[HN Gopher] Earth's rotation, with the camera locked to the sky ...
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Earth's rotation, with the camera locked to the sky instead of the
ground
Author : behnamoh
Score : 189 points
Date : 2023-06-12 19:10 UTC (3 hours ago)
(HTM) web link (mastodon.social)
(TXT) w3m dump (mastodon.social)
| hospitalJail wrote:
| I wish there was a way to experience this first hand, but it gets
| a bit boring looking at the same point in space for 24 hours.
|
| Even watching the video, I still feel like its the sky that
| moves, not us. Its wrong, but I can't shake that feeling.
| [deleted]
| mannykannot wrote:
| I get the impression that this shows a sort of 'double-dip'
| sunset where, just before it goes completely dark, it brightens
| briefly (and the converse at dawn.) It seems to be there when I
| step through the frames. Can someone say if this is an illusion
| (or a personal delusion on my part), a meteorological effect, a
| camera sensitivity-adjusting effect...?
| someweirdperson wrote:
| It doesn't seem to change in intensity, but in what is
| illuminated. While high, sun itself appears bright, when
| dropping lower the things lighted from the side, and at the end
| scattered light at the horizon.
| julienchastang wrote:
| The 21st century version of a Foucault pendulum [0]
|
| [0] https://en.wikipedia.org/wiki/Foucault_pendulum
| felipeerias wrote:
| This is a good illustration of how unintuitive heliocentrism
| really was, specially before we had a theory of gravity: it
| really made more sense to assume that the heavens were populated
| by ethereal bodies floating around a heavy, immobile Earth.
| zokier wrote:
| Also featured on NASAs APOD:
| https://apod.nasa.gov/apod/ap200701.html
|
| Its a classic effect, there are many examples, for example:
| https://www.youtube.com/watch?v=w8OK7M2_hUg ... I wonder where
| this idea got started
|
| Once you start looking there are all sorts of interesting ones,
| like this one showing different perspectives/projections
| https://www.youtube.com/watch?v=JmCNNHQ86NE
| mentos wrote:
| Heres a song I suggest a listen to when contemplating the
| universe https://youtu.be/9mvZ-FjdgLw
| xwdv wrote:
| Ah, Black Hole Sun.
| abstrakraft wrote:
| I can't decide whether I'm relieved or disappointed that you
| didn't take advantage of the fantastic rick-rolling
| opportunity.
| [deleted]
| bitwize wrote:
| Do a barrel roll!
|
| Reminds me of when I would make myself dizzy by pretending the
| sky was down and the earth up, and it felt like the only thing
| keeping me from falling trillions of lightyears through the inky
| void was that I was stuck to the ceiling of my home planet.
| acegopher wrote:
| A bunch more examples here, which show how your latitude changes
| how the rotation looks:
|
| https://www.youtube.com/watch?v=72hBReBQRAg
|
| and a few more:
|
| https://www.youtube.com/watch?v=1zJ9FnQXmJI
|
| https://www.youtube.com/watch?v=zRTJ5ISmVXE
| mytailorisrich wrote:
| Straight to the source:
|
| https://artuniverse.eu/gallery/190705-rotation24h
| Freebytes wrote:
| How is this actually accomplished, though?
| worldsavior wrote:
| Instead of turning with the earth, it stays "in place".
| Meaning it turns to the opposite of the Earth's rotation.
| diggernet wrote:
| The camera was on an equatorial telescope mount.
|
| "An equatorial mount is a mount for instruments that
| compensates for Earth's rotation by having one rotational
| axis, the polar axis, parallel to the Earth's axis of
| rotation."
| Smoosh wrote:
| It is easier to understand if you imagine that the observer
| is at the south pole looking up, instead of thinking of them
| on the equator going around. In reality, they are somewhere
| between the two extremes.
| taejo wrote:
| An equatorial mount keeps the camera pointing in a fixed
| celestial direction by rotating at the same rate as the Earth
| in the plane of the equator. It's essential for any long
| exposure of the sky where you don't want star trails, the
| unusual thing here is having the horizon in frame.
| shagie wrote:
| Mount Sky-Watcher Star Adventurer Tripod Manfrotto
| MT055XPRO3
|
| The tripod is a good, heavy, stable one.
| https://www.manfrotto.com/us-en/055-aluminum-3-section-
| tripo...
