Could You Really Dig a Hole to China?

In theory, yes. In practice, your journey through the planet might be hampered by the planet’s molten core.

There’s also the matter of finding a spot for all you’re digging through to make your tunnel. Let’s not rule out the possibility of mole people, dinosaurs and graboids living down there, either. Keep in mind, too, that you would need to build some sort of DIY digging contraption. Even the biggest and best digging operations in the world haven’t breached the Earth’s crust yet and to even get close, they had to start digging from the ocean floor. I’m going to guess you’re starting from your backyard, which means you don’t have a chance.

But we can dream, can’t we? And who am I to step on your dreams?

Let’s have a little fun and speculate, then, about what physicists say a trip through the planet might be like. To make your journey a little easier, we’ll assume certain ideal conditions:

1. You did your homework and know that if you dig a straight hole down in the United States, you’ll come out the other side not in China, but in the Indian Ocean. To avoid this very wet ending and get to China, you started digging in Argentina. Good for you.

2. You managed to actually dig a tunnel with your fancy homemade digging machine and found a place for all the rubble. You’re now standing there, peering into the hole and ready to jump in, passing Argentinians eyeing you warily.

3. The Earth’s core is not molten, so your digging machine did not melt and neither will you.

4. The Earth has the same density throughout. At the center, you have approximately equal amounts of mass on all sides of you, which cancel each other out and result in no net gravitational force acting on you.

5. The Earth isn’t rotating, which made it easier to dig your hole and will keep you from bouncing around in your tunnel and getting all bruised up.

6. There’s no friction, no air resistance, and no mole men.

update: some helpful readers have pointed out other conditions that I neglected in the original post...

7. Either Bernoulli’s principle doesn’t apply or you're wearing some sort of breathing apparatus and oxygen tank, that way your high travel speed won't affect your ability to breath.

8. The air pressure at your starting point, throughout your tunnel and at your end point is uniform, so you don't get squished into goo.

It’s a lot of concessions to make (and I'm sure we could even think of a few more), and we’re now on an Earth very much unlike the one we know and love. Whatever. It’s a small price to pay for the thrill ride you’re about to take.

So go on. Step into the hole. Or maybe dive in headfirst; you’ll have a better view. As you fall through your tunnel, gravity pulls you down towards the center, and you gain speed. As you get closer to the center, you’re closer to that balance of mass we assumed. Gravity doesn’t pull on you as much and while you’ll still gain speed, you won’t do it as fast. Once you hit the center of the Earth, you’ll be in zero gravity, but going at maximum speed (some 18,000 mph), you won’t even notice.

As you pass the center, gravity starts to work against you, pulling you back towards the core. You’ll start to decelerate at exactly the opposite rate that you accelerated during the first half of the trip. When you reach the opposite end of the tunnel (the trip would take you, appropriately, 42 minutes), you’ll come to a dead stop for an instant just as you pop out of the exit hole. Unless some considerate Chinese person happens to be near the hole and grabs you, all of Earth’s mass will pull you back towards the core and you’ll go back down (or up, as it were) the hole again.

If no one catches you at either end of the tunnel, you’ll spend the rest of your life oscillating back and forth, the human yo-yo at the center of the Earth.

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The Body
10 Facts About the Appendix
Illustration by Mental Floss / Images: iStock
Illustration by Mental Floss / Images: iStock

Despite some 500 years of study, the appendix might be one of the least understood structures in the human body. Here's what we know about this mysterious organ.

1. THE ANCIENT EGYPTIANS CALLED IT THE "WORM" OF THE BOWEL.

The human appendix is small, tube-shaped, and squishy, giving ancient Egyptians, who encountered it when preparing bodies for funerary rites, the impression of a worm. Even today, some medical texts refer to the organ as vermiform—Latin for "worm-like."

2. THE APPENDIX SHOWS UP IN LEONARDO DA VINCI’S DRAWINGS.

The earliest description of a human appendix was written by the Renaissance physician-anatomist Jacopo Berengario da Carpi in 1521. But before that, Leonardo da Vinci is believed to drawn the first depiction of the organ in his anatomical drawings in 1492. Leonardo claimed to have dissected 30 human corpses in his effort to understand the way the body worked from mechanical and physiological perspectives.

