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I've sometimes heard of galaxies that are millions or billions of light years away but if we could instantly travel 786 trillion light years in any direction, what are we likely to find? And what if we continued on for another 786 trillion light years?

PS: I'm not a physicist.

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3 Answers 3

We would likely find galaxies. The universe, as far as we can observe, is very uniform on the large scale. Depending on the geometry of the universe, may be the place we left for travalling. For a fixed cosmic time the spacetime seems to be curved in a way that the universe looks finite when travelling along a straight (geodesic) line, although without boundary.

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There is one principle that says "The universe is isotropic". It means it looks the same (on large scales) from any point you look from.

This means, in turn, that if you travel 786 trillion light years instantaneously in some direction, you'll find a very differnt sky but with exactly the same general structure: stars, galaxies, clusters of galaxies, and attractors.

Altough you can NOT travel so far so fast, you can make this mind experiment:

Send a spaceship so far at (almost) speed of light with a photo camera, take a 360º photo, come back, arrive 1572 triilion years afterwards. While awaiting for the spaceship return, wait 786 trillion light years, take a 360º photo, wait the othe 768 trillion years.

Compare the two photos. They were taken at the same "Cosmic time", one of them 768 trillion years ago, here, and the other one maybe two or three years of spaceship time ago, 768 trillion light years afar.

The photos will look the the same on the rough scale.

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Well, considering that the Big Bang is less than 14 billion years ago, and the observable universe can't expand faster than the speed of light, nobody knows what's farther than 14 billion light years away, or if there is a "786 trillion light years" away. We certainly have no information from such a place, and as far as we know, there is no place farther than 14 billion light years away.

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this is not true, the universe itself seemingly CAN expand faster than light (nothing can travel through space fasther than light, but space can do what the hell it wants, according to wiki for example the radius of the ovservable universe is about 47 billion lightyears. –  DrCopyPaste Feb 10 at 11:03
So, have we any way of knowing what's a trillion light years away? Can we know if there is a trillion miles away? At least can we know that now? –  Marc Feb 10 at 18:38
from what I've heard: no, we cannot. We cannot see past the CMB (radiation from supposedly ~350,000yrs after the big bang), because it is opaque –  DrCopyPaste Feb 12 at 14:54
One trillion miles away is actually about 1/6 of a light-year, so we can definitely see that far. One trillion light years, on the other hand, . . . –  HDE 226868 Aug 5 at 20:19
I meant trillion light years, not miles, as I said in the original answer. –  Marc Aug 5 at 23:45

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