The Information Paradox of Black Holes

[Jingleheimer]

While not knowing their motivations for postulating parallel universes, it's not like this is a new notion in physics that they are pulling out of their asses. Search for 'many worlds' or Bell's Theorem. There are some paradoxes and implications of quantum mechanics that mant people hypothesize parallel universes to help explain.

Sort of weird, but not necessarily more implausible than other aspects of quantum mechanics!

[Borodog]

yes; in the absence of non-conservative forces, you do indeed get "perpetual motion". That's why the moon doesn't crash into the earth.

[Borodog]

PS. Missed the bit where you were talking about tidal forces. Clearly my simple analysis neglected such effects.

[MrWookie]

All,

The Many-Worlds Interpretation has been around for a while now, although this may be a novel application of the hypothesis. The theory was developed as an alternative to the idea of wave function collapse. This is probably best explained in the context of Schroedinger's cat, which is probably the best-understood example quantum system by the folk here. So, "everyone" knows that in our special radioactive booby-trap box, the cat is in a superposition state where it is both dead and alive. This superposition of states is described by its wave function. Then, when we open the box the wave function "collapses" into one of the two available states: dead or alive. The actual state of the cat, then, is intimately tied to the presence or absence of an observer. This is a hard concept to grasp, but it's the most familiar interpretation of the oddities of quantum mechanics. Still, the question of why physics should depend on an observer is a tough one, and accepting it as fact is not easy for many to do. The old question of, "If a tree falls in a forest, and there's no one there to hear it, does it make a sound?" is really easy to answer in a classical mindset: it clearly makes a sound. I suppose you could stubbornly debate about how it's not actually a sound until is registered by our brains, but the tree clearly sends out sound waves whether or not someone is listening. The physics is the same no matter who's around. In the wave function collapse world, the question about our tree is not so easy to answer. The presence of the observer plays a direct role in what we observe.

This is where the many-worlds hypothesis comes in. One of its main goals and strengths as a theory is to remove the observer dependence from physics. In this explanation, rather than a wave function collapsing due to the presence of an observer, we have two parallel universes, one in which the cat is alive, and one in which it is dead. This removes the problem of the observer changing the physics: there's a dead cat universe and a living cat universe whether or not anyone is looking. However, it then creates the problem of, well, many universes.

[TheWorstPlayer]

[ QUOTE ]
However, it then creates the problem of, well, many universes.

[/ QUOTE ]
Ya. The many universes answer has always seemed like the most idiotic thing ever. No matter what problem you're trying to avoid, can it possibly be worse than the supposition that there are many (infinite?) universes?

Like if I say, "There must be a God because otherwise Plank's constant couldn't have been exactly as it is and if it were different the universe wouldn't hold together." and you answer "you have no evidence for a God! It is unreasonable to believe something outlandish with no evidence! Instead, I believe that there are infinite universes and that therefore Plank's constant is what it is in this universe by pure chance, because it takes all values throughout the infinite universes." Does that sound any more reasonable to anyone? And yet people argue this type of thing all the time. I'm sure I'm just misunderstanding it, but I've tried to understand it and apparently cannot.

[MrMon]

[ QUOTE ]
Mon,

Same difference. I just can't fully grasp the prospect of figuring out some stuff regarding something I am working on and then thinking, hmmmm that all seems to add up, but something just isn't right, I must be missing something. Oh, wait, I get it now, I neglected to factor in the possibility of parallel universes, that's it!

[/ QUOTE ]

Well, you just need to work on bigger problems. [img]/images/graemlins/grin.gif[/img]

Actually, you probably do see this effect in the problems you solve, it's just not something as grand as parallel universes. Suppose you're working on your kitchen and you want to install some cabinets. You want to install them so that the bottom is 60" off the floor. You measure from the floor to the bottom of the cabinets, but when you get done, the cabinets don't look like they're in a straight line, they look tilted. You measure again, making sure you didn't measure wrong, but find out that the are all 60" above the floor beneath them. Then you measure the floor and find out it's not level, which is why they look tilted. They ARE tilted, you just never noticed before that the entire house is tilted. Which means calling out the piering guys to untilt your house.

