Primes and Squares

The Rollercoaster Zipline

12:02 AM

...so I just found out about roller coaster ziplines

I really want to build one now

I've literally spent the last hour looking at land to buy and then build on

►

I also emailed a company for a quote

I'm kind of hoping it's super expensive so I can move on :P

either that or cheaper than I expect

12:56 AM

@NathanMerrill Oh that's cool.

1:34 AM

yep, it's expensive. Like, I could see somebody building a personal one, but it's a bit too much for me :)

the guy said that projects range from 300K to 700K

so, you can either buy a home, or a zipline

I mean, I know which one is more fun

2:05 AM

Lucky for you! :P

3 hours later…

5:00 AM

This is actually making me think.

I wonder if there's a useful (for some vague notion of usefulness) coordinate system where the behavior is the same along both basis vectors.

5:38 AM

@El'endiaStarman You'd have to go the route of North forever

because having East randomly stop and become West across some line is just arbitrary

but yeah, I could see that being useful

especially if you are wanting to describe the flight of a plane, for example

You can say "This plane is headed North from Canada to Russia"

and it's consistent the entire time

Also, I found this rather funny:

Womb is pronounced Woom
Tomb is pronounced Toom
Bomb is pronounced ...

6:00 AM

Hah, I like that one too.

Also reminds me of this pair of lines from Hark the Herald Angels Sing:

> Late in time behold Him come
Offspring of a Virgin's womb

All other couplets rhyme at the end. This one doesn't because the pronunciation of "come" (I think?) changed over time.

9 hours later…

Laikoni

2:57 PM

@NathanMerrill Another approach to the same problem by oracle which launched yesterday: oracle.github.io/graphpipe/#

4 hours later…

6:52 PM

@El'endiaStarman you mean on a sphere?

@NathanMerrill this somehow looks sketchy AF :)

@flawr Yep, on a sphere.

PhiNotPi

So a spherical coordinate system where you can move an "unlimited" amount in both directions?

not really a classical coordinate system, you could however "draw" a space filling curve, where each point on the sphere corresponds to a number in the interval [0,1).

But it doesn't make sense talking about directions then.

PhiNotPi

I think this gem is actually relevant here:

Hairy ball theorem

The hairy ball theorem of algebraic topology (sometimes called the hedgehog theorem in Europe) states that there is no nonvanishing continuous tangent vector field on even-dimensional n-spheres. For the ordinary sphere, or 2‑sphere, if f is a continuous function that assigns a vector in R3 to every point p on a sphere such that f(p) is always tangent to the sphere at p, then there is at least one p such that f(p) = 0. In other words, whenever one attempts to comb a hairy ball flat, there will always be at least one tuft of hair at one point on the ball. The theorem was first stated by Henri Poincaré...

@El'endiaStarman Just drill a hole through the earth in order to get a torus =P

6:56 PM

@flawr Hah, I thought of a torus too when you asked "on a sphere?". :P

PhiNotPi

If you take a sphere and draw "east-west" vectors at every point, then there has to be some singular points (like the north and south poles). Whatever your north-south vectors are, there's no good way for them to be defined at those points.

@PhiNotPi I mean, that's technically already true. It's just that with longitude, you can go from +180 degrees to -180 deg to +180 deg indefinitely, but with latitude, you cannot go from -90 deg to 90 deg in either direction without crossing 0 deg (the equator).

@NathanMerrill You can also build fun ziplines that are straight, for quite a lot less money:)

Or maybe you even have some vie ferrate near you that include zip lines?

Oh and giant swings are cool too:)

I think building those things is usually half the fun:)

7:37 PM

@flawr those don't really appeal to me that much

A swing, though, does

@PhiNotPi true. East-west has to change

like, they can't be parallel

two parallel lines define two points on a sphere

@flawr to me, the "bouncing rail" definitely increases the appeal, but I think that that is where the "sketchiness" comes from

7:56 PM

@NathanMerrill in case we ever meet where I live I'd love to take you to some nice locations where we could build something like that:D

I found some spots as well. The land wasn't too bad: it was near me, on some mountainous terrain. 60K for 40 acres

where do you live, BTW?

in switzerland

(jura mountain range)

yeah...not a huge chance of that happening anytime soon

I was actually looking at plane tickets last night, and if you are ok with layovers, they can get quite cheap

400 dollars from SLC to France (roundtrip)

that's not bad!

I'm not familiar with flight prices, but that certainly looks quite cheap. But I imagine it greatly depends on the season and how much in advance you buy the tickets?

8:13 PM

yeah, it is

I found a fantastic website

kayak.com

I can basically say "Starting in SLC where are the cheapest spots to go"

and it'll give you prices around the world

yeah, so SLC to Zurich is at least $710