I mean if I drop a rock into a lake, its makes circles and the outermost circles are the oldest. Or if I blow something up, the furthest debris is the oldest.
In: Physics
The center is in the 4th dimension, time. If you back far back to the beginning, there is a point in time when it all started.
Picture the surface of a balloon. The entire universe is that 2 dimensional surface. When you blow up the balloon it expands and the entire 2 dimensional surface gets bigger, but there is no “center” that everything is moving away from. Now imaging a 3 dimensional sphere in 4 dimensional space. It started as a single point and expanded in every direction, but there is no center everything is moving away from. Everything is getting further from everything else.
Where is the center of the surface of the earth?
The only difference is that the curvature of the earth is expressed in two dimensions, but our universe’s in three dimensions.
Pick any point on the planet, travel from it in any direction, and if you travel far enough, you´ll end up back where you began.
The universe kind of works the same way.
Now imagine instead of a planet, we have a balloon. It’s still the same object and the same rule applies – pick any point on the surface of the balloon, move across it and eventually you will end up where you started. There are no edges, and therefore no center. This journey is of course unimaginably impossible, because of how massively, mind-destroyingly large the universe is, but as far as we know, this is the principle that pplies.
The balloon is also expanding. Once upon a time the entire balloon was tiny but ever since the big bang it has been expanding, like someone is blowing air into the balloon. Every point on the balloon is therefore moving further away from every other point. From any point, if you stay there and look around you, it looks like every other point is rushing away from you, but if you were over there rather than over here, the same would apply.
Remember, this balloon has a 3D surface – not a 2D one.
Imagine a number line. The number line extends infinitely in both directions, but imagine you are looking at the portion of it that goes from -10 to 10. Each integer has a tick mark.
Now squish the tick marks closer together. Now the portion of the number line you are looking at goes from -100 to 100.
Squish them closer together again. Now the portion of the number line you are looking at goes from -1000 to 1000.
Keep squishing them.
This is like working backwards towards the Big Bang (if our universe were 1D).
The moment of the Big Bang would have been when all the tick marks are squished as close together as they can possibly be. The number line is still infinite in extent, though, so there is no center of it.
After the Big Bang, all the tick marks start expanding away from each other at the same time. So the Big Bang didn’t happen at one spot — it happened everywhere.
You can imagine that all the tick marks start expanding away from 0. Or you can imagine that they all start expanding away from 5. Or you can imagine that they all start expanding away from 100.
Every single point on the number line can be thought of as the center of expansion.
The universe does not have a center because it is either infinite or closed in on itself. Additionally, it is homogeneous and isotropic. This means that, on a large scale, the universe looks the same in every direction and at every point.
If the universe is infinite, it has no edges and no center. There is an infinite amount of matter, distributed evenly throughout.
If the universe is closed (like the surface of a sphere), it is finite but unbounded, meaning you could travel indefinitely without ever encountering an edge. In this case, matter is still evenly distributed, so there is no unique center point.
Here’s a detailed explanation:
1. **Infinite Universe**: If the universe is infinite, it has no boundaries. Every point in the universe is essentially the same as every other point because there is no edge or center. Imagine an infinite flat plane; no matter where you are on that plane, it stretches out infinitely in all directions.
2. **Closed Universe**: If the universe is closed, it is like the surface of a sphere. A sphere’s surface is finite but unbounded. If you travel in a straight line on the surface of a sphere, you will eventually return to your starting point without encountering an edge. In this model, the universe is finite in size but does not have a boundary or center.
3. **Homogeneity and Isotropy**: The universe is homogeneous, meaning matter is distributed evenly when viewed on a large scale. It is also isotropic, meaning it looks the same in every direction. These principles contribute to the idea that there is no special point or center in the universe.
So, because of these properties, the universe has no center. Instead, every point in the universe is essentially equivalent to any other point.
However, if we consider the possibility that the universe has only a finite amount of matter, the situation might be different. If the homogeneity and isotropy only apply to the observable universe or certain regions, then it’s conceivable that there could be a gravitational center where the distribution of all matter is balanced. This would mean that while the observable universe appears uniform, there could be regions far beyond our observational limits where the distribution of matter becomes sparse or nonexistent, leading to the presence of a gravitational center in the larger context.
Not an answer but my own layperson’s questions and check on my own understanding:
1. Is Einstein’s special and or general ToR the genesis of the Big Bang concept, in this scientifically accurate conceptualisation? Ie. there is no “centre”, even though others previously may have conceived a single “dot” “exploding” “into” space?
2. Is my idea that rather than a “dot” the Big Bang is more like an instantly appearing “universe loaf” that can be “sliced” into freeze-frame moments with all instances of everything having a place somewhere in the “loaf” and we are in it, and all freeze frame moments exist equally within it, even if we access (via “time” and “consciousness”) a few of those moment-slices? (Ref Brian Greene pop physics books, esp Fabric of the Universe.)
Thank you for helping me continue to try to grasp all this stuff that is quite simply humanity’s greatest achievement, why would any human not work to grasp this stuff, the payoff of closing in on understanding it is, well, infinite in its own right!
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