factoids – Where is the longest visible line of sight on Earth from point A to point B?

We’ve had some interesting questions on being able to see country A from B, and on visibility for miles in every direction.

For a 6 ft tall person, the horizon in a ‘flat’ area is meant to be about 5km. Obviously the higher you are, the further you can see, if nothing is obscuring your view.

So somewhere on Earth (point A) presumably, you can see all the way, unobscured to Point B, which is further away than any other two visible points on earth.

Where would this line be – that is, between which two points A and B?

javascript – Como obter valores de uma lista no Google Earth Engine?

Bom dia pessoal!
Vocês poderiam me tirar essa dúvida por favor?

Preciso retirar os valores de uma coleção de imagens da variável: prec_year que indica a precipitação acumulada anual e imprimir no console.

// Importando os Estados:
var estados = ee.FeatureCollection("FAO/GAUL_SIMPLIFIED_500m/2015/level1"); 

// Selecionando um Estado:
var estado = estados.filter(ee.Filter.eq('ADM1_NAME', 'Paraiba'));

// Criação da variável chirps a partir do dataset importado:
var chirps = dataset.select('precipitation')
                    .filterDate('2010-01-01','2019-12-31')
                    .sum(); 
// ------------------------------------------------------------------------------

// Criação uma sequência dos anos do estudo:
var years = ee.List.sequence(2010, 2019); 

// Função responsável por selecionar os anos do estudo e realizar a soma de cada ano:
var sum_year_chirps = function(years){
    var year= ee.Number(years);
    var chirps_year = ee.ImageCollection(dataset.filter(ee.Filter.calendarRange(year,year,'year')));
    return chirps_year.sum();
};

var prec_year= ee.ImageCollection(years.map(sum_year_chirps));
print(prec_year);

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dnd 5e – Can the Erupting Earth spell be cast somewhere that isn’t on “ground”?

Yes, it can be cast on other kinds of surfaces as well

In this case, the term “on the ground” only exists to make sure it’s not in the air/floating. The rules don’t clarify “ground” any further.

While it may not make sense for the ground to be covered with dirt after casting the spell inside a dungeon, on top of a roof, or inside a gazebo, it is easy to reflavor the spell to have the ground be covered in rocks, chunks of wood, or another material that creates the same effect.

dnd 5e – Can Erupting Earth be cast somewhere that isn’t on “ground”?

The spell Erupting Earth says:

Choose a point you can see on the ground within range.

Does the use of the word “ground” limit this spell to floors that would be considered an “exposed surface of the earth”? Other possibilities include:

  1. An indoor room on an upper level or over a basement
  2. An outdoor deck or patio
  3. A raised platform like a stage or pulpit
  4. A roof
  5. A balcony
  6. The deck of a ship

Related: Does the spell Erupting Earth disrupt the surface it’s cast on?

Middle earth mythology forum | Forum Promotion

where on earth – Can an original of “The Great Wave off Kanagawa” be viewed in Japan?

According to the Wikipedia article for “The Great Wave off Kanagawa”, copies are stored in various places around the world.

There are various copies of this work throughout the world. The Metropolitan Museum of Art in New York,(30) the British Museum in London,1 the collection of Claude Monet in Giverny, France,(31) the Sackler Gallery,(32) the Guimet Museum(26) and the National Library of France(33) are some of the places where this work is on exposition. A collection of woodblock Thirty-six Views of Mount Fuji prints, contained in the wellness spa of the Costa Concordia was lost during the collision of the ship on January 13, 2012.(34)

Some private collections also have a copy, as is the case of the Gale collection in the USA.

This article (accessed May 14 2014) does not list one place I would expect – Japan! Is it possible to view this woodcut in Japan, or are all of the copies overseas?

great wave

edit: See answers below but there is an idea that there is no “original” because it’s a woodcut, the same way there is no “original” of a photograph because you can print many copies from a negative.

What on earth does this C program do and how does it work?

Yes, I know the title is very, very vague. But just hear me out.

Yesterday, someone showed me this:

#include <stdio.h>

int main(void)
{
    unsigned long foo = 506097522914230528;
    for (int i = 0; i < sizeof(unsigned long); ++i)
        printf("%u ", *(((unsigned char *) &foo) + i));
    putchar('n');

    return 0;
}

And this outputs:

0 1 2 3 4 5 6 7

I am… very confused. What significance does the number 506097522914230528 have? How does this output 0 1 2 3 4 5 6 7? I think *(((unsigned char *) &foo) + i) is a verbose way of writing ((unsigned char *) &foo)(i), but what exactly is being indexed? foo, an unsigned long? And what does an unsigned char * have to do with this? I really don’t get much of anything in this.

Where can I go to see the Earth is round?

There are many ways to see that the Earth is round. Some of them require traveling to specific places.

