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Could You Really Dig a Hole to China?

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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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science
Geological Map Shows the Massive Reservoir Bubbling Beneath Old Faithful
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iStock

Yellowstone National Park is home to rivers, waterfalls, and hot springs, but Old Faithful is easily its most iconic landmark. Every 45 to 125 minutes, visitors gather around the geyser to watch it shoot streams of water reaching up to 100 feet in the air. The punctual show is one of nature’s greatest spectacles, but new research from scientists at the University of Utah suggests that what’s going on at the geyser’s surface is just the tip of the iceberg.

The study, published in the journal Geophysical Research Letters, features a map of the geological plumbing system beneath Old Faithful. Geologists have long known that the eruptions are caused by water heated by volcanic rocks beneath the ground reaching the boiling point and bubbling upwards through cracks in the earth. But the place where this water simmers between appearances has remained mysterious to scientists until now.

Using 133 seismometers scattered around Old Faithful and the surrounding area, the researchers were able to record the tiny tremors caused by pressure build-up in the hydrothermal reservoir. Two weeks of gathering data helped them determine just how large the well is. The team found that the web of cracks and fissures beneath Old Faithful is roughly 650 feet in diameter and capable of holding more than 79 million gallons of water. When the geyser erupts, it releases just 8000 gallons. You can get an idea of how the reservoir fits into the surrounding geology from the diagram below.

Geological map of geyser.
Sin-Mei Wu, University of Utah

After making the surprising discovery, the study authors plan to return to the area when park roads close for the winter to conduct further research. Next time, they hope to get even more detailed images of the volatile geology beneath this popular part of Yellowstone.

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Animals
Why Do Female Spotted Hyenas Give Birth Through Their Pseudo-Penises?
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YouTube

At the zoo, you can sometimes tell the difference between male and female animals by noting their physical size, their behavior, and yes, their nether regions. Hyenas, however, flip the script: Not only are lady spotted hyenas bigger and meaner than their male counterparts, ruling the pack with an iron paw, they also sport what appear to be penises—shaft, scrotum, and all.

"Appear" is the key word here: These 7-inch-long phalluses don't produce sperm, so they're technically really long clitorises in disguise. But why do female hyenas have them? And do they actually have to (gulp) give birth through them? Wouldn't that hurt … a lot?

The short answers to these questions are, respectively, "We don't know," "Yes," and "OW." Longer answers can be found in this MinuteEarth video, which provides the full lowdown on hyena sex. Don't say we didn't warn you.

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