
Earth and Sun - davezatch
https://ciechanow.ski/earth-and-sun/
======
ColinWright
This is absolutely superb - just brilliant.

This is a personal reflection on the way it's presented. I'm sure that there
are people who already know some of the content, and I found myself skimming
over things, nodding, and thinking "Nothing new here." Then realised that
there was something I missed, or an explanation that was especially nice, and
I had to go back and re-read, wondering what else I might have missed.

So I found it all very smooth, clean, informative, but there was no story, no
arc, no narrative, nothing to make me want to sit with a coffee (or other
beverage of choice) and simply _read_ like a novel. There wasn't the "Hook;
Narrative; Reveal" structure that keeps the reader involved.

Which is a bit of a shame, because the bits I did take time over are really,
_really_ nice.

It's really nice.

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bitpow
What a beautiful, well designed and informative explanation of the complex
earth / sun relationship. Well done!

One thing I would love to see is the path of the sun across the sky for
different times of year, and different locations on earth.

Here in Seattle, the difference is fairly dramatic between winter and summer,
and I've come to realize that the sun is never directly overhead, not even in
summer. It would be interesting to see the difference between polar regions vs
in the tropics also.

~~~
elliottkember
At my school we had this weird climbing frame called the "Pipehenge". I
climbed on it for years before we eventually did a class on it and learned
that it was an astronomic map:
[https://www.youtube.com/watch?v=BM4d02tjTqk](https://www.youtube.com/watch?v=BM4d02tjTqk)

~~~
Tepix
Looks they are no longer made, or are they?

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novaRom
It's like I just read an epic story, still under impression ...

Quote: One day we’ll colonize other planets, those planets will have different
suns, orbits, and rotations periods, yet a simple second will forever be tied
to Earth and Sun.

I would definitely give my 'best web page 2019' to it. Bravo!

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sixQuarks
I’d like to know what tools were used to make these. Works great on mobile,
usually these things break pretty badly, I didn’t see any bugs

~~~
d6e
Looks like it's just hand written javascript and webgl
[https://ciechanow.ski/js/earth_sun.js](https://ciechanow.ski/js/earth_sun.js)

~~~
airstrike
One of the many ways you can tell how much passion went into this beautiful
piece

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twic
I remember spending a lot of time playing with a planets-and-gravity simulator
on the Mac when i was a kid. I wrote a crappy clone of it as an applet for one
of my first jobs!

This is the best web-based equivalent i found with a quick search:

[https://hermann.is/gravity/](https://hermann.is/gravity/)

And this is a rather fine tutorial on writing your own:

[https://css-tricks.com/creating-your-own-gravity-and-space-s...](https://css-
tricks.com/creating-your-own-gravity-and-space-simulator/)

~~~
perl4ever
I played with a simple program like that for the Amiga when I was younger, and
then I discovered that there was an O(n log n) algorithm[1] rather than the
obvious O(n^2) one. Never was up to writing a program to use it.

[https://en.wikipedia.org/wiki/Barnes%E2%80%93Hut_simulation](https://en.wikipedia.org/wiki/Barnes%E2%80%93Hut_simulation)

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disqard
I used it on an iPad. For me, this was a beautiful example of how to leverage
the strengths of a touchscreen to present information. (too often, I find
myself shaking my fist at how we’ve "bolted" a magazine onto a high-dpi
display)

Wonderful stuff... thank you for making and sharing!

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novaRom
Very good made! I recently started astrophotography, it is a lot of fun. Just
learning all those different stars and galaxies, it's incomprehensible how big
is the space. Nice thing it's really doable to appreciate it live from your
backyard. A lot of technical things are still desirable, a big opportunity for
innovative ideas.

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pacoverdi
Wow. What a great explanation. I'd love it to be translated in other languages
so I can have my younger kids spend some useful screen time on it!

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folli
Very well made and very educational!

An often used algorithm for the calculation of the apparent sun position
(given a date and latitude/longitude of the observer) is SPA of Reda et al.
[1]. If you're interested, I wrote an Android app (Sun Locator [2]) that
implemented this algorithm.

[1]
[https://www.sciencedirect.com/science/article/abs/pii/S00380...](https://www.sciencedirect.com/science/article/abs/pii/S0038092X0300450X?via%3Dihub)

[2]
[https://play.google.com/store/apps/details?id=com.genewarrio...](https://play.google.com/store/apps/details?id=com.genewarrior.sunlocator.lite)

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macrael
This is what the web is for. Charming, intimate. Thank you

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kwoff
Very nice visualization. It'd be interesting to see it extended to the galaxy,
as in [https://www.physicsforums.com/threads/orientation-of-the-
ear...](https://www.physicsforums.com/threads/orientation-of-the-earth-sun-
and-solar-system-in-the-milky-way.888643/)

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oska
> The Earth rotates around its axis from west to east, or, when seen from
> above, counter-clockwise.

 _North is not up._

When seen from above the South Pole, the Earth is rotating clockwise.

But really doesn't make much sense to talk about the rotation of a sphere by
analogy to a 2D clockface. The Earth rotates from West to East; that's all
that needed to be said here.

