[Disco King]

Originally Posted by redbreegull

ah, I understand now. Yeah man I have no fucking conception. Kind of interesting to think about what would a star collapsing into a black hole look like? Theoretically, should not the same principal be true, that once the singularity is "open" we can never see the rest of the supernova or whatever travel inside, just freeze statically around it? Yet black holes are only detectable by their gravity, so clearly we can't see the light of collapsing supernovas forever trapped around them, or the light of victim stars frozen for eternity around the singularity. Or can this be explained by redshift?

Yeah, the only thing I can think of is that all black holes we detect have their mass hovering just outside the event horizon rather than inside of it, but an object like that looks indistinguishable from an actual black hole, because everything is so redshifted that we can't see it, so it looks black either way.

The only thing I can think of that would complicate things is the idea that "a black hole has no hair," which is a metaphor for the idea that information "disappears" in a black hole, and the only information that describes the state of a black hole is mass. I think they mean by this that it doesn't matter what falls in, the sort of things that fall in have no effect on what the black hole will be like. Only the mass, spin, and charge matter, and only the mass, spin, and charge describe it. But, if all the stuff hasn't really fallen in yet, it would seem to me that, in principle, the surface would have the contours of everything just outside of it, and the information wouldn't be lost yet, so it would have "hair." A black hole that swallowed a potato would be distinguishable from a black hole of equal mass that swallowed an apple. I dunno, though.

Originally Posted by redbreegull

I believe that this is the case, that there is a known equation relating the way light bends around an object in front of it to the gravity exerted by said object. I'm certain this is how probably black holes are identified anyway. I know mass can be discerned by measuring how different objects act on each other with gravity as well, such as why we think there is missing matter in the solar system. I'm not sure, but I don't think this can be applied to something light years away... I mean the solar system thing requires a pretty intimate knowledge of the exact mass of the planets and all the moons, asteroids, etc.

I think that we only know the masses of other objects in our own solar system through Kepler's Laws, as well. I think this this article explains how the masses of celestial bodies are found.

http://www.stronggravity.eu/how-to-m...ack-hole-mass/

They could use gravitational lensing (bending of light) as well, I don't see why not.

Originally Posted by redbreegull

I think string theory has fallen out of favor. But the idea that our universe is a projection from a 2D surface like the "eye" of a black hole is increasingly popular. One possibility is that our universe is like a sheet of paper, and there are infinite other universes stacked around us, also flat. One thing I read asserted that the next dimension could in literal terms be a fraction of a millimeter away from us but we are unable to detect it or go there because we are actually living on a flat plane.

I think that some scientists like Peter Woit and Neil DeGrasse Tyson have criticized string theory for it's inability to produce testable hypotheses. I remember watching one Tyson video where he is sort of making fun of a string theorist, and comparing how quickly the formulations of relativity and quantum mechanics became progressive and produced results to how string theory is yet to be confirmed by evidence yet.

From what I got from Hawking's A Brief History of Time, string theories came about to try to harmonize relativity and QM and get rid of the bizarre infinities that the combination of the two theories produces. The last attempt to do this, supergravity, fell apart, so string theory became the only game in town. I think that string theory is mostly conjecture that plugs in values, not because they are deduced from theory, but because they conform with already-existing observations. I think that it posits other dimensions to explain why gravity is much weaker than other fundamental forces. Like, gravity works in more dimensions or something. But there's the issue of the fact that orbits would be unstable and would not look like what they are observed to look like if there were more dimensions, so they conjecture that these dimensions are "small" and "curled up." I have no idea what that even means, though (I just think of a dimension as a direction perpendicular to other directions... so how can it have a "size" or be curled?). From what I get, it's mostly brute-force math to get things to make sense and conform to what we already know and harmonize things, but doesn't yet have any testable implications. Karl Popper would probably hesitate to call it a "theory," but I dunno, scientists are smarter than me, so even though it doesn't seem falsifiable, it seems to me that scientists have good reasons for pursuing it if they are. Maybe one day, technology will catch up to the point where we can actually test string theory, so working out the math doesn't seem a bad idea.

The idea of multiple universes "stacked" is pretty cool. Like, there is another dimension perpendicular to the ones we know that we just can't access, because we're flatlanders. I remember Michio Kaku once saying that dark matter could be gravity from adjacent universes interacting with our own.

Geek time: Earlier this year, DC Comics released a miniseries called "The Multiversity." It was this Grant Morrison story that was the standard DC Crisis "characters from different universes team up to save the multiverse" fare, but because it was Grant Morrison, it was a bit more than that, and used cool spacey ideas and post-modern techniques to sort of play with the conventions of comic-book story-telling. Before the comic was released, they released a "map of the Multiverse," which shows each of the 52 universes like this combination of an atomic diagram and those old-school celestial maps.

Originally Posted by Elphenor

Do we know anything about other dimensions other than guessing that they could exist?

We can't observe other dimensions, but string theories posit 10, 11, or 26 dimensions, depending on the theory. Other theories probably posit extra dimensions, too. But for now, we can't verify these through evidence, and they are just a consequences of the theories.