How do we know the shape of the Milky Way if we are in it?

The challenge of discerning the shape of our Milky Way, while residing within it, is akin to a person tethered to a tree in a vast forest trying to fathom the forest's entirety. Yet, our understanding has evolved through scientific and technological progress. In 1785, William Herschel's pioneering attempt to map the galaxy, though flawed, marked the first step. Until the early 20th century, the Milky Way was thought to be the entire Universe, until Edwin Hubble's revelation transformed our cosmic perspective.

Modern classification identifies galaxies into elliptical, spiral, and irregular types. Observations of the Milky Way's strip-like appearance suggest a spiral shape. Space telescopes like Gaia contribute to our understanding, providing detailed maps and revealing the rotation of our Galaxy.

Harlow Shapley's study of globular clusters offered insight into our solar system's position, situating it in the galaxy's periphery. Advances in radio astronomy and infrared observations unveiled hidden features, including a supermassive black hole at the galactic center. Research on spiral arms, initially contentious, now indicates four major arms.

The galaxy's intricacies persist, with rotation curves challenging Kepler's dynamics and proposing dark matter's existence. Technological advancements continually refine our perception of the Milky Way, exemplified by the European Space Agency's Gaia telescope. As we unravel these celestial mysteries, our journey within the Milky Way unveils the vastness and complexity of our cosmic home.

links to the videos I used as background:
1)   • Journey to the Center of the Milky Wa...  
2)    • 1 Hour of Exploring the Universe + Re...  
3)    • Big Bang Animation/Simulation  
4)    • Animation of a variable star  
5)   • Zooming in on the heart of the Milky Way  
6)    • Black hole live wallpaper  
7)   • the rotation of our milky way galaxy ...