3. IT'S ABOUT THE SIZE OF A PINKY FINGER.

The appendix is a small pouch connected to the cecum—the beginning of the large intestine in the lower right-hand corner of your abdomen. The cecum’s job is to receive undigested food from the small intestine, absorb fluids and salts that remain after food is digested, and mix them with mucus for easier elimination; according to Mohamad Abouzeid, M.D., assistant professor and attending surgeon at NYU Langone Medical Center, the cecum and appendix have similar tissue structures.

4. CHARLES DARWIN THOUGHT IT WAS A VESTIGIAL ORGAN …

The appendix has an ill-deserved reputation as a vestigial organ—meaning that it allegedly evolved without a detectable function—and we can blame Charles Darwin for that. In the mid-19th century, the appendix had been identified only in humans and great apes. Darwin thought that our earlier ancestors ate mostly plants, and thus needed a large cecum in which to break down the tough fibers. He hypothesized that over time, apes and humans evolved to eat a more varied and easier-to-digest diet, and the cecum shrank accordingly. The appendix itself, Darwin believed, emerged from the folds of the wizened cecum without its own special purpose.

5. … BUT THE APPENDIX PROBABLY EVOLVED TO HELP IMMUNE FUNCTION.

The proximity and tissue similarities between the cecum and appendix suggest that the latter plays a part in the digestive process. But there’s one noticeable difference in the appendix that you can see only under a microscope. “[The appendix] has a high concentration of the immune cells within its walls,” Abouzeid tells Mental Floss.

Recent research into the appendix's connection to the immune system has suggested a few theories. In a 2015 study in Nature Immunology, Australian researchers discovered that a type of immune cells called innate lymphoid cells (ILCs) proliferate in the appendix and seem to encourage the repopulation of symbiotic bacteria in the gut. This action may help the gut recover from infections, which tend to wipe out fluids, nutrients, and good bacteria.

For a 2013 study examining the evolutionary rationale for the appendix in mammal species, researchers at Midwestern University and Duke University Medical Center concluded that the organ evolved at least 32 times among different lineages, but not in response to dietary or environmental factors.

The same researchers analyzed 533 mammal species for a 2017 study and found that those with appendices had more lymphatic (immune) tissue in the cecum. That suggests that the nearby appendix could serve as "a secondary immune organ," the researchers said in a statement. "Lymphatic tissue can also stimulate growth of some types of beneficial gut bacteria, providing further evidence that the appendix may serve as a 'safe house' for helpful gut bacteria." This good bacteria may help to replenish healthy flora in the gut after infection or illness.

6. ABOUT 7 PERCENT OF AMERICANS WILL GET APPENDICITIS DURING THEIR LIFETIMES.

For such a tiny organ, the appendix gets infected easily. According to Abouzeid, appendicitis occurs when the appendix gets plugged by hardened feces (called a fecalith or appendicolith), too much mucus, or the buildup of immune cells after a viral or bacterial infection. In the United States, the lifetime risk of getting appendicitis is one in 15, and incidence in newly developed countries is rising. It's most common in young adults, and most dangerous in the elderly.

When infected, the appendix swells up as pus fills its interior cavity. It can grow several times larger than its average 3-inch size: One inflamed appendix removed from a British man in 2004 measured just over 8 inches, while another specimen, reported in 2007 in the Journal of Clinical Pathology, measured 8.6 inches. People with appendicitis might feel generalized pain around the bellybutton that localizes on the right side of the abdomen, and experience nausea or vomiting, fever, or body aches. Some people also get diarrhea.

7. APPENDECTOMIES ARE ALMOST 100 PERCENT EFFECTIVE FOR TREATING APPENDICITIS.

Treatment for appendicitis can go two ways: appendectomy, a.k.a. surgical removal of the appendix, or a first line of antibiotics to treat the underlying infection. Appendectomies are more than 99 percent effective against recurring infection, since the organ itself is removed. (There have been cases of "stump appendicitis," where an incompletely removed appendix becomes infected, which often require further surgery.)

Studies show that antibiotics produce about a 72 percent initial success rate. “However, if you follow these patients out for about a year, they often get recurrent appendicitis,” Abouzeid says. One 2017 study in the World Journal of Surgery followed 710 appendicitis patients for a year after antibiotic treatment and found a 26.5 percent recurrence rate for subsequent infections.

