why time slows down as you go faster

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Thank you so much for all the answers, they have all be so helpful. 🙂

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Anonymous 0 Comments

It has to do with the speed of light and special relativity. As you gain speed, you gain mass. When you gain mass, things that are not as massive as you look like they’re moving in slow motion. When you get very close to the speed of light, like 99% the speed of light, you gain so much mass that things not moving as fast as you look like they’re standing still.

Anonymous 0 Comments

Real ELI5: Everyone, no matter how fast they are moving, sees light to travel at the same speed. The time dilation and all of that are necessary for the math to work, and are observable.

Anonymous 0 Comments

Because you’re catching up to the speed of time.

A photon traveling at the speed of light is also traveling at the same speed at which time “happens.” Because it’s going the same speed as time, the photon doesn’t experience time passing at all.

When you go faster and faster, the difference between time’s speed and your speed decreases (from your perspective). Should you ever get to light speed, it would seem to you as if time had stopped.

Anonymous 0 Comments

I kind of imagine this as a ping-pong ball going up and down. The ping-pong ball always travels at the speed of light.

Now ping-pong ball is put on a ship, and that ship starts travelling. The ping-pong ball is still moving at the speed of light, but as the ship travels faster and faster the ping-pong ball is moving sideways. From inside the ship the ping-pong ball is going up and down (and time stays normal, but only from the perspective of the observer that’s travelling with the ping-pong ball). From an outsiders perspective the ping-pong ball is going to move in a zig-zag movement. As the ship goes faster the zig and zags will be longer and longer, and so (since the ball always travels at the speed of light) it’s going to travel up and down slower.

Now. This is applied to all reactions between particles. Everything is going to move slower and slower since their movement is capped at the speed of light and more and more of their movement is taken up by keeping up with the movements in realspace. Until, when the ship travels at the speed of light, time becomes infinitely slow.

Anonymous 0 Comments

Space and time are related. We call them together ‘spacetime’.

You have a *limited* and *fixed* speed through spacetime.

If you are statioanry, then all your speed goes into time. You get to go the maximum rate through time. We’ll call it aging 1 second per second.

If you move, then you have to split your speed between time and space. If you move slowly through space, then you might age 0.999999 seconds per second, which is hardly a ntoicible difference. If you move very fast through space, then you might age 0.10 seconds per second, which is a very noticible.

Some objects move just fast enough, and need precision timing enough, that we notice it. Like software that works with GPS satellites needs to account for the tiny time dilation between them, because that tiny difference would make a difference in where the GPS believes you are.

Anonymous 0 Comments

Short answer:
It had been decided that light will always move at a specific speed no matter who or what observes light and even time itself would bend to make that be always true.

Long answer:
Let’s start with understand a bit about relativity. Let’s say you’re on a train with a friend and your friend gets up and walks towards the bathroom. From your perspective you see your friend moving at about walking speed towards the bathroom. It’s not particularly fast. But what about someone outside the train? Let’s say a man is standing a safe distance away from the train tracks and your train zooms past this man. This man sees your friend who was walking to the bathroom. From his perspective, she is going really fast and is zooming past the man. Now your friend has 2 speeds. One really fast speed from the perspective of the man outside the train and a slow speed from your perspective. Both speeds are correct and it all depends on what the speed of the observer is. Everyone will have many different speeds just like your friend and that is what relativity is.

But here’s the thing. Light is special because it will always have 1 speed: c! No matter who the observer is and how fast the observer moves, light will always move at the same speed(in vacuum) which is a specific number that is roughly about 300 million meters a second. Now obviously this would seem to contradict the earlier point about relativity but here’s the magical thing that lets light move at c. The observers looking at light will either have their time sped up or slowed down to make it such that light is moving at c. So if you try to run really really fast to try and catch up to light, light won’t appear to have a lower speed, it would still be moving at c by magic because time slows down for you and light will appear to go faster to make it so it moves at c.

Anonymous 0 Comments

As if you’re 5??

Ok I’ll try. All of us are always moving, even if we think we are standing still. You see, even if you stand as still as you can, time still passes for you. You’re still moving through time.

Scientists have determined that this stuff we move around in, this…space, this reality it’s actually part of the same stuff as time. We can call it spacetime.

