Unveiling the first-ever image of a black hole [video]

Post by wallace_f » Sat, Apr 13, 2019, 12:11 PM UTC

khamoud wrote: post #412

wallace_f wrote: post #339

Earlier quoted context omitted.

That's also not even wrong. You can't see why? Let's say we're imagining what Uranus would look like. I draw a picture, and say it should look like a "fuzzy Jupter." But you ask, why should it look that way? Do you have a reason? And I say you should be confident, but don't provide an argument. By the end, I start talking about how it might look like Saturn. Then I come along and say, "it should be obvious the fuzzin…

He isn't explaining why the blackhole would look like a fuzzy coffee mug stain. He's explaining why the _picture_ of the blackhole will look like a fuzzy coffee mug stain. To your point, it's like taking a picture of Uranus with film and waiting for it to develop. People familiar with the matter can guess what the _image_ will look like not what Uranus actually looks like. This is all very clear in the first 25 secon…

Post by lostmsu » Tue, Apr 16, 2019, 3:35 PM UTC

codethief wrote: post #482

codethief wrote: post #428

Earlier quoted context omitted.

Could you elaborate on your definition of volume here (are you talking about spatial volume or spacetime volume?) and how the curvature going to infinity at the singularity should imply its infiniteness? My thought process here is the following: The inside of an (eternal) black hole carries four (Schwarzschild) coordinates t, r, theta, phi – r now being time like and confined to the interval (0, 2M) and t now being s…

I should add: 1. In the interior of the BH, the determinant of the metric is bounded since the Schwarzschild factors in the metric cancel out. So the volume measure doesn't do anything crazy as one gets closer to the singularity and boundedness of coordinates implies boundedness of the volume. Again, I'm disregarding the spacelike t coordinate because to me the relevant fact is that all matter reaches the singularity…

Post by lostmsu » Sat, Apr 27, 2019, 7:17 PM UTC

lostmsu wrote: post #523

codethief wrote: post #482

Earlier quoted context omitted.

I should add: 1. In the interior of the BH, the determinant of the metric is bounded since the Schwarzschild factors in the metric cancel out. So the volume measure doesn't do anything crazy as one gets closer to the singularity and boundedness of coordinates implies boundedness of the volume. Again, I'm disregarding the spacelike t coordinate because to me the relevant fact is that all matter reaches the singularity…

Unfortunately, I am not strong on mathematical part of GR, so feel free to disregard the rest of this idea, if math's the sole thing you are looking for. A thought experiment: imagine we have a clock, falling into Schwarzschild black hole. Obviously, any real clock would have some non-zero size in all space dimensions. Here we will be concerned with just two: r and any orthogonal one. So for simplicity let the clock…