[alancalverd]

Look at a photograph. Or even what I have written here. You are seeing the past. Everyuthing we see is the result of photons that left the object some time ago. Big deal? I think not.

[guest39538]

OK, I'm just going to give some examples of why continuing this discussion is pointless, too much disconnect.

you - ''All we ever see is through light entering the eye  ''

Consider your own words of through, ask yourself why do you say ''through.''

I used 'through' with the meaning of 'because of' or 'due to'
Although we are immersed in light, it is only that light entering the eye and focussed onto the retina by the lens that gives us the image we see. Light from eg behind goes straight past and does not give us an image.

And until you shine a torch through it , it is ''visually-opaque'' is it not?

No it is not. It is just a lack of light entering my eye.

added - let us imagine (lol) you  had a single photon and I had a single photon in the dark. We released them at the same time in the direction of each others eye, when you receive the photon , you see me, when I receive the photon I see you  . Now do you see? 

This is just what we've been trying to tell you, but think..
If I were on the moon (5mins light travel away you say) my photon arrives with you and you say "Ah, he is standing on that rock", however, that was 5 mins ago, I have moved and am now hiding behind the rock, but you won't know this for another 5 mins. So you are only seeing what was happening 5 mins ago.

Now do you understand why our 2 views of what is happening are not reconcilable and further discussion is pointless.

This is the point you are failing to grasp and why it is worth continuing the discussion.

If I was on the moon, and ''ah I see Colin standing on that rock'' however, that was 5 minutes ago , I would not disagree with you it took 5 minutes for the photons to enter your eye that travelled from Earth.


HOWEVER,  while the photons from you begun their journey from 0_t, your geometrical position, my photons also made a journey from me to you, they also took 5 minutes exactly to reach your eyes, ''ah look there is the box sitting on the moon'', Colin is seeing the Box from 5 minutes ago in his past.


So if you are seeing me 5 minutes ago, and I am seeing you 5 minutes ago, when are we seeing each other?


 

[guest39538]

I have quoted from another forum a better explanation from a mod.

''Suppose you and I stand still on a road, 30 metres apart. The fastest signal of any kind that can travel between us will take 100 nanoseconds to travel from you to me or vice versa.

If I wave my hand at you, you'll see that wave 100 ns later. If you wave your hand at me, I'll see your wave 100 ns later. So, you are seeing my waving hand as it was 100 ns in the past, and I am seeing your waving hand as it was 100 ns in the past.

If we both happen to wave our hands at each other at the same time, then we'll both see the other person wave 100 ns after it actually happens, but we'll both see the waves simultaneously.''

[puppypower]

When we look into outer space, we see light from the past, not the present. Light from a galaxy, 1 billion light years away, shows us what that galaxy did a billion years ago. This is not what galaxy is doing today. As we look deeper and deeper into space, we go further and further back into time. We get the energy signal today, but it is really a snap shot of the past. It is like finding old photos in the attic from when your parents were your age. If mom had the big hair in that old photo, this is not the stye she has today. It represents a by-gone past.

The most distant and therefore oldest objects, we can see in space, tend to have the most red shift. This light or snap shot represents the most distant past (when your parent were young) and therefore reflect a time in history when the universe expanded the fastest; most red was 15 billion years ago. What we see is light (big hair) from the distant past, not the present.

If we start with a big bang or big boom, the initial explosion should propel matter the fastest. Inflation moves very fast to begin the propulsion. The oldest should have the most red shift since these photos reflect time, are right after the boom. As time goes on, it would then slow due to gravity. This would be proven if light from closer objects in time, have less red shift. This is observed.

Although this takes into account the time delay, this is not how the oldest universe data is interpreted. Why is there a difference when we are talking about the near past versus the distant past? Why does the brain interpret the immediate past, present and future, differently from the oldest past, present and future?

We currently assume our universe is expanding to the future, based on data from the distance past (baby pictures of your parents) as though past, present and future are interchangeable. If we talk about a something a nano-second between past, present and future, the interpretation is different and more in line with the above analysis.

The parts of the brain being used to interpret this, may have to do with whether we can directly prove something or not. If we can only indirectly prove something, we have more creative liberty, therefore another part of the brain can super impose on the time interpretation part, and adds its two cents; composite image.

For example, if you see a picture of mom with big hair, you may not be able to visualize her as a young wild big hair band groupie, who thinks with the spirit of youth. Instead, you see this picture in terms of your present day responsible and dull mom, but looking very young. The reason is, the present mom is based on hard observable data, whereas, young mom from the past, is unprovable and subjective. One may unconsciously opt for tangible data and superimpose that on the picture, which is also tangible. We can see the present clearly, therefore old pictures can take on present day attributes; two hard data superimposed, but not related is intuitively sensed to be better than one objective and one subjective. 

Consider this scenario:

Say we had a spherical bomb. This bomb is full of tiny metal spheres. One sphere of the bunch is a receiver, and the rest are transmittors. We explode the bomb, in the air. After it goes boom, all the tiny metal spheres are propelled in all directions. Some balls project further, while others lag behind to create a full debris field. 

If we look at the biggest picture, from our protective bunker, we see the blast accelerate the spheres in all directions from the bomb's center. Wind resistance slows the balls as they spread out; deceleration.

We will also look at this explosion from the POV of the single receiver sphere. From that POV we see the blast field, expanding away from this center. Most of the balls will appear to be red shifted. This red shift will be highest at blast time, for any given sphere, (oldest readings at boom time) and slower as time goes on (more current readings).

Also at any point in time, the most distant spheres, on the opposite side if the blast field, will move farther away at the fastest rate and have the most time lag, between when they transmit and when we receive. The signal does not reflect their true position properly, but needs a math adjustment to adjust for lag time. The closer balls have less time lag and will need less adjustment. We can't see all the balls in the debris field, simultaneously, with this worse with time. 

[Colin2B]

S∀

I have quoted from another forum a better explanation from a mod.

''Suppose you and I stand still on a road, 30 metres apart. The fastest signal of any kind that can travel between us will take 100 nanoseconds to travel from you to me or vice versa.

If I wave my hand at you, you'll see that wave 100 ns later. If you wave your hand at me, I'll see your wave 100 ns later. So, you are seeing my waving hand as it was 100 ns in the past, and I am seeing your waving hand as it was 100 ns in the past.

If we both happen to wave our hands at each other at the same time, then we'll both see the other person wave 100 ns after it actually happens, but we'll both see the waves simultaneously.''

This is what we've been trying to tell you, but without the numbers. Everything we see is in the past, we never see anything in the present.
However, as Alan said it's not a big deal, everyone is aware of it and for practical, everyday purposes it can be ignored.
It becomes important when considering communicating with astronauts and when looking at stars.

Hopefully you will now understand something about light, and why sight is not instantaneous, and why the both-way trip does not cancel out.