Eli5: How does gravity affect time, dumb it down for me as much as possible
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This is about as “simple” as such a complicated topic gets:
You move through the universe at a fixed rate: *c*. You are always moving at this velocity, the only question is how much of that velocity is through time, and how much is through space?
If you’re moving at *c* through space, then time essentially stops for you, since space velocity + time velocity must equal *c*, thus if your space velocity is c, then your time velocity *must* be zero. Likewise, if you stop moving completely, you are moving at maximum velocity through time, and zero velocity through space. This is why people often say that a photon is emitted at the exact moment it strikes an object, from its own frame of reference. Photons have no mass, and thus travel at maximum velocity through space (*c*, aka “the speed of light in a vacuum).
Gravity dicks this up because when spacetime is curved, you are effectively accelerating through time even then you appear stationary. Earth isn’t just moving, it’s *accelerating* at a rate of 9.8m^2, and as long as you’re sitting on Earth, it’s pushing you along with it. If you jump our of an airplane, you temporarily remove yourself from Earth’s frame of reference – not completely, since Earth is still pushing air through spacetime and that air is pushing you – but you hitting the ground (hopefully after opening a parachute) is Earth “catching up” to you since you stopped accelerating when you jumped out of the plane but Earth never did.
So essentially, mass curves spacetime, which means objects with mass are always “accelerating” through time at some rate or another, meaning their movement through time is always going to vary based on the intensity of the gravity well they’re residing in.
I want to reiterate: This is an ***extremely simplified explanation*** of a phenomenon humans still aren’t super clear on.
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