Slashdot Mirror
The Science of a Bottomless Pit
StartsWithABang writes It's the ultimate dream of many children with time on their hands and their first leisurely attempt at digging: to go clear through the Earth to the other side, creating a bottomless pit. Most of us don't get very far in practice, but in theory, it should be possible to construct one, and consider what would happen to a very clever test subject who took all the proper precautions, and jumped right in. Here's what you would have to do to travel clear through the Earth, come out the other side, and make the return trip to right back where you started.
This very topic is discussed in "Entertaining Physics" printed first in 1912. And I'm sure it has been discussed even earlier.
Mathematically it's an example of a degenerate orbit with one zero semi-axis, and the orbital period can be simply calculated from Kepler's laws.
What's more interesting, it even holds true if you do not move through the center of the Earth! For example, a train from any place on Earth to any other place on Earth will move all by itself and always arrive at destination in about 45 minutes (neglecting the oblateness of the Earth and need to compensate for Coriolis forces and friction) if you put it inside a completely straight tunnel.
Worst. Haiku. Ever.
systemd is Roko's Basilisk.
No. In today's university, the entire first undergraduate semester is spent on sensitivity awareness, wymyn's studies, black history, and overcoming white privilege.
24 hours *if* you have air resistance. And then you're moving so slow that you barely get past the center.
Note that no vacuum is perfect so you will lose velocity. Their scenario should have started the person off at the south pole, not the north, for the extra altitude.
Note that the heat isn't really the materials problem that they make it out to be - it's an energy problem. You don't need a material that can withstand 4000, you just need cooling. And not linearly high cooling, but an exponential decline. The longer you cool the rock down to your target temperature, the deeper your effect on the rock temperature behind your tunnel walls, and thus the shallower the temperature gradient, and thus the lower the rate of heat loss. It's like trying to cool a hot house - the air conditioner really struggles in the beginning but it gradually becomes easier with time as the walls and everything inside the house cool down.
Now, the pressures, those are insane, and the normal approach to pressure maintenance on deep drilling - filling with a heavy mud - obviously wouldn't work here.
We gotta go to a crappy town where I'm a hero.
The article suggests that the earth's rotation would cause the dropped to hit the wall on the way down. So why can't the tunnel curve to account for this? Presumably it would curve the other way as it exits. It also suggests that going from North to South pole wouldn't work because of their relative altitudes, but is there an antipodal point where the altitudes are close enough feasibly go from one side to another - e.g. build a tunnel / raised platform to bring each side to the same altitude. I realise this is all completely hypothetical, bad movie remakes notwithstanding.
Their scenario should have started the person off at the south pole, not the north, for the extra altitude.
Um, hello?
Everyone knows that north is on top, and you can't fall upwards.
The level of scientific illiteracy here is disgraceful.
To have a right to do a thing is not at all the same as to be right in doing it
I actually live near a REAL one.
http://www.sciencebuzz.org/blo...
No, seriously, it's a hole in the ground, into which half of a decent-sized river dumps.
They have put everything from dye, to pingpong balls, to (amusingly) a car - and none of it has ever come up anywhere.
-Styopa
I always told my kids it takes longer to drive north because it's all uphill.
Interesting to watch their reactions over the years go from unquestioning acceptance, to cognitive dissonance. to enlightened disagreement, to "Daaaaaaad!!!", to "When are we stopping to dinner?'.
When Fascism comes to America, it will call itself Anti-Fascism, and tell you to give up your guns.
Fun fact, during the space race there was also a less well known "Drill race" between the Soviet Union and America to see who could dig down the farthest. The Soviets won this by a long shot and as always found a lot of things that changed what we know about the composition of the Earth's crust. Most notably the farther they went down they noticed that the mud that bubbled up contained hydrogen and lots of water. They also noticed that the rock type didn't change at those depths (the reason seismic waves travel around the center of the earth instead of through it). The rock actually began to behave more like plastic at those depths! Learn more here http://en.wikipedia.org/wiki/K...
Mathematically it's an example of a degenerate orbit with one zero semi-axis, and the orbital period can be simply calculated from Kepler's laws.
No, it can't; it's not a Keplerian problem. You could calculate the period using Kepler's laws if the Earth were a point mass. But it's not. You could calculate the period using the Brachistochrone calculation if the Earth were a uniform sphere. But it's not. The Earth is layered, with the density changing as you go closer to the center. Only way to solve the problem correctly is numerical integration.
(I'd actually be interested in seeing the calculation done in the article.)
http://www.geoffreylandis.com
We've always been at war with Oceana.
"Unheard of means only it's undreamed of yet,
Impossible means not yet done." ~~ Julia Ecklar
Additionally, you would void the Earth's warranty.
When someone says, "Any fool can see