Light-Years, Horizons & the Age of the Universe

In summary: This is a difficult question. If you consider the concept of 'time dilation' then anything that is more distant than the CMB will appear younger than the CMB itself. This is because the CMB takes a very long time to reach us, and during that time the thing that is more distant has already passed by. However, even though the thing that is more distant is 'younger' than the CMB, it is still located at the same distance from us. So in a way, it is possible for something to be more distant than the CMB and still be located at the same distance from us.Thanks for asking!
  • #1
CosmiCarl
7
0
Is it accurate to say:

The Light-Year distance from Earth to the Surface of Last Scattering (= CMB location) EQUATES TO the Age of the Universe (13.73 Gyr)? (ignoring units conversion factors).

Would an observer, say 13.0 G Light-yr from us, ALSO see the CMB the same distance away?

Where is our Particle Horizon thought to be located, relative to the CMB? (Or Cosmological Horizon, whichever is greater).

Is it presently thought a significant portion of the Universe lies beyond our Particle Horizon? If so, would not at least a part of that portion have to be OLDER than anything we can observe, including the CMB?

Thanks in advance for everyone's time and thoughts!

CosmiCarl
 
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  • #2
CosmiCarl said:
Is it accurate to say:

The Light-Year distance from Earth to the Surface of Last Scattering (= CMB location) EQUATES TO the Age of the Universe (13.73 Gyr)? (ignoring units conversion factors).

Would an observer, say 13.0 G Light-yr from us, ALSO see the CMB the same distance away?

Where is our Particle Horizon thought to be located, relative to the CMB? (Or Cosmological Horizon, whichever is greater).

Is it presently thought a significant portion of the Universe lies beyond our Particle Horizon? If so, would not at least a part of that portion have to be OLDER than anything we can observe, including the CMB?

Thanks in advance for everyone's time and thoughts!

CosmiCarl

You are off by about a factor of 3, Carl.

The present distance to the last scattering surface is estimated to be about 45 billion LY.
 
  • #3
45 Glyr

Thanks, Marcus.

Is that number only theoretical, or is there some obsevational data to support it?

CosmiCarl
 
  • #4
That number is theoretical, Carl. It is possible the universe is larger than we can observe, but irrelevant. The unobservable portion, if any, will be forever unobservable. Such theories appear suspiciously similar to a temple priest fishing for disciples.
 
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  • #5
CosmiCarl said:
Thanks, Marcus.

Is that number only theoretical, or is there some obsevational data to support it?

CosmiCarl

This comes from observations, and the theory that has been developed given those observations. You can't directly point a telescope somewhere and find this kind of information. This, and related things such as the age of the Universe are always 'theory dependent', so if a different theory comes along that also explains the observations, but is favoured for some other reason (or by newer data) then these 'theory dependent' numbers change, even though the observations don't. Therefore you can't say they are determined either by theory or observations alone, the combination of the two is what defines these types of quantities.
 
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  • #6
Older than the Universe?

I understand all the underpinnings, thanks, guys.

But now I am a little confused:
If the age of the universe is thought to be 13.7 Billion Years, and nothing can travel faster than light, how can anything be more than 13.7 Billion Light Years distant? This just seems logically impossible.
 

1. What is a light-year and how is it used in astronomy?

A light-year is a unit of measurement used in astronomy to measure distance. It is the distance that light travels in one year in a vacuum, which is approximately 9.46 trillion kilometers. Light-years are used to measure the vast distances between objects in space, such as stars and galaxies.

2. How do scientists determine the age of the universe?

Scientists determine the age of the universe by measuring the rate of expansion of the universe and then calculating backwards to determine when the expansion began. This is known as the Big Bang Theory, which is currently the most widely accepted explanation for the origin of the universe.

3. What is the observable universe and why is it limited?

The observable universe is the portion of the universe that we can see and detect with our current technology. It is limited because the universe is expanding and the light from objects that are too far away has not had enough time to reach us yet. Therefore, there are parts of the universe that we cannot see or observe.

4. What is the cosmological horizon and how does it relate to the age of the universe?

The cosmological horizon is the boundary of the observable universe, beyond which we cannot see or detect anything. It is determined by the age of the universe and the speed of light. As the universe continues to expand, the cosmological horizon also expands, allowing us to observe more of the universe.

5. Can objects in the universe be older than the age of the universe?

No, objects in the universe cannot be older than the age of the universe. According to the Big Bang Theory, the universe began approximately 13.8 billion years ago. Therefore, the oldest objects in the universe cannot be older than 13.8 billion years. However, there are some theories that suggest the possibility of objects existing before the Big Bang, but these are still being studied and debated by scientists.

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