Question

clarify why parallax just works for stars that r less than 200 light years away.

It is because of the smaller angles involved in the greater distances, which cause to many observation errors for calculations to be valid.

Please correct me if I'm wrong, thanks

Answer 1

You are 100% correct...I think...

Answer 2

you are correct. The errors are inherent in any observation, but at small angles, those tiny errors in the calculations are the major factor.

Picture your mom 10 feet away, then 10,000 feet away. Think you could see if her eyes were looking at you at that distance? No, the error in your resolution would be greater then the size of her eye ball.

Answer 3

thanks bobpursely, I really like your example:-)