~~~
mathgladiator
Dont all maps have north 'up's? I'm curious if there are maps that invert
this.

~~~
oska
We're not talking about a map here, we're talking about the real thing, the
Earth, hanging in space.

(But yes, there are many maps that don't have north at the top).

~~~
TheSpiceIsLife
Your just using your preferred frame of reference.

It seems reasonable to call north up because that frame of reference is how
maps usually look.

To subsume your frame of reference, we could say the Earth isn’t _hanging_ in
space, it’s in free fall around the sun.

There are other frames of reference at progressively larger scales.

Edit: Also, the word ‘hanging’ usually implies an ‘up’.

~~~
oska
> Your just using your preferred frame of reference.

No I am not. What I said was that they should have left it as just that the
Earth rotates from West to East (no frame of reference). I only talked about
how it would look like from above the South Pole to show that the described
anti-clockwise direction of motion was _relative_ to the frame of reference
that was being, unnecessarily, assumed.

The Earth has two poles and they are equal, just like with any (approximate)
sphere. If you are going to describe how the Earth's rotation looks from above
one pole then you should also describe how it looks from above the other. But
once you describe it from both poles it becomes obvious that you're not really
imparting any useful information because, while it looks clockwise from above
one pole it looks anti-clockwise from above the other. Better to not use any
frame of reference at all. We _know_ that the sun rises in the East and sets
in the West. With just a little thought it is then obvious that the Earth is
rotating from West to East and that is all that needs to be said.

~~~
TheSpiceIsLife
> Better to not use any frame of reference at all.

Ok

> We know that the sun rises in the East and sets in the West.

You didn’t even try!

~~~
oska
Frankly, it's pathetic that you play games with the words I use - 'hanging',
'rises' \- which everyone understands are not actual descriptions of reality
and _don 't_ engage with the argument at all, which is about reality.

~~~
TheSpiceIsLife
You started it:

> North is not up

~~~
oska
You remain blind to, either willfully or unconsciously, my argument. Instead
you come back with puerile rejoinders.

Look at the original quote from the article - "when seen from above". There
was an assumption there that seen from above means seen from above the North
Pole. Thus an assumed frame of reference _when none was needed_.

I do not assume seeing the Earth from above means seeing it from above the
North Pole. Neither would an astronaut, who don't have to assume, they live
the experience of seeing the Earth from all orientations.

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baxtr
I can’t upvote this enough. Beautifully crafted website

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srigi
Last couple of months I started thinking about sidereal vs. solar year. The
first one is determined by distant stars, the second one by our Sun.

The thing I'm thinking of is if small deviations accumulate over years, how
night sky is changed at the same date across, let's say, 20 years?

~~~
beerandt
If you think that can get complicated, check out the different global geodetic
reference systems. Between the Earth's precession, plate tectonics, the Earth
_changing mass_ cyclically (collecting space debris and off-gassing
atmosphere), and the fact that the center of our planet is a freaking wobbly
blob of molten iron, well, things can get tricky.

