"My flabber was completely gasted." - Rating Pending
Question #91709 posted on 10/07/2018 8:12 a.m.

Dear 100 Hour Board,

Last night, my daughter told me that it's been scientifically proven that on a clear, dark night, you can see the light from a single candle thirty miles away. Got that little tidbit in one of her college Biology classes.

While I'm not doubting the fact, when she told me it got me wondering where they could have done such an experiment. Maybe I'm a little sheltered, but where on this continent could they have gotten a piece of land level enough to see a candle thirty miles away? In my travels I don't think I've ever seen a stretch of land that flat, with not undulations or trees or buildings in the way. Nebraska and Kansas came to mind immediately, of course, but there are small hills and lots of trees in the way there, too.

Where, oh where, could such a place be?

Thank you.

-Flat-land Lenny


Dear Lenny,

You don't need flat land to see something thirty miles away. All you need is to be on top of a mountain (or tower, I guess) that's taller than everything else in the region. For example, if I'm just chilling in Salt Lake City proper, there's no way I can see the Great Salt Lake, because there are far too many buildings and trees and hills in the way. But if I hike up to the top of a mountain, even if it's actually farther from the lake itself, I can easily see the lake (assuming it's one of the, like, two days when there's not wildfire smoke or an inversion blocking my view of everything in the valley).

However, not to rain on your parade or anything, but I'm about to rain on your parade. Ardilla found this article, which casts serious doubt on humans being able to see a candle flame from 30 miles away. Apparently it's a common belief, but some physicists tested it out and found that the farthest away the naked eye would be able to see a candle flame is 2.76 kilometers, or about 1.6 miles. Physicists, always the bearers of bad news. That article does talk about the issue of finding somewhere where a candle even just 1.6 miles away would still be unobscured by other intervening objects, though, if you're interested in the logistics of how scientists could test this (ultimately these scientists did it by comparing star and candle brightness and using lots of math).



Dear Kravitz,

If you're looking for the smoothest places on earth, there's quite a number of places with thirty miles of smooth area (yes, I'm linking to Quora, it's a reasonably good answer and they've already done the work), including the wildly overrated Salar de Uyuni in Bolivia (a tirade for another day, just visit the Bonneville Salt Flats instead). Alas, because of the curvature of the earth, the furthest point of the horizon you'd be able to see in one of these smooth places would be just 2.9 miles away, and as we've already established you likely wouldn't be able to see a candle even at that distance. Bummer, eh?

Jonathan Johnson, rattling away in the aformentioned Quora article, notes "The largest truly flat areas on earth are found in particle accelerators. Particle accelerators are built accounting for the curvature of the earth; the extreme ends of linear accelerators are not perpendicular to the direction of gravity."



--Ardilla Feroz

P.S. Whoa, learned something new today! Apparently Salar de Uyuni holds 5.4 million of the world's 11 million tons of known lithium reserves, lithium being a critically important component of many of the rechargeable batteries used in phones, battery-powered cars and those weird scooters that showed up this summer. I do not know what will happen to Salar de Uyuni, it will be interesting to watch and see (okay let's be real here they'll totes mine that).

posted on 10/09/2018 7:51 p.m.
More essential than flatness is the clear dark night, which is not very common these days! I work in the outdoor industry and get to take university students out into the wilderness, many for their very first time, and for many of them, it is the very first time they get to see more than a handful of the brightest stars, let alone the milky way. Goblin Valley in southern Utah is world renowned for its dark skies, and well worth a trip. I was down there this past weekend with students, and while most had seen stars before, they were all surprised at just how many shooting stars we could see with it being so dark (we counted five in about fifteen minutes)!
Turns out our dark skies are of great value too; not just to anyone interested in seeing beyond the haze (so, I'm guessing...everyone?), but to astronomers and the military too. Yes, military, cuz guess how and from where they are going to spot those meteors and aliens coming at earth? Telescopes in Southern Utah.
I'm not affiliated with them, but if you want to learn more about dark skies, here is a website with more info (and ways you can improve our skies!) http://darksky.org/

-Corsica S.