Curtis: He thought there were many galaxies, 10,000 pc across each, with the Sun at the centre and that nebulae were separate from the Milky Way
Both: Shapley was right about the Sun being away from the centre of our galaxy, but Curtis was right about the multiple galaxies and that the nebulae were far away from the Milky Way
Shapley: He believed there was one galaxy, 100,000 pc across, with the Sun away from the centre, and that nebulae were part of the Milky Way
Neither
7. The parallax angle of a star is...
half the angle that a star moves in nine months, against a background of very distant stars
...half the angle that a star moves in six months, against a background of very distant stars
half the angle that a star moves in three months, against a background of very distant stars
...quarter the angle that a star moves in six months, against a background of very distant stars
