WEBVTT 00:00:00.000 --> 00:00:02.540 All right, so we've got two papers for you today. 00:00:02.899 --> 00:00:05.960 And get this, they're both by Albert Einstein 00:00:05.960 --> 00:00:10.259 from 1935, back in 1935. Two months apart. Yeah, 00:00:10.320 --> 00:00:12.660 two months apart. And the thing is, Einstein 00:00:12.660 --> 00:00:15.759 himself, he didn't actually connect the dots 00:00:15.759 --> 00:00:18.000 between them at all. Right. He really thought 00:00:18.000 --> 00:00:20.289 they were about. completely different things. 00:00:20.530 --> 00:00:22.850 Super worlds of physics, yeah. Exactly. One was 00:00:22.850 --> 00:00:24.690 all about quantum mechanics. That's the rule 00:00:24.690 --> 00:00:26.890 book for the super tiny, you know, the really, 00:00:26.910 --> 00:00:29.390 really small stuff. Right, the microscopic. Yeah, 00:00:29.410 --> 00:00:32.429 exactly. And then the other paper was tackling 00:00:32.429 --> 00:00:35.229 the huge scale of the universe, like gravity 00:00:35.229 --> 00:00:38.509 and space time itself. The realm of general relativity. 00:00:38.770 --> 00:00:40.789 Exactly, general relativity. And here's the kicker 00:00:40.789 --> 00:00:42.350 for you. And then this is what makes us so exciting. 00:00:43.150 --> 00:00:45.549 a bunch of scientists, now they're starting to 00:00:45.549 --> 00:00:47.090 think that these two papers, they're actually 00:00:47.090 --> 00:00:50.469 deeply connected. And that's kind of mind -blowing, 00:00:50.689 --> 00:00:53.009 right? Well, it is. It's really profound because 00:00:53.009 --> 00:00:57.369 it's hinting at this fundamental link between 00:00:57.369 --> 00:01:00.729 how the smallest bits of reality work and the 00:01:00.729 --> 00:01:02.929 grand structure of the entire universe. Yeah, 00:01:02.990 --> 00:01:04.989 it's like they're two sides of the same coin. 00:01:05.030 --> 00:01:07.189 That's a good way to put it. And that's what 00:01:07.189 --> 00:01:09.829 we're going to dive into today in this deep dive, 00:01:09.890 --> 00:01:12.650 just for you. Your express route. Exactly. It's 00:01:12.650 --> 00:01:15.250 like a shortcut to understanding this cutting 00:01:15.250 --> 00:01:18.909 edge area of physics. It really is. And to appreciate 00:01:18.909 --> 00:01:22.049 how we got here, it's helpful to think about 00:01:22.049 --> 00:01:25.769 the historical context for you. OK. For centuries, 00:01:26.370 --> 00:01:29.689 Newtonian physics reigned supreme. Yeah, the 00:01:29.689 --> 00:01:31.909 clockwork universe. Yeah, exactly. The idea was 00:01:31.909 --> 00:01:34.670 if you knew where everything was and how fast 00:01:34.670 --> 00:01:37.269 it was moving, you could predict the entire future. 00:01:37.390 --> 00:01:40.379 Like a perfect machine. precisely. And it worked 00:01:40.379 --> 00:01:42.819 incredibly well for everyday stuff, you know, 00:01:43.079 --> 00:01:45.640 like planets orbiting stars. But then in the 00:01:45.640 --> 00:01:48.819 early 20th century, physicists started looking 00:01:48.819 --> 00:01:51.540 at the really, really tiny stuff, the microscopic 00:01:51.540 --> 00:01:53.439 realm. And that's when things started to break 00:01:53.439 --> 00:01:55.359 down. It's like Newton's laws just couldn't keep 00:01:55.359 --> 00:01:56.900 up. They just didn't apply anymore, this whole 00:01:56.900 --> 00:01:58.700 new ball game. Yeah. And that's where quantum 00:01:58.700 --> 00:02:00.700 mechanics comes in, right? Absolutely. It was 00:02:00.700 --> 00:02:02.900 this incredible period of intellectual ferment, 00:02:03.299 --> 00:02:05.739 and these brilliant minds came together. Yeah, 00:02:05.920 --> 00:02:08.460 like Planck, Bohr, Heisenberg. Schrodinger -Bohrn. 00:02:08.460 --> 00:02:10.419 Yeah. Yeah, they really revolutionized physics. 00:02:10.719 --> 00:02:14.020 And they created this whole new way of understanding 00:02:14.020 --> 00:02:16.400 reality, right? They did. And one of the key 00:02:16.400 --> 00:02:18.819 things for you to grasp is that there was this 00:02:18.819 --> 00:02:23.520 massive shift from certainty to probability. 