (Corner cubes and the hexagonal foil strips used on stop signs and street signs work in a different way, as do the “Cat’s eye” retroreflectors used in traffic control) They used to make startling little beads covered with such tiny glass beads that “lit up” when the light was behind you. And, back around a century ago, people used to make paintings and cover them with tiny glass beads that adhered to the paint and made the painting “light up” when the light was behind you. It was called “pastinella work”, and I have seen it derided as a “bastard art” and “kitsch”. But references to it are hard to come by. Lokking at a search engine, the only reference to it I find is one of my own old SDMB posts:
http://boards.straightdope.com/sdmb/archive/index.php/t-261700.html
Here: Beethoven, String Quartet No. 15 in A Minor (opus 132), 3rd mvt. (Heiliger Dankgesang) - YouTube
Now leave me alone. I need my sl
Quasi
In German, the ‘ë’ is used rarely, and only to signify that an ‘e’ is to be pronounced separately (in a hiatus), rather than as part of a diphthong – so the combination ‘ie’ would indicate an elongated ‘i’ (an ‘ee’ sound in English) in a single syllable, while ‘ië’ would indicate the ‘i’ and the ‘e’ to be part of different syllables, and thus the ‘e’ to be pronounced separately.