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Fairy castles in the air

When people accuse you of building castles in the air, they are not usually congratulating you on an incredible engineering feat, but more likely trying to bring you back down to earth with a thud. Synonymous with daydreams, pipe dreams, and all other dreams unlikely to come to fruition, castles in the air are at best a hopeful vision, and at worst, a hopeless illusion.

Although the phrase “castles in the air” (the original phrase was “castles in Spain”) is most often used to describe imaginary constructions, it can also be used to describe a very real optical phenomenon—the fata morgana effect—in which different levels of hot and cold air distort the appearance of objects on the horizon to make them look like, well, castles in the air.

Tempting Fata

Fata Morgana is the Italian name for Morgan le Fay, the half-sister of King Arthur in Arthurian legend. Reputedly a sorceress and able to change shape at will, Morgan le Fay was sometimes said to live below the sea in a crystal palace that could also rise above the surface. The fata morgana effect was so named for the superstitious belief among sailors that she created illusory visions to lure men into a false port and to their death. The term first entered English usage in 1818, when it was used to describe an occurrence of the phenomenon in the Strait of Messina, a narrow body of water between Sicily and the region of Calabria in southern Italy.

Technically, fata morganas are a type of mirage, related to those visions of water in the desert, or less exotically, to those seeming pools of water on the highway on a hot day. However, the latter two are examples of inferior mirages, while fata morganas are classified as superior mirages. It’s not that fata morganas are inherently better than the others; the difference lies in the way each mirage is produced.

Refract Up

Although the word mirage is derived from the French verb se mirer, meaning “to be reflected,” a more apt description of a mirage is that it is refracted. As light passes through layers of air with varying densities (density being determined by factors such as pressure and temperature), it bends, or more specifically, refracts, according to each layer’s characteristics.

In the case of inferior mirages, light bends upwards when it moves from a denser layer of cold air into a less dense layer of hot air, like that created above a highway on a hot day. As light hits the surface of the road and bends upwards, it looks to our eyes as if we are seeing a reflection in the road of what is just above it—in this case, the blue sky. This is because we perceive that light travels in a straight line to our eyes, even when that is factually not so.

Lake Superior

A superior mirage is the reverse of this; what we perceive to be higher in the sky is actually lower to the ground. Light is bent downwards when it hits a layer of cold air, making it appear as if what is below our sight line is actually straight ahead or above us because we are seeing the inverted image of what is on the horizon projected above it. This can be further complicated when there are multiple layers of hot and cold air, creating a highly distorted image as the light refracts through them.

Superior mirages occur wherever the surface temperature is colder than the air above it, usually over bodies of water and areas with ice or snow on the ground. The term fata morgana is most often used to describe superior mirages occurring over water. In these instances, objects on the horizon, such as ships, islands, cliffs, or icebergs, appear taller than they are because their inverted image is reflected above or superimposed on them. This elongation of objects on the horizon may make it appear as if there are turrets or towers rising up from the water, leading to the description of fata morganas as castles in the air.

As this effect can occur with ships, making them look higher above the horizon than they are, some have speculated that this is the origin of the Flying Dutchman legend, in which a ghostly ship is doomed to sail the seas for eternity.

There are many other types of superior mirages; one of them, the fata bromosa, or “fairy fog,” is created under the same conditions as the fata morgana, but has a different appearance. It appears as a bank of fog, with varying degrees of brightness, but without the fine detail of the fata morgana.

Fata Complete

Since its introduction into regular usage, the term fata morgana has come to mean more than just an optical phenomenon; although it has kept its original meaning of referring to something that is illusory, its use has been expanded throughout popular culture. It provided the title for a Henry Wadsworth Longfellow poem, an 1868 polka by Johann Strauss, and an Agatha Christie crime novel. It’s the name of a French publishing house, a character in Sergei Prokofiev’s opera, The Love for Three Oranges, and a film by Werner Herzog composed solely of desert landscape images.

