Tunnelling through a Mountain - Numberphile
600,287
Published 2022-01-23
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All Comments (21)
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Another interesting fact is that the meeting point in the middle isn't perfectly straight, Eupalinos was afraid they wouldn't intersect if they had done the math wrong, so to make sure he instructed to bend both tunnels to the same side so that a crossing point was guaranteed, even if both tunnels were originally parallel to each other.
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I found the best technique is using F3 to get the coords of both ends.
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As a Greek person, I can tell you that"Polycrates'" name means, "a whole lotta crates."
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I believe the main reason to excavate from both ends is to gain time. When opening a tunnel, you are limited by the number of people that can work at the same time. To increase the number of workers you need a bigger tunnel, so you gain nothing. But working both ends you half the time for a given tunnel size 😊
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My grandfather was a civil engineer on the team that built the tunnel through Zion National Park (in Utah). The story I heard was that using only slide rulers to calculate, they dug from both ends and were only an inch or two apart when they met. The "Mt Carmel Tunnel" is 1.1 miles long (1.6 km) and is not a straight path through the mountain, which I always thought was a pretty impressive feat.
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Looking forward to a future video where Matt Parker and Hannah Fry build a kilometre long stick to dangle from a mountain 😅
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As an old tunnel surveyor I know how difficult this is, even with modern equipment! Impressive. Great video as always. And no, GPS won’t work in a tunnel. We use modern total stations that measures angles and distances very accurate. For very long tunnels we also use gyro theodolites to help find the correct direction. :)
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It's because of that 60 cm mismatch that we even know that they used this ingenious method. If they had gotten it perfectly then the "likely" explanation would've been that they dug it from one side all the way through
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when doing those right angle steps around, because the steps are relatively small, we could possibly build planks between the marking poles and use the water level test.
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It is always so pleasurable listening to Hannah Fry
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That pronunciation of "Polycrates" reminds me of the way Bill & Ted said "Socrates". (Watching Bill & Ted's Excellent Adventure as a child spoiled my mental pronunciation of Greek names ending "-es" for life.)
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Solution to the level problem: temporarily build a trough around the mountain, filling it with water as you build it. The water level in the trough at the tunnel entrance will always be at the same altitude as the level at the tunnel exit. The trough could be as simple as a clay-lined ditch in the ground.
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It's just nice to hear Brady's voice in a video once in awhile.
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2:24 "Keep looking behind you" moves camera behind him I liked that a lot haha
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She is fantastic! She speaks so clearly! I'm a non-native English speaker but she's so easy to follow... Love her!
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0:47 "So let's say you want to go in here, doo doo dooo ♫♩ and you want to come out here" squeak squeak squeak ♫♩
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I used this technique 5 months ago in Minecraft for a 300 block tunnel in the nether
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She's a great teacher
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The pronunciation of "Poly Crates" reminded me so much of "So Crates" in Bill & Teds Excellent Adventure.
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I think I know a decent solution to make sure both entrances are the same altitude. Dig a smallish trench outside from Point A to Point B, and use the water trick you described to keep the trench level. Once you have your reference trench, you can use that to get roughly equal starting points.
