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psychothumbs ,

How can any line that is on the surface of a sphere by straight rather than a curve?

sorter_plainview ,

Haa, here people, we found a flat earth denier…

lolcatnip ,

Earth is a lie.

CapeWearingAeroplane ,

GET THE ROUNDIE!

affiliate ,

it’s a bit of a “spirit of the law vs letter of the law” kind of thing.

technically speaking, you can’t have a straight line on a sphere. but, a very important property of straight lines is that they serve as the shortest paths between two points. (i.e., the shortest path between A and B is given by the line from A to B.) while it doesn’t make sense to talk about “straight lines” on a sphere, it does make sense to talk about “shortest paths” on a sphere, and that’s the “spirit of the law” approach.

the “shortest paths” are called geodesics, and on the sphere, these correspond to the largest circles that can be drawn on the surface of the sphere. (e.g., the equator is a geodesic.)

i’m not really sure if the line in question is a geodesic, though

itslilith ,
@itslilith@lemmy.blahaj.zone avatar

You are absolutely correct, but to add on to that even more:

When we talk about space, we usually think about 3D euclidean space. That means that straight lines are the shortest way between two points, parallel lines stay the same distance forever, and a whole bunch of other nice features.

Another way of thinking about objects like the earth is to think of them as 2D spherical manifolds. That means we concern ourself only to the surface of the earth, with no concept of going below the surface or flying up into the sky. In S2 (that’s what you call a 2D spherical manifold), and in spherical geometry in general, parallel straight lines will eventually cross, and further on loop back and form a closed loop. Sounds weird, right? Well, we do it all the time. Look at lines of Longitude, for example.

We call the shortest line connecting two points in curved manifolds geodesics, as you said, and for all intents and purposes, they are straight. Remember, there is no concept of leaving the sphere, these two coordinates is all there is.

What one can do, if one wants to, is embed any manifold into a higher-dimensional euclidean one. Geodesics in the embedded manifold are usually not straight in higher-dimensional euclidean space. Geodesics on a sphere, for example, look like great circles in 3D.

lightnsfw ,

Stop making up bullshit to justify it. It’s not a straight line so don’t say that it is. Words have meaning.

LustyArgonianMana ,
@LustyArgonianMana@lemmy.world avatar

What is the slope of a straight line, a linear function? Now what is the slope of a nonlinear function, aka a curved line?

A geodesic would only be accurately labeled a “straight line” IF it was on a plane. On a curved or uneven surface it’s a nonlinear function.

mathworld.wolfram.com/Geodesic.html#:~:text=A geo….

affiliate ,

i think it depends on what you mean by “accurately”.

from the perspective of someone living on the sphere, a geodesic looks like a straight line, in the sense that if you walk along a geodesic you’ll always be facing the “same direction”. (e.g., if you walk across the equator you’ll end up where you started, facing the exact same direction.)

but you’re right that from the perspective of euclidean geometry, (i.e. if you’re looking at the earth from a satellite), then it’s not a straight line.

one other thing to note is that you can make the “perspective of someone living on the sphere” thing into a rigorous argument. it’s possible to use some advanced tricks to cook up a definition of something that’s basically like “what someone living on the sphere thinks the derivative is”. and from the perspective of someone on the sphere, the “derivative” of a geodesic is 0. so in this sense, the geodesics do have “constant slope”. but there is a ton of hand waving here since the details are super complicated and messy.

this definition of the “derivative” that i mentioned is something that turns out to be very important in things like the theory of general relativity, so it’s not entirely just an arbitrary construction. the relevant concepts are “affine connection” and “parallel transport”, and they’re discussed a little bit on the wikipedia page for geodesics.

LustyArgonianMana ,
@LustyArgonianMana@lemmy.world avatar

Thank you for the informative answer

DahGangalang ,

Yup, found the round earther.

OutsizedWalrus ,

By defining the coordinate system as a sphere.

Basically, there are multiple right answers, but the most correct answer depends on how you define coordinates.

In “simple”, xyz it’s not a line.

In Euclidean geometry, a straight line can follow a curved surface.

In bullshit physics, everything is warped relative to spacetime so anything can or cannot be a line, but we won’t know.

