This week, Stephen Hawking launched a new research initiative into black holes, working with the Harvard-Smithsonian Center for Astrophysics to learn more about what are increasingly strange celestial phenomena. And he said something that got people overly excited, namely that “Things can get out of a black hole, both from the outside and possibly through another universe.” But what does that mean, precisely?
Taken out of context of Hawking’s lecture, it sounds like he’s claiming we’re about to see visits from an alternate reality, but that’s not quite the case. As we’ve all been told, not even light can escape a black hole, except, well, Hawking proved that wasn’t entirely true in 1974, by discovering Hawking radiation. And recently Hawking and his Harvard counterpart Andrew Strominger have theorized that black holes have “hair”, long strings of zero energy particles that might tell us what fell into a black hole over time. But what about the stuff that falls into a black hole itself?
Every particle, in physics, has “information,” or, basically, the stuff that makes it distinct. This is especially important in quantum physics where two seemingly distinct and separate particles can act on each other, even at a great distance. So what happens when one of those particles is sucked into a black hole? Where does the information go? Does it still act on its counterpart?
That’s a bigger deal than you might think, because science is built on determinism; you gather information and use that information to build a conclusion. That is potentially impossible to do in a black hole, and as Hawking points out, that has some troubling implications. If determinism can break down in black holes, it might break down elsewhere. Imagine for a moment the idea that history and our memories are just illusions, and that what we know to be true based on what we’ve learned might cease to exist in a moment. Trust us, Hawking finds that just as terrifying as you do.
Which brings us to the comment about “things from another universe.” What Hawking is saying is that the particles that fall in might go to another universe, their information preserved, just not accessible to us. That would preserve determinism, although it raises the interesting question of whether that’s a two way street and particles from other realities are filtering into our universe. That said, there are other possibilities; perhaps those particles become holograms, for example.
So, don’t worry, a ship from an alternate reality where the Nazis won is not going to come flying through a black hole to our universe any time soon. What to take away from this is that we have so much more to discover about the universe we live in, and the more we learn, the more wondrous it becomes.