ELIF: how is time relative?
In: Physics
A lot of the answers here are explaining why time is relative in an observation of events sense, which isn’t what the OP is going for. I assume they want to know about the theory of relativity, so I’ll give it a go:
Imagine you’re driving a car at 30mph, and another car overtakes you at 60mph. Common experience tells us that someone standing stationary at the side of the road will observe the overtaking car going at 60mph, whereas from your perspective it is going at 30mph.
Now imagine that you are driving a car at 30mph (13.4m/s) and your shine a light. From your perspective the light is travelling at the speed of light ( 299 792 458 m/s). Common experience tells us that the person at the side of the road will see that light travelling at 30 mph + the speed of light (299 792 471 m/s). But that doesn’t happen, both observers see the light travelling at the exact same speed (299 792 458 m/s). Einstein’s theory says that the speed of light can never be broken no matter what frame of reference you measure it from. That means if someone is another car travelling at half the speed of light, the light shone is still travelling at 299792458 m/s relative to them.
So how does this work? Well, speed is distance over time – so for speed to be fixed distance or time have to change within your frame of reference. Turns out both do depending on your reference frame. But for the car, time slows down relative to the guy who is stationary. The effect is very negligible until you reach speeds close to the speed of light.
It’s not just a theory, it’s been verified using atomic clocks.
As to how/why this works? I have no clue, I’m not sure anyone does.
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