ChaoticNeutralCzech , (edited )

It can get longer if sailing between Madagascar and the rest of Africa but Pakistan-Russia does not have the same ring to it, I guess.
https://cdn.prod.www.spiegel.de/images/53807d2f-0001-0004-0000-000001283586_w1600_r1.6125_fpx71.32_fpy47.webp
https://cdn.prod.www.spiegel.de/images/4df68877-0001-0004-0000-000001283592_w1600_r1.6125_fpx71.32_fpy45.webp

Tobberone ,

That’s not a straight line, although it is possible to follow without changing direction😊

ChaoticNeutralCzech ,

I KNOW IT’S BASICALLY A CIRCLE IN 3D SPACE. There is an exact amount of pedantry at play here, and you’re going over.

Wogi ,

In our space time frame of reference, we never change direction, we travel in a straight line. It’s a straight line.

PeriodicallyPedantic ,

Would you say that they… crossed the line?!?! 😏😏😏

Crashumbc ,

Correct! Technically :P

Tlaloc_Temporal ,
@Tlaloc_Temporal@lemmy.ca avatar

Would straight plane be as understandable?

techt ,

But following the surface of a sphere causes you to constantly change direction

sem ,

Dude that’s awesome. How did you make these images??

Tlaloc_Temporal , (edited )
@Tlaloc_Temporal@lemmy.ca avatar

This reminds me of some maps by Andy Woodruff.

They weren’t made to find long lines, and picking out a single line can be a tad difficult, but it’s very interesting nonetheless.

https://andywoodruff.com/blog/wp-content/uploads/2016/03/sea-1700.jpg

Rentlar ,

Well there’s the one guy in Northern India who gets a peek at South America from between Madagascar and the African continent.

Tilgare ,

There is also just the one straight path from the US east coast (Florida) to Asia.

Akasazh ,
@Akasazh@feddit.nl avatar

South America’s reach is incredible, compared to size that is

ChronosTriggerWarning ,

And it’s mystery is exceeded only by it’s power.

superkret ,

*folds world map in half
*sticks pencil through

cmgvd3lw ,

I honestly believe that sometimes, my genius, it generates gravity.

vonxylofon ,

HYPERSPACE

Viking_Hippie ,

You youngsters with your Einstein Rosen-bridges! Always in too much of a hurry to take the scenic route!

asexualchangeling ,

A straight line may be the shortest distance between two points, but it is by no means the most interesting.

-The Third Doctor, Doctor Who

Karyoplasma ,

Reminds me of the movie Event Horizon.

Iheartcheese ,
@Iheartcheese@lemmy.world avatar

And like 5 million other movies

NigelFrobisher ,

Space-time itself is curved, therefore there is no such thing as a straight line.

sushibowl ,

We have geodesics for that.

Urist , (edited )
@Urist@lemmy.ml avatar

If anyone wants to grasp the basics: here is some fun reading (leading on to some beautiful math). Changing the idea of parallelity leads to hyperbolic geometry and other fun stuff. :)

HereIAm ,

Please correct my layman understanding if I’m wring here. But isn’t everything traveling in a straight line until an external force is applied. For example the earth orbiting the sun is traveling in a straight line in a curved apacetime. Also if you jump, the moment you leave the ground until you touch it again coming back down you were traveling in a straight line.

sem ,

In my understanding, since gravity is acting on us, an external force is applied when we jump. That’s why a jump is a parabola. “Gravity’s Rainbow”

Zink ,

What they are getting at is that gravity is not a force so much as your mass trying to travel in a straight line through curved spacetime. The weight you feel is because the surface of the earth is in your way.

Get into low earth orbit and that straight path has you going in apparent circles around the planet. You are very much within the earth’s gravity but you don’t feel “weight” because the surface of the earth is no longer blocking your path. You still have mass and inertia and all that, of course.

KillingTimeItself ,

Also if you jump, the moment you leave the ground until you touch it again coming back down you were traveling in a straight line.

relative to the body of earth, including its rotation it would be an arc path, and including it’s tilt it would be 3d, if we also include the travel around the sun in orbit, that elongates it around the orbit, so uh.

