We all know that black holes have event horizons, and the universe itself has them, the event horizon of the universe is actually closer to us than the particle horizon (the boundary of the observable universe), according to our most accurate measurement parameters, the event horizon of the universe is about 16 billion light-years away from us, which means that we can never reach or even communicate with the universe of space.
In a way, we see only the mirror image of the part of the universe that we can never touch. As the universe expands, more and more cosmic space will pass through the event horizon, and in the end almost all the universe will no longer belong to the event horizon!
But what if we could break through the limits of the speed of the universe? Einstein's theory of relativity shows that it is impossible for any object to move faster than the speed of light, but there can also be relative speeds faster than the speed of light between the two places, in which the warp engine is used as a power to achieve faster-than-light operation.
Imagine having a curvature ship like this, and we are chasing particle horizons with the energy of the entire planet, what can we find? There is no doubt that in addition to the universe is still the universe. Particle horizons are only defined by the boundaries of our current field of vision, no matter in that direction, we are surrounded by the universe, and the particle horizon is also expanding, and finally enter the particle horizon, you will see the milky way like a prototype cosmic microwave background radiation cluster appear in the particle horizon.
It can be assumed that you will be in an environment that is very similar to the cluster structure of the galaxies you have now. So what about further down? What's beyond that border?
It depends on the geometric structure of the universe. On the whole, the geometry of space-time is very flat, and on the small scale of stars and galaxies, space-time is indeed undulating, but macroscopically it is smooth, a bit like the shape of planes and waves.
The distribution of galaxies and measurements of the cosmic microwave background radiation confirm that the universe is flat and has extremely high (but not infinite) accuracy. If space-time were really completely flat, then simply by quoting Einstein's consensus, we would conclude that the universe is infinite.
And now everyone says so, so if this is true, what happens when you cross the particle horizon? The universe will stretch forever!
Infinity is the most amazing monster, and it also comes in all shapes, including some of the infinite repetitions in this universe. But is our universe really completely flat? We look at the surface of the Earth very flat, because the curved parts of the Earth are invisible to us. But a walk around the International Space Station reveals that the Earth is round.
So, what if the curvature of the universe is so small that we can't see that far, or can't make accurate enough measurements to detect it? It is possible that the universe actually has a bend hidden in an uncertain part of the best measurements so far, and if that bend is real, then the universe may really be a hypersphere surface, a three-dimensional surface in four-dimensional space!
In that case, our curvature engine shuttle will eventually circle the supersphere and finally return to the starting point! So how long are we going to sail?
According to a recent calculation of the minimum radius of the universe's curvature, it is necessary to travel an distance of 18 times the distance to the particle's event horizon to return to the starting point. Assuming that the expansion of space throughout the journey is at rest, we still have to bear in mind that in the assumption of the geometric structure, we can simply and crudely use Einstein's formula to infer.
But general relativity is not enough to explain everything, such as the question of the origin of the universe. Our universe may be in an infinite bubble slowly expanding in an exponentially expanding multiverse, and the bubble universe has boundaries, but what about the world on the other side of the boundary? The laws of physics there can even be very different from ours here!
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