As a basic example, one argument from antiquity that the Earth is round is to observe boats disappearing over the horizon (you see that the bottom of the boat disappears first, and the horizon gradually progresses up to the top. If you think about the geometry, this only makes sense if the Earth is round.) To see this, you need to travel to a body of water with ships. It takes some effort to do this properly, since you have to keep watching while a boat slowly travels a long distance, and it’s only really convincing if you invest some time to watch it happen repeatedly, and convince yourself that the effect has nothing to do with waves or any number of other issues.

I think you can also get on an airplane and look out the window, and maybe convince yourself that the horizon looks curved rather than flat. But especially on a commercial airliner, the view is not really good enough to do this convincingly, and it’s very easy to believe that you’re just fooling yourself into seeing the effect.

But if you’re willing to travel somewhere more specific than just any old airport or seaport, you can see a similar effect to the one with the boats more easily and the experience can be more fun. For instance, go to Warren Dunes State Park in Michigan on a clear day. From the beach, you can’t see the Chicago skyline (80 miles drive away, a bit less as the crow flies across Lake Michigan) (I’m going by memory — it’s possible you can see the tops of the tallest skyscrapers like the Willis Tower from the beach). But as you climb the large dune behind the beach (probably a few hundred feet high), the Chicago skyline comes into view. Moreover, as you climb, you first see the tops of the skyscrapers, and as you go higher you see lower and lower down the skyscrapers. This makes perfect sense for a round Earth, but zero sense for a flat Earth.

There’s a lot to consider about what makes this so convincing:

  1. The conditions are pretty specific: the body of water allows you to see very far with an unobstructed view, and the dune enhances your perspective even more. The change in elevation is essential too.

  2. Everything is very static. You can’t really argue that the skyscrapers in Chicago are moving or anything.

  3. You can walk back up and down the dune as many times as you like to repeat the experiment.

  4. You can’t argue that there’s anything obstructing your line of sight. The only thing moving between you and Chicago are the waves on the lake, and they are obviously not tall enough to block out skyscrapers.

  5. The fact that you see the skyscrapers from one spot, and then don’t from a very nearby spot means you can’t argue that it’s haze in the atmosphere blocking your view or anything like that.

  6. It’s clear and easy to see when more or less of the skyscrapers are in view. This stands in contrast to the way mountain vistas change as you climb a mountain, because the surrounding mountains are not as vertical as a skyscraper, so the changes in the way they look are more subtle.

Here’s a picture of the beach with the dune behind it.

Anyway, I’m asking the following:

Question: Where can I go, besides Warren Dunes, to see that the Earth is round in a fun, easy, and convincing way?

Tentatively, it seems that the ideal location will satisfy the following basic criteria:

  1. There will be two components: an observing target (e.g. the Chicago skyline), and an observing platform (e.g. the big dune), separated by a distance most likely on the order of 10-100 miles, and both static, non-moving objects.

  2. The observing platform will be something tall which you can go up and down (probably a hill or a building).

  3. From the top of the observing platform, the observing target will be mostly or completely visible.

  4. From the bottom of the observing platform, the observing target will be mostly or completely below the horizon.

  5. The ideal horizon is the only thing substantially preventing you from seeing parts of the observing target from any part of the observing platform. In practice, I think this means there needs to be a large body of water or else a flat expanse of land between the platform and target, and the observing target needs to be much bigger than any small features like waves or trees breaking up the horizon.

(Mountain settings are again problematic for (5) — the surrounding mountains modify where the horizon is so that it’s not set by the curvature of the Earth. Similarly, (5) is an annoyance with the boat example because waves around the boat modify the horizon. In the Warren Dunes example, waves are still present, but they are way smaller than the skyscrapers we’re using as an observing target, so they can be neglected more comfortably.)

In addition, there are a few more specific criteria:

  1. You can go up and down the observing platform freely at your own will, ideally in a matter of minutes rather than hours.

  2. You can observe the observing target continuously as you go up and down, or at least at regular intervals.

  3. The observing target is such that it’s easy to compare what it looks like when more or less of it is hidden by the horizon (e.g. a vertical skyscraper is better than a complex-shaped mountain).

(It occurs to me that there are definitely a lot of places you can get a similar effect by changing your observing position horizontally rather than vertically. The problem with these is that you necessarily have to move horizontally a much bigger distance than is required in this “vertical observing platform” scenario. This makes it less convincing, even if you’re in a car or something and so it doesn’t take much time. It’s less convincing because necessarily there’s a lot of other things changing about your view at the same time which are distracting. You might also start worrying about atmospheric changes as you move, etc.)

For a start, I bet the Great Lakes afford some other similar opportunities. E.g. from the docks in Toronto, you can see a couple of American cities across Lake Ontario. Maybe going up and down the CN tower or something could allow you to see a similar effect, but I don’t actually know (and as noted in the comments, it likely fails some of the “ideal criteria”). I think there are probably examples not requiring water or skyscrapers, but I haven’t come up with any.

I asked an early form of this question on Skeptics.SE. It was closed there as not being in scope for the site, but Nate Eldredge suggested it might fit here.