[SolarNet]

Because this expansion is so infinitesimal on that scale as to be negligible. It's about 7%/Gyr, or a billion years for an unbound structure's "space" to grow by 7%. Or about 70 picometers (10^-12) per meter every year. Or in other words, about a water molecule per meter every four years.

At that rate nearly every other force (from chemical bonds to gravity) prevent anything but the largest cosmological structures (like galaxies) from being effected. They simply continue with their system as they always have, and the extra space shows up as distance between galaxies.

[lifeformed]

> Or in other words, about a water molecule per meter every four years.

That still sounds measurable though. Has there been any multiyear experiments that try to measure something like that?

[SolarNet]

How? Gravity will make all such changes impossible to measure except at galactic scales.

Again any "new space" doesn't stick around where it was created. The atomic forces, chemical forces, and gravity maintain the system distances we are used to.

[naveen99]

Where was gravity when the universe was hot and dense ?

[metiscus]

Sometime after around 10^-43 seconds apparently is when it started having effects.

https://www.quora.com/When-did-gravity-first-arise-in-the-un...

[drran]

At this time, it was denser and heavier than any black hole. Why it didn't collapse back then?

[metiscus]

I am going to preface this by saying I'm no scientist. I think it is because the expansion velocity is so high. It would be nice to get a definitive answer.

[naveen99]

Also, how is space expanding in time when space is already intertwined with time. Is the block universe expanding in meta time ?