So how do we know?

Firblog

The size of the milky way

The shape of the milky way

Our location within the milky way

Brought on when I read that voyager 1 is nearly 1 light day away from earth - after 47 years, a huge distance but a mere smidgen relatively speaking, Its like you've figured out what shape the pentagon building is, your location within it, and you've only been able to take a single step in the room where you've always been inside it..

If it's mad maths that's used just say that, and I'll shake me head and mutter about mad genius mathematicians and how the f they figure that sh*t out.

endacl

Mad Maths. All of it.

LambshankRedemption

Interesting article here:

https://www.astronomy.com/science/how-we-learned-the-shape-of-the-milky-way/

You might be surprised to learn that ireland plays a part in the mad maths.