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Name: Yossi
Status: student
Grade: 9-12
Location: NY
Country: USA 
Date: Spring 2013


Question:
When we have something like the big bang where there are no outside factors affecting the explosion, Should we expect all the particles and energy to fly apart in exactly evenly spaced directions with the same amount of space between one particle and the next, making the formation of clusters of particles (like stars planets or even atoms) impossible? Would not any particle would have no reason to get pulled toward one neighboring particle over the other neighboring particle causing it to stay balanced in between? But we do have a universe made up of clusters of particles, how did the balance get tipped?


Replies:
Yossi,

This may not be a misconception you have, but it is such a common visualization problem that I would like to discuss this first before answering the core of your question. There is a very common visualization error that the Big Bang is like an explosive material that explodes, sending substances outward from the explosion. This is a very poor analogy because it makes us imagine that the universe is now expanding outward from a certain fixed point (which raises the question of "expanding into what?" and "where in space is the center of the explosion?" - all false questions). It is a better visualization to imagine a universe that was without matter and then, at the Big Bang, filled up with matter - everywhere. The Big Bang and the expansion of the universe then is not so much like dynamite exploding and sending matter outward, increasing the spaces in between objects, but more like an empty ocean that suddenly got filled with fish and then the fish find that - without moving or swimming - the water in between fishes seem to be stretching out and increasing the space between every fish.

So in answer to your question, since there is no "force" that is sending the particles "flying apart" - there is only this fundamental property of space that seems to be increasing in dimension, we need not consider how this non-existent "force" affects the particles. In effect, the particles are essentially stationary with the space between particles increasing. So, any imbalance in gravitational force - caused by any imbalance in mass, will result in motion. Let us say that there is a sea of *stationary* particles with a mass of "1" and it so happened that in that sea there is one particle that has a mass of 1+x, no matter how small that x is, it will cause the particle to exert a slightly stronger gravitational attraction to the surrounding particles. This will cause motion toward this one particle. And as soon as the particles clump up, the gravitational attraction will only increase exponentially.

Greg (Roberto Gregorius) Canisius College


Yossi,

You are correct that there should be a some kind of symmetry at the very beginning of the universe. However, it is theorized that asymmetry soon followed. There is a theory called "symmetry breaking" which combines concepts from quantum physics, baryogenesis, etc. which helps describe how, as matter decoupled from energy, different forms of particles were created. Unfortunately, my own understanding of this part of cosmology is not very strong and I can't explain it properly. You may want to ask the physicists in this forum.

Greg (Roberto Gregorius) Canisius College



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