Wednesday, April 15, 2015

Ponder Ponder Ponder

Someone had to ask the question that threw me into infinite loops back in school: What would happen if I dug straight down, at a speed of 1 foot per second? What would kill me first?

Well not that question in particular threw me into brain disharmony, but what happens to air pressure at the center of the earth. Not just me either -- from Scientific American circa 1920:

Googling only makes the confusion worse, but it's comforting to know that many people have thought about this question.

My best guess is that enlightenment may be down the path of analyzing the forces that at on a molecule of gas at the center of the earth, then on a molecule 50 feet "up" then one 50 feet further... all the way to the surface.

But it's all too much for right now, I have a tax extension to get in the mail.

Question, what forces are acting on that envelope? The pressure question is pulling it away from the mailbox even though the question has no mass or gravity.


Veeshir said...

Well, before you get a few miles down you'll burn to death so unless you can stand 1,000 degrees, I'd say that air being too light is the least of your problems.

The Earth is 7-8000 miles thick, going down 5 miles means you're still 7-8000 miles from the center.

Surellin said...

As for the air pressure, if you managed to get to the center, there wouldn't be any. No gravity, right? Or, rather, gravitational pull is equal in all directions. Maybe.

lumberjack said...

Or, think of each gas molecule as a penny. You'd have a stack of pennies going all the way to the top. It wouldn't matter that the ones at the bottom didn't weigh much because the lucky pennies at the top would be pressing down on them. (and laughing probably)

Or think of a garden hose going all the way to the center of the earth....

Lumberbrudi said...

As you know, and as I know you know, and as you know I know you know, Randall Munroe is the author of the web comic and also a book called "What If..."

I purchased "What If..." in electronic form on the day it came out, which gives me the ability to search it. I searched both "dug" and "dig". Randall Munroe has not yet applied his ruthlessly funny analysis to this important question. HOWEVER...

"What If..." is also a free section of his website:

I would not deny you the wondrous thrill of Randall Munroe answering your question. I will not ask it of him, so that you you can.

Lumberbrudi said...

... or you can can.

lumberjack said...

Ah, but you didn't search "digging".
(which, should show up under dig, you would think)

Anyway, I knew I should have reformatted the text "What would happen..." It's a link to What If, but I usually put links in the plain text portion of the post... That's why you missed it.;v=5;m=3;l=401071;c=776283;b=3368032;dct=http%3A//

Anonymous said...

There is a pressure gradient that decreases as you move closer to the center of the Earth. At the center of the Earth, the gradient is zero and then starts going the other way as you move past the center. The pressure at the center is the result of the accumulation of that gradient for 4,000 miles.

Not that it matters. You'll be killed by the hole collapsing on top of you before air pressure becomes too much of a problem.

Or as the tour guide at Ruby Falls cave said, "We don't need insurance. If anything happens down here, you'll be covered."

Veeshir said...

So I've been thinking about this and it just keeps getting more confusing.

First, you have to have an adamantine-shored tunnel all the say through, you couldn't have it to the middle or the other half of the Earth would cause a half-gravity.

As we all know, adamantine blocks all radiation, including heat, and can withstand great pressure.

The problem that makes is that there would be no gravity straight down, all gravity would have a lateral component, and the greater the vertical component, the less the gravity.

I don't think we really know how air pressure would change in an area where gravity changes not just in intensity but in direction.

But let's contemplate the sphere at the center, 1/2 gravity would be pulling in all directions from the center to the edge of the hollowed sphere.

The very center. Not a ten-thousandth of an angstrom from the center, so all the air, except maybe a hydrogen molecule, would be pulled to the walls of the sphere so there would be no air.

Next up, why hell is endothermic.

lumberjack said...

The best time to ponder this kind of question is just as you're dropping off to sleep.

Veeshir said...

I find alcohol helps too.