If the universe is expanding, do planets get smaller the further away they are from where the Big Bang occured?


The Big Bang pushed a finite amount of matter outward to form planets, moons, stars, etc, so would it be reasonable to assume that larger planets exist near the center and things created towards the outskirts become tiny? I’m comparing this to an explosion; a volcano for example produces large boulders that land nearby while smaller fragments land further away.

Secondly, once all matter has been separated into its respective creation, won’t there then become an endless void?

In: Physics

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The Big Bang didn’t happen at a specific place. It was not the explosion of a dense ball into an empty void, it was the transition of the universe from hot and dense *everywhere* to cool and mostly-empty everywhere. Space itself grew, causing the overall density of the universe to drop.

There are a few misconceptions here, but let me start by saying I’m not a cosmologist nor am I an astronomer.

First: the universe has no center, there is no point from which the universe expanded, that point has become the whole universe.

Secondly: This expansion occurs nearly everywhere. The places where the universe doesn’t expand are places where gravity is acting with some certain intensity. Planets dont expand because the force of gravity overcomes the expansion. Whereas the space between galaxies or galaxy clusters (I assume) has sufficiently weak gravity that the expansion can take place. This is why the solar system is not noticeably expanding.

I dont think an explosion is a great model for the big bang, although I struggle to explain why or give a better example. Additionally the amount of mater in existence at the time of the so called big bang is not necessarily the same as what exists now, because mass and energy can be converted between each other, so where objects with mass began may not exactly reflect the state of the universe now.

As for the endless void I think the current school of thought is that there will be islands of mass (galaxy formations) that will be separated by an ever increasing void.

Again I’m not an expert in this so if this gains traction and someone who is formally educated in this, or just knows a lot about it is bothered by any inaccuracies please feel free to point out any shortcomings.

Not sure about your first question. For your second question: Do you mean an endless void past wherever the expansion stops? No, because there isn’t a void beyond the edge of universe. The universe has no borders. Basically there is no “outside the universe.” The universe isn’t expanding at the “edges”; it’s expanding everywhere, because new space is popping up in between everything else. This is thought to be driven by dark energy.

This video explains the expansion:

The second half of this video explains the dark energy part: