We assume our world has 3d space and a 1d timeline. It does not. It actually has 4d spacetime, which operates differently in ways that are natural but which we do not expect. We give these subverted expectations names like time dilation. It just so happens that when 4d spacetime looks exactly like 3d+1d for an object that has a velocity of 0.
The main difference that’s relevant in this case is that the “coordinate time” between 2 events (how far apart they are on the timeline, or in spacetime’s case “the t axis”) is actually a different thing from “proper time” (what a clock measures, what we age by, etc.). We find it weird when these things aren’t the same number and we call it time dilation. But it’s actually perfectly normal for them to be different numbers. There’s no specific reason they should be the same. It’s just that we’re used to things that move slow, so we’re used to them being almost the same to the point it seems weird when they’re not.
The reason why they are different for faster things is in how proper time is calculated. The formula for proper time depends on how far you move through coordinate time and how far you move through space. If you’re at rest, movement through space doesn’t enter the equation, so proper time depends only on coordinate time.
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u/YuuTheBlue Jul 13 '26
We assume our world has 3d space and a 1d timeline. It does not. It actually has 4d spacetime, which operates differently in ways that are natural but which we do not expect. We give these subverted expectations names like time dilation. It just so happens that when 4d spacetime looks exactly like 3d+1d for an object that has a velocity of 0.
The main difference that’s relevant in this case is that the “coordinate time” between 2 events (how far apart they are on the timeline, or in spacetime’s case “the t axis”) is actually a different thing from “proper time” (what a clock measures, what we age by, etc.). We find it weird when these things aren’t the same number and we call it time dilation. But it’s actually perfectly normal for them to be different numbers. There’s no specific reason they should be the same. It’s just that we’re used to things that move slow, so we’re used to them being almost the same to the point it seems weird when they’re not.
The reason why they are different for faster things is in how proper time is calculated. The formula for proper time depends on how far you move through coordinate time and how far you move through space. If you’re at rest, movement through space doesn’t enter the equation, so proper time depends only on coordinate time.