How Does a Pool Table Recognize the Cue Ball?

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iStock

If you’ve ever considered becoming a pool shark in the vein of Minnesota Fats—or perhaps Tom Cruise in The Color of Money—you might have first considered how a nonsentient object like a pool table can tell the difference between the cue (white) ball and the 15 object balls in play. This is something most tables can do automatically, spitting the cue ball back out after a player sinks—or “scratches”—the ball by accidentally dropping it into a pocket.

You can tell small children it’s sorcery and they’ll probably believe it. But for older people, there’s a non-mystical explanation.

At coin-operated pool tables, players deposit money that allows the table to release the balls from a storage area under the playing surface. As players sink each ball, they return to the collection area until more money is inserted. When the cue ball is sunk, it doesn’t go to the same depository. A table can tell the difference in one of two ways: Either the cue ball is slightly larger—usually about 1/8-inch bigger in diameter than the standard 2.25-inch billiard ball—or it’s housing a magnetized center.

If the ball is oversized, it won’t be able to pass through the return chute and will instead be diverted to an accessible slot once it fails to clear a shunt that’s just a hair over 2.25 inches. If the ball is magnetized, a process first patented by pool table manufacturer Valley-Dynamo in 1966 will trigger a sensor that reroutes the ball along a track that will immediately spit it back out so players can continue. Some balls may instead be covered or dotted with metal so a magnet inside the table will pull it into position.

Both methods generally work well for casual play, but advanced hustlers might find fault with them. A larger ball can feel “off” to someone used to standard-sized cue balls, while the magnetized version can roll in subtle and different ways. Balls covered in metal are known as “mudballs” and are frowned upon for their slightly uneven surface. Better is the “cat’s eye” approach, which holds a steel bearing and closely resembles an unaltered ball.

Pro hustlers may steer clear of these doctored balls, but for your standard night out at a bar or family fun center, either one will do the job.

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Why Are Sloths So Slow?

Sloths have little problem holding still for nature photographers.
Sloths have little problem holding still for nature photographers.
Geoview/iStock via Getty Images

When it comes to physical activity, few animals have as maligned a reputation as the sloth. The six sloth species, which call Brazil and Panama home, move with no urgency, having seemingly adapted to an existence that allows for a life lived in slow motion. But what makes sloths so sedate? And what horrible, poop-related price must they pay in order to maintain life in the slow lane?

According to HowStuffWorks, the sloth’s limited movements are primarily the result of their diet. Residing mainly in the canopy vines of Central and South American forests, sloths dine out on leaves, fruits, and buds. With virtually no fat or protein, sloths conserve energy by taking a leisurely approach to life. On average, a sloth will climb or travel roughly 125 feet per day. On land, it takes them roughly one minute to move just one foot.

A sloth’s digestive system matches their locomotion. After munching leaves using their lips—they have no incisors—it can take up to a month for their meals to be fully digested. And a sloth's metabolic rate is 40 to 45 percent slower than most mammals' to help compensate for their low caloric intake. With so little fuel to burn, a sloth makes the most of it.

Deliberate movement shouldn’t be confused for weakness, however. Sloths can hang from branches for hours, showing off some impressive stamina. And because they spend most of their time high up in trees, they have no need for rapid movement to evade predators.

There is, however, one major downside to the sloth's leisurely lifestyle. Owing to their meager diet, they typically only have to poop once per week. Like going in a public bathroom, this can be a stressful event, as it means going to the ground and risking detection by predators—which puts their lives on the line. Worse, that slow bowel motility means they’re trying to push out nearly one-third of their body weight in feces at a time. It's something to consider the next time you feel envious of their chill lifestyle.

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Are Any of the Scientific Instruments Left on the Moon By the Apollo Astronauts Still Functional?

Apollo 11 astronaut Neil Armstrong left the first footprint on the Moon on July 20, 1969.
Apollo 11 astronaut Neil Armstrong left the first footprint on the Moon on July 20, 1969.
Heritage Space/Heritage Images/Getty Images

C Stuart Hardwick:

The retroreflectors left as part of the Apollo Lunar Ranging Experiment are still fully functional, though their reflective efficiency has diminished over the years.

This deterioration is actually now delivering valuable data. The deterioration has multiple causes including micrometeorite impacts and dust deposition on the reflector surface, and chemical degradation of the mirror surface on the underside—among other things.

As technology has advanced, ground station sensitivity has been repeatedly upgraded faster than the reflectors have deteriorated. As a result, measurements have gotten better, not worse, and measurements of the degradation itself have, among other things, lent support to the idea that static electric charge gives the moon an ephemeral periodic near-surface pseudo-atmosphere of electrically levitating dust.

No other Apollo experiments on the moon remain functional. All the missions except the first included experiment packages powered by radiothermoelectric generators (RTGs), which operated until they were ordered to shut down on September 30, 1977. This was done to save money, but also because by then the RTGs could no longer power the transmitters or any instruments, and the control room used to maintain contact was needed for other purposes.

Because of fears that some problem might force Apollo 11 to abort back to orbit soon after landing, Apollo 11 deployed a simplified experiment package including a solar-powered seismometer which failed after 21 days.

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

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