|
| The head is https://www.skywatcherusa.com/collections/star-
| adventurer/pr... which is a bit more fancy than the old
| school equatorial mounts.... but Star
| Adventurer 2i multi-function equatorial tracking mount with
| built-in Wi-Fi control
|
| It's still an equatorial mount.
|
| https://astrobackyard.com/equatorial-telescope-mount/
|
| https://en.wikipedia.org/wiki/Equatorial_mount
|
| You adjust the base to the latitude that you are at so that
| the mount can rotate to match the Earth's rotation on one
| axis, and then the other axises can track ascension and
| declination - which remain constant in the sky.
|
| This differs from the altazimuth mount (
| https://en.wikipedia.org/wiki/Altazimuth_mount ) where a
| celestial object is that that location now, but moves.
|
| Sirius is at 06h 45m 08s RA and -16deg 42' 57"... but as I
| type this, as seen from Greenwich, United Kingdom it would be
| at -27.4deg altitude (below the horizon), 277.5deg azimuth -
| and that coordinate system moves.
| meghan_rain wrote:
| Very interesting content but... why can I not download it? Whats
| a crappy website that tries to force me to stay with them
| hospitalJail wrote:
| That peeved me too. I wanted to save something cool.
| googlryas wrote:
| That's really your user agent's fault, not the site. I can
| right click on the video and click "Save As" without issue.
| arprocter wrote:
| yt-dlp works on the artuniverse page
| autoexec wrote:
| I share this complaint with nearly every podcast site. We all
| know the episode is just an MP3, but sites generally refuse to
| have a clear download link, and often just push you onto
| pointless sites like Apple Podcasts or Spotify. As someone who
| uses a very locked down browser, podcasts should be one of the
| most easily accessible forms of media and yet they all seem to
| go to a lot of trouble to hide the actual files from users.
| gsich wrote:
| Podcasts without RSS are not podcasts.
| jwilk wrote:
| Direct link to the video:
|
| https://files.mastodon.social/media_attachments/files/110/53...
| wizzwizz4 wrote:
| Works fine for me. Have you tried Firefox?
| evo wrote:
| This gave me a bunch of insight into the workings of those old
| survival tricks of using analog watch hands to find cardinal
| directions:
|
| - Since the video starts at solar noon, the sun is always at
| 12:00 relative to the video.
|
| - Swapping reference frames, if you had a clock face with 24
| hours on it, and aligned the "12:00" to point at the equator, the
| "0:00-12:00" axis would define a longitudinal plane through the
| Earth, and the hour hand would define a second plane that would
| intersect with the sun--the hour hand would "follow" the sun.
|
| - Conversely, if you pointed your clock's hour hand at the sun,
| you would know your "12:00" would be due north/south (depending
| on hemisphere).
|
| - The same is true for conventional 12-hour watches and clocks,
| but you must find the "half-way" mark between your hour hand and
| noon, because the hour hand is moving at twice the speed relative
| to the hypothetical 24-hour clock.
|
| Neat!
| Anonasty wrote:
| Flat earthers will just say its the Photoshop AI.
| dataviz1000 wrote:
| Interesting. Maybe they will say that the flat Earth is doing a
| barrel roll?
| B1FF_PSUVM wrote:
| Sheesh, it's no wonder the flat-earthers have such an easy time
| baiting "scientists".
| MeteorMarc wrote:
| Train your mind and imagine how this video would look on the
| north pole and south pole! Guess such footage already exists on
| YouTube.
| jhoechtl wrote:
| I tried and it's easy to think of looking straight 'up' along
| the rotation axis. While keeping the horizon in the focus is
| not so easy.
| ithkuil wrote:
| Yes. But you can also point your camera in directions other
| than straight up and get different paths.
|
| For example if you point it towards the horizon the camera
| will rotate 360 degrees and it will record a full view of all
| the land around the camera.
|
| If you're on the equator and you point the camera "up"
| towards the azimuth, then after 6 hours it will be pointed
| towards the horizon on the west. After 6 hours the camera
| will be pointing straight down to the ground etc.
|
| But if you're in the equator and point the camera to the
| horizon towards the north, then the camera will roll and
| you'll see the ground rotate around similar to this video
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(page generated 2023-06-12 23:00 UTC)