Avi Loeb

If you expand the balloon very fast, if you blow it up quickly, the ants would not be able to visit the entire balloon.

They would be limited to a small region.

and less and less of it as it expands.

And so that's the analogy that if space itself is expanding in an accelerated fashion in the universe, then photons, particles of light, will not be able to bridge the gap being opened between two different points on the surface of the balloon.

So, as a result, we remain isolated, and if you have a friend in another galaxy far away, you would be able to know about their whereabouts only up to a certain time in the future, once they reach the speed of light, you won't be able to know what's happening there.

It's sort of like the horizon of a black hole.

If your friend gets into a black hole, you don't know what happens after that.

And the only image you get is when the friend crossed the horizon.

It's sort of like the final picture at the ending of a Western movie where the cowboy waves his hand and the image freezes.

That's what you would see if a friend falls into a black hole or if a friend is in another galaxy in an accelerating universe.

And we will be left in the dark, in empty space.

The only thing available to us is whatever is within the region around the Milky Way galaxy that is bound gravitationally and doesn't participate in the expansion.

So all the stars that we see in the Milky Way will still be here.

But in other galaxies, we won't be able to see them anymore in the distant future.

Wouldn't time be slowing down as well?

No time keeps progressing.

It's just that the space is expanding as they reach the speed of light.

oh, the translation between the time in the frame of those friends and in your frame breaks down, because you can't actually learn about what happens to them, just like when someone enters a black hole.

So it's a fascinating concept, and you might say, oh, there wouldn't be any stars left.

No, actually, the most common stars are about a tenth of the mass of the sun, and they can live up to