From what I understand: all points in space are being pushed away from each other; from two atoms in your hand to two atoms across the universe. The reason objects aren't getting bigger is because atomic/nuclear/gravitational forces hold nearby objects together: if you stretched the earth to be a millimeter wider (massive amount), the earth would just collapse down to the same size it was before. Objects are held together locally, but pushed apart globally.

My dumb answer: the universe is an expanding balloon being inflated by The Big Bang. If you were a standing on one point on the surface of the balloon, objects relative to your observable distance would be moving away from you. This observation can be measured by a phenomenon known as the redshift.

I'm lost from here..

> Are the physical distances between things changing?

Yes.

> Is new space being created?

I’m not sure what you mean by this question.

Imagine ants living on the surface of a balloon which is inflating, and, I think that’s not that far off? (Except, the balloon is compact and wraps around, and the universe likely doesn’t.)

Here's a rabbit hole you may wish to go down:

https://www.physicsforums.com/threads/what-is-the-fabric-of-...

From a basic perspective: Yes, new space is being created. And, yes, the physical distance between things are changing.

The [Hubble constant](https://www.wolframalpha.com/input/?i=hubble+constant ) is roughly (2.2 * 10^-18)/s -- often written as, e.g., 68 km/s/Mpc (same thing).

Which basically asserts that, every second, each unit of space is increasing by 2.2*10^-18.

For example, if we suppose that there's a ball 1 meter away from you, then in a second, it'ld be ~1.0000000000000000022 meters away from you. Not that it moved away from you, but rather that ~2.2*10^-18 meters of space was created between you and it.

At least, in basic theory. There're a lot of reasons to not take it too literally. For example, at local-scales, forces may resist expansion, instead pulling things back together. For another, the idea that the value is constant seems dubious. But, it's really simplified/approximate/speculative/etc..

Note that this does imply that things can, in a sense, move faster than the speed of light without violating Einstein's Relativity. Because Einstein's Relativity asserts that things can't move faster than light locally; however, the expansion of space isn't considered to be a factor in that. Which is relevant to the main-article above: when something's so far that space is being created between you and it faster than the speed-of-light, it's theoretically outside of the universe that's relevant to you, and thus outside of one (disfavored) notion of "the observable universe".

For example, say that two aliens are separated by such a distance that the expansion-of-space between them is greater than the speed-of-light. Then, even if both aliens blasted off at nearly the speed-of-light toward each other, they'd still approach each other more slowly than the distance is expanding, such that they wouldn't reach each other. (At least, under a lot of assumptions.)

That distance-of-separation is currently [estimated at about 14-billion light-years](https://www.wolframalpha.com/input/?i=%28speed+of+light%29+%... ), called the [Hubble length](https://en.wikipedia.org/wiki/Hubble%27s_law#Hubble_length ).

tldr, energy density of the universe remains same while the universe is expanding, so yes space is being created, and yes physical distances between things are changing (outside of the local influence of gravity that is, so no distance between earth and moon is not changing for example).

Now a longish answer, space is like a stage or a backdrop, it's not made of anything, yet we can model the behavior of radiation and matter within space, also we cannot talk only about space, we have to talk about both space and time since they are intertwined. So spacetime has geometry, ie it can be curved by presence of matter, and space tells matter how it can move (geodesics),

As for the expansion of space itself, Hubble observations found that every star outside the local group is moving away from earth and not only are they moving away from earth but they are speeding up as they move away from us, also we observe that the acceleration is proportional to the distance to those stars, for example a star 100 light years away is racing away 2x faster than a star 50 light years away (we inferred this based on the redshifting of the light coming from these stars that are moving away from us), based on these observations, we can conclude that the space between stars itself is expanding at rate proportional to the distance between stars, ie something like the opposite of positive pressure is pushing stars away and the further they are from each other the stronger the push away, we have some sort of always accelerating negative pressure affecting everything. This negative pressure is referred to as dark energy and it is responsible for this expansion of space. To put it another way outside of local cluster of galaxies, gravity is losing the battle against this negative pressure expanding force we call dark energy and eventually everything would be so far away that light from these distinct racing away stars won't ever make it to earth no matter how long we wait, which is why the author ends with future astronomers would see a barren universe.

disclaimer: I am no physicist, just another nerd who's watched a lot of documentaries and thinks he understands a thing or two about this stuff but could totally be drawing the wrong analogy or incorrect in some technical way for the above explanation, so I am happy to be corrected and learn.