Anthony Aguirre - What happens in Black Holes?

Anthony I've been fascinated about the universe for as long as I can remember and when I first heard about black holes it seemed incredible and the more I've talked to my physicist friends the more it becomes this laboratory for testing quantum mechanics and general relativity and quantum gravity without ever doing any experiments on that black holes because not only are they far away but they're being possible if we were we were there so there's a theoretical experiments that you do how does that work and what are you discovering when you think about black holes they're kind of a ultimate manifestation of some of the most interesting parts of Einstein's theory of general relativity so people think of Einstein theory of gravity as a theory of gravity which of course it is but almost more fundamentally it's a theory of causal connections it's a theory of what events what happenings can be observed by what other regions of space-time and which ones can't and the sort of fundamental entity in in general relativity is the metric that tells you how what the space-time distances between things but it also tells you the causal relation that tells you you know if I it's not my fingers here somebody over in the Andromeda galaxy can cannot know about that you know for a long time no nothing that I do here can affect the Andromeda galaxy for millions of years so it's a theory of those causal relations which are fairly simple in our day to day life even even if we go to high speeds we have to use Einstein's special relativity but they get really complex when gravitational fields get really strong and when we try to do physics we realize that well we have to think really carefully about what it is that we mean of this is the physical system that we're measuring you're looking at what is the information that we can and can't get from it what where are the fields that we're using to probe this thing going and what can we say and what can't we say about them and black holes are a really ultimately this because they're there this one-way barrier where there's a sense in which in principle once something some events happen on the other side of that barrier they can't affect you and not only that but that barrier stays there so what I mean by that barrier stays there is if I just take you know some region of space-time say the this interesting jungle area that we're sitting in I can say here's the state of that jungle area and I can predict what's going to happen if I knew all the data and I knew all the laws of physics I could predict what's going to happen here sort of because I could predict it but it could be that there's some really high energy particle flying in from the Andromeda galaxy at the speed of light that's just going to smack us in one second there's no way I could know anything about that because I my data doesn't cover the Andromeda galaxy so there's a there's a causal limit to how much data I can gather and that only allows me to predict with certainty what's going to happen for a short amount of time if I want to predict for longer I need a bigger initial surface so that's a limit to what you can measure and predict that's given just by this finite speed of light now a black hole is kind of like that you that it's a barrier that you that sort of is a limit to what you can know about and predict but it's not one like like the one here that changes with time it's one that just sits there so the black hole just sits there and you can never get that information whereas in here if we wait long enough we'll get farther and farther more and more information so I think that black holes are most fascinating because they give us a fairly unique setting where these deep questions to prove general relativity and how it plays with quantum mechanics and how it plays with field theory really are sort of in their strongest form and in a system that's beautifully simple to understand if you try to make some calculation even about the Earth's gravitational field that it's pretty hard people can do it and they do it to make the GPS satellites work even in general relativity but a a black hole is a theoretical entity is beautifully simple you can you can write down the complete description of it and one little one little equation and you can teach it to your undergraduates and they get it so it has the the as a laboratory black holes have this advantage that they're both incredibly subtle and incredibly sophisticated in terms of the physics is goes into them but mathematically relatively simple intractable okay so what is some of the work that you've done recently in terms of understanding some of the paradoxes or the problems with black holes one of the things I've I'm coming to believe more and more is that although black holes are really neat they're not actually all that's special in the sense that what they really are is their region of the universe that we don't need to know about in order to make some predictions about the rest of the universe so just like I don't need to know about the Andromeda galaxy to know the predictions of what happens here in the next five minutes I never need to know what's inside of a black hole so there's a sense that they're a boundary to the region that we have to know about in order to make full predictions so that boundary could be in you know one that we just decide on by how much data we've taken or it could be a more permanent one in the black hole or it could be in an inflationary universe there's the cosmological horizon which is such a boundary so I think there are boundaries that we imposed by the problem that we have chosen that the calculation that we want to do we create these boundaries and black hole horizons cosmological horizons other horizons those are special cases of those boundaries that we choose and a lot of the confusion I think that has arisen in a lot in many black hole questions like the information loss paradox has come from simply not being careful about saying this is the system that we're going to study carefully looking at what that relativistic system is or this is the system we're going to study and carefully looking at that one but using them both at once interchangeably uncharitable and there's an idea that's fairly old called black hole complementarity which is one version of that argument but I think it's a more general one that there that we methodologically and this is something I've been thinking a lot about lately methodologically need to once we carefully define what the system is and think about the limits of how to measure that system we can make a unified view of the different types of horizons in a way that I think is going to untangle some of these horrible conundrums that have been arising

Channel: Closer To Truth

Views: 8,467

Rating: 4.7823129 out of 5

Keywords: Anthony Aguirre, Closer To Truth, Universe, Black Holes, Cosmology, Cosmos, Interstellar, Space, Physics, Astrophysics

Id: dru1U4PtDeE

Length: 7min 3sec (423 seconds)

Published: Tue Oct 18 2016