Our universe, everywhere and in all directions, is filled with stars and galaxies.
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 unreachable by us.
As the universe expands, the space between all unbound objects increases over time.
Beyond distances of ~14.5 billion light-years, space’s expansion pushes galaxies away faster than light can travel.
Over time, the expansion rate still drops, but remains positive and large because of dark energy.
Dark energy, inherent to space itself, never decreases, even as the universe expands.
All galaxies beyond a certain distance always remain unreachable, even at the speed of light.
The present “reachability limit” has a boundary ~18 billion light-years away.
All galaxies closer than that could be reached if we left today; all galaxies beyond that are unreachable.
Only 6% of presently observable galaxies remain reachable; 94% already lie beyond our reach.
Each year, another ~160 billion stars — enough to compose one major galaxy — become newly unreachable.
The final ones, in the M81 group, will become unreachable after another ~100 billion years.
After that, only our Local Group will remain within reach.
Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.
This article was originally published on our sister site, Big Think. Read the original article here.