In my undergrad physics course we were taught the basics of relativity. It was explained to us that something moving near the speed of light can somewhat time travel when compared to a stationary observer. So, how much younger would [Astronaut Koch](https://www.google.com/amp/s/amp.usatoday.com/amp/4676940002) be than us and how does this phenomena work?
In: Physics
Space is not empty. What to us appears as nothing more than a dark, empty void; is actually a construct, a facade held fast by the goings-on at a quantum level – Where the seeds of our macro universal constants and laws of euclidian physics take root – the very threads of space, woven to those of time.
The two are inseparable by all but a few catalogued types of events.
And so; spacetime.
Space is elastic, it can be pulled and pushed and distorted to extremes. Near the center of a celestial object – star, planet, moon, etc – space is gathered tighter together; literally pulled together by the mass of an object.
The tighter space is squeezed, the faster time proceeds (to an outside observer, anyway). The further you get from an object’s center of mass – As space “loosens it’s slack” – Time moves slower.
Over the unimaginable distances of the cosmos, those heavy little “clouds” of contracted space exist at a slightly faster rate than the surrounding, dilated space; and that’s just fine.
It’s important to remember that time looks different to observers in differently dilated space. Even on the surface of the Earth, gravity (and thus, time) is not perfectly spherical. Earth’s gravity, for example, exists as peaks and troughs.
So, the local progression of time for you, might be infinitesimally faster or slower than time for an observer elsewhere. So small in fact, that you wouldn’t ever notice it with your natural senses.
The miniscule differences will never matter to current day astronauts, much beyond the fact that the temporal inconstancies are indeed numerically quantifiable.
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