As I understand it, a gravitational singularity is a point where gravitational force is infinite and consequently time stops (from the viewpoint of any outside observer), light from a source at the singularity would become infinitely red-shifted after traveling zero distance (in other words light couldn't leave the singularity), escape velocity is infinite, and tidal forces are infinite. I don't think any of these effects can occur anywhere by itself, without the other effects. You can't have stopped time without also having infinite tidal forces. If the speed of light "appears" to approach zero, that really means c is constant but time dilation is approaching infinity, which means tidal forces are approaching infinity, which means an object approaching that point would be torn apart (in any reference frame, although different reference frames would disagree on where that point is located on their coordinate axes.)(adsbygoogle = window.adsbygoogle || []).push({});

I have read in many places that the only physical singularity is at the center of a black hole. The singularity at the Schwarzschild radius is only a mathematical singularity due to the choice of coordinate system. In other words, in the Schwarzschild metric from a stationary frame, the physical singularity "appears" to be at the Schwarzschild radius, but it's actually at the center. In the stationary reference frame, the event horizon is like a goldfish bowl that makes the singularity/fish at the center look like it's on the outside of the bowl.

When a free-falling observer passes the Schwarzschild radius, he is not passing a physical singularity. So, he is not torn apart by infinite tidal forces. If he looks back, he does not see the universe blue-shift to infinity. He does see finite blue-shifting behind him as he approaches the singularity, but he will see no infinite blue-shift until he actually reaches the singularity. If, just short of the singularity (but well inside the Schwarzschild radius), he turns on his retro-rockets with thrust equal to the gravitational force at that point, then he will shift back to the stationary frame and he will see himself hovering just outside the Schwarzschild radiius instead of just outside the singularity. But, when he was free-falling toward the singularity, he observed a huge but finite blue-shifted time interval behind him. Now that he's back in the stationary frame, he still see that same amount of blue-shift behind him - he still sees that the universe behind him has aged enormously (but not infinitely). From the stationary frame, he expains all this as the effect of being very close the event horizon.

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# There is only one True Singularity and It is at the Center

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