# Planets collapsing into black holes?

Lamdbaenergy
If you had a planet with the exact same mass and radius as the Earth, and adjusted the gravity constant to some value five-hundred million times larger, the schwarzschild radius should become considerably big, right? Instead of being about 8 millimeters, it would now be about 60 to 70 percent the radius of the body itself. So would this cause the planet to start collapsing immediately, and just how strong would the gravity have to be to cause the surface of the planet to start falling in on itself?
Also, what does GM/c2 mean compared to 2GM/c2?

I totally know that changing the gravity constant is impossible, let alone to that ridiculously high value.

Staff Emeritus
Yes, if you plug in a different and unphysical value for G, you get a different and unphysical value for R.

Also, what does GM/c2 mean compared to 2GM/c2?

It's half as big. (I think we're missing some context here)

Lamdbaenergy
Yes, if you plug in a different and unphysical value for G, you get a different and unphysical value for R.

It's half as big. (I think we're missing some context here)

Why does the schwarzschild radius have to be twice as big as GM/c2? Is GM/c2 another special kind of radius that is always half the length of the schwarzschild radius? Thanks.

Staff Emeritus