how do astronomers know about the future collision of andromeda and the milky way?

Question

a. the milky way has changed course to head toward andromeda
b. all galaxies will collide at some point
c. astronomers have observed their movements over time
d. the two galaxies have collided previously

Answer 1

The correct answer is:

c. astronomers have observed their movements over time.

Astronomers have been able to track the movements and velocities of both the Milky Way and Andromeda galaxies using various observational techniques, including measurements from telescopes and space missions. By analyzing this data, they can predict that these two galaxies are on a collision course that will occur in about 4.5 billion years.