Why Are There Crushed Stones Alongside Railroad Tracks?

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Why are there crushed stones alongside rail tracks?

David S. Rose:

This is a good question with an interesting answer. The crushed stones are what is known as ballast. Their purpose is to hold the wooden cross ties in place, which in turn hold the rails in place.

Think about the engineering challenge faced by running miles of narrow ribbons of steel track on top of the ground: they are subject to heat expansion and contraction, ground movement and vibration, precipitation buildup from rough weather, and weed and plant growth from underneath. Now keep in mind that while 99 percent of the time they are just sitting there unburdened, the remaining one percent of the time they are subject to moving loads as heavy as one million pounds (the weight of a Union Pacific Big Boy locomotive and its tender).

Put all this together, and you have yourself a really, really interesting problem that was first solved nearly 200 years ago, and hasn't been significantly improved since.

The answer is to start with the bare ground, and then build up a foundation to raise the track high enough so it won't get flooded. On top of the foundation, you deposit a load of crushed stone (the ballast). On top of the stone, you lay down (perpendicular to the direction of the track) a line of wooden beams on 19.5 inch centers, 8.5 feet long, 9 inches wide and 7 inches thick, weighing about 200 pounds ... 3249 of them per mile. You then continue to dump crushed stone all around the beams. The sharp edges of the stone make it difficult for them to slide over each other (in the way that smooth, round pebbles would), thus effectively locking them in place.

The beams are made of hardwood (usually oak or hickory), and impregnated with creosote for weather protection. In the U.S. we call them "cross ties" (or, colloquially, just "railroad ties"); in the UK they are known as "sleepers"; European Portuguese, "travessas"; Brazilian Portuguese, "dormentes"; Russian, шпала (read "shpala"); French "traverses." While 93 percent of ties in the U.S. are still made of wood, heavily trafficked modern rail lines are increasingly trying alternatives, including composite plastic, steel, and concrete.

Next, you bring in hot-rolled steel rails, historically 39' long in the U.S. (because they were carried to the site in 40' gondola cars), but increasingly now 78', and lay them on top of the ties, end to end. They used to be joined by bolting on an extra piece of steel (called a "fishplate") across the side of the joint, but today are usually continuously welded end-to-end.

It would seem that you could just nail them or bolt them down to the ties, but that won't work. The non-trivial movement caused by heat expansion and contraction along the length of the rail would cause it to break or buckle if any of it were fixed in place. So instead, the rails are attached to the sleepers by clips or anchors, which hold them down but allow them to move longitudinally as they expand or contract.

So there you have it: a centuries-old process that is extremely effective at facilitating the movement of people and material over thousands of miles ... even though nothing is permanently attached to the ground with a fixed connection!

The ballast distributes the load of the ties (which, in turn, bear the load of the train on the track, held by clips) across the foundation, allows for ground movement, thermal expansion and weight variance, allows rain and snow to drain through the track, and inhibit the growth of weeds and vegetation that would quickly take over the track.

This post originally appeared on Quora. Click here to view.

What’s That Thing That Hangs Off a Turkey’s Face?

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iStock.com/JZHunt

That thing is called a snood. And it's there to let the other turkeys know that its owner is kind of a big deal.

When a male turkey—known as a tom—wants to mate, he faces two hurdles. One is his potential mates, the female turkeys (a.k.a. hens). In the realm of turkey mating, the hens wield the power of choice and the toms have to get their attention and win the opportunity to reproduce. Come mating season, a tom will strut around, gobble, puff out his chest, fan his tail, and drag his wings to attract the hens, who then pick which of the toms they’ll mate with.

The second problem for a tom looking for love is the other toms in the area. They’re all competing for the same limited number of hens. Sometimes a good mating display isn’t enough to win a mate, and toms will attack and fight each other to secure a hen. 

This is where the snood comes in. That goofy-looking piece of dangling flesh helps a tom both with choosy hens and with competition from rival males. Having a long snood almost always means that a hen will want to mate with him and that another tom will back down from a fight.

