How math tells us that something exists in outer space ?

Question

I was watching a video about black holes, and when they mentioned that Einstein proved black holes exist with maths, it hit me.
I’ve never asked myself that question, how do numbers tell you that something exist in outer space and what to expect from it? especially things that we never knew they existed in the first place (exp black/white holes) ?

In: 407

Answer 1

Ancient pacific islanders could tell that there were landmasses beyond the horizon by patterns in currents. This is similar. Black holes have gravitational effects that can be noticed.