00:02:23.900 --> 00:02:26.080 OK. So instead of saying, this is definitely 00:02:26.080 --> 00:02:28.979 going to happen. Quantum mechanics says, here's 00:02:28.979 --> 00:02:31.180 the likelihood of this or that outcome. So it's 00:02:31.180 --> 00:02:33.500 all about possibilities. Exactly. It's all about 00:02:33.500 --> 00:02:35.400 probabilities. It's a very different way of looking 00:02:35.400 --> 00:02:37.909 at the world. Yeah, and Einstein, even though 00:02:37.909 --> 00:02:40.430 he was a major figure in the early days of quantum 00:02:40.430 --> 00:02:43.129 theory, he always felt like it wasn't the whole 00:02:43.129 --> 00:02:45.810 story. He had this gut feeling that it was incomplete, 00:02:46.650 --> 00:02:48.689 you know? Yeah, like it was a stepping stone 00:02:48.689 --> 00:02:51.009 to a deeper understanding. Exactly, and that's 00:02:51.009 --> 00:02:52.650 a really important point for you to understand 00:02:52.650 --> 00:02:55.990 about Einstein's mindset. Okay. He famously said, 00:02:56.169 --> 00:02:58.909 God does not play dice. Yeah, I've heard that 00:02:58.909 --> 00:03:01.569 one. And that quote really captures his deep 00:03:01.569 --> 00:03:04.270 discomfort with the randomness at the heart of 00:03:04.270 --> 00:03:05.990 quantum mechanics, you see. So it wasn't that 00:03:05.990 --> 00:03:08.650 he thought quantum mechanics was wrong? No, not 00:03:08.650 --> 00:03:11.650 at all. His predictions were and still are amazingly 00:03:11.650 --> 00:03:13.830 accurate. It just didn't sit right with him. 00:03:14.150 --> 00:03:16.789 Right. He believed that eventually a more fundamental 00:03:16.789 --> 00:03:18.930 theory would emerge for you. One that didn't 00:03:18.930 --> 00:03:21.129 need probabilities. Yeah, one that would restore 00:03:21.129 --> 00:03:23.110 that sense of determinism that Newton had given 00:03:23.110 --> 00:03:27.020 us. Okay, so he was kind of hoping to find flaws 00:03:27.020 --> 00:03:29.539 in quantum mechanics. He was. He actively tried 00:03:29.539 --> 00:03:32.099 to expose inconsistencies within the theory. 00:03:32.259 --> 00:03:34.400 And that leads us to the first paper we're looking 00:03:34.400 --> 00:03:37.439 at today. The EPR paper. Exactly. Published in 00:03:37.439 --> 00:03:40.860 May 1935. Co -authored with Boris Podolsky and 00:03:40.860 --> 00:03:44.229 Nathan Rosen. Right, so Einstein, Podolsky, and 00:03:44.229 --> 00:03:46.870 Rosen, they thought they'd found a major weakness, 00:03:47.009 --> 00:03:50.050 a potential Achilles heel of quantum mechanics. 00:03:50.229 --> 00:03:53.349 Through this very strange phenomenon called quantum 00:03:53.349 --> 00:03:55.370 entanglement. Entanglement, yeah, I think a lot 00:03:55.370 --> 00:03:56.889 of people have heard that word, but let's break 00:03:56.889 --> 00:03:58.889 it down for you. Okay. So imagine you're flipping 00:03:58.889 --> 00:04:01.430 two coins. Right. In our everyday experience, 00:04:01.629 --> 00:04:04.150 each coin is going to land on either heads or 00:04:04.150 --> 00:04:06.629 tails completely randomly. Right, they're independent 00:04:06.629 --> 00:04:08.770 of each other. Exactly. Now here's where quantum 00:04:08.770 --> 00:04:12.419 mechanics gets really weird. Okay. world, before 00:04:12.419 --> 00:04:14.960 we look at a particle, it can actually exist 00:04:14.960 --> 00:04:17.339 in this blurry state called a superposition. 00:04:17.560 --> 00:04:20.540 It's like the coin is both heads and tails at 00:04:20.540 --> 00:04:22.800 the same time. Until we actually observe it. 00:04:23.000 --> 00:04:25.779 Right. The act of measurement forces it to choose 00:04:25.779 --> 00:04:28.379 one state or the other. So imagine now that you 00:04:28.379 --> 00:04:31.480 have two particles that are entangled. They've 00:04:31.480 --> 00:04:34.160 interacted in a way that links their fates. Okay. 00:04:34.300 --> 00:04:36.519 Even if you separate them by a huge distance. 00:04:36.579 --> 00:04:38.639 Like across the galaxy. Yeah, potentially even 00:04:38.639 --> 00:04:42.519 further. their destinies remain intertwined for 00:04:42.519 --> 00:04:45.720 you. So if you measure one particle and find 00:04:45.720 --> 00:04:48.319 out, let's say its spin is up... The other particle 00:04:48.319 --> 00:04:50.839 instantaneously has to have the opposite spin 00:04:50.839 --> 00:04:53.279 down. And that happens no matter how far apart 00:04:53.279 --> 00:04:55.160 they are. It's as if they're communicating faster 00:04:55.160 --> 00:04:57.379 than the speed of light. Yeah, that's what Einstein 00:04:57.379 --> 00:04:59.939 called spooky action at a distance. He really 00:04:59.939 --> 00:05:01.620 didn't like that. Yeah, it just seemed to go 00:05:01.620 --> 00:05:03.519 against everything he knew about the universe. 