Then there are the different eliosoidal (and soon geoid with NVD22) shapes
that are the basis for every other reference system, most based on similar,
but slightly different geodetic network adjustments. Some systems, like NAD83,
remain relatively fixed in reference to a particular land mass (North America
Datum 1983). Some will then progress with the land mass as it moves on the
Earth's plates, others will remain fixed based on a (the) prime meridian, or
in reference to the center of gravity of the Earth as it shifts, or in
reference to Polaris, etc.

So now you have multiple measuring systems each referencing different
geometric/geodetic/astronomic points/lines, and further it matters what time
it was when you defined those points/axises. WGS80 is the basis for many
modern systems, including NAD83. ITRF is similar, but defines a yearly amount
of progression since ~1980 to account for things like continental drift. They
coincided around the time when they were defined, and have been diverging some
number of millimeters per year since then.

Once you agree on a definition of a system, you further have to define _how_
to measure it. Will North be a point in time, or a rolling average? Will the
center of gravity of the Earth be based on changing rate of Earth's rotation,
or with respect to a geodetic benchmark or network, or maybe based on
millimeter fluctuations in deviations of the orbits of the NAVSTAR / GPS
satellites? Should Euro/ Chinese/ Russian / Indian versions of GPS satellites
be taken into account?

I'm over simplifying things, as there are additional layers of complexity
involving the actual tools for surveying and measurement, the precise steps
for any network adjustments or translations, rounding rules and certain
geometric assumptions made for different types of math, and way, way more.
(You can't actually stretch a tape measure around the equater.)

Take all of that, _and then_ contemplate how all of this is spinning around
arbitrarily in space. Sidereal vs solar is only one of 100s of aspects of how
we measure these things. _It 's not just time, but also geometric space_.

Everything's relative.

~~~
beerandt
Also, you can try to explain this to people, most of whom will complain that
it's way too complicated, and we don't need anything to be that precise. They
say it's ridiculous.

Then you can ask the same person for directions to their house, and they'll
turn around and text you GPS coordinates to 12 digits.

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cosmosa
This is excellent. I had been wanting to see something like this for a long
time. It was difficult for me to imagine the orbit of earth around the sun,
and nothing I found showed it well. Thanks for making this!

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excalibur
Amazing how he got the clouds to stand still for an entire year :)

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lxe
This is excellent. Are all the interactions custom made?

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carrozo
This is so excellent. Put it on school curricula!

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m0skit0
Excellent visualization of these astronomy concepts, amazing job, my sincere
congratulations!

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mrfusion
I’m not sure if it’s related but I can’t seem to understand the international
date line.

~~~
cuspycode
The international date line is needed when you use local times instead of UTC,
because the local date is incremented on midnight local time. So, if it's
October 19 just after your local midnight, every timezone to the east should
also have October 19, while every timezone to the west should still have
October 18 because they haven't had local midnight yet. But that doesn't work,
since east ultimately meets west when you track both directions far enough. So
by convention we have defined a line (or rather a crooked boundary between
timezones) where the date jumps back a day in the calendar when you pass over
it in an eastwards direction.

~~~
mrfusion
Thanks but that much I understand. I guess for people living in that border it
doesn’t make sense to me how they can jump back and forth 24 hours.

~~~
cuspycode
If I had to live there, I think I would campaign for using UTC only, and
forget completely about local time.

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naringas
really good, I wonder if there's a "Earth and Moon"?

~~~
ryanseys
If you would like to make it yourself, check out my library!
[https://github.com/ryanseys/lune](https://github.com/ryanseys/lune)

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trileansoftware
Are all the interactive infographics custom made? Amazing.

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justajester
wow. Excellent read. much respect. Labor of love.

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known
This is the best I've seen till date;

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beders
This was fantastic! Thanks!

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exiladodecapela
Excellent work!

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olivermarks
this is wonderful

