Spacetime

This discovery, of the most distant object ever seen, finally got me understanding why space and time are inextricably related...

As you know, when we talk of astronomical distances, we talk of time. We talk in "light years" and "light seconds," not "miles" or "gigameters" or anything like that. And there's a simple reason for it - as most of us have known since elementary school, when we see something that's 1 light year away, we're actually seeing it as it was 1 year AGO.

My breakthrough came in realizing that there's a marked difference between what something was a year ago and what it is today. And thus, since we can only see what other spatial bodies USED to be, they only exist, for us, in that past state.

Let's take the moon, for example. Light from the moon takes 1.3 seconds to get here, which means we have no idea what the moon looks like right now, unless we wait 1.3 seconds. Even if we had someone stationed on the moon, while they'd be able to see what the moon's like right now, they wouldn't be able to tell us without using radio, which takes....1.3 seconds. If the moon simply disappeared, the oceans might get a little choppier, but we still probably wouldn't find out for 1.3 seconds, no matter what.

The sun? Same thing, but 8 minutes. The center of the Milky Way? About 25,000 years. We know that there was a black hole at the center of our galaxy 25,000 years ago, but have absolutely no idea now.

It's like the legendary Schrodinger's Cat thought experiment - put a cat in a box and come back a day later, but don't open the box. Is the cat alive? Is it dead? Does it have 8 legs because of the crazy radiation coming from the scary experiment next door? All of these possibilities exist, and you'll never know which is true until you open the box again.

Now imagine seeing back more than 13 billion years. This newfound galaxy could truly be anywhere in the universe now, if it hasn't gotten swallowed by a mega-black hole or vaporized by a collision with another galaxy.

For us to open Schrodinger's box on this distant galaxy, we'd have to travel 13 billion light-years to where it was back then, and then another 13 billion light-years to where it is now. And even then, even if we could travel the speed of light, it would still be another 26 billion light-years away (if not more, since the universe is expanding at much faster than light speed).

Basically, we couldn't catch the galaxy, even if we were a photon and had an eternity to try! So there's no way to find out what that galaxy is doing now.

When we talk about things that are huge distances away, we can't talk about them as they are now. We can only talk about these distances as related to the time it takes information to get from there to here. And thus, we see the absolute intertwining of space and time.