RedSteadEd t1_itn0q4z wrote on October 24, 2022 at 9:02 PM

Reply to comment by AcidShAwk in Webb reveals unprecedented glimpse of merging galaxies. Because light takes time to travel to us, when we look at objects like this one in the very distant regions of the universe, we're seeing light that was emitted about 11.5 billion years ago by Wagamaga

>11.5b years for the light to reach us.. Our physical position in space was not here 11.5b years ago. We would have been a lot closer to to wherever this light originated.

Imagine throwing a baseball at somebody, but you're both running backwards away from each other. That's basically what's happening, but on a bigger scale - light is traveling from the galaxy to us, but the space between us is always expanding.

>Does that mean it's taken 11.5b years for that light to finally overtake our position ?

Yes. The image we see when we look at the galaxy left the galaxy 11.5b years ago and carries with it a picture of what the galaxy looked like back then. However, when that light was created 11.5b years ago, the galaxy would have been much closer than 11.5b lightyears. Imagine if I was standing next to you and then traveled instantly to that galaxy. You might think that it would take 11.5b years for you to finally see me (that's how long it would take for the light to reach our original position), but that doesn't factor in how much the space between us would expand during those 11.5b years of travel. The light would have to keep going beyond the 11.5b years to reach you, but I don't know the math, so I can't tell you how much further.

>What have we taken images from literally 180 degrees from that image above to view 11.5b years from the completely opposite direction?

I'm not sure if I understand this... yes, we have pictures facing the opposite way in the universe that also have light that originate from 11.5b years away. Or, are you asking what it would look like if, 11.5b years ago, someone in that galaxy took a picture of us?

>I'm trying to understand at what point we look at ourselves and say there is light from 11.5b years ago.. in every direction

As I understand it, this is part of how we know the universe is expanding - there's light (well, radiation) coming towards us from every direction that's almost as old as the universe. It's called the Cosmic Microwave Background.

AcidShAwk t1_itnc0gz wrote on October 24, 2022 at 10:20 PM

> I'm not sure if I understand this... yes, we have pictures facing the opposite way in the universe that also have light that originate from 11.5b years away. Or, are you asking what it would look like if, 11.5b years ago, someone in that galaxy took a picture of us?

Take a volume of space, and position a spherical point within that space.. now draw a vector away from the sphere from 6 equal-distant positions on the spheres surface.

Take a picture from each vector origin in the same direction as the vector.

That would give you 6 distinct images from every possible direction away from the sphere.

Do we have images of 11.5b years ago from every single direction away from the earth?

[deleted] t1_itqwr2l wrote on October 25, 2022 at 5:24 PM

[removed]

pittaxx t1_itu6ly7 wrote on October 26, 2022 at 10:23 AM

Still no idea what you are talking about.

Humanity had the capability to take pictures for so little time that on the scale of the universe earth is a point that doesn't move.

And the 11.5b years only apply to the objects really far away. How far into the objects pay we see is directly proportional to how far away the object is. The closest star is only 4 light years away, so we see it as it was 4 years ago. (Estimated) 13.3b years for the oldest point of light we found so far.

If you want to think in vectors, you have to add a fourth dimension - time. You draw a vector from earth, but you extend it over time, and for each 1 light-year of length you are turning the galaxy simulation back one year. Only the objects that intersect the tip of the vector are visible to us, nothing else is.

Now repeat that with infinite number of vectors and you have an expanding bubble. Everything on the surface of that bubble is equally old, but since objects don't move faster than light, we only have one snapshot of them.