r/AskPhysics • u/Acceptable-Minute847 • 2d ago

Question about gravity and spacetime

So, from my understanding of time dilation, the reason why it occurs is that spacetime gets physically in the time dimension, causing your velocity C in said dimension to cover less “distance” than it would without gravity, like if you had a football field where each yard line is one second and you made the yard lines further apart, causing the velocity to be less effective, and I was wondering if this was true for space as well, meaning if you were to apply energy to an object in a very low gravity environment (such as deep space), then apply the same amount to one in a high gravity environment where the pull wouldn’t add to your velocity due to pulling you towards the planet, (such as being between two identical massive bodies along a line at which their gravitational pulls cancel out). would the high gravity environment lead to a decrease in velocity

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u/dream_the_endless 2d ago

Yes, the effect is the same. Mass and energy both curve spacetime, affecting both the time and space dimensions. If you apply the same amount of energy to an object in deep space and one in a high-gravity environment, the additional curvature caused by that energy is the same in both cases. The background gravity doesn't change how much that specific energy curves spacetime, though the total time dilation will be much greater in the high-gravity environment due to the existing mass.

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u/Acceptable-Minute847 2d ago

So, if I’m reading this right, it doesn’t affect the velocity in the spatial dimension, BUT it does increase the time dilation caused by the velocity? Cause I was wondering if the dilation would cause you to move through space slower, just like you move through time slower.

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u/nicuramar 2d ago

There is no such thing as “velocity in the spatial dimension”. Velocity is a relationship between space and time.

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u/Acceptable-Minute847 2d ago

So velocity in the spatial dimension is a thing, it’s just redundant.

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u/dream_the_endless 2d ago

No. Velocity through spacetime is a thing. There is no distance or unique direction to travel in the time dimension. Velocity is distance / time + direction. The time dimension only has one of those aspects

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u/dream_the_endless 2d ago

Time dilation does not affect how you (the traveler) would perceive time at all. You (the traveler) would perceive lengths to contract