00:05:03.899 --> 00:05:06.720 It violated his intuition about the independence 00:05:06.720 --> 00:05:09.560 of objects that are far apart. And that... no 00:05:09.560 --> 00:05:11.720 influence should be able to travel faster than 00:05:11.720 --> 00:05:15.339 light. Right. It was as if there was some invisible 00:05:15.339 --> 00:05:18.600 thread connecting these distant particles. But 00:05:18.600 --> 00:05:20.939 Einstein also had another problem with entanglement 00:05:20.939 --> 00:05:23.540 that he found really unsettling. Yeah. He was 00:05:23.540 --> 00:05:25.600 also bothered by the fact that in quantum mechanics, 00:05:25.819 --> 00:05:28.819 you can know everything about the combined state 00:05:28.819 --> 00:05:31.939 of two entangled particles, but know nothing 00:05:31.939 --> 00:05:34.540 specific about the individual properties of either 00:05:34.540 --> 00:05:37.490 particle until you make a measurement. So it's 00:05:37.490 --> 00:05:39.610 like knowing you have two gloves, a left and 00:05:39.610 --> 00:05:41.990 a right. But not knowing which glove is which 00:05:41.990 --> 00:05:44.290 until you look. Yeah, and that really bothered 00:05:44.290 --> 00:05:47.269 him. It struck him as deeply problematic for 00:05:47.269 --> 00:05:50.050 you. I can see why that would be confusing. It 00:05:50.050 --> 00:05:51.470 is. It's one of those things that really makes 00:05:51.470 --> 00:05:53.350 your head spin. And if you're feeling a bit lost 00:05:53.350 --> 00:05:55.370 right now, you're not alone. A lot of people 00:05:55.370 --> 00:05:58.110 struggle with this. Even physicists. Yeah, we 00:05:58.110 --> 00:06:00.490 can use entanglement in technology and we can 00:06:00.490 --> 00:06:03.389 predict its effects with incredible accuracy. 00:06:03.389 --> 00:06:05.870 Right. But actually understanding what's really 00:06:05.870 --> 00:06:08.360 going on. That's a different story. It's like 00:06:08.360 --> 00:06:11.040 our intuition just can't quite grasp it. The 00:06:11.040 --> 00:06:14.339 key takeaway here is this concept of non -separability. 00:06:15.139 --> 00:06:18.300 Okay. Entangled systems are fundamentally linked 00:06:18.300 --> 00:06:20.720 in a way that classical physics just doesn't 00:06:20.720 --> 00:06:24.120 allow for. So going back to the EPR paper, what 00:06:24.120 --> 00:06:26.579 was Einstein really trying to achieve with that? 00:06:26.879 --> 00:06:28.939 He wasn't just trying to point out the spookiness 00:06:28.939 --> 00:06:32.810 for you. Okay. His real goal was to expose a 00:06:32.810 --> 00:06:34.889 contradiction within quantum mechanics itself. 00:06:35.149 --> 00:06:37.970 So he was trying to prove it was wrong, somehow. 00:06:38.310 --> 00:06:41.509 In a way, yes. He was trying to show that it 00:06:41.509 --> 00:06:43.230 was incomplete, that it couldn't be the whole 00:06:43.230 --> 00:06:45.870 story. And how did he plan to do that? Through 00:06:45.870 --> 00:06:48.430 a thought experiment involving entangled particles. 00:06:48.490 --> 00:06:51.610 Okay. They proposed that by carefully choosing 00:06:51.610 --> 00:06:55.230 what to measure on one particle, either its momentum 00:06:55.230 --> 00:06:58.930 or its position, you could indirectly gain knowledge 00:06:58.930 --> 00:07:00.850 about the corresponding property of the other 00:07:00.850 --> 00:07:03.029 particle without actually measuring it. Okay, 00:07:03.069 --> 00:07:05.110 so because you could choose to measure either 00:07:05.110 --> 00:07:07.550 momentum or position on the first particle. It 00:07:07.550 --> 00:07:09.670 seemed to imply that the second particle must 00:07:09.670 --> 00:07:12.569 have definite values for both momentum and position 00:07:12.569 --> 00:07:15.149 all along, even before the measurement. And wouldn't 00:07:15.149 --> 00:07:17.329 that violate Heisenberg's uncertainty principle? 00:07:17.629 --> 00:07:19.730 Exactly, because the uncertainty principle states 00:07:19.730 --> 00:07:21.850 that you can't know both the precise momentum 00:07:21.850 --> 00:07:24.550 and position of a particle simultaneously. So 00:07:24.550 --> 00:07:27.370 Einstein was basically saying that If a measurement 00:07:27.370 --> 00:07:29.810 in one place can tell you something about a particle 00:07:29.810 --> 00:07:32.370 far away instantly, then that distant particle 00:07:32.370 --> 00:07:34.250 must have already had that property for you. 00:07:34.290 --> 00:07:36.529 Like it couldn't have just popped into existence 00:07:36.529 --> 00:07:38.310 when you measured it. Right. The measurement 00:07:38.310 --> 00:07:40.930 shouldn't magically create that property in a 00:07:40.930 --> 00:07:44.209 distant location. And that felt wrong to Einstein. 