# What if our galaxy didn't have a SMBH?

From my understanding, it is believed that almost every big galaxy and especially spiral galaxies have supermassive black holes (SMBH's) at the center. Also, from what I've read, a SMBH isn't required for a galaxy to exist since and in layman's terms, the matter inside a galaxy such it gas clouds and formation of stars will keep it gravitational-ly in check.

If I am right or even wrong, then would there be significant difference if our galaxy did not have a SMBH at the center? Significant enough for noticeable differences even here on Earth?

The supermassive black hole (SMBH) in the center of the Milky Way (MW) — called Sgr A* [Sagittarius A-star] — has no direct impact on our galaxy. Its mass is only a few million Solar masses, and if you remove it$^\dagger$, it will only affect the most central stars, which would suddenly continue in straight paths out through the MW. These stars would almost surely not hit any other stars or something like that (since stars are really, really far apart), but some of them have velocities high enough that they may escape the MW.
$^{^\dagger}$Removing Milky Way's SMBH is left as an exercise for the reader.