This isn't mine but I love the way whoever wrote this. I just wanna know where I can find the original post or the further explanation. I know most of you not gonna read through everything. When I read this, I felt woke af. So, here it goes.
"There are a lot of simple, intuitive explanations of this to be had out there… but I kind of hate them all. You might google around a bit and find discussion of something called “relativistic mass”, and how it requires more force to accelerate an object that is already moving at a high speed, stuff like that. That is a venerable way of interpreting the mathematics of special relativity, but I find it unnecessarily misleading, and confusing to the student who is just dipping his first toe into the ocean of modern physics It makes the universe sound like a much different, and much less wonderful place than it really is, and for that, I kind of resent it. When I talk about this subject, I do it in terms of the geometric interpretation that’s consistent with general relativity. It’s less straightforward, but it doesn’t involve anything fundamentally more difficult than arrows in pieces of paper, and I think it offers a much better understanding of the universe we live in than hiding behind abstractions like “force” and outright falsehoods like “relativistic mass”. Maybe it’ll work for you, maybe it won’t, but here it is in any case. First, let’s talk about directions, just to get ourselves oriented. “Downward is a direction. It’s defined as the direction in which things fall when you drop them. “Upward” is also a direction; it’s the opposite of downward. If you have a compass handy, we can define additional directions: northward, southward, westward and eastward. These directions are all defined in terms of something - something that we in the business would call an “orthonormal basis”. - but let’s forget about that right now. Lest pretend these six directions are absolute, because of what we’re going to do, they might as well be. I’m going to ask you now to imagine two more directions: futureward and pastward. You cant point in those directions, obviously, but it shouldn’t be too hard for you to understand the intuitively. Futureward is the direction which tomorrow lies; Pastward is the direction in which yesterday lies. There eight direction together – upward, downward, southward, northward, eastward, westward, pastward and futureward – describe the fundamental geometry of the universe. Each pair of directions we can call a “dimension”, so the universe we live in is four dimensional. Another term for this four dimensional way of thinking about the universe is “spacetime”. I’ll try to avoid using that word whenever necessary, but is I slip up, know that “spacetime” basically means “the universe”. So that’s the stage. Now let’s consider the players. You, sitting there right now are in motion. It doesn’t feel like you’re moving. It feels like you are at rest. But that’s only because everything around you is also in motion. No I’m not talking about the fact that the Earth is spinning or that the sun is moving through our galaxy and dragging us along with it. Those thing are true, but we’re ignoring that kind of stuff right now. The motion I’m referring to is motion in the futureward direction. Imagine you are in a train car, and the shades are pulled over the windows. You can’t see outside, and let’s further imagine (just for the sake of argument) that the rails are so flawless and the wheels so perfect that you can’t feel it at all when the train is in motion. So just sitting there, you can’t tell wheter you are moving or not. If you looked out the window you could tell – you’d either see the landscape sitting still, or rolling past you. But with the shades drawn over the windows, that’s not an option, you really can’t tell whether or not you’re in motion. But there is one way to know, conclusively, whether you’re moving. That’s just to sit there patiently and wait. If the train is sitting at the station, nothing will happen. But if it’s moving, then sooner or later you’re going to arrive at the next station. In this metaphor, the train car is everything that you can see around you in the universe – your house, your pet, the most distant stars in the sky, all of it. And the next station is tomorrow. That’s what it means to be in motion in the futureward direction. You and everything around you is currently moving in the futureward direction, towards tomorrow. You can’t feel it, but if you sit there and wait for a bit, you’ll know that it’s true. So far, I think this has been pretty easy to visualize. A little challenging maybe; it might not be intuitive to think of time as an direction and yourself as moving through it. But I don’t think any of this has been difficult so far. Well, that’s about to change. Because I’m going to have to ask you to exercise your imagination a bit from this point on. Imagine you’re driving in your car when something terrible happens: the brakes fail. By a bizarre coincidence, at the exact same moment your throttle and your gearshift lever both get stuck. You can neither speed up nor slow down. The only thing that works is the steering wheel. You can turn, changing your direction, buy you cant change your speed at all. Of course, the first thing you do is turn towards the softest thing you can see in an effort to stop the car. But let’s ignore that right now. Let’s focus on peculiar characteristics of you malfunctioning car. You can change you direction, but you cant change your speed. That’s how it is to move through our universe. You’ve got a steering wheel, but no throttle. When you sit there as apparent rest, you are really careening toward the future at top speed. But when you get up to put the kettle on, you change your direction of motion through spacetime, but not your speed of motion through spacetime. So as you move through space a bit more quickly, you find yourself moving through time a bit more slowly. You can visualize this by imagining a pair of axes drawn on a sheet of paper. The axis that runs up and down is the time axis, and the upward direction points toward the future. The horizontal axis represents space. We’re only considering one dimension of space, because a piece of paper only has two dimensions total and we’re all out, but just bear in mind that the basic idea applies to all three dimensions of space. Draw an arrow starting at the origin, where the axes cross, pointing upward along the vertical axis. It doesn’t matter how long the arrow is: just know that it can only be one length. This arrow, which right now points towards the future, represents a quantity physicists call “four velocity”. Its our velocity through spacetime. Right now, it shows you not moving in space at all, so its pointing straight in the futureward direction. If you want to move through space – say, to the right along the horizontal axis – you need to change your “four velocity” to include some horizontal component. That is, you need to rotate the arrow. But as you do, notice that the arrow is now points less in the futureward direction – upward along the vertical axis – than it did before. You are now moving through space, as evidenced by the fact that your four velocity now has a space component, but you have to give up some of your motion toward the future, since the “four velocity” arrow can only rotate, never stretch or shrink. This is the origin of the famous “time dilation” effect everybody talks about then they discuss special relativity. If you are moving through space, then you are not moving through time as fast as you would be if you were sitting still. Your clack will tick slower than the clock of a person who isn’t moving. This also explains why the phrase “faster than light” has no meaning in our universe. See, what happens if you want to move through space as fast as possible? Well, obviously you rotate the arrow – your four velocity – until it points straight along the horizontal axis. But wait. The arrow cannot stretch, remember. It can only rotate. So you’ve increased your velocity through space as far as it can go. There’s no way to go faster through space. There’s no rotation you can apply to that arrow to make it point more in the horizontal direction. Its pointing. Its pointing as horizontal as it can. It isn’t really meaningful to think about something as belong “more horizontal than horizontal”. Viewed in this light, the whole idea seems rather silly. Either the arrow point straight to the right or it doesn’t, and once it does, it can be made to point any straighter. It’s as straight as it can ever be. That’s why nothing on our universe can be faster than light. Because the phrase “faster than light”, in our universe is exactly equivalent to “straighter than straight” or “more horizontal than horizontal”. It doesn’t mean anything."