As we look further and further into the known Universe, what would be the meaning of not being able to see anything else at all? What could be ascertained by seeing absolutly nothing at all in the deepest reaches of space?
That you’re looking at the unpainted back wall of the Restaurant at the End of the Universe. Or something else that you can’t see through.
Well, you’re looking “longer and longer ago” as well as “farther and farther away”. Maybe there’s stuff out there NOW but there wasn’t stuff out there as many billions of years as there would have had to have been in order for the light from it to be reaching us here now.
Of course, I have no idea how it could’ve gotten there in the mean time.
As you look further and further out, you’re also looking further and further back in time, eg. looking out at something 10 billion light years away means you’re seeing it as it was 10 billion years ago.
Let’s assume that the Universe is 15 billion years old. Then, if you tried to see further than 14.9997 billion light years away, you’d run into a problem. Specifically, it wasn’t until 300 thousand years after the big bang that the Universe became transparent to light. So, you can’t keep looking further and further out into the “deepest reaches of space”. Eventually, you’ll run into this ‘wall’.
Karl:
It appears to me that what you are saying is that no matter where we look into the known Universe we are looking back, then where can we look to see where we are going? I am very comfused here. It makes me feel like I am riding in a car that only has a rear window and the car never goes in reverse.
The future?
I eagerly await someone more knowledgeable than I to come around and elaborate, or correct me.
Anything you look at is “looking back in time” the more time the farther the object. It’s easily detectable when talking to someone on the phone in another continent as it takes a noticable time for the signal to get to the other end via wire or satellite communications. If Buzz Aldrin had waved at me and said “I can see your house from here” I wouldn’t see him wave until about 1-1/4 seconds after he did it. If the sun blew up we wouldn’t see it for about eight minutes IIRC. Keep going further in the cosmos and eventually the time delays is longer than the earth has been around (6,000 years for Jack Chick, 4.5 billion for most of the rest of us). There is no “backwards direction” so consquently no direction we can see forward in time.
You seem to be misunderstanding: We can look backward in time because the light that we see from distant objects takes some time to get from the object to your eyes. For instance, Light from the sun takes approx. 8.5min to reach earth. so when you were a kid staring at the sun, the photons burning your retina had left the sun eight and a half minutes ago: you were observing the sun as it was eight minutes previously (until you went blind, that is).
This happens on a much larger scale with stars: the closest is 1.4 light years away from us (meaning that it’s light takes 1.4 years to reach us) so when we look at it, we are seeing it as it looked 1.4 years into the past. It could have disappeared since than, and we wouldn’t know it for 1.4 years.
We can’t look into the future, simply because all light that reaches us comes from the past (due to the fact that time as we know it only flows in one direction)