Sagittarius-Earth is the most ambitious conspiracy theory of all
Unlike the lizardmen, the secret world governments that slurp the blood of innocent children, the Sagittarius-Earth theory is cosmic in scale: its premise is that our planet is not where many people remember it, but in another part of the Galaxy. Nelson Mandela died in 2013, not in the 1980s, the Monopoly man is not wearing a black eye, the protesters in Tiananmen Square were not run over by a tank - to name just a few examples of what is known as the Mandela effect, precisely because of Mandela. But some people (for example even Hive users, like 
The whole theory could easily be demystified by a cheap bit of psychologising: amid the uncertainties of a changing world, some people use this strange, sci-fi method to transform the "bygone Golden Age" into a whole place where beer was cheaper and Star Wars movies were better (and this urge may be behind both Paradise and Lost Atlantis and countless other mythical places). However, it is also somewhat easier than the average conspiracy theory to get caught up in the uncertainties of the scientific world when it comes to Sagittarius-Earth, especially as regards the movement, or even the position, of the solar system within the galaxy.
The Milky Way
Image source: https://upload.wikimedia.org.
Wherever exactly the Earth is located, everyone agrees that our planet is in a galaxy called the Milky Way. And the Milky Way is a spiral galaxy, a spiral galaxy with spokes, 100 000 light years in diameter. We have to try to work it out somehow, but there's nothing special about the Milky Way: it's the most common type of galaxy in the Universe, with about two-thirds of all galaxies in this group.
From above, our galaxy looks like an octopus that has suddenly spun around, or like a cup of cappuccino that has been swirled in its foam. The Milky Way has two large arms and two slightly smaller arms, and there are two smaller arms - one of which is Orion, where the current view is that the Earth is located, and Orion is located between the two larger arms, Perseus and Sagittarus. So for those who believe the 'theory' explained above, the Earth was located in the Sagittarius arm and somehow moved into the Orion arm.
Is the Solar System moving within the Galaxy?
Image source: https://upload.wikimedia.org.
One way to keep sanity, but also to keep the lizard-man well fed, is to find out that our planet is not only moving within the Solar System, but also with the system in the Galaxy. Fortunately, this is the case (but unfortunately, the planet does not move from one arm to the other in a few years).
Everything in the Universe is in motion, but this is true not only for celestial bodies, but also for entire solar systems (and even galaxies). Our own solar system, for example, is hurtling along at an average speed of 828 000 km/h, which in most places would get us arrested for speeding. But even at that speed, it takes 230-250 million years to orbit the Milky Way, which has an incredibly huge black hole at its centre, many billions of times the mass of our Sun - and everything in the Galaxy orbits around the Milky Way, with everything closer to the black hole orbiting faster and everything further away (like the Solar System) orbiting slower.
This has been known for a long time, but it came to the public's attention again when NASA researcher Jessie Christiansen created the animation above, which shows that dinosaurs, for example, lived on the far side of the galaxy, because that's where the Earth was orbiting at the time. Christiansen was interviewed by CNN, where she explained that the Stegosaurus, for example, could have seen a completely different sky overhead than we do. The solar system also encountered and stumbled into a number of hazards that threatened life on Earth. Indeed, in 2013, the Independent published a study that explained many of the past climate changes (and some of the current ones) by changes in the galactic environment of the Solar System.
But Christiansen added in the 2019 interview that astronomers are only just beginning to understand how the Sun orbits the center of the galaxy. The video also shows that our current position is about 250 million years ago, so we're about one cycle complete, and the last time we were here, Earth was in the middle of the Triassic, the time when the first dinosaurs appeared. The conclusion of the video, and Christiansen's thought-provoking question, is what the planet will look like in another 250 million years when it returns to this place.
From Sagittarius to Orion
Image source: https://upload.wikimedia.org.
Of course, the arms move too, but as a statement to Indenpendent in the 2013 study mentioned above shows, they are much slower than the stars, and should be thought of as a traffic jam, which is why stars are born here, and even short-lived stars get stuck in these arms and reach the end of their lives. And the authors of the study also explained the cooling and warming partly by where the Earth is and the galactic environment that surrounds it. According to the researchers, we have (relatively speaking) recently left behind the Sagittarius arm, which has resulted in a colder climate on Earth, and we are now in the Orion arm, which will result in a warming in a few million years, followed by cooling again when we enter the Perseus arm.