Now, there is a max speed you can move through spacetime. We don’t really know why, it’s just a rule of the universe. If you stand as still as possible, you move through time as fast as you can. 1 second a second. If you start moving though, you increase your…spacespeed. You start subtracting from your timespeed.

Now the way the conversion ratio works, if you’re moving as you normally do, you don’t really slow down moving through time much. You have to move really really fast, like light speed fast, to have a significant effect on your timespeed. And as you get closer and closer to lightspeed, your timespeed gets closer and closer to zero, because you’re taking that travelling speed away from time and putting it into spacespeed.

Anonymous 0 Comments

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Anonymous 0 Comments

This is a tricky one, but I’ll try to keep it simpler. I’m not certain that what I’m about to say is 100% consistent with the math of relativity, but it’s reasonably close enought to at least understand why time dilation occurs.

With that out of the way:

First, the speed of light is not really about light. The fact that light travels at that speed is a consequence of the nature of photons. The speed of light is the ultimate speed limit of the universe – you could call it the speed of causality more accurately. In fact, in a sense *everything* travels at the speed of light – that might not seem accurate, but I’ll explain more in a little bit.

Second, what is speed? It’s how fast something is moving in a particular direction. All movement is directional – you don’t just arbitrarily go fast. You travel along a path. Typically, we think of this path as three-dimensional. If you’re flying in an airplane, for example, then relative to a stationary object, you’re moving upwards at a certain speed, to the left or right at a certain speed, and forward at a certain speed. Add those together according to some relatively basic math, and you have your overall speed and direction of travel.

Third – what I just explained isn’t actually correct, because it ignores something rather huge that all of us take for granted – time. You see, we don’t travel a three-dimensional path. We travel a four-dimensional path. And that fourth dimension is time. For most objects traveling at the speeds most humans deal with, time is actually the largest part of our velocity. That’s why time seems to pass at the same rate at the scales that you’re used to dealing with – the differences between your time velocity and something traveling at 60 mph is so miniscule that it’s impossible for a human to notice it.

Fourth – remember how I said everything travels at the speed of light? Well, that’s why time dilation is a thing. Your total velocity through four dimensions must remain constant. So if you are traveling through space faster, then the only way for you to do that is to travel through time slower. So as you speed up, your experience of time slows down. However, because you have mass, you can never actually reach the speed of light. What happens instead is that as you get faster, the extra energy actually makes you more massive.

Incidentally, because photons travel at the speed of light, they don’t experience the flow of time. From the point of view of the photon, its entire lifespan (from the moment it’s emitted until it’s absorbed by another particle) passes instantaneously and simultaneously. This happens because photons don’t have mass, and so their velocity in the “time” dimension is 0.

Anonymous 0 Comments

You have to think about us (and all other matter) as not moving separately through space and through time, but rather moving through *spacetime*.

On a ferris wheel, you are always moving at the same speed, right? However, the faster you are moving in the vertical direction, the slower you are moving in the horizontal direction, and vice versa. Your *speed*, the magnitude of your velocity, remains constant, rather it is the weighting of the horizontal and vertical components that make up that speed that changes with time.

Spacetime works the same way: Imagine a 4 dimensional analogue of velocity that tracks how “quickly” you move through spacetime. This quantity (rather unimaginatively named “4-velocity”) is constant for all matter. In the same way as the ferris wheel, that means the faster you move through space, the slower you move through time. The magnitude of your 4-velocity remains fixed; it is only the weighting of the spatial components vs the time component that changes.

Humans are, relative to each other, effectively stationary: Nearly all of our motion through spacetime is, from any of our reference frames, through time. This is why we can, in daily life, treat space and time as unrelated quantities. u/DoctorKokktor’s answer is a great example of how that breaks down in more extreme environments. If you ask why the universe behaves this way, we could point to the fundamental fact that the speed of light appears to be the same in every frame of reference, from which all the rest of this is derived. As for why that’s the case, in physics the answer to “why” questions is always eventually “that’s just how the universe seems to work”.

One thing physics teaches you is that our brains evolved over millions of years to keep us alive on a cold, fairly small, low energy rock where nothing is moving very fast. The universe in more extreme environments is under no obligation to make sense to our extremely limited intuition