How Much Does the Moon Weigh?


How much does the moon weigh?

C Stuart Hardwick:


Okay, I’m being a bit pedantic. The mass of the moon, which might be what you mean to ask, is approximately 7.3476× 10^22 kilograms.

But the moon doesn’t weigh anything.

Weight is directly related to mass, but it’s not the same thing as mass (even through we call units of weight and mass by the same names). Weight is the force exerted by gravity against a body resting against a larger mass. The moon is in freefall—in orbit—so it doesn’t weigh anything. If it were placed on the surface of the Earth, it would weigh about 7.3476 × 10^22 kilograms—but only for a moment. Then it would collapse under its own weight and become a rather disastrous pimple on the Earth until it broke through the crust.

That would be a bad day.

But fortunately, there is no realistic way that could ever happen. The moon is in orbit, which means it’s falling toward Earth (which is why it doesn’t “feel” our gravity—it’s weightless), but it’s also coasting away into space such that for every meter it falls toward us, it moves far enough for Earth’s surface to curve away one meter. Therefore, like any orbiting body, it goes round and round and round.

This weight versus mass thing confuses a lot of folks because in colloquial English we use pounds and kilograms for both measurements of weight and mass. That is because we figured all this stuff out on Earth, where it was simple and practical to measure mass by measuring weight.

In other words, because we are earthlings, we define units of mass as equal to the observed units of weight as measured on Earth.

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Where Did the Phrase 'Red Herring' Come From? Darmell Darmell

You may have seen a red herring in a recent book or movie, but you probably only realized it after the fact. These misleading clues are designed to trick you into drawing an incorrect conclusion, and they're a popular ploy among storytellers of all stripes.

If you've seen or read the Harry Potter series—and really, who hasn’t?—then you may recall some of the many instances where J.K. Rowling employed this literary device. That endearing plot twist about the nature of Snape's character, for example, is likely one of the longest-running red herrings ever written.

Sometimes they aren't even subtle. Agatha Christie's murder mystery And Then There Were None directly mentions red herring in reference to a character's death, and a statue of a red herring appears in Lemony Snicket's A Series of Unfortunate Events. Perhaps most blatantly, a character in the cartoon A Pup Named Scooby-Doo who was constantly being blamed for myriad crimes was named—you guessed it—Red Herring.

But where does this literary device come from, and why is it named after a fish? For a bit of background: herring are naturally a silvery hue, but they turn reddish-brown when they're smoked. Long before refrigerators were invented, this was done to preserve the fish for months at a time. They can also be pretty smelly. As Gizmodo's io9 blog points out, it was believed that red herring were dragged against the ground to help train hounds to sniff out prey in the 17th century. Another theory was that escaped prisoners used the fish to cover their tracks and confuse the dogs that tailed them.

However, io9 notes that red herring were actually used to train horses rather than dogs, and only if the preferred choice—a dead cat—wasn't available. The idea was that the horses would get used to following the scent trail, which in turn would make them less likely to get spooked while "following the hounds amid the noise and bustle of a fox hunt," notes British etymologist and writer Michael Quinion, who researched the origin of the phrase red herring.

The actual origin of the figurative sense of the phrase can be traced back to the early 1800s. Around this time, English journalist William Cobbett wrote a presumably fictional story about how he had used red herring as a boy to throw hounds off the scent of a hare. He elaborated on this anecdote and used it to criticize some of his fellow journalists. "He used the story as a metaphor to decry the press, which had allowed itself to be misled by false information about a supposed defeat of Napoleon," Quinion writes in a blog. "This caused them to take their attention off important domestic matters."

According to Quinion, an extended version of this story was printed in 1833, and the idiom spread from there. Although many people are more familiar with red herrings in pop culture, they also crop up in political spheres and debates of all kinds. Robert J. Gula, the author of Nonsense: Red Herrings, Straw Men and Sacred Cows: How We Abuse Logic in Our Everyday Language, defines a red herring as "a detail or remark inserted into a discussion, either intentionally or unintentionally, that sidetracks the discussion."

The goal is to distract the listener or opponent from the original topic, and it's considered a type of flawed reasoning—or, more fancifully, a logical fallacy. This application of red herring seems to be more in line with its original usage, but as Quinion notes: "This does nothing to change the sense of red herring, of course: it's been for too long a fixed part of our vocabulary for it to change. But at least we now know its origin. Another obscure etymology has been nailed down."

What Is the Shelf Life of Donated Eyes?

Zoe-Anne Barcellos:

I can only answer for cornea and eye donation.

The FDA does all oversight (no pun intended) of organ disposition.

The main organs—heart, liver, pancreas, lungs, etc.—are transplanted within hours. They are just not viable if they are not being perfused constantly.

The other tissues—like bone, skin, tendons, etc.—do not need to be transplanted immediately. But I am not sure on the regulations of when they need to be transplanted.

With the eyes, there are four tissues that can be recovered.

We recover whole eyes for research and education purposes. These usually go much faster, but we can hold them up to a year.

Conjunctiva can also be recovered; conjunctiva is a clear covering over most of the eye (it is what gets irritated when you have pink eye). I have been working as a recovery tech for five years, and our office has not had a request for "conj" in all that time. I believe it is mostly used for research, but I could be wrong.

Sclera is the white area of your eye. It is fairly thick and flexible. If you have ever touched a reptile egg, that is what it reminds me of. We recover sclera for transplant. They use it for several things, but mainly to patch punctures. Similar to if you pop the inner tube of your bike and repair it. Sclera can also be used to repair ear drums. We can hold on to this for up to a year.

The main thing we recover is corneas. In the U.S., we must transplant these within seven days of recovery. (Recovery is usually within hours of death, but we can push it up to 20 hours after if needed.) Sometimes we have more corneas than we need, and then they are shipped overseas and transplanted up to 14 days after recovery. There is no real different outcome with the later transplant time, but the FDA in the U.S. made the rules. (You can sign up to be an organ, tissue, and eye donor here.)

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