[malux85]

One thing I have always wondered, since gravity is proportional to the mass of the two objects and inversely proportional to the square of the distance between them, if the universe was smaller with the same mass, wouldn’t gravity have been more “dense” in an earlier universe?

And since we know that gravity affects the rate of flow of time, wouldn’t the rate of time be enormously distorted earlier universe?

I’m not trained in any of this, so hopefully there are greater minds here who can help me understand

[ben_w]

> inversely proportional to the square of the distance between them

As I understand it, that’s an approximation for Euclidean space because the area of a sphere is also proportional to the square of the radius in such a space, but it’s not true of non-Euclidean spaces like in GR because the area-radius relation is different.

IIRC, the cosmic microwave background has a gamma factor of about 1100, so the area of that shell is the same as one 1100 times closer or 1/1100^2 times the area as a Euclidean sphere with that radius.

> And since we know that gravity affects the rate of flow of time, wouldn’t the rate of time be enormously distorted earlier universe?

Time did indeed slow down then compared to now, although it’s not entirely obvious to me that this has any physical interpretation when it happens “everywhere”: https://youtu.be/66V4RSmDqYM

[MattPalmer1086]

My understanding is that time was not slower (whatever that would mean), only that the expansion of the universe means that light is stretched. So events in the early universe appear to happen 5 times slower.

[candiodari]

We know that the force carrying particles of all forces have a frequency, just like any other particle. That means that if particles on average move faster than, say, double that frequency, they can't exist.

So there must have been a time when electromagnetism, the weak and even the strong force just didn't exist. They couldn't. So particles would just have totally ignored those forces.

We don't know if gravity is the same, but ... why wouldn't it. Though of course according to relativity gravity just wouldn't care, but that just raises a lot more questions than it answers.

[addaon]

> particles on average move faster than, say, double that frequency

What does it mean to compare ("faster") a velocity and a frequency (inverse time)?

[candiodari]

I don't think there's a good answer to this question, at least not when it comes to the nature of particles and light, because we don't have a good answer to what movement and time are. We already know both light and particles are you moving relative to fields. Light is you moving relative to an electromagnetic field. If you move towards a magnetic field you would find it starts "glowing", in fact, that is what light is. But it's not like a magnetic field reacts to you because you start moving.

The issue is that movement and time are fundamental to the universe, yes, in the way relativity describes but also in a totally different unknown way. In some ways particles are "just" things moving relative to one another. Which, for one thing, brings the perspective question (if you accelerated to a "real" speed, would you see a different universe? Because you would disagree with us slowpokes here on earth on what particles exist at least in some cases. But would you see an entirely different universe?)

[malux85]

This is a really interesting answer, the “light and particles are you moving relative to fields” would make a great blog post

[mensetmanusman]

If the energy density was too high to allow for quarks to exist, maybe there were no strong forces present.