That still was too much for me to grasp. His explanation was great but it still didn't seem to describe what is at the "end" of space at 15 billion light years away.
As Tyson suggested in the video, "nothing". He implies that you cannot look beyond the birth of our Universe because there simply is nothing there. That is why scientists are attempting to look at what took places prior to the Big Bang Theory
14 billion light years away is the "end" of our horizon in space. It's the farthest we can see, because with the Universe being 14 billion years old, the farthest we can see is how far light can travel in that time. 14 billion light years. We can't see beyond that horizon because the light beyond that horizon would need longer than 14 billion years to reach us... which is older than the universe.
Space doesn't end at 14 billion lightyears away. We just simply can't see beyond that distance due to the time it takes the light from distant stars, galaxies, and other phenomena to reach us.
Neil Degrasse Tyson said:"Just to clarify, so it takes light time to reach us, and the Universe hasn't been here forever. If you combine those two facts, you get an "Edge of the Universe". So, the universe has been here for 14 billion years, the farthest thing that could send us any information is 14 billion light years away."
So when he says "nothing" is beyond our universal horizon, he means that a telescope could never see beyond 14 billion light years. There's nothing to see because there's no way any information (light) could have been sent from farther away and reach us in the time available. He doesn't mean that there's no universe beyond 14 billion lightyears away.
Neil deGrasse Tyson said:"We don't know wether or not the ENTIRE universe is infinite, the universe could be twice our horizon or infinitely larger than our horizon... ...so if we go there (the edge of earth's universal horizon) that would be the center of their own horizon... and whatever the age of the universe is, for them at that time, that would be the radius to their horizon..."
So, for an alien species 13 or 14 billion lightyears away, they could see 13 or 14 billion lightyears farther than us, relative to us here on Earth.
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