Dear PF Forum, I have a question about the size of "singularity" This question has already been asked here, Question about Schwarzschild radius But what I want to know is this density thing that I'd like a confirmation. Actually it's 2.9511896078372906 KM according to his http://hyperphysics.phy-astr.gsu.edu/hbase/astro/blkhol.html 1. But what if it were squeezed to 3.1 KM, the "sun" radius is still 3.1KM, right. It's density will be 18400 trillion of water. Can we, theortically, "measure" the sun with a ruler if it's radius is 3.1KM? Once it goes below 2.951 KM, it's radius will be 0 KM, singularity. Is that right? 2. Still according to Schwarzschild calculator, for an object (star? nebulae?) 1 G solar mass it's Scharwzshild radius is 2.95E9 KM. It's density is 1.84 percent that of water. Did I make a mistake in my calculation? If that objects is squeezed to 2.94E9, will it disappear and become a black hole? 3. Still using that calculator above. According to Wikipedia The universe mass is 1E53Kg So it's Schwarzshild radius is 1.48E26 metres. Dividing it by seconds/minutes/hours/days/years I find this: 15.6 billion light years. And our universe is 13.6 billion years old. So?? Are we living in a black hole? If the question number 1 and 2 are true, about "squeezing object below it's Schwarzshild radius", why aren't we squeezed into a singularity? Did I make a mistake in my calculation, again? 4. Is it possible for a very massive object below it's schwarzshild radius, but doesn't become a black hole? Doesn't become a singularity? Thanks for any explanation.