7
votes
3answers
235 views

Parallax, obliquity, precession, and Orion?

Today, the obliquity of the earth is about 23.4°. 6500 years ago, it was about 24.1° Imagine the blue square is the constellation of Orion, and the yellow star is the sun. Viewpoint B is you, on ...
0
votes
1answer
91 views

Other than the motion of the Earth, what else would cause parallax?

Wikipedia has this to say about the discovery of the aberration of light: In 1728, while unsuccessfully attempting to measure the parallax of Eltanin, James Bradley discovered the aberration of ...
5
votes
1answer
381 views

When and how were relative distances to the planets first measured?

I understand that the absolute distance to a planet can be measured using earth-baseline (e.g., diurnal) parallax, and that the first reasonably accurate such measurement was made for Mars by Cassini ...