00:00Time is nothing but a magician's trick. Or is it? We're used to time zipping along
00:06like a car, always pointing into the future. It creates cause and effect, lining events
00:11up one after another, like dominoes. Sometimes it stretches between moments, getting so slow
00:17it might even want to stop. And it's got a spotlight on right now because that's
00:22the only moment that truly matters. But there's a new theory that it might not exist at all.
00:29We usually think of space as having three dimensions, up and down, left and right, forward
00:38and back. And everyone thought that time was a separate thing, just a universal clock ticking
00:43away in the background, and it's the same for everyone. But then Einstein came forward.
00:49He decided to surprise everyone back in 1905 when he introduced his special theory of relativity.
00:56It said that time is another dimension, just like the others, and they're all tied together
01:01in one big space-time. Based on this, it turned out that time can change depending on the
01:07speed at which you move. Now imagine that we take two twins. Twin A stays on Earth.
01:14Twin B takes a journey into space on a spaceship, moving at a speed close to the speed of light.
01:20Let's say 90% of that speed. Twin B travels to a distant star and then returns to Earth.
01:27For Twin B, it feels like the journey only took a few years. But when they come back
01:31to Earth, it turns out that Twin A has aged significantly more. They find out that 20,
01:3730, or even more years have passed on Earth. That's all because of the phenomenon called
01:43time dilation. It happens when we're reaching speeds close to the speed of light, causing
01:48time to slow down for the traveler relative to someone who stays in one place.
01:55Ten years later, Einstein proposed his theory of general relativity. That's when we learned
02:00that time changes not only based on your speed, but also based on gravity. Back in the day,
02:06Newton thought that gravity was some magical force that makes objects attract each other.
02:11However, Einstein proposed that this isn't a force, but more like an after-effect. Picture
02:17the space as some huge cloth. When you throw a heavy ball on a cloth, it curves. Now, if
02:23you throw some small balls around it, they will naturally approach the heavy ball.
02:30At the same time, massive objects like stars and planets cause space-time to curve around
02:35them. When there's something super-heavy in space-time, it curves the matter around
02:40it. This curvature tells objects how to move. And this is what we call gravity.
02:46This idea created all sorts of cool predictions that later turned out to be true. Bending
02:51of light by gravity, black holes, and time dilation around these black holes, just like
02:56in Interstellar. This theory revolutionized our view on everything, but we might be on
03:02the verge of another revolution.
03:07Some philosophers have a crazy claim. They say that the things we believe about time
03:12are all just ideas in our heads, not facts of the physical world. This idea, which breaks
03:18the traditional view of time, is called the Bloch universe. It's backed up by Einstein's
03:24theory of relativity, but extends it and makes it more complicated. Imagine the universe
03:29as a huge sandwich. This sandwich contains every moment of time, past, present, and future,
03:36all at once. Each layer or slice of the sandwich represents a different moment in time. And
03:42all these layers exist simultaneously, rather than one after the other. In this model of
03:47our world, the past, present, and future are all equal. Unlike our everyday experience,
03:53where the past is gone, the future hasn't happened yet, and only the present is real,
03:58the Bloch universe says that every point in time is just as real as every other point.
04:04Imagine, your birth, this moment right now, and what you'll be doing in 10 years from
04:09now all exist together in this Bloch. It also says there's not really a flow of time. We're
04:16used to time flowing from one moment to the next, even with Einstein's theory. But in
04:21the Bloch universe, the feeling of time moving is more about how we experience and remember
04:26events than about how time itself works. It's like reading a magical book. All the pages
04:32exist at once, but you can only experience the story page by page.
04:36Now, this implies some scary things, like destiny, and whether free will actually exists.
04:45If everything is already laid out, does what we do matter? For example,
04:50you clicking on this video was already predetermined in the Bloch universe. Every
04:55choice you've ever made was an illusion. You're just a program following a code,
04:59but with an ability to understand its consequences. This would explain why we
05:04order junk food at midnight, knowing that it's a bad idea that we're going to regret.
05:09But some scientists argue that time's flow and direction are as real as it gets,
05:14because cause and effect still exist. If your birth, current moment, and you in the future
05:20with gray hair all existed at the same time, you'd be able to visit your past self at any
05:26moment and already knew what your future self is like. So this whole debate might just be about
05:32how we piece together our stories of the past, not proof that the future isn't waiting to unfold.
05:38There's also a never-ending battle between general relativity and quantum mechanics,
05:45which only adds spice to the debate. On one hand, general relativity plays with time like
05:51it's a stretchy Play-Doh. The flow of time can stretch or compress depending on the speed or
05:57gravity. On the other hand, in quantum mechanics, time isn't something that can be manipulated or
06:03changed. It's a constant stage upon which the particles and forces of the universe perform.
06:09These two fields have been fighting for a long time now, and scientists are struggling to unite
06:15them in one cohesive theory of everything. Although there are some candidates who try
06:20to merge them in a logical way, like string theory. String theory sounds scary, but it's
06:25simply saying that the entire universe, with all its particles and atoms, is made up of ultra-tiny
06:32vibrating strings. Each string can vibrate in separate ways, like the strings on a guitar,
06:37and in many dimensions. The way these strings vibrate determines what type of particle they
06:43will be, like an electron or a quark. Another idea, called loop quantum gravity,
06:49says that space and time are made of tiny loops. Whether it's strings or loops, unfortunately,
06:58they would be so tiny that we simply don't have strong enough equipment to check them out yet. So,
07:04until we test these theories, they can't be proven. What's interesting is that both ideas
07:09don't really need time to explain how the universe works. We think of things like tables and chairs
07:15as real, even though physics doesn't describe them directly. We say they emerge from the tiny
07:21particles that make up the universe. But with time, we're not sure how it would emerge from
07:26something else. But no matter what the answer is, you're going to be okay. If it turns out that it
07:32doesn't really exist, then it could make everything feel pointless. But think about this. We still
07:38lead our lives, and we still experience what feels like causation and make sense of everything. It
07:44still feels like it was our choice to order that junk food at midnight. So, does that being
07:50predetermined really matter? In any case, we've been wrong about plenty of things we thought were
07:56set in stone. Right now, there's a big split between the block universe and our traditional
08:00theories. But we'll learn the truth over time. That's it for today! So, hey, if you pacified
08:10your curiosity, then give the video a like and share it with your friends! Or, if you want more,
08:15just click on these videos and stay on the Bright Side!
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