00:07:44.370 --> 00:07:46.750 It just didn't make sense to him. So what happened 00:07:46.750 --> 00:07:49.250 with the EPR paper? Did it achieve its goal? 00:07:49.730 --> 00:07:52.230 It became incredibly influential, but Einstein 00:07:52.230 --> 00:07:54.430 himself wasn't completely satisfied with it. 00:07:54.509 --> 00:07:57.709 Why not? Well, Schrödinger wrote to him congratulating 00:07:57.709 --> 00:08:00.189 him on the paper. Okay. But Einstein's reply 00:08:00.189 --> 00:08:03.269 is quite telling. He felt that his main point 00:08:03.269 --> 00:08:05.509 got buried in all the technical details. So it 00:08:05.509 --> 00:08:07.370 didn't quite come out the way he wanted. Yeah, 00:08:07.370 --> 00:08:09.550 he felt like the paper didn't fully capture his 00:08:09.550 --> 00:08:12.290 intended message for you. Interesting. And what 00:08:12.290 --> 00:08:15.230 was that message? Well, Lenny Suskin, a very 00:08:15.230 --> 00:08:17.589 prominent physicist, has argued that Einstein's 00:08:17.589 --> 00:08:20.149 real concern was with the nature of physical 00:08:20.149 --> 00:08:23.189 reality itself. What does that even mean? It's 00:08:23.189 --> 00:08:26.220 a deep philosophical question about What is real 00:08:26.220 --> 00:08:29.740 right what exists independently of our observations? 00:08:30.699 --> 00:08:32.720 You know okay, so it was more than just about 00:08:32.720 --> 00:08:34.700 the uncertainty principle. It was about the very 00:08:34.700 --> 00:08:37.220 foundations of reality for you Okay, so that 00:08:37.220 --> 00:08:42.480 was May 1935 now. Let's jump ahead just two months 00:08:42.480 --> 00:08:46.000 to July 1935. Another Einstein paper. Yeah, another 00:08:46.000 --> 00:08:47.980 one. This time it's just him and Nathan Rosen. 00:08:48.120 --> 00:08:49.960 Right. And this one seems completely different. 00:08:50.080 --> 00:08:52.759 It's about bridges in space time. Yeah. These 00:08:52.759 --> 00:08:55.860 are now known as Einstein, Rosen, bridges or 00:08:55.860 --> 00:08:58.820 more popularly wormholes. Wormholes. Yeah, I've 00:08:58.820 --> 00:09:01.240 heard of those too. But to understand them, we 00:09:01.240 --> 00:09:03.340 need to talk a bit about general relativity. 00:09:03.559 --> 00:09:05.860 Absolutely. Einstein's masterpiece from 1915. 00:09:05.940 --> 00:09:07.779 Which totally changed our view of gravity, right? 00:09:07.980 --> 00:09:10.259 It completely revolutionized our understanding 00:09:10.259 --> 00:09:13.259 for you. OK, so before For Einstein, we had Newton's 00:09:13.259 --> 00:09:16.200 idea of gravity as this force acting at a distance. 00:09:16.279 --> 00:09:18.100 Yeah, like the Earth pulling on the moon. But 00:09:18.100 --> 00:09:20.059 Einstein came along and said, no, it's not a 00:09:20.059 --> 00:09:21.779 force. It's about the curvature of spacetime 00:09:21.779 --> 00:09:24.519 itself. Exactly, caused by mass and energy. OK, 00:09:24.519 --> 00:09:26.740 so imagine like a bowling ball on a stretched 00:09:26.740 --> 00:09:29.320 rubber sheet. Yeah, that's a good analogy. The 00:09:29.320 --> 00:09:32.320 bowling ball creates a dip, and that dip influences 00:09:32.320 --> 00:09:35.220 how smaller objects move around it. It's a simplified 00:09:35.220 --> 00:09:38.039 picture, but it helps to visualize how gravity 00:09:38.039 --> 00:09:40.299 works in Einstein's theory for you. So gravity 00:09:40.299 --> 00:09:43.299 is like warping the fabric of space and time. 00:09:43.679 --> 00:09:46.039 Precisely. And shortly after Einstein published 00:09:46.039 --> 00:09:48.820 his theory, Carl Schwarzschild found this remarkable 00:09:48.820 --> 00:09:52.179 solution to his equations. Okay. And his solution 00:09:52.179 --> 00:09:55.000 described the space -time around a spherical 00:09:55.000 --> 00:09:58.610 object like a star. And that led to a pretty 00:09:58.610 --> 00:10:00.929 startling discovery. It did. Schwarzschild showed 00:10:00.929 --> 00:10:03.490 that if an object is massive enough and collapses 00:10:03.490 --> 00:10:06.529 to a small enough size, the curvature of spacetime 00:10:06.529 --> 00:10:08.889 becomes so extreme that it creates a point of 00:10:08.889 --> 00:10:11.389 no return. The event horizon. Exactly. Nothing. 