It makes no sense to me that we know where we are in the Milky Way
Milky way is what we named our galaxy so how ever it looks its still a galaxy and we call it milky way if you are having a hard time understanding this take this example conversation
"Hey john"
"Yes!"
"how do you know you're john"
"because that's what people named me and more importantly that's what people call me"
we know its a spiral but yet we haven't had a spacecraft venture out of the galaxy?!
It is actually a rather complicated deductive exercise using lots of data in radio astronomy and other fields. The most compelling reason is based on a very simple observation.
This image was taken with the Kuiper Airborne Observatory in the direction of the constellation Sagittarius. I can't post the most common view that you get of the Milky Way because that kind of picture, taken by a simple camera pointed up at the sky, is usually copyrighted.
Recently, astronomers using the 2MASS infrared sky survey imaged the entire sky, and put together this dramatic image of the complete Milky Way
This is the galaxy NGC 4565 taken by Dr. Crowe and his summer students at the University of Hawaii. Note, the Milky Way image was taken from INSIDE our galaxy. We cannot travel outside our galaxy to see what it really looks like because the distance (over 100,000 light years) is too far to travel.
Detailed studies of the motions of interstellar gas clouds fills in this picture considerably by letting us plot the locations and speeds of these clouds, and in most versions of these studies, a distinct spiral pattern emerges like the sketch
This map is one of the first made by astronomers when they began to map the locations of major neutral Hydrogen clouds using radio telescopes. By knowing how a spiral galaxy rotates (following the laws of Kepler) you can relate the velocity of a cloud and the direction of detection to a specific location in this map. Many such maps have been created using different spiral arm tracers (HII regions, molecular clouds etc) and the results are pretty consistent.
TL:DR we map the stars and gas & hydrogen clouds and use mathematical laws that we know work because they have been proven by observations on other galaxies , them we use existing data of our galaxy and create a map
