First, a light year isn’t a measure of time, but of distance. It would take tens or hundreds of thousands of years to get a spacecraft outside the galaxy, in order to see the entirety of it at once. We don’t have the technology to get a spacecraft even close to the speed of light in a vacuum (c). The closest star to our Solar System is Proxima Centauri, which is four light years away. That means that light (or other EM radiation) would take four years to reach Proxima, or vice-versa. However, if Voyager 1, which is moving pretty fast, were headed towards Proxima (which it isn’t), it would take forty thousand years to reach that star. Point is, we don’t have the technology to accelerate a spacecraft even close to c. But we HAVE been to the Moon, with both crewed and uncrewed spacecraft. We currently have spacecraft in lunar orbit, carefully mapping the surface in detail. We’ve even seen the six landing sites, and have observed the descent stages of the six missions that landed there 50 years ago. I remember watching the later missions, which had lunar rovers (Apollo 15, 16, and 17) which had a television camera attached to the rover, which allowed those astronauts to cover much more ground than Apollo 11. The suits had been upgraded also, allowing EVAs of several hours in length, giving the astronauts much more time to explore, and cover much more ground. They also had three EVAs, so they were on the lunar surface much longer than the crew of Apollo 11. NASA pushed the boundary with each successive mission. And the current satellites orbiting the Moon have good enough resolution to even detect the tracks of the rovers, and even observe the rovers themselves, which were abandoned on the surface. Finally, astronomers can use other methods of observing our galaxy than by trying to send a probe outside the galaxy. We can see a good part of the disk, even with the naked eye, if you are lucky enough to live in an area with little light pollution. And astronomers can, and have observed many other galaxies, and thus can categorize the various types of galaxies, and then try to categorize our own galaxy. It is believed to be a barred spiral galaxy, the second largest in our Local Group of nearby galaxies. Andromeda is the largest, thought to be twice our own mass and size. We also can penetrate the dust that obscures much of our galaxy, by observing using other parts of the electromagnetic (EM) spectrum than visible light. We have many different kinds of telescopes in space that observe every part of the spectrum from gamma rays, X-rays, ultraviolet, infrared (that’s the part of the spectrum that the James Webb Space Telescope observes), and radio. Using other parts of the em spectrum, we have observed the center of our galaxy, including the supermassive black hole at or near the center. Dust clouds obscures much visible light, but not infrared, or other parts of the EM spectrum. As the technology improves, so will our ability to observe our own Milky Way. It’s important to remember that most of the galaxy is empty space.

Actually I don’t think the distance is really changing that much, especially over a period of 500 years. The changes in estimates of the distance between our solar system and the center of the Milky Way are much more likely be due to steadily improving technology, and improved telescopes. A pair of good binoculars are likely better than Galileo’s telescope. We are also able to launch various telescopes into orbit, something only achievable for less than 100 years. We also now have the capability to observe other types of electromagnetic (EM) radiation than visible light. We’ve got gamma ray observatories, X-ray, ultraviolet, infrared, and radio. That capability allows us to observe the center of our own galaxy, for the dust clouds which obscures much visible light telescopes, don’t block all other parts of the EM spectrum. We have observed the supermassive black hole at the center of the Milky Way (it’s dubbed Sagittarius A). All of this improved technology allows for more accurate measurements.

Made in china... untrust worthy.

It could change hands several times. It could be repacked more than twice and they don't have to precise how exactly, it just erases what's been before.