Question

How do we measure distance in space?

Answer 1

Around our Solar System, and in our neighborhood of the galaxy, astronomers use trigonometry to discover the distance to objects. They measure the location of a star in the sky at one point of the year, and then measure again 6 months later when the Earth is on the opposite side of the Solar System.
To measure distances in the universe, it is need to construct what is commonly referred to as a "cosmic distance ladder.