NigelFrobisher ,

I dunno lol

kazaika ,

Space-time itself is curved, therefore everything is moving in a straight line, it only appears to be curved to the outside observer

nobleshift ,
@nobleshift@lemmy.world avatar

THAT would be one god damn brutal sail. Both horns, Southern Atlantic crossing followed up by the Indian Ocean.

The range of foulies you would need to bring would be 3/4 of your pack. Foulies underwear and A sock (you’re going to lose one anyways)

anachronist ,

I assume you mean “both capes.” While this line does come within a few thousand miles of the Horn of Africa, that’s not known as an especially hard sailing area but maybe for pirates.

Sailing this line in the other direction would be considerably harder.

nobleshift ,
@nobleshift@lemmy.world avatar

Lolololol. Bro I’ve been around Africa in a 30 foot sailboat with an 8 foot draft. ‘Not hard sailing’ ? You have obviously never been on a boat at sea, let alone around either horns, capes, or whatever. Look up Shipbreakers, it’s a type of wave, then come tell me its not a hard sailing area.

Lololol GTFO of here with that bullshit.

anachronist ,

Cmon man. Yes I’ve been a few places in sailboats. North sea in the winter for one. You clearly were trying to refer to Cape Horn and The Cape of Good Hope (or Cape Agulhas). Just take the L and don’t be a twat.

taiyang ,

Would clarifying words have helped? “If you only sailed with forward force…” or “Following along the surface of the earth…” or… what?

Obviously they mean that you don’t need to make any turns and that straight means an arc around the earth and not through the Earth, unless someone has a very different idea what sailing means…

LustyArgonianMana ,
@LustyArgonianMana@lemmy.world avatar

Yes I think they mean it’s a continuous line, not a “straight” line. As in the line is uninterrupted (continuous). It’s also possible they mean the line qualifies as a nonlinear function since it also doesn’t double back over itself (A function is a relationship where each input value (X) will create only one output value (Y)).

Math is hard. Describing lines like this is math - calculus actually due to the curve, and actually not just basic calculus but vector calculus because it involves an x,y, and z axis. Most laypeople will struggle to describe a line with the correct jargon.

Ultraviolet ,

Depends on what you mean by help. Yes, it would communicate the point better, but it’s engagement bait, so the ambiguity is a feature rather than a bug.

xlash123 ,
@xlash123@sh.itjust.works avatar

Low IQ: it’s not a straight line

Medium IQ: it’s a geodesic on a sphere, so it is a straight line

High IQ: it’s not a straight line

callouscomic ,

https://lemm.ee/pictrs/image/38936a3a-8591-491c-9228-cd4c253d32ee.jpeg

He’s right, you know.

About the line?

About everything, damn it!

Wilzax ,

It’s a straight line through non-euclidean space

yetiftw ,

unfortunately in reality it is a curved line on a sphere

Wilzax ,

In actual reality there would be wind and water currents diverting any ship sailing that route from the depicted “line” anyway so the whole argument is pointless

The only straight line paths in the universe are followed by electrostatically uncharged non-accelerating objects in free fall in a vacuum. Or massless particles.

SnotFlickerman ,
@SnotFlickerman@lemmy.blahaj.zone avatar

Nuh uh. My fifth grade math teacher told me that if I drew a line with an arrow on graph paper and no other line intersected it, that it would continue on into infinity!

zalgotext ,

What if we assume the ship is actually a spherical cow

DogWater ,

Whole Universe eh? That exists and is bounded on a curved space time.

I’m just joking, but you can really take this to the extreme lol

Wilzax ,

Spacetime is curved. Inertial paths through spacetime are straight.

Euclidean space is not the only space where straight lines are possible.

lugal ,

Globists will argue that on a globe this is a straight line. Seen these arguments before, don’t work on me

essell ,

Nice. Be proud.

Dunno what of, but be proud anyway!

lugal , (edited )

Thanks! I’m very proud of seeing the truth. Watch this short video and you will being to understand. But watch it to the end, it’s short enough

Quacksalber ,

The ending really brings the whole video together. Thanks for sharing!

IndiBrony ,
@IndiBrony@lemmy.world avatar

You know, I’d never actually thought of it that way. Very informative video for it’s short length. Thank you for sharing.

