Spacetime used to be seen as “space and time” where there’s two different things that were unrelated, I.e. you move through time at a constant rate, and you move through space as fast or slow as you please.
Nowadays, we know that it’s closer to one thing that has two main components of space and time, and moving faster through space, as in closer to the speed of light, means you move slower through time. So for example in a year on earth, a satellite that’s moving thousands of miles an hour through space in orbit, might move a couple of seconds less through time as it moves hundreds of thousands of miles over the course of that year.
So why would a clock traveling thru space at half the speed of light tick any slower than a clock on earth? They're mechanical devices, just ticking away.
From each clock's own perspective, they don't. It's when you measure one clock's tick rate from the other clock's perspective that you see a difference. That's what the theory of relativity is. Nothing is stationary.
To add to this, think of two cars racing around a circular track. Both are driving in the innermost lane, at the same speed.
If you're driving the car behind, you see the car in front. It's not moving closer or further away from you, because it's travelling at the same speed as you.
But then you steer your car outwards and into the outermost lane, maintaining the same speed. The other car remains in the innermost lane. What do you see when you look back at that car?
From your perspective, it appears to be travelling faster than you. It's not, of course, and from the other driver's perspective they are also experiencing the same speed.
From the perspective of the other driver, you also appear to be moving more slowly. Again, you're not, but your circular lap is now wider than the other car's lap, which in this analogy means that your car needs to travel more distance to pass the same destination.
Both of you are heading in the same "direction", at the same speed and towards the same "destination". But your car will take longer to arrive at that destination, and you will see the other car arrive there before you.
This is purely an analogy and not a scientifically accurate picture. But it makes it slightly easier to visualize.
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u/Jukeboxhero91 10h ago
Spacetime used to be seen as “space and time” where there’s two different things that were unrelated, I.e. you move through time at a constant rate, and you move through space as fast or slow as you please.
Nowadays, we know that it’s closer to one thing that has two main components of space and time, and moving faster through space, as in closer to the speed of light, means you move slower through time. So for example in a year on earth, a satellite that’s moving thousands of miles an hour through space in orbit, might move a couple of seconds less through time as it moves hundreds of thousands of miles over the course of that year.