How Much Weight Would Santa Gain From Eating Milk and Cookies at Every House He Visits?


Dave Consiglio:

This is a simple question for the Factor Label Method. This method, also known as dimensional analysis or unit analysis, make problems a breeze. I highly recommend it to anyone interested in doing seemingly hard math problems like this one. Here’s how you use it:

  1. Write your given—in this case “1 Santa Claus”—on the left side of your paper
  2. Write your desired answer—in this case “pounds”—on the right side of the paper
  3. Make a chain of units from left to right (no numbers required).
  4. Fill in the numbers
  5. Multiply by all the tops
  6. Divide by all the bottoms
  7. Clean up

In just 7 simple steps you’ve got an answer. Here’s my answer. (Note: I assumed a cookie has 200 calories and a glass of milk has 100 calories. Your results will vary based on the type of cookie. I also assumed around 2 billion houses.) Here’s my Factor Label Method:

Answer: 400,000,000 pounds.

One of the best things about mathematics of this kind is that, by approximating in this way, you can see the magnitude of your answer. This answer is 400 million pounds, but it might be 300 or 500 million, depending on your assumptions. So what?

Well, while we may not know the precise answer, what we do know is that the answer is very large.

This kind of answer can be really helpful. You don’t always have to have the precise answer. A “good enough” answer can give you a pretty good idea of where you stand.

By the way: We’re assuming that Santa burns no calories during his trip. If he burns calories like a normal man his size and age, he will probably only gain around 399,999,999 pounds. But if Santa uses calories to propel his sleigh around the world (perhaps he has a “fat to magic” converter?), then he might be able to travel the whole world using only the calories from his cookies and milk and gaining no weight at all. Magic is a tricky thing to quantify.

But for the real world, the Factor Label Method is the next best thing to magic.

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

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.