The enduring popularity of the term shows how compelling it is as an idea—that there are mysterious phenomena, benign or malevolent, that are beyond our understanding. Or it may be that we continue to be enamored of our castles in the air, despite the knowledge of their illusory nature, as the last stanzas of Longfellow’s poem conclude:

So I wander and wander along,
And forever before me gleams

The shining city of song,
In the beautiful land of dreams.

But when I would enter the gate
Of that golden atmosphere,
It is gone, and I wonder and wait
For the vision to reappear.

Note: This is an updated version of an article that originally appeared on Interesting Thing of the Day on July 24, 2006.

This week, another book just for Mac users! As the amount of data we store continues to grow, figuring out where to put it and how to access it becomes more complicated. Every Mac includes internal storage in the form of a hard drive, SSD, or Fusion drive. But you may also have one or more external devices (such as hard drives, flash drives, SD cards, or RAID devices), not to mention network-attached storage (NAS) devices or cloud storage (like Dropbox or iCloud Drive). Making sense of all your options, managing your stored data, choosing new devices or services when you’re running out of space, or even just figuring out what’s where can drive anyone to distraction.

Jeff Carlson covers all this and much, much more in his book Take Control of Your Digital Storage. For example, the book helps you choose a new (internal or external) hard drive, SSD, or hybrid drive; determine how much storage space you need; understand APFS, Apple’s new filesystem; format, partition, and repair disks using Disk Utility; choose and use a NAS, RAID, flash drive, or SD card for use with your Mac; work with disk images; and decide among local, network, and cloud storage for various types of files.

This book, like all Take Control titles, comes as an ebook, and you can download any combination of formats—PDF, EPUB, and/or Kindle’s Mobipocket format—so you can read it on pretty much any computer, smartphone, tablet, or ebook reader. The cover price is $14.99, but as an Interesting Thing of the Day reader, you can buy it this week for 30% off, or just $10.49.

The controversial theory of Peak Oil

Whatever your feelings about the cost of oil, the means of obtaining it, or the effect that burning it has on the environment, one thing’s for sure: there’s a finite amount of it, so sooner or later it has to run out. At least, I hope so, because once all the oil’s gone, perhaps the planet will finally have a fighting chance against global warming. Many people, however, would take a decidedly negative view of the impending disappearance of the world’s oil reserves for all the obvious reasons. Either way, just how long will the oil last?

In 1956, a geophysicist named Marion King Hubbert developed a theory to predict future oil production. He assumed that for any given oil field, production follows a bell curve. After the well’s discovery, production quickly ramps up as new wells are added. But eventually, as the oil is drained from the underground reservoirs, the production rate hits a peak after which it begins to decline, eventually returning to zero. And what is true of an individual oil field should, Hubbert reasoned, be true for the entire planet as well. Using these assumptions and the best data he had available at the time, he plotted historical oil production on a curve and estimated that oil production in the United States would peak by 1970, and worldwide by the mid-2000s. The moment at which global oil production peaks came to be known as Peak Oil (or Hubbert’s Peak), while the overall theory that production of oil (or other products based on non-renewable natural resources) follows a bell curve in this way was called the Hubbert Peak Theory. After that time, there would of course still be plenty of oil, but the production rate would drop at about the same rate it rose, until eventually it was all gone.

Peak Performance

So now, over 60 years later, how did those predictions work out? Within the United States, at least, Hubbert’s prediction seemed for a while to have been off by just a year, as domestic oil production did indeed peak in 1971. But after several decades of decline, the number started rising again, and in 2018, U.S. oil production reached an all-time high. That false peak was due, in part, to the development of new techniques for extracting previously unreachable oil (such as hydraulic fracturing, commonly known as fracking, and the exploitation of oil sands). Presumably, if Hubbert had access to current data and knowledge of the latest technologies, he’d have had to revise his date forward considerably.