Image source: https://upload.wikimedia.org.
So, as you can see, the planet is indeed travelling between the arms, but we are talking about millions of years, not a few years. And Sagittarius Earth 'proponents' argue that they woke up almost overnight to find the planet in the Orion arm, not the Sagittarius arm. Forget about how many of us start the day (week, month or year) by checking which galactic arm the planet is in, let's concentrate on the arguments! Most people cite several inconsistencies, one of which is NASA's website, another is a TV programme featuring the 'astrophysics celebrity' Neil deGrasse Tyson.
NASA, Tyson and an accidental clue
Let's start with the NASA site!
On this site, NASA writes no more than a few sentences about where our planet is located in the Milky Way. The full text reads:
The Milky Way Galaxy is organized into spiral arms of giant stars that illuminate interstellar gas and dust. The Sun is in a finger called the Orion Spur.
That is, the part we are interested in: the Sun is located in a finger (a reference to the fact that Orion is not a full-fledged arm), called Orion. However, according to many people, the old archived version of the website did not say this, but instead indicated the Sagittarius arm as the location of our planet. The earliest archived version is from 16 November 2012, and it contains the exact sentence quoted above. The attached image is also unchanged:
Image source: http://web.archive.org.
But NASA also writes about the galactic position of our planet on another page, and this is what it says:
Our Sun lies near a small, partial arm called the Orion Arm, or Orion Spur, located between the Sagittarius and Perseus arms.
That is: our Sun is located near a smaller, partial arm, Orion, which is located between the Sagittarius and Perseus arms. So it is not written here that the Sun is located within Orion's arm, but that it is located next to it. If you look at the pictures on the website, the inconsistency is immediately clear (and may also explain several later 'clues'): the Sun is located at the very edge of Orion.
But for now, let's save this information for later and take a look at the TV show!
As you can see and hear, celebrated astrophysicist Neil deGrasse Tyson is indeed telling the world that the Earth is in Sagittarius.
Finally, while putting this Hive blockchain (Proof of Brain) article together, I myself came across a 'clue' in a New Scientist article on the galactic path of the solar system. In the article, they talk about the Orion Nebula, which is located in a nearby arm, Orion. The text reads:
In a nearby spiral arm of the Milky Way, more than 1000 light years away from our solar system’s present position, lies the Orion nebula, a birthplace of giant stars.
In other words, they say that Orion (in which the Orion Nebula is located) is a spiral arm close to us - which implies that our Sun is not located within that arm. So the question is:
What is going on?
The situation is perhaps a little clearer if you look at the image below, which not only shows the arms, but also the Sun's orbit around the centre of the Galaxy. This means that we have left Sagittarius and are now at the very edge of Orion. So from here we can say that we are in Orion's orbit, but we can also say that we are close to it. So it's a bit like driving on the highway and explaining to someone on the phone where you are. You can say that you are on the highway, but that won't help them out, or you can mention the mileage, but that may not tell you much either. Finally - and this is probably the best way to do this when travelling abroad - you can specify the major city you are in the vicinity of, whether you have just left it or are approaching it.
Image source: https://earthsky.org.
So, when Neil deGrasse Tyson said that the Earth is located in Sagittarius, he was probably giving a larger, more familiar arm in a layman's show, rather than saying that the solar system has left Sagittarius and is now located on the outer edge of Orion's arm, because the whole system orbits the centre of the Galaxy, and therefore our position changes over millions of years.
It's also worth remembering what Jessie Christiansen said in the dino video: that the Sun's movement around the centre of the Galaxy is only just beginning to be understood by scientists. It was not long ago, in 2016, for example, that it was realised (the deGrasse Tyson video is older than that, having been uploaded to YouTube in 2016) that Orion's arm might be longer than previously thought.
In other words, our knowledge about this is still fragile, and scientists are passing it on to us lay people in various simplifications when they promote science. So the most rational argument is this: the Earth did not migrate from point A to point B in the Galaxy overnight (but it did move over hundreds of millions of years), but our knowledge of its position and the Sun's galactic orbit in general is being refined, and since there are no clear positional markers in the Galaxy, there are many legitimate ways to give the Sun's position, especially if one tries to summarise the point quickly. And the Earth is a worse place than it was not because it has somehow merged an old, nicer world with a distorted new one - natural disasters, an ever more intense Sun and all the other inconveniences - but because we have made it so through long and persistent work.