So the question is, would you have been better off never installing the cabinets? After all, you were perfectly happy before you installed the cabinets, living in ignorance of your homes tilt. But the house was tilted anyway, it was solving the tilted cabinet problem that allowed you to discover a more fundamental flaw in the entire structure. Now just scale up to black holes and parallel universes.

[Dilznoofus]

[ QUOTE ]
[ QUOTE ]
[ QUOTE ]
This shook up the scientific community because it goes against one of the basic tenets of physics: information does not just "go away." The particles of the universe will always remain, no matter what form they take.


[/ QUOTE ]

No it didn't "shake up" anything. It was seen as a problem with the current working theory, that something was certainly amiss and needed more work to clear up. In general the basic Standard Model + General Relativity model of the universe is incredibly accurate for almost every phenomenon in the universe; there are however a few very extreme cases where the physics isn't completely worked out and more work needs to be done.

[ QUOTE ]

If Hawking's equation is correct, then cause and effect is meaningless and the universe is basically chaos. Naturally, a lot of scientists do not feel this could be true even while agreeing that Hawking's equation is simply elegant.


[/ QUOTE ]

That's a preposterous conclusion. Even if black holes did do something bizarre to information (which they probably don't) that doesn't invalidate the physical laws across the universe.


In the real world, there has been a lot of work on the entropy (information content) of "quantum hair" on black holes. I'm not sure what the latest results are but there is no "paradox".

Certainly black holes are one of the cases where the difficulty of merging quantum field theory with gravity come into play. That doesn't invalidate either of those theories, we already know that they are only models which are accurate within certain domains.


ps. this is why non-scientists shouldn't be allowed to have opinions on scientific matters such as global warming, stem cell research, corn ethanol, evolution, or any of the other scientific issues that they completely misunderstand and make horrible policies about.

[/ QUOTE ]

I didn't make my own conclusions. The information you quoted is both from the TV special I watched, as well my doing a quick google research on The Information Paradox. I haven't made any assumptions, I'm just relaying information that I thought was interesting. I'd be even more interested in hearing pros and cons on them by someone who knows what they are talking about - like yourself, perhaps.

[/ QUOTE ]

cbloom almost never posts twice in the same thread, which kinda makes me think he doesn't read past his own posts. Makes it kinda pointless to respond to him.

[gumpzilla]

[ QUOTE ]

Right now, my main reaction is that I find it tough to grasp the idea that there are people actually spending their time seriously researching things like "parallel universes."

[/ QUOTE ]

This is inscrutable to many physicists, too.

[tomdemaine]

[ QUOTE ]
[ QUOTE ]
What he figured out from this is that information is not in fact lost in a black hole, rather, it is "spread" across the Event Horizon and does not "go away."

[/ QUOTE ]

It always struck me how obvious this was in retrospect. As you observe something approach the event horizon of a black hole, you observe time slow down for it. In fact, you never actually see the object cross the event horizon; rather, you see it approaching infinitely close as time slows down and stops just as it reaches the horizon; meanwhile the light from it is redshifted to infinite wavelength and it appears to disapper. But it should still be there; compressed into an infinitely thin layer on the surface of the black hole.

So the information is there, on the surface, and since nothing ever really reaches any infinitudes, it's still always theoretically accessible.

But I have to wonder what is wrong about my understanding of the subject. Since if I find it that "obvious" and Stephen [censored] Hawking disagreed for decades, well I must be [censored] wrong, right?

[/ QUOTE ]

Isn't this just a modern day zeno's paradox?

[burningyen]

[ QUOTE ]
I have a question. Let's say you drill a 4' diameter hole completely through the earth, directly through the center. We will assume the earth is a perfect sphere so we have an idea what "center" means. We will also assume no effect due to the missing mass lost by digging the hole, just in case that matters somehow. You jump in that hole. What happens?

[/ QUOTE ]
You'd have the ride of your life until the air pressure squashes you.