This is the Miller's planet. It's the closest planet to the fictional black hole Gargantua. So what's so special about this scene? Well, just in the span of this 5-second clip from this planet, a lot has happened on Earth. I mean A LOT. In this video, we're going to explain time dilation while bringing the context of what happens in Interstellar. We touched upon the fundamentals of this topic from our previous video, about Einstein's relativity. You can check out the video here. But just to give you a brief summary, we can say the following. Under the influence of a strong gravitational field, time slows down. So if you're just hanging out a near massive object, you will experience the effect of time going slower. But gravity isn't the only thing that can warp time. According to another one of Einstein's theories, special relativity, time slows down for an object when it moves. Combining these two concepts together, we could consider this scenario. Suppose that we walked up a flight of stairs. Our body is slowly moved away from Earth, meaning that we will experience time going faster. But at the same time, since we are not stationary while going up we should experience time going slower. So being farther from the pull of gravity, causes our clock to tick faster. But moving counteracts this effect. Of course this is all oversimplified and the devil's in the details. But let's not forget why we're here, talking about time dilation. Let's consider two comparable cases. We have person A, floating nearby a massive object with a lot of gravity. And person B just casually floating in an empty void of space. Person A shines a green laser beam towards person B. Because light is a form of vibration, the laser beam has a colour that corresponds to 600 trillion vibrations each second. Now, light is also a form of energy. And as that beam of light comes out of that gravity of the massive object it loses a lot of energy. This loss means that there is a decrease in frequency. So by the time that beam of light reaches person B, its frequency will have decreased by some factor. That means, instead of the green light at 600 trillion vibrations a second person B gets only -let's say 10 billion vibrations per second which is a microwave radio beam. This phenomenon is called gravitational redshift. But not so fast. Individual wiggles don't just go anywhere and disappear. Since person A creates 600 trillion wiggles every second, while person B only gets 10 billion every second. The only way this can happen is if one second on one astronaut's clock is not the same as one second on the other astronaut. In other words, it only takes one second for person A to create those 600 trillion wiggles. But it will take 60,000 seconds, or nearly a day for person B to receive them. So this is what happens. Our clocks run at widely different rates. And by clocks I don't mean just mechanical or electronic devices but also biological clocks like your heart, lungs, your brains, etc. Person A takes a breath, and takes another breath and measures a few seconds between the two. For him, everything feels normal. Clocks tick the way they are supposed to. On the other hand person B, watching person A through a telescope sees everything in slow motion. With several days passing between the two breaths. So now revisiting this scene again from Interstellar, you should get a better But don't worry, we're not done yet. Stick around if you want to learn more about time dilation in the next part of the video. According to Einstein's special relativity, the greater the acceleration of an object the slower that it will move through time. On Earth, where time is slowed by only a few microseconds per day, gravity's pull is modest. On the surface of a neutron star, where time is slowed by a few hours per day, gravity's pull is enormous. And at the surface of a black hole, time is slowed to a halt. Where the gravity is so humongous that nothing can escape. Not even light. So if we apply Einstein's relativity here, we would know that Miller's planet would experience time at a very slow rate. But here on Earth, the gravity is at a modest rate. And the gravitational force of the sun is also a billion times weaker than Gargantua. So people on Earth experience time faster than that of the three astronauts on Miller's planet. And of course all of this information is brought to you from the book "The Science of Interstellar" written by the scientific consultant of the film. In real life, this process is happening everywhere in space. One interesting example is our International Space Station. At the ISS, time runs slower as compared to time here on Earth. Technically speaking, it is a different time reference than we are. So by calculating the difference through Einstein's equations we could correct the time at the ISS. Because we use a lot of references to the movie Interstellar here we might as well just take one case study of how filmmakers do this time dilation feel in the movie. In the opening scene when Cooper and his team stepped on Miller's planet an intense music with clock-ticking elements starts. The tempo changes over the course of the song. where time dilation takes effect because of the proximity to a singularity. Roughly we'll get about 221 million seconds in seven years. This gives us a conversion factor of about 61,400 seconds which pass on earth for every second spent on Miller's planet. Multiply this by the interval between each tick, and you'll get 77,000 Earth second. Or about 21 hours. So each tick you hear is almost a whole day passing on Earth. And this is side by side of what happens on Miller's planet versus earth in real-time. After grasping all of this piece of information, of course we want to ask the question. Is this extreme time dilation possible on such a planet? Could we even walk on the surface of it? At one point, we are told that the gravity on this planet is 130% of the Earth's gravity. We see the actors panting. A little bit under duress because of the extra gravity. But is this enough for this kind of time dilation? Well, actually not even close. If you've visited the surface of our sun which is not a supermassive body but still much more massive than Earth, you would gain about 66 seconds per year. To get to an extreme dilation where one hour corresponds to seven years, you would need such a strong gravitational field. Essentially the event horizon of a black hole. There is simply no planet that can have this kind of gravity and if you try to land on the surface, it'll be so strong that it would crush you. The weight of the astronauts would be several million tons, and that's even without doing the math. But anyhow, if they wanted to get all the science right, we wouldn't be able to enjoy the movie. After all, it's science fiction. And to make a great film, a superb filmmaker often pushes things to the extreme. But in our case today, it's sufficient enough to turn the concept of time dilation into a beautiful film. "We'll find a way professor. We always have".