DUDES AND THEIR SNOODS

When two toms are trying to establish dominance, they’ll size each other up. Then they'll either fight, or one will flee.

In the late 1990s, Richard Buchholz, an animal behaviorist who focuses on turkeys, wanted to figure out which, if any, characteristics of a tom turkey could predict how they fare in dominance fights. That is, did bigger turkeys tend to win more scuffles? Did older ones? He also wanted to see if the turkeys used any of these predictive cues when sizing each other up. He looked at various characteristics of dominant toms that fight and win, and compared them to those of subordinate toms that lose fights or run from them. Of all the characteristics he looked at, only “relaxed snood length” seemed to be a reliable predictor of how a tom would do in bird-vs-bird combat. The dominant males, the ones who won fights and got a choice mate, had longer snoods.

With that in mind, Buchholz looked at how toms reacted to other toms with snoods of varying sizes. The birds tended to avoid confrontation with other males with longer snoods, and wouldn’t even feed near them. A big snood, this suggests, says to the other turkeys that this is a tom you don’t want to tangle with. Buchholz noted that snood length correlates with age, body mass, and testosterone, so, to competitors, the snood could be a good indicator of a tom’s aggressiveness, age/experience, size, and overall condition and fighting ability.

IN THE SNOOD FOR LOVE

Once the males have established who’s going to have a chance to mate, the final choice goes to the hen. While the mating display is the main draw for getting a hen to check him out, a tom’s snood helps him out again here.

Like it did for the other males, a tom’s snood signals a lot of information to a female assessing potential mates—it indicates how old and how big he is, and even says something about his health. In another study, Buchholz found that longer-snooded toms carried fewer parasites. If a hen wanted to choose a mate with good genes that might help her offspring grow large, live long, and avoid parasites, a tom’s snood is a good advertisement for his genes. In that study, hens showed a clear preference for toms with longer snoods. In another experiment years later, Buchholz found that healthy hens again showed a strong preference for long snoods and that hens with their own parasite problems were less picky about snood length and checked out more potential mates—perhaps, Buchholz thinks, because the hens recognized their own susceptibility to infection and were willing to invest more time searching for a tom with genes for parasite resistance that would complement their own—but still showed some preference for longer ones.

While a snood might look goofy to us, for a turkey, it’s integral to the mating game, signaling to other toms that they should get out of his way and letting hens know that he’s got what they’re looking for.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

An earlier version of this article ran in 2013.

What's the Difference Between Stuffing and Dressing?

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For carbohydrate lovers, nothing completes a Thanksgiving meal quite like stuffing—shovelfuls of bread, celery, mushrooms, and other ingredients that complement all of that turkey protein.

Some people don’t say stuffing, though. They say dressing. In these calamitous times, knowing how to properly refer to the giant glob of insulin-spiking bread seems necessary. So what's the difference?

Let’s dismiss one theory off the bat: Dressing and stuffing do not correlate with how the side dish is prepared. A turkey can be stuffed with dressing, and stuffing can be served in a casserole dish. Whether it’s ever seen the inside of a bird is irrelevant, and anyone who tells you otherwise is wrong and should be met with suspicion, if not outright derision.

The terms are actually separated due to regional dialects. Dressing seems to be the favored descriptor for southern states like Mississippi, Tennessee, South Carolina, and Georgia, while stuffing is preferred by Maine, New York, and other northern areas. (Some parts of Pennsylvania call it filling, which is a bit too on the nose, but to each their own.)

If stuffing stemmed from the common practice of filling a turkey with carbs, why the division? According to The Huffington Post, it may have been because Southerners considered the word stuffing impolite, and therefore never embraced it.

While you should experience no material difference in asking for stuffing or dressing, when visiting relatives it might be helpful to keep to their regionally-preferred word to avoid confusion. Enjoy stuffing yourselves.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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