How is new space created as the universe expands? Einstein discovered that empty space is not nothing, so what is responsible for new space appearing into existence, when energy and matter cannot?

Question

[Nasa.gov](https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy) explains dark energy like a property of space, and go on to say:

> Albert Einstein was the first person to realize that empty space is not nothing. (…) The first property that Einstein discovered is that it is possible for more space to come into existence.

But they never elaborate on how Einstein knows this. I know this is a field without concrete answers, but I’m curious about Einstein’s explanation.

In: Physics

Answer 1

There’s no easy way to conceptualize but imagine a balloon being blown up – between any two points there’s more distance than there was before – the distance itself is “created” by the balloon material (the rubber); so just like “empty” space is not empty, think of space being the rubber, or material, of space.