Why Are Manhole Covers Round?

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iStock

If you’re in the habit of looking down at your feet as you walk, you may have noticed that most manholes, and their covers, are round. Or perhaps you’ve been in a job interview where your prospective employer asked this question (which apparently happens enough that it was included in the third edition of The Complete Idiot’s Guide to Job Interviews). He wants to know about your ability to think on your feet, and isn’t so much interested in the correct answer, but it is a good question. Of all of the potential shapes for manholes, why was a circle chosen?

There are a number of reasons, according to Larry Scheckel in his book Ask A Science Teacher: 250 Answers to Questions You've Always Had About How Everyday Stuff Really Works. Manholes are round because “it is the best shape to resist the compression of Earth around it.” Round shapes are easier to manufacture than square or rectangular shapes, and because manhole covers are heavy, being round makes them easier to move from place to place (just roll them!). As an added benefit, workers don’t need to line up the covers with any angles, making round covers easy to slip into place.

But perhaps the biggest reason that manhole covers are round is that round covers can’t fall through a circular opening. “For all manholes, there is a ‘lip’ around the rim of the hole, holding up the cover, which means that the underlying hole is smaller than the cover,” Scheckel writes. “A round manhole cover can’t fall through its circular opening, because no matter how you position it, the cover is wider than the hole. But a square, rectangular, or oval manhole cover could fall in if it was inserted diagonally into the hole,” which would be bad news for unobservant pedestrians and drivers alike.

What’s the Difference Between Crocheting and Knitting?

djedzura/iStock via Getty Images
djedzura/iStock via Getty Images

With blustery days officially upon us, the most pressing question about your sweaters, scarves, hats, and mittens is probably: “Are these keeping me warm?” If you’re a DIY enthusiast, or just a detail-oriented person in general, your next question might be: “Were these knitted or crocheted?”

Knitting and crocheting are both calming crafts that involve yarn, produce cozy garments and other items, and can even boost your mental well-being. Having said that, they do have a few specific differences.

To knit, you need needles. The size, material, and number of those needles depends on the project; though most traditional garments are made using two needles, it’s also possible to knit with just one needle, or as many as five. But regardless of the other variables, one or both ends of your knitting needles will always be pointed.

While crocheting calls for a similar long, thin tool that varies in size and material, it has a hooked end—and you only ever need one. According to The Spruce Crafts, even if you hear people refer to the tool as a crochet needle, they’re really talking about a crochet hook.

crotchet hook and garment
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Part of the reason you only use one hook brings us to the next difference between crocheting and knitting: When crocheting, there’s only one “active loop” on your hook at any given time, whereas knitting entails lining up loops down the length of your needles and passing them between needles. The blog Darn Good Yarn explains that since each loop is attached to a long row of stitches, accidentally “dropping” one off the end of your needle might unravel the entire row.

Of course, you have a better chance of avoiding that type of manual error if you’re using a knitting machine or loom, which both exist. Crocheting, on the other hand, has to be done by hand. Since machines can create garments with extremely small stitches, some knit clothes can be much more lightweight or close-fitting than anything you’d be able to crochet—and knitted clothes can also be mass-produced.

When it comes to what the items actually look like, crochet stitches characteristically look more like knots, while knit stitches seem flatter and less bulky. However, materials and techniques have come a long way over the years, and now there’s more crossover between what you’re able to knit and crochet. According to The Spruce Crafts, socks and T-shirts—traditionally both garments that would be knitted—can now technically be crocheted.

knitting needles and garment
Sedan504/iStock via Getty Images

And, believe it or not, knitting and crocheting can even be used to depict complicated mathematical concepts: see what a crocheted hyperbolic plane, Lorenz manifold, and more look like here.

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

What Happens to Leftover Campaign Funds When a Candidate Drops Out?

After nearly one year of campaigning for the Democratic presidential nomination, Kamala Harris has officially bowed out of the 2020 election. She's not the only would-be president to call it quits so far. So what happens to all the leftover campaign funds when a candidate drops out?

One thing's for sure: Upset candidates can't console themselves by putting the dough toward a new yacht and sailing off to recuperate. The Federal Election Commission has strict rules about what federal candidates can and can't do with leftover campaign money, and the biggest directive is that they can't pocket it for personal use.

Here's what a campaign committee is allowed to do with any lingering cash: it can donate the funds to charities or political parties; it can contribute $2000 per election to other candidates; and it can save the money in case the candidate chooses to run again. However, those regulations don't apply to the relatively new super PACs (Political Action Committees); this is only the third election where they have played a role, and there are currently no rules to stipulate what happens to that money beyond that it cannot go to fund another federal candidate. Much of that money tends to be returned to its original donors, used to wrap up the failed campaign, or donated to back a state-level candidate. The goal, however, is always to spend all of that money.

Running a campaign is an expensive proposition—Barack Obama spent nearly $750 million on his 2008 White House bid, and in 2012 he spent $985 million on reelection while challenger Mitt Romney spent $992 million—and insufficient cash is often a reason campaigns go belly up.

As for winning (or sometimes losing) politicians, they'll often put their leftover funds toward their next race. If they choose not to run, they have to abide by the same FEC rules. Wonder why this law is in effect? Until 1993, U.S. Representatives who took office before January 8, 1980, were allowed to keep any leftover campaign cash when they retired, but a study showed that a third of Congress kept and spent millions in campaign donations on personal items like clothing, jewelry, artwork, personal travel, and dry cleaning. Embarrassed, Congress passed a law negating this custom for the House; the Senate already had provisions in place so this wouldn't happen.

In reality though, officials can usually find a way to make that cash still work for them (and state laws differ from federal ones). After Chris Christie won reelection as New Jersey's governor in 2014, his campaign was granted permission to use some of its remaining war chest to cover the legal fees Christie incurred during the Bridgegate scandal. And this was well before he dropped $26.7 million on his failed 2016 presidential bid.

An earlier version of this article originally ran in 2012.

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