00:10:11.590 --> 00:10:13.750 Not even light can escape from beyond that horizon. 00:10:13.929 --> 00:10:15.629 And we call those black holes, right? We do. 00:10:15.710 --> 00:10:18.070 They're regions of spacetime where gravity is 00:10:18.070 --> 00:10:20.090 so strong that nothing can escape. So in their 00:10:20.090 --> 00:10:23.909 1935 paper, were Einstein and Rosen specifically 00:10:23.909 --> 00:10:26.470 talking about black holes? Not explicitly. but 00:10:26.470 --> 00:10:28.710 the math they were exploring turned out to have 00:10:28.710 --> 00:10:30.830 deep connections to black holes for you. What 00:10:30.830 --> 00:10:33.690 did they actually find? They discovered a theoretical 00:10:33.690 --> 00:10:36.929 way that two black holes could be connected in 00:10:36.929 --> 00:10:39.750 space -time. Connected like how? By a tunnel 00:10:39.750 --> 00:10:41.929 or a bridge. Like a shortcut. Yeah, you could 00:10:41.929 --> 00:10:44.570 think of it that way. Instead of having to travel 00:10:44.570 --> 00:10:48.789 vast cosmic distances through normal space, you 00:10:48.789 --> 00:10:51.309 could potentially... pass through this wormhole 00:10:51.309 --> 00:10:54.049 and emerge in a totally different location. So 00:10:54.049 --> 00:10:56.009 it's like folding that rubber sheet we were talking 00:10:56.009 --> 00:10:57.970 about earlier. Yeah, exactly. You fold it so 00:10:57.970 --> 00:11:00.309 that two distant points touch, and you create 00:11:00.309 --> 00:11:03.429 a shortcut through warp spacetime for you. That's 00:11:03.429 --> 00:11:05.590 pretty wild. But at the time, was there any link 00:11:05.590 --> 00:11:07.929 between these wormholes and quantum entanglement? 00:11:08.210 --> 00:11:10.149 Not at all. They were considered completely separate 00:11:10.149 --> 00:11:11.870 areas of physics. But that's where things start 00:11:11.870 --> 00:11:14.570 to get really interesting. Yeah. Because in recent 00:11:14.570 --> 00:11:16.710 years, there's been this amazing new proposal 00:11:16.710 --> 00:11:18.990 that wormholes and entanglement are actually 00:11:18.990 --> 00:11:21.889 connected. Exactly. And it's a profound idea 00:11:21.889 --> 00:11:24.889 that has huge implications, not just for our 00:11:24.889 --> 00:11:27.090 understanding of black holes, but for the very 00:11:27.090 --> 00:11:30.529 nature of space and time. So how did this connection 00:11:30.529 --> 00:11:34.269 come about? It started in the 1970s with Stephen 00:11:34.269 --> 00:11:37.210 Hawking's work on black hole radiation. Contrary 00:11:37.210 --> 00:11:40.710 to what we used to think, Hawking showed that 00:11:40.710 --> 00:11:43.559 black holes aren't completely black. Wait, so 00:11:43.559 --> 00:11:46.220 they don't just suck everything in? They do, 00:11:46.500 --> 00:11:49.039 but they also emit a faint thermal radiation 00:11:49.039 --> 00:11:51.340 from their event horizon. So they kind of glow 00:11:51.340 --> 00:11:53.799 a little bit? In a way, yes. And here's how it 00:11:53.799 --> 00:11:56.600 works in the quantum world. Pairs of virtual 00:11:56.600 --> 00:11:59.019 particles and antiparticles can just pop into 00:11:59.019 --> 00:12:01.960 existence, even in empty space. Out of nothing? 00:12:02.100 --> 00:12:04.059 Well, sort of. They borrow energy from the vacuum, 00:12:04.100 --> 00:12:06.220 and usually they quickly annihilate each other. 00:12:06.220 --> 00:12:09.139 OK. But near the event horizon of a black hole, 00:12:09.659 --> 00:12:11.840 something really interesting can happen. What? 00:12:12.019 --> 00:12:13.980 One particle of the pair can fall into the black 00:12:13.980 --> 00:12:16.980 hole while the other escapes and radiates way 00:12:16.980 --> 00:12:19.299 into space. So it's like the black hole is slowly 00:12:19.299 --> 00:12:22.080 losing energy. Exactly. And here's the key point 00:12:22.080 --> 00:12:24.419 for you. Those pairs of particles, even when 00:12:24.419 --> 00:12:26.799 they get separated, they're entangled. So even 00:12:26.799 --> 00:12:28.360 though one falls into the black hole and the 00:12:28.360 --> 00:12:30.879 other escapes, they're still linked. They are. 00:12:31.000 --> 00:12:33.320 They share this spooky connection. And this led 00:12:33.320 --> 00:12:35.700 to a big problem, right? The black hole information 00:12:35.700 --> 00:12:39.049 paradox. It did because Hawking radiation carries 00:12:39.049 --> 00:12:41.830 away energy from the black hole, causing it to 00:12:41.830 --> 00:12:44.590 slowly shrink and eventually evaporate completely. 