8. AN INFECTED APPENDIX DOESN’T ACTUALLY BURST.

You might imagine a ruptured appendix, known formally as a perforation, being akin to the "chestbuster" scene in Alien. Abouzeid says it's not quite that dramatic, though it can be dangerous. When the appendix gets clogged, pressure builds inside the cavity of the appendix, called the lumen. That chokes off blood supply to certain tissues. “The tissue dies off and falls apart, and you get perforation,” Abouzeid says. But rather than exploding, the organ leaks fluids that can infect other tissues.

A burst appendix is a medical emergency. Sometimes the body can contain the infection in an abscess, Abouzeid says, which may be identified through CT scans or X-rays and treated with IV antibiotics. But if the infection is left untreated, it can spread to other parts of the abdomen, a serious condition called peritonitis. At that point, the infection can become life-threatening.

9. SURGEONS CAN REMOVE AN APPENDIX THROUGH A TINY INCISION.

In 1894, Charles McBurney, a surgeon at New York's Roosevelt Hospital, popularized an open-cavity, muscle-splitting technique [PDF] to remove an infected appendix, which is now called an open appendectomy. Surgeons continued to use McBurney's method until the advent of laparoscopic surgery, a less invasive method in which the doctor makes small cuts in the patient's abdomen and threads a thin tube with a camera and surgical tools into the incisions. The appendix is removed through one of those incisions, which are usually less than an inch in length.

The first laparoscopic appendectomies were performed by German physician Kurt Semm in the early 1980s. Since then, laparoscopic appendectomies have become the standard treatment for uncomplicated appendicitis. For more serious infections, open appendectomies are still performed.

10. AN APPENDIX ONCE POSTPONED A ROYAL CORONATION.

When the future King Edward VII of Great Britain came down with appendicitis (or "perityphlitis," as it was called back then) in June 1902, mortality rates for the disease were as high as 26 percent. It was about two weeks before his scheduled coronation on June 26, 1902, and Edward resisted having an appendectomy, which was then a relatively new procedure. But surgeon and appendicitis expert Frederick Treves made clear that Edward would probably die without it. Treves drained Edward's infected abscess, without removing the organ, at Buckingham Palace; Edward recovered and was crowned on August 9, 1902.

11. THE WORLD'S LONGEST APPENDIX MEASURED MORE THAN 10 INCHES.

On August 26, 2006, during an autopsy at a Zagreb, Croatia hospital, surgeons obtained a 10.24-inch appendix from 72-year-old Safranco August. The deceased currently holds the Guinness World Record for "largest appendix removed."

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Science Has a Good Explanation For Why You Can't Resist That Doughnut
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Unless you’re one of those rare people who doesn’t like sweets, the lure of a glazed or powdered doughnut is often too powerful to resist. The next time you succumb to that second or third Boston cream, don’t blame it on weak willpower—blame it on your brain.

As the New Scientist reports, a Yale University study published in the journal Cell Metabolism provides new evidence that foods rich in both carbohydrates and fats fire up the brain’s reward center more than most foods. For the study, volunteers were shown pictures of carb-heavy foods (like candy), fatty foods (like cheese), and foods high in both (like doughnuts). They were then asked to bid money on the food they wanted to eat most, all while researchers measured their brain activity.

Not only were volunteers willing to pay more for doughnuts and similar foods, but foods high in carbs and fat also sparked far more activity in the striatum, the area of the brain where dopamine is released. (Chocolate is one of the foods most commonly associated with increases in dopamine, working in the same way as drugs like cocaine and amphetamines.)

Presented with these findings, researcher Dana Small theorized that the brain may have separate systems to assess fats and carbs. Modern junk foods that activate both systems at once may trigger a larger release of dopamine as a result.

This study doesn’t entirely explain why different people crave different foods, though. Much of it has to do with our habits and the foods we repeatedly gravitate towards when we want to feel happy or alleviate stress. Another study from 2015 found that certain treats associated with high levels of reward in the brain—like pizza, chocolate, chips, and cookies—were considered to be the most addictive foods (doughnuts didn’t make the top 20, though).

It's still possible to turn down foods that are bad for you, though. While many people try to improve their self-control, one of the most effective ways to avoid an undesired outcome is to remove the temptation completely. Free doughnuts in the break room? Stay far away.

[h/t New Scientist]

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