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Longest Lines of Sight on Earth

beyondhorizons.eu

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Re: Longest Lines of Sight on Earth

#91

Post by KozmoNau7 »

yread wrote: post #82

The link in the "done" column doesn't work - it should point to https://beyondhorizons.eu/2016/08/03/pic-de-finestrelles-pic... It's a report how they made an actual photograph of a sunrise over 443km far. Quite amazing! BTW if you ever get the chance to go up Mt. Canigou, go for it. Since it's the first big mountain in Pyrenees from the east you have really spectacular views and it's not that difficult to hike up th…

There's something utterly awe-inspiring about huge distances, especially if you're simply not used to viewing objects at those scales.

I live in a country where the highest point above sea level is ~171m. Walking in the Scottish highlands was a transcendental experience for me.

Re: Longest Lines of Sight on Earth

#92

Post by Double_a_92 »

dbrgn wrote: post #86
polymatter wrote: post #38

Earlier quoted context omitted.

Londoner here. Nope, we use a comma as a thousands separator. I believe some European countries use a period though.

Switzerland uses the period as separator too.

As decimal separator maybe, but not for thousands. E.g. 1'000'000.123

Nobody really cares what those sings are. The difference is top and bottom.

Re: Longest Lines of Sight on Earth

#93

Post by davidmanescu »

liuhenry wrote: post #85
kijin wrote: post #78

Earlier quoted context omitted.

That question is ambiguous. If you only need a single cat to go under the rope at some point, you just add a small arch for the cat to walk through. This requires a length of rope somewhat less than twice the height of the cat. 2 x Pi x Cat would levitate the rope by the height of the cat along the entire circumference of the Earth, allowing a billion cats to go under it simultaneously. You could even make do with no…

The answer to the first interpretation is considerably less than twice the height of the cat, and I think it's an interesting result as well: Assuming a 0.3 meter high cat, you only need ~0.12mm of extra rope (about the width of two sheets of paper) to be able to pull it up at a point and let the cat through.

Follow-up question - after extending the rope by 0.12mm and pulling it up to allow the cat to pass under it, how far away are each of the two points where the rope lifts off the ground?

Re: Longest Lines of Sight on Earth

#94

Post by KozmoNau7 »

Nition wrote: post #35
tristanj wrote: post #18

Earlier quoted context omitted.

Under certain atmospheric conditions it may be possible to see further https://en.wikipedia.org/wiki/Mirage#Superior_mirage

I wonder what the maximum you can ever see is due to atmosphereic fog. I suspect it's less than 538km. The site has photos listed for up to 381km, although the link for that one is broken.

This one is the longest: https://beyondhorizons.eu/2016/08/03/pic-de-finestrelles-pic...

Fog is definitely a factor.

Re: Longest Lines of Sight on Earth

#95

Post by pm215 »

BurningFrog wrote: post #70
anyfoo wrote: post #63

Earlier quoted context omitted.

In this case the "arbitrary filter" was filtering applicants to a university for very basic math knowledge, so I think assuming that it's correlated with success at that university is not very far fetched.

Sure, but it also filters for people like me, who have seen this problem at least a dozen times.

When I did my university entrance interview (for maths, at Cambridge) the interviewers were clear that they expected that some subset of candidates would have seen the problem before, and some wouldn't -- for those in the first set they'd get them to quickly go through the problem and move onto the later parts which would be new to them; for those in the second set they'd provide sufficient guidance to let the candidate walk through the problem. The point was to get any particular candidate to a point in the problem sequence where this was something new to them, and then see how they tackled things. The idea that some applicants (usually from public schools) would have been very highly prepped for interview and others (usually from state schools) would not was clearly something they were well aware of and setting their interview design up to handle.

Re: Longest Lines of Sight on Earth

#96

Post by mamon »

davidmanescu wrote: post #93
liuhenry wrote: post #85

Earlier quoted context omitted.

The answer to the first interpretation is considerably less than twice the height of the cat, and I think it's an interesting result as well: Assuming a 0.3 meter high cat, you only need ~0.12mm of extra rope (about the width of two sheets of paper) to be able to pull it up at a point and let the cat through.

Follow-up question - after extending the rope by 0.12mm and pulling it up to allow the cat to pass under it, how far away are each of the two points where the rope lifts off the ground?

Haven't done any calculations but I would guess half of the Earth circumference? because if you want to minimize the length of the rope then you have to maximize distance between those two points.

Re: Longest Lines of Sight on Earth

#97

Post by rishabhsagar »

seanmcdirmid wrote: post #65
anyfoo wrote: post #63

Earlier quoted context omitted.

In this case the "arbitrary filter" was filtering applicants to a university for very basic math knowledge, so I think assuming that it's correlated with success at that university is not very far fetched.

Euclidean geometry games are hardly what people do in the real world, but if it floats your boat: https://www.euclidea.xyz I don't think after playing 20 or so levels I was much smarter for it. It turned out to be a bunch of rules that were extremely limited. You do begin to appreciate trig much more. If you are being given a geometry subject test and are prepared for it, this is fair game. If the question is just gi…

Thank you. Here goes the 2 or so hours of me doodling away.. :)

Re: Longest Lines of Sight on Earth

#98

Post by pmontra »

polymatter wrote: post #38
ianai wrote: post #37

Earlier quoted context omitted.

Pretty sure England does.

Londoner here. Nope, we use a comma as a thousands separator. I believe some European countries use a period though.

Italy should use a dot at the top (we did when I was little and learned to write), but it's not on any keyboard, even Italian ones, so we write 1'000'000,00. But 1.000.00,00 is also common.

I don't know what Excel does but LO Calc uses this format #.###,00 for the Italian locale.

Re: Longest Lines of Sight on Earth

#99

Post by Nition »

YZF wrote: post #57
kovek wrote: post #42

Earlier quoted context omitted.

I had this question worded differently asked to me when I interviewed to do an undergrad at Cambridge. If you have a rope that is wrapped around earth and you lift it off the ground as much as possible, and you see that it is 10km above the ground, then how long is the rope? I was not able to answer that question right away, and their hint to draw it helped a lot. I did not end up getting accepted.

The version I got, in a tech company interview, was how much longer would you need to make the rope to allow a cat to go under it. They were basically just look for 2 x Pi x Cat in this case.

I think that's a bit different. I tried to draw a diagram: http://i.imgur.com/XT3uGdM.png

If kovek's question was like the first image there, it'd be a simple radius/circumference calculation (2 * pi * 5km). But it sounds like the second image to me - which makes it into more of a horizon line problem.

Re: Longest Lines of Sight on Earth

#100

Post by ant6n »

kbenson wrote: post #32

Mt. McKinley (6.194 m.) What country uses '.' as the thousands separator but speaks English? Or is this someone mixing their native language thousands separator with English? Or is there some weird interaction between country and language that makes this the preferred, or at minimum an acceptable standard form? I'm actually hoping it's one of the latter options, that would be something new to me.

Most of the countries of the world speak some English.
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