00:12:44.730 --> 00:12:46.789 And that creates a problem because one of the 00:12:46.789 --> 00:12:50.049 fundamental principles of physics is that information 00:12:50.049 --> 00:12:52.769 is never lost. Right, so if something falls into 00:12:52.769 --> 00:12:56.029 a black hole, where does the information about 00:12:56.029 --> 00:12:59.019 that object go? if the black hole disappears. 00:12:59.200 --> 00:13:01.500 That's a good question. It is. And Hawking's 00:13:01.500 --> 00:13:03.399 initial calculations suggested that the emitted 00:13:03.399 --> 00:13:05.620 radiation was just random thermal radiation. 00:13:05.919 --> 00:13:08.080 So it wouldn't carry any information about what 00:13:08.080 --> 00:13:10.559 fell in. Right. Which created a conflict with 00:13:10.559 --> 00:13:12.419 quantum mechanics, because in quantum mechanics, 00:13:12.919 --> 00:13:15.220 time should be reversible and information should 00:13:15.220 --> 00:13:18.100 be retrievable. So how do we resolve that paradox? 00:13:18.240 --> 00:13:20.100 That's where the holographic principle comes 00:13:20.100 --> 00:13:23.860 in. OK. This was a really radical idea, championed 00:13:23.860 --> 00:13:26.600 by Leonard Susskind and Gerard Tuft. What did 00:13:26.600 --> 00:13:29.200 they propose? They suggested that all the information 00:13:29.200 --> 00:13:31.620 contained within a volume of space could actually 00:13:31.620 --> 00:13:33.639 be encoded on its two -dimensional boundary. 00:13:33.840 --> 00:13:36.480 Like a hologram? Exactly like how a hologram 00:13:36.480 --> 00:13:38.700 stores a three -dimensional image on a flat surface. 00:13:38.940 --> 00:13:41.279 So all the complexity of the universe could be 00:13:41.279 --> 00:13:44.460 encoded on some kind of cosmic boundary? That's 00:13:44.460 --> 00:13:47.960 the idea. And Susskind's work in string theory 00:13:47.960 --> 00:13:51.259 actually led him to this insight. How so? He 00:13:51.259 --> 00:13:54.080 realized that if you probe a fundamental quantum 00:13:54.080 --> 00:13:57.210 string with more and more energy, it actually 00:13:57.210 --> 00:13:59.769 appears to spread out in space. So it's not really 00:13:59.769 --> 00:14:02.409 a point -like particle? No, it's more like a 00:14:02.409 --> 00:14:06.370 fuzzy, extended object. Interesting, so the information 00:14:06.370 --> 00:14:08.529 isn't localized in the way we usually think. 00:14:08.649 --> 00:14:10.529 Right, it's more spread out, maybe even sort 00:14:10.529 --> 00:14:12.230 on the boundary of the system for you. Okay, 00:14:12.309 --> 00:14:14.750 so the information about something falling into 00:14:14.750 --> 00:14:17.250 a black hole could be encoded far away on the 00:14:17.250 --> 00:14:19.509 event horizon. Or even further out, potentially. 00:14:19.750 --> 00:14:21.409 Okay, but the story doesn't end there, does it? 00:14:21.529 --> 00:14:24.240 It doesn't. In 2012, a group of physicists published 00:14:24.240 --> 00:14:26.679 a paper that presented a new challenge to our 00:14:26.679 --> 00:14:28.879 understanding of black holes. This is the AMPS 00:14:28.879 --> 00:14:31.320 paradox, right? It is named after the authors 00:14:31.320 --> 00:14:34.440 Harry, Marolf, Pulchinski, and Sully. And what 00:14:34.440 --> 00:14:36.740 was their paradox? It focused on the entangled 00:14:36.740 --> 00:14:39.120 nature of Hawking radiation. For that outgoing 00:14:39.120 --> 00:14:41.740 radiation to carry information about what fell 00:14:41.740 --> 00:14:44.919 into the black hole, the early radiation and 00:14:44.919 --> 00:14:47.059 the later radiation would also have to be entangled 00:14:47.059 --> 00:14:49.100 with each other for you. OK, but I thought you 00:14:49.100 --> 00:14:51.340 said entanglement was like a one -to -one connection. 00:14:51.519 --> 00:14:54.419 It is. And that's the problem. Quantum mechanics 00:14:54.419 --> 00:14:57.720 has this rule called the monogamy of entanglement. 00:14:58.059 --> 00:15:00.639 Which means? A quantum system can't be maximally 00:15:00.639 --> 00:15:03.419 entangled with two independent other systems 00:15:03.419 --> 00:15:06.039 at the same time. So it's like having one phone 00:15:06.039 --> 00:15:08.860 line. You can only have one clear conversation 00:15:08.860 --> 00:15:11.500 at a time. That's a good analogy, and this created 00:15:11.500 --> 00:15:13.519 a crisis for our understanding of black holes. 