Singularity
The general theory of relativity predicts that a so-called "singularity" is hidden in a black hole (i.e. behind an event horizon).
A thought experiment from school physics:
A space capsule is on the moon. The astronauts want to teach back to earth. To do this, they have to overcome the moon's gravitational field. If they only had a catapult instead of a rocket drive, this would have to throw the space capsule into space at a certain speed so that it does not fall back onto the moon.
Escape speed
This speed can be calculated solely from the mass of the object to be left and its radius (position of the space capsule on the surface). For the moon it is: 2.3 km/s.
If the astronauts not only want to leave the moon, but also our solar system via catapult, the escape speed is 42.1 km/s, and for our galaxy: 320 km/s. In order to leave our universe, however, our atronauts would have to be faster than light. However, since physics does not allow mass to ever move faster than light through space, neither astronauts nor anything gross can ever leave our universe "outward".
According to the general theory of relativity and space-time, this is justified because the mass of our universe bends space so that even emitted light falls back again. That means there are no geodesics that lead out of our universe.
A journey to the edge ...
In my thoughts I stand at the "edge" of our visible universe and look back at our universe, which with its geodesics of light particles should look like a ball of wool. When I turn around, the event horizon surrounding us is still unreachably far away. I move away from our universe in Gefanken and move through the purest black towards the event horizon. Our visible universe in the rearview mirror is getting smaller and smaller, but I've only got a little closer to the event horizon. I keep traveling. Only a tiny dot is left of our universe.
From this perspective at the event horizon, our unimaginably large universe "shrinks" to a grain – to a "singularity".
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[1] Event horizon (Wikipedia, 09/25/2017)
[2] Sinularity (Wikipedia, 25/09/2017)
[3] Escape speed (Wikipedia, 25/09/2017)
[4] Geodesics (Wikipedia, 25/09/2017)
A thought experiment from school physics:
A space capsule is on the moon. The astronauts want to teach back to earth. To do this, they have to overcome the moon's gravitational field. If they only had a catapult instead of a rocket drive, this would have to throw the space capsule into space at a certain speed so that it does not fall back onto the moon.
Escape speed
This speed can be calculated solely from the mass of the object to be left and its radius (position of the space capsule on the surface). For the moon it is: 2.3 km/s.
If the astronauts not only want to leave the moon, but also our solar system via catapult, the escape speed is 42.1 km/s, and for our galaxy: 320 km/s. In order to leave our universe, however, our atronauts would have to be faster than light. However, since physics does not allow mass to ever move faster than light through space, neither astronauts nor anything gross can ever leave our universe "outward".
According to the general theory of relativity and space-time, this is justified because the mass of our universe bends space so that even emitted light falls back again. That means there are no geodesics that lead out of our universe.
A journey to the edge ...
In my thoughts I stand at the "edge" of our visible universe and look back at our universe, which with its geodesics of light particles should look like a ball of wool. When I turn around, the event horizon surrounding us is still unreachably far away. I move away from our universe in Gefanken and move through the purest black towards the event horizon. Our visible universe in the rearview mirror is getting smaller and smaller, but I've only got a little closer to the event horizon. I keep traveling. Only a tiny dot is left of our universe.
From this perspective at the event horizon, our unimaginably large universe "shrinks" to a grain – to a "singularity".
--
[1] Event horizon (Wikipedia, 09/25/2017)
[2] Sinularity (Wikipedia, 25/09/2017)
[3] Escape speed (Wikipedia, 25/09/2017)
[4] Geodesics (Wikipedia, 25/09/2017)
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