Perhaps information doesn't get stuck to the surface, but instead is left behind in some sort of crunchy nugget just as the black hole finishes evaporating. While this would rescue all of known physics, nobody has been able to find a satisfactory way to actually, you know, make this happen. Maybe Hawking's original analysis was too simple, and by careful observations of the radiation we could painstakingly reconstruct the books and cats and spaceships that fell in. Maybe somehow the information stuck to the surface of the black hole does end up threading its way into the emitted radiation.
The black hole cracked#
Or maybe Hawking radiation isn't all it's cracked up to be. And black holes are the only places where we've run into trouble with this whole information-preserving thing, so is it really worth reinventing all our physical knowledge just to accommodate this one special case? And yet, we've had to rewrite all of physics before, so it's not like it would be the first time, and black holes are very compelling objects. Although this may seem like a simple statement, it involves rewriting almost all known physics. Maybe, for example, information is preserved after all. We don't have a resolution to the black hole information paradox, but that hasn't stopped starry-eyed theorists from dreaming up a host of potential solutions over the decades. So if the information didn't leak out with the Hawking radiation, and the black hole goes away, what happened to all the information? which means it eventually disappears, along with all the information it was carrying. But as the black hole produces Hawking radiation, it loses energy, which means it loses mass. Which is fine and dandy the information on the surface is still there, minding its own business. Nothing else: No matter what you throw into a black hole, from books to cats to spaceships, its Hawking radiation will stay the same. That means that the amount and temperature of the radiation emitted depends only on the mass, spin and charge of the black hole. It’s just random heat, just like your body gives off. What's more, this conveniently named Hawking radiation is completely thermal. That situation isn't that big of a deal for information, which is neither created nor destroyed.Įxcept when the black hole evaporates, which creates a tiny problem.Īs Stephen Hawking first discovered in the 1970s, black holes aren't entirely black. From the point of view of an external observer (i.e., us watching safely from a distance), nothing ever falls into a black hole - it just gets pasted onto the surface (of course it’s a little more complicated than that, but that’s enough to understand the current dilemma). Stuff falls into black holes, along with their information. Thus the raw information of the system - everything there is to know about it - is preserved across time it just gets rearranged, not created or destroyed.Īt first glance black holes seem to treat information innocently enough. If I know everything there is to know about a system - the positions and velocities of all the particles, their spins and electric charges, and all the other stuff - then the laws of physics tell me how all those particles will behave past and future.
It's this reversibility that allows us to make the leap that information is preserved. If we know all there is to know about a system, then the same laws of physics that extend into the future also extend into the past - we can run the clock forward or backward, seeing how that system has behaved or will behave with equal ease. Whether it's a particle sitting in a box or a complex chemical reaction or the whole entire universe, our knowledge of physics allows us to make firm, reliable predictions that take our knowledge from the present into the future.Īnd that same technique allows us to dig into the past. That's kind of the entire point of physics. Physics is ruled by determinism: we can use the laws of physics to predict the future behavior of a system. First, we need to decide what we mean by "information" and why it ought to be preserved.
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