00:15:13.779 --> 00:15:15.559 Because it seemed like the entanglement needed 00:15:15.559 --> 00:15:17.580 for information to be preserved was forbidden 00:15:17.580 --> 00:15:19.620 by quantum mechanics. Exactly. It was a real 00:15:19.620 --> 00:15:21.539 puzzle. So how did they get out of this mess? 00:15:21.720 --> 00:15:24.240 This is where the truly mind -blowing proposal 00:15:24.240 --> 00:15:27.019 of ER -EPR comes in. OK. This was put forward 00:15:27.019 --> 00:15:30.399 by Juan Maldicena and Leonard Susskind. ER equals 00:15:30.399 --> 00:15:32.720 EPR. What does that even mean? Well, ER stands 00:15:32.720 --> 00:15:36.080 for Einstein -Rosen bridges or wormholes. Right. 00:15:36.259 --> 00:15:39.019 And EPR stands for Einstein -Podolsky -Rosen, 00:15:39.559 --> 00:15:41.320 the entanglement paper we talked about earlier. 00:15:41.320 --> 00:15:44.379 Right. Their radical proposal was that these 00:15:44.379 --> 00:15:46.980 two seemingly distinct phenomena are actually 00:15:46.980 --> 00:15:50.460 equivalent for you. Equivalent how so? They said 00:15:50.460 --> 00:15:52.940 that if two regions of space are entangled at 00:15:52.940 --> 00:15:56.240 the quantum level, there must be a wormhole connecting 00:15:56.240 --> 00:15:58.529 them. Even if those regions are super far apart. 00:15:58.710 --> 00:16:00.549 Even if they're on opposite sides of the universe. 00:16:00.909 --> 00:16:03.750 So entanglement creates wormholes. That's the 00:16:03.750 --> 00:16:06.730 idea and it's a really profound one because it 00:16:06.730 --> 00:16:09.470 completely changes how we think about both entanglement 00:16:09.470 --> 00:16:11.409 and wormholes. Okay, so let's go back to the 00:16:11.409 --> 00:16:14.789 black hole paradox. How does EREPR solve that? 00:16:15.169 --> 00:16:17.990 Remember that the distant Hawking radiation escaping 00:16:17.990 --> 00:16:21.320 the black hole is entangled with something inside 00:16:21.320 --> 00:16:25.700 the black hole. According to EREPR, that entanglement 00:16:25.700 --> 00:16:28.759 implies a wormhole connecting the radiation to 00:16:28.759 --> 00:16:30.820 the black hole's interior. So the information 00:16:30.820 --> 00:16:32.879 isn't lost, it's traveling through the wormhole. 00:16:33.100 --> 00:16:35.580 Exactly. The information is encoded in the entanglement 00:16:35.580 --> 00:16:39.000 and that entanglement creates a bridge, a wormhole 00:16:39.000 --> 00:16:41.139 connection. So the distant radiation isn't really 00:16:41.139 --> 00:16:43.080 that distant after all. Not in this entangled 00:16:43.080 --> 00:16:45.720 reality for you. It's amazing that Einstein published 00:16:45.720 --> 00:16:48.159 his papers on entanglement and wormholes just 00:16:48.159 --> 00:16:50.759 two months apart. It is, and he probably had 00:16:50.759 --> 00:16:53.200 no idea that they were connected in this way. 00:16:53.580 --> 00:16:56.019 But the story goes even deeper, right? It does. 00:16:56.379 --> 00:16:58.480 Mark Van Ramsdonk did some really interesting 00:16:58.480 --> 00:17:01.039 work that takes this even further. What did he 00:17:01.039 --> 00:17:04.099 do? He used the holographic principle to explore 00:17:04.099 --> 00:17:07.519 the relationship between entanglement and the 00:17:07.519 --> 00:17:09.660 structure of space -time itself. Okay, so he 00:17:09.660 --> 00:17:12.079 was thinking about space -time as a hologram. 00:17:12.380 --> 00:17:14.700 Yeah, and he imagined that the underlying quantum 00:17:14.700 --> 00:17:17.460 system resided on a boundary. Like the surface 00:17:17.460 --> 00:17:20.480 of a sphere. Right. And he asks this fascinating 00:17:20.480 --> 00:17:24.359 question. What happens if you theoretically snip 00:17:24.359 --> 00:17:26.779 the threads of entanglement between different 00:17:26.779 --> 00:17:29.200 parts of that quantum system? Snip them. How? 00:17:29.200 --> 00:17:31.220 Just imagine you could somehow remove the entanglement 00:17:31.220 --> 00:17:34.240 between those regions. OK. And his calculations 00:17:34.240 --> 00:17:36.759 suggested that if you do that, the corresponding 00:17:36.759 --> 00:17:38.740 regions of spacetime would literally start to 00:17:38.740 --> 00:17:41.000 pull apart. Like the fabric of space is being 00:17:41.000 --> 00:17:43.759 torn? In a way, yes. And they could even become 00:17:43.759 --> 00:17:46.640 completely disconnected. So entanglement is holding 00:17:46.640 --> 00:17:49.400 spacetime together. That's what his work suggests, 00:17:49.779 --> 00:17:52.500 and it's a revolutionary idea for you. It is. 00:17:52.579 --> 00:17:55.000 It's saying that entanglement isn't just some 00:17:55.000 --> 00:17:57.759 weird phenomenon happening within space time. 00:17:58.220 --> 00:18:00.359 It's saying that entanglement might be fundamental 00:18:00.359 --> 00:18:03.559 to the very fabric of space time itself. So space 00:18:03.559 --> 00:18:06.660 itself might emerge from this network of quantum 00:18:06.660 --> 00:18:09.460 entanglement. That's the mind blowing implication. 