Time is subjective. I mean we live on planet were people are experiencing different times on in the same hemisphere. As far as astrophysics is concerned, time is the the length towards entropy aka "heat death" of the universe. We can't comprehend universal time scale as for the universe, BILLIONS OF YEARS could be like
to it. For us, since we have short life spans
, we only experience a tiny fraction of the movements of the universe. From the universal time scale, the Earth itself is a ever moving, ever evolving living organism. The continents move around all the time but to us, they take millions of years to make these movements.
We know the big bang theory is most accepted theory on our creation. Universe was once this dense gas that exploded into what you see now. Some sources say we are still expanding at a finite speed maybe we will contract back into that dense gas then explode again like pulse
. Time and light are like the guiding principles of our universe. Light is how we are able to fathom these universal time scales where events can last for MILLIONS OR BILLIONS OF YEARS. Light year is just the measurement of how long it takes light to travel and be seen between any two points. If a planet is 4 light years away, it takes light 4 years traveling at 186,000 PER SECOND
to reach the next point. So with that said, the further we look into space, and further the object appear, we look further INTO THE PAST.
Thats why we can see the past because the light from those regions in space are just now reaching our planet. As of right now, some of these systems could destroyed, gone but that event will take BILLIONS OF YEARS for us to see it.
As for the aliens? Well the reason why we haven't contact them, is because we haven't become visible to each other yet. We just now getting views of the outer planets outside our solar system.
I fukkING LOVE SPACE