What’s true in the United States also goes for worldwide oil production. Although it appeared for a while that we had in fact already passed the peak worldwide—perhaps in 2004 or 2005—newer estimates put the peak far in the future, though experts are seriously divided as to how far. For every apologist of Peak Oil there’s also a naysayer, and the arguments against the theory are both wide-ranging and passionate.

Numerous researchers have taken exception to Hubbert’s math as well as his fundamental assumptions. To some extent, it appears that he started with a theory and tried to come up with data to support it, rather than the other way around. There’s no particular reason to assume, a priori, that oil production should follow a bell curve. It could have any number of dips and spikes, for many different reasons, over a long period of time; the aforementioned development of new extraction techniques is a case in point. Another type of claim is that anyone who buys into Peak Oil must have an agenda, either political or financial in nature; oil simply can’t, mustn’t, and won’t disappear any time soon. In any case, most critics admit that yes, there must logically be a worldwide peak in oil production eventually—with an end to oil production some time long after that—but that whenever this happens, it will be so far in the future as to make worrying now seem silly.

Increasingly, commentators have noted another factor: demand. Hubbert didn’t envision decreasing demand for oil, but if that occurred, then ipso facto, production would also decrease. Indeed, it looks increasingly likely that within our lifetimes, that will happen—even if peak production capacity has not occurred. In other words, “peak” doesn’t necessarily mean what Hubbert thought it meant.

Just Add Oil

But the most surprising criticism of Peak Oil is based on the claim that Earth can never run out of oil, because it simply keeps manufacturing more. We all learned in school that oil is a fossil fuel, created over many millennia by heat and pressure acting on the remains of plants and animals that lived and died eons ago. Because all that biological matter hasn’t been regularly replenished, once the planet’s supply of fossil fuel is gone, it’s gone. But according to supporters of the abiogenic petroleum origin hypothesis, oil never came from biological matter at all. It’s produced within the Earth’s crust and mantle by heat and pressure acting on ordinary and plentiful substances such as carbon dioxide, hydrogen, and methane. And what’s more, the production of new oil has never stopped: look in the right places in the right ways, and you’ll see oil reservoirs being replenished. This hypothesis first appeared in the 1870s, but it has never had much traction outside Russia and the Ukraine. Still, that hasn’t stopped Peak Oil opponents from using it to bolster their position.

Well, what if oil did run out—and what if that happened within, say, the next few decades? Once again, the reactions to this scenario vary dramatically. Some predict it will lead to a collapse of the worldwide economy, mass starvation, and perhaps even the end of the human race. Most pundits say it won’t be that bad; between now and then, we’ll develop the necessary technology to replace oil with something else for large-scale applications such as transportation; given the rapid progress in electric vehicles, that seems entirely plausible. And in between are survivalists who fear the worst but are figuring out how to live petroleum-free lives when the day comes.

Peak-a-Boo

What I find most striking about this entire debate is its emotional intensity. Websites both pro and con often consist of extremely long, sometimes boring, and often inscrutable rants accusing the other camp of all sorts of diabolical motives, along with insults and name-calling a-plenty. And all this over a theory that might never be proven one way or another—we could always end up finding massive, unexpected oil reserves (or easy ways of getting at more of the existing oil) far in the future, creating an entirely new production curve. Meanwhile, we already have the technology to generate our own oil from garbage, an infinitely renewable resource.

In short, if you want to worry about the price of oil, fine. If you want to worry about global warming, fine. I heartily support any and all efforts to develop alternative energy sources, conserve fuel, and protect the environment. But I can’t bring myself to worry about running out of oil. Either it will happen or it won’t, and if it does, it’ll be either sooner or later. But my money is on much later, by which time I fully expect the world will have either gotten over its oil dependence for other reasons or destroyed itself in any of several increasingly plausible ways. Either way: nothing to worry about.

Note: This is an updated version of an article that originally appeared on Interesting Thing of the Day on July 17, 2006.