RattlerSix ,

I’ve seen that video a hundred times and it never fails to disappoint

JackbyDev ,

You’ve made a believer of me.

vaquedoso ,

One of the most compelling arguments I’ve heard. I must say I was a skeptic before but this really opened my eyes

lunarul ,

Don’t know about other clients, but vger shows a thumbnail of the video

lugal ,

Better?

superkret ,

Got error: “Sign in to confirm that you’re not a bot”

Hmm, really makes you think…

aberrate_junior_beatnik ,

Ridiculous. This line is clearly gay.

Telodzrum ,

This is bi erasure.

JackbyDev ,

Not even 10 am and I’m being erased.

StopJoiningWars ,
@StopJoiningWars@discuss.online avatar

Saying that it’s bi erasure is gay erasure.

flicker ,

https://lemmy.world/pictrs/image/70f32fb8-8e0e-491d-ae46-539c6b6f3741.jpeg

We claimed it is erasure first, and now here’s our flag.

Tlaloc_Temporal ,
@Tlaloc_Temporal@lemmy.ca avatar

Hey, you even have the eraser right there is the middle! I suppose that makes it convenient?

flicker ,

I really do love convenience!

4am ,

Never thought I’d get to use “bisectional” outside of JD Vance jokes

helios ,
@helios@social.ggbox.fr avatar

This whole map is woke.

jaybone ,

It’s bi sectional.

MossyFeathers ,

deleted_by_author

    •
    Varven OP ,
    @Varven@lemmy.world avatar

    Because going in that route would make it touch land which in the twitter post it says straight line without touching land

    essell ,

    I’ve always thought Australia was a trouble maker.

    MossyFeathers ,

    deleted_by_author

    •
    supamanc ,

    India. You would have to set off somewhat perpendicular to the Indian coastline to be perfectly straight.

    ironhydroxide ,

    For some reason I don’t think this is true.

    A straight line connecting two things does not necessarily have to connect to said things perpendicular to their border.

    ChaoticNeutralCzech , (edited )

    Not to mention, India’s coastline is very much not straight on a local scale. You’re bound to find a place where it turns perpendicular to the journey close to the theoretical starting point anyway.

    supamanc ,

    Yeah but, I’m talking about this particular case, not making a mathematical rule. You have to move away from the coast, and then cannot turn, so you have to head towards Africa. You can’t set off toward Australia. Although I hadn’t considered that you can just move the starting point. So, there’s that.

    Bassman1805 ,

    Alaska, Canada, Russia, a few on the -stans.

    This is the longest straight-line all-water route on earth.

    bstix ,

    The picture was about sailing the longest direct line.

    It’s not the longest anyway, but that’s what it was about. Technically one could sail infinitely many times around Antarctica in a straight line.

    ChaoticNeutralCzech , (edited )

    around Antarctica in a straight line

    No, that’s not Earth’s great circle, you’ll be turning slightly. It only seems straight on most map projections because they want latitudes to be horizontal.

    bstix ,

    Well, I stand corrected. I guess we’ll need to wait for the ice on the North pole to melt before we can make a more stupid voyage.

    lolcatnip ,

    It would, however, seem like a straight line to whoever was on the boat, because they’d be traveling due west the whole time, and the course corrections they’d have to make to keep going west would look the same as course corrections needed to account for wind, ocean currents, etc.

    ChaoticNeutralCzech ,

    I know but you need to be the right amount of pedantic. Too little and any sufficiently large curve seems straight, too much and you point out that there is no straight line on the surface of a sphere.

    pH3ra ,
    @pH3ra@lemmy.ml avatar

    Every line is a straight line in one dimension

    Zacryon ,

    Today on the internet: Fun with spherical geometry.

    massive_bereavement ,

    Your dad and I think you should start looking for a job.

    Varven OP ,
    @Varven@lemmy.world avatar

    I can’t legally work in my country I’m not old enough

    Telodzrum ,

    But still, don’t you hunger for the mines?

    inbeesee ,

    Fuck it

    Eats the mines

    BeigeAgenda , (edited )
    @BeigeAgenda@lemmy.ca avatar

    Toiling in the meme mines.

    Edit: I have just finished reading The Neverending Story and this reminds me of the last part where Bastian works in the picture mines until he finds the right picture.

    SapphironZA ,

    Line that is straight in two dimensions.

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