The universe is expanding, with every galaxy beyond the Local Group speeding away from us. Today, most of the universe's galaxies are already receding faster than the speed of light. All galaxies currently beyond 18 billion light-years are forever unreachable by us, no matter how much time passes.
Our universe is full of stars and galaxies everywhere and in all directions.
From our vantage point, we observe up to 46.1 billion light years away.
Our visible universe contains an estimated ~ 2 trillion galaxies.
However, most of them are already permanently unavailable for us.
As the universe expands, the distance between any unbound objects increases over time.
Beyond distances of ~ 14.5 billion light years, the expansion of space is pushing galaxies away faster than light can travel.
Over time, the rate of expansion will still decrease, but it will remain positive and large due to the dark energy.
Dark energy, inherent in the space itself, never diminishes even as the universe expands.
All galaxies beyond a certain distance always remain inaccessible, even at the speed of light.
The current “reachability limit” has removed a limit of ~ 18 billion light years.
Any galaxies that are closer could be reached if we break up today; all galaxies beyond that are inaccessible.
Only 6% of the currently observable galaxies can still be reached; 94% are already out of our reach.
Every year another ~ 160 billion stars – enough to form a large galaxy – become inaccessible.
The last ones in the M81 group will be unreachable after another ~ 100 billion years.
After that, only our local group remains within reach...
This article was originally published on Big Think. Read the original article here.