00:18:09.680 --> 00:18:12.319 Wow. So where does all this leave us in our quest 00:18:12.319 --> 00:18:15.259 to understand the universe? Well, it's challenging 00:18:15.259 --> 00:18:17.259 the traditional approach of trying to quantize 00:18:17.259 --> 00:18:19.490 gravity. You know, applying the rules of quantum 00:18:19.490 --> 00:18:22.769 mechanics to Einstein's general relativity. Exactly. 00:18:22.950 --> 00:18:25.690 But this new research is suggesting that maybe 00:18:25.690 --> 00:18:28.049 quantum mechanics and gravity are already intertwined 00:18:28.049 --> 00:18:29.970 from the get go. Like they're two sides of the 00:18:29.970 --> 00:18:32.089 same coin. That's a good way to put it. And it's 00:18:32.089 --> 00:18:34.569 possible that quantum mechanics has been knowing 00:18:34.569 --> 00:18:37.349 about space and gravity all along in ways we 00:18:37.349 --> 00:18:39.190 hadn't realized. So we might have to rethink 00:18:39.190 --> 00:18:41.809 everything. We might. And it all ties back to 00:18:41.809 --> 00:18:45.349 those two seemingly unrelated papers that Einstein 00:18:45.349 --> 00:18:49.319 published in 1935. It's incredible how much those 00:18:49.319 --> 00:18:51.700 papers have shaped our understanding of the universe. 00:18:52.059 --> 00:18:54.480 They've really opened up entirely new avenues 00:18:54.480 --> 00:18:56.880 for exploration. So here's a final thought for 00:18:56.880 --> 00:19:01.299 you to ponder. OK. What if space itself, the 00:19:01.299 --> 00:19:03.829 very arena in which everything happens. isn't 00:19:03.829 --> 00:19:07.490 a pre -existing stage, but rather a manifestation 00:19:07.490 --> 00:19:10.430 of quantum entanglement. That's a truly mind 00:19:10.430 --> 00:19:13.029 -bending idea. It is. It means that the very 00:19:13.029 --> 00:19:16.269 fabric of reality might be woven from these spooky 00:19:16.269 --> 00:19:19.049 connections between quantum particles. It all 00:19:19.049 --> 00:19:21.769 started with Einstein's papers and the realization 00:19:21.769 --> 00:19:23.670 that they're deeply connected in ways he could 00:19:23.670 --> 00:19:26.049 never have imagined. So the revolution in our 00:19:26.049 --> 00:19:28.109 understanding of the universe continues, and 00:19:28.109 --> 00:19:30.549 it's full of surprises. It is, and it's all about 00:19:30.549 --> 00:19:32.890 these unexpected connections that are changing. 00:19:32.750 --> 00:19:35.450 how we view reality itself for you. And who knows 00:19:35.450 --> 00:19:37.849 what other amazing discoveries await us as we 00:19:37.849 --> 00:19:40.730 continue to explore the mysteries of quantum 00:19:40.730 --> 00:19:43.589 gravity holography and the profound implications 00:19:43.589 --> 00:19:46.980 of ER, EPR. It's an exciting time to be a physicist. 00:19:47.180 --> 00:19:48.900 That's for sure. And who knows, maybe one day 00:19:48.900 --> 00:19:51.140 we'll fully understand the deep connection between 00:19:51.140 --> 00:19:53.859 the very small and the very large. I can't wait. 00:19:54.039 --> 00:19:56.680 Me neither. This is incredible stuff. It really 00:19:56.680 --> 00:19:58.880 is. Thanks for joining us for this deep dive 00:19:58.880 --> 00:20:01.680 into Einstein's mind -blowing papers. My pleasure. 00:20:01.779 --> 00:20:04.039 It's been a fascinating journey. And until next 00:20:04.039 --> 00:20:07.039 time, keep exploring the universe. And keep wondering 00:20:07.039 --> 00:20:09.160 about those deep connections. You never know 00:20:09.160 --> 00:20:11.549 what you might discover. That's the beauty of 00:20:11.549 --> 00:20:14.509 science. Absolutely. Always more to learn. Always 00:20:14.509 --> 00:20:16.849 more to uncover. Yeah, it's a never -ending adventure. 00:20:16.970 --> 00:20:19.289 And that's what makes it so exciting. Absolutely. 00:20:19.549 --> 00:20:21.369 Alright, thanks again and see you next time. 00:20:21.829 --> 00:20:22.210 See you then.