There is no absolute direction for a galaxy’s spin—it’s always relative to the observer’s perspective.
So I’d suspect they’re saying time and distance would need to be factored in rather than just looking at static images relative to our position today since our own spin may have caused a particular galaxy to appear to have been spinning in a different direction at another point in space-time
I don't understand this logic. To me, that's equivalent to saying "there's no absolute direction for which way a wheel spins, it's relative to the speed of the observer". Which makes no sense to me, because my definition of spin is measured against the axis of rotation of the object itself.
I don't see how time-intermittent frame captures from our own position affect that interpretation. Or are we using an astonomy-specific definition of spin here?
It's true, there is no absolute direction for which way a wheel spins. It's relative to the observer.
If you are standing on the side of a road, and a bicycle goes by, then you may observe the wheels to rotate clockwise, while an observer on the other side of the road will observe the same wheels to rotate counter-clockwise.
The sun is said to rotate around the centre of the milky way galaxy once every 225 million years. Over that time frame, some of the galaxies we observe will flip between clockwise and counterclockwise rotation as our viewpoint changes.
But that isn't relevant here. The Space article is too vague and handwavy to make any conclusions about the research, and should be ignored. Only the original scientific paper is worth reading: https://academic.oup.com/mnras/article/538/1/76/8019798?logi...
Section 5.2 "Physics of Galaxy Rotation" seems particularly relevant.
> due to the Doppler shift effect galaxies that rotate in the opposite direction relative to the Milky Way are expected to be slightly brighter than galaxies that rotate in the same direction relative to the Milky Way. Therefore, more galaxies that rotate in the opposite direction relative to the Milky Way are expected to be observed from Earth, and the difference should peak at around the Galactic pole. That observation is conceptually aligned with the empirical data of Fig. 10, and the observation using JADES described in Section 3.
It’s the same as saying you can only work out how fast something is moving in relation to something else. Your car is doing 50mph on the highway, but the earth is spinning round the sun and the sun is moving around the centre of the galaxy and the galaxy is moving compared to other galaxies and so on.
> There is no absolute direction for a galaxy’s spin—it’s always relative to the observer’s perspective.
Not entirely. The galaxy is bound by gravity and the stars rotate in the galaxy around its baricenter. We can compute how fast it must be rotating from the amount of visible matter. Enter dark matter and various complications, but still, you can tell that it's rotating and which way.
And for galaxies we see edge on we can use the difference if redshift on one end versus the other to tell which way it is turning.
I don't necessarily agree, in the presence of a universe (and under some reasonable cosmological assumptions) you can't just get rid of an observed rotation by a change of inertial frame. You can rotate along with it, but you'll produce a tell-tale fictitious force.
Nice thing about SQLite is you can “clone” the repository by copying a single file. And in cases where you need incremental sync, you can use an SQLite of diff’s as a single packfile (similar to git).
Things like cr-SQLite also have a lot of potential to make single SQLite per client a lot more viable. But I’m interested to see what you think the problems are? Have you found a solution or alternative?
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Is there a public git repo available somewhere that represents a Kart repository?
Are the raw files in the working repository GeoPackages? How is it tracking the changes made inside the geopackages? What happens if it's replaced with an updated copy of the geopackage the was edited via some other application? How does it diff the changes?
> Are the raw files in the working repository GeoPackages?
The working copy for a vector/table dataset can be in a GeoPackage or a SQL database like PostGIS. For rasters/point-clouds they're flat files.
> How is it tracking the changes made inside the geopackages?
In general, triggers which store RowIDs/PKs of inserts/updates/deletes. Then when you ask for a diff or make a commit Kart figures out any actual row-level (or schema) differences.
> What happens if it's replaced with an updated copy of the geopackage the was edited via some other application?
If it's edited by something else (QGIS, ArcGIS, python/go/whatever application, SQL CLI, whatever) it'll work: you do edits where you want to. If it's replaced by something else, it won't work.
> How does it diff the changes?
Comparing the features/rows in the repository (and their schemas) against the rows in the working copy database. It uses the stored list of modified rowids to make this fast.
I assume it’s using WASM for browser based web encoding? Is local encoding always guaranteed to be faster or could some internet connections be fast enough that an upload would beat out the client side encoding depending on device capabilities?
Automatic captioning and clipping based on transcripts are great features.
I wonder if language translation will be one of the "killer apps".
Especially if it can be done real-time and according to the context/level of the audience/listener. Even within the same language, translation from a more technical/expert level to a simplified summary helps education/communication/knowledge transfer significantly.
In scenarios where an individual customer/tenant can have isolated data this makes sense.
Is there any reason why the client application itself can't be one of the nodes in the distributed system? Does LiteFS support a more peer-2-peer distribution model (similar to a git repo) where the client/customer's SQLite database is fully distributed to them and then it's just a matter of merging diffs?
No, LiteFS just does physical page replication. We don't really have a way to do merge conflict resolution between two nodes. You may want to look at either vlcn[1] or Mycelite[2] as options for doing that approach.
Is there any documentation on the native schema used to store the documents. Is it sane enough that you could manually roll your own JSON1 queries in SQL to facilitate more relational join like features?
Some time ago, we wrote a blog post about it: https://blog.ferretdb.io/pjson-how-to-store-bson-in-jsonb/ A few details changed after that (for example, type information is not mixed with values anymore), but the general idea is the same. We probably need to document it better.
So I’d suspect they’re saying time and distance would need to be factored in rather than just looking at static images relative to our position today since our own spin may have caused a particular galaxy to appear to have been spinning in a different direction at another point in space-time