Distance and Time: A Big Question

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Discussion Overview

The discussion revolves around the concepts of distance and time in relation to astronomical observations, particularly in the context of the Big Bang and the light travel time from distant objects. Participants explore the implications of observing objects at various distances and how that relates to the early universe.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about the implications of observing stars at different distances, particularly regarding what those observations mean for understanding the Big Bang.
  • Another participant confirms that seeing an object 13.6 billion light years away would allow one to observe the universe shortly after the Big Bang.
  • A participant questions the interpretation of observing two objects at different distances, suggesting that the farther object represents the beginning of time, while the closer object does not.
  • Another participant argues that even if a second object is 6 billion light years away, it would still be observing the Big Bang, just at a different temporal perspective.
  • A later reply notes the limitation of current observational capabilities, stating that nothing beyond the Cosmic Microwave Background (CMB) can be observed.

Areas of Agreement / Disagreement

Participants express differing interpretations of what it means to observe objects at various distances, particularly in relation to the Big Bang. There is no consensus on the implications of these observations.

Contextual Notes

Participants discuss the complexities of light travel time and its implications for understanding the universe's history, but there are unresolved aspects regarding the interpretation of distance and time in cosmology.

Serpens
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I'm new here and my question could sound stupid but I'm a little bit confused.

The Big Bang did happen 13.6 billion years ago. The Universe burst into life and after a while stars burst into life. Some of these stars are close to Earth like Sun and some of them are far far away.

Let's say one of them is 5 million light years away. That means what we see is actually what that star looked like 5 million years ago.It may be not there now, right? Let's say I saw an object which is 13.5 billion light years away. Does that mean I'm seeing something which belongs to the early Universe?
 
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Yes, exactly.
 
So let me get this stragiht if I would see an object which is 13.6 billion light years away, that would probably be the Big Bang?

There is still some unresolved paradox here. Let's say I saw two objects one of them is 13,6 billion light years away the other one is 6 billion light years away. For me the first object would be the beginning of time. However as for the second object it would be something which is 7,7 billion light years away, it wouldn't mean the beginning of time and space.
 
Serpens said:
So let me get this stragiht if I would see an object which is 13.6 billion light years away, that would probably be the Big Bang?
Basically; you would be seeing something soon after the big bang, yes.


Serpens said:
Let's say I saw two objects one of them is 13,6 billion light years away the other one is 6 billion light years away. For me the first object would be the beginning of time. However as for the second object it would be something which is 7,7 billion light years away, it wouldn't mean the beginning of time and space.
I'm sorry, I don't understand what you mean.
 
What I'm saying is basically when I see an "object" 13,6 billion light years away it is the Big Bang. But the second object is close to the first "object". So the distance between them is just 7,6 billion light years. So let's say that second object is a planet. If people on that planet see the first "object" for them that is not the Big Bang.
 
No, it would still be 'the big bang.' The people on the 'planet' are looking back at the big bang 6 billion years ago, when the big bang was closer (spatially and temporally) to them.
 
Got it, thanks :)
 

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