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This doesn't add up.

Furyan5
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10/18/2015 6:16:40 PM
Posted: 1 year ago
If the edge of the observable universe is 45 million light years away, then the light reaching us now, left there 45 million years ago. That's approximately 31 million years before those stars were created, seeing as the universe is estimated to be 14 billion years old. Can someone explain how?
TBR
Posts: 9,991
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10/18/2015 6:21:09 PM
Posted: 1 year ago
At 10/18/2015 6:16:40 PM, Furyan5 wrote:
If the edge of the observable universe is 45 million light years away, then the light reaching us now, left there 45 million years ago. That's approximately 31 million years before those stars were created, seeing as the universe is estimated to be 14 billion years old. Can someone explain how?

You have a very basic question.

The universe is expanding. At some point, it was smaller.

Much more detail.
http://usersguidetotheuniverse.com...
Furyan5
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10/18/2015 6:51:13 PM
Posted: 1 year ago
At 10/18/2015 6:21:09 PM, TBR wrote:
At 10/18/2015 6:16:40 PM, Furyan5 wrote:
If the edge of the observable universe is 45 million light years away, then the light reaching us now, left there 45 million years ago. That's approximately 31 million years before those stars were created, seeing as the universe is estimated to be 14 billion years old. Can someone explain how?

You have a very basic question.

The universe is expanding. At some point, it was smaller.

Much more detail.
http://usersguidetotheuniverse.com...

Yes it's expanding. That means what we see as the edge is 45 billion years old and its now actually further away. 45 billion is the edge of the observable universe. That's how far we see it. I still don't see how stars can shine 31 billion years before the big bang.
TBR
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10/18/2015 6:54:17 PM
Posted: 1 year ago
At 10/18/2015 6:51:13 PM, Furyan5 wrote:
At 10/18/2015 6:21:09 PM, TBR wrote:
At 10/18/2015 6:16:40 PM, Furyan5 wrote:
If the edge of the observable universe is 45 million light years away, then the light reaching us now, left there 45 million years ago. That's approximately 31 million years before those stars were created, seeing as the universe is estimated to be 14 billion years old. Can someone explain how?

You have a very basic question.

The universe is expanding. At some point, it was smaller.

Much more detail.
http://usersguidetotheuniverse.com...

Yes it's expanding. That means what we see as the edge is 45 billion years old and its now actually further away. 45 billion is the edge of the observable universe. That's how far we see it. I still don't see how stars can shine 31 billion years before the big bang.

It, the star, did not. It is only further away.
Furyan5
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10/18/2015 7:08:51 PM
Posted: 1 year ago
At 10/18/2015 6:55:27 PM, TBR wrote:
You are looking at light-years (distance) and implying age. That is not the case.

To my understanding, it takes light a year to travel one light year. So light from a star 45 billion light years away took 45 billion years to get here. That sun had to exist 45 billion years ago and is probably burnt out by now. How is it not the case?
TBR
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10/18/2015 7:18:08 PM
Posted: 1 year ago
At 10/18/2015 7:08:51 PM, Furyan5 wrote:
At 10/18/2015 6:55:27 PM, TBR wrote:
You are looking at light-years (distance) and implying age. That is not the case.

To my understanding, it takes light a year to travel one light year. So light from a star 45 billion light years away took 45 billion years to get here. That sun had to exist 45 billion years ago and is probably burnt out by now. How is it not the case?

OK. Again, don't try to mix the distance measurement like that. Let's say the light started its journey when the universe was much much smaller. If the universe would NOT have grown, the light would have gotten here quicker, right? BUT, the universe grew in the time it took for that light to arrive, right? The thing that is now further away from us is SO far away, the NEW light from it would take 45 billion years to get here. BUT WAIT, there's more. The universe is STILL expanding.

Make some sense?
DanneJeRusse
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10/18/2015 7:23:54 PM
Posted: 1 year ago
At 10/18/2015 7:08:51 PM, Furyan5 wrote:
At 10/18/2015 6:55:27 PM, TBR wrote:
You are looking at light-years (distance) and implying age. That is not the case.

To my understanding, it takes light a year to travel one light year. So light from a star 45 billion light years away took 45 billion years to get here. That sun had to exist 45 billion years ago and is probably burnt out by now. How is it not the case?

Most everything in the universe is moving away from everything else, that's how expansion works. Here's a basic diagram of some galaxies, for the sake of argument, we'll say that each galaxy is moving away from each other at 10,000 kilometers per hour.

A<----->B<----->C<----->D< ----->E

A is moving away from B at 10,000 kph
B is moving away from C at 10,000 kph
C is moving away from D at 10,000 kph
D is moving away from E at 10,000 kph

A is moving away from E at 40,000 kph Even though both A and E are moving at 10,000 kph. When distances of billions of light years are involved, galaxies that span those distances are moving away a near light speeds.
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Furyan5
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10/18/2015 7:27:08 PM
Posted: 1 year ago
At 10/18/2015 7:18:08 PM, TBR wrote:
At 10/18/2015 7:08:51 PM, Furyan5 wrote:
At 10/18/2015 6:55:27 PM, TBR wrote:
You are looking at light-years (distance) and implying age. That is not the case.

To my understanding, it takes light a year to travel one light year. So light from a star 45 billion light years away took 45 billion years to get here. That sun had to exist 45 billion years ago and is probably burnt out by now. How is it not the case?

OK. Again, don't try to mix the distance measurement like that. Let's say the light started its journey when the universe was much much smaller. If the universe would NOT have grown, the light would have gotten here quicker, right? BUT, the universe grew in the time it took for that light to arrive, right? The thing that is now further away from us is SO far away, the NEW light from it would take 45 billion years to get here. BUT WAIT, there's more. The universe is STILL expanding.

Make some sense?

Lol none whatsoever. It's obviously beyond my grasp. Thanks for trying though.
kp98
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10/18/2015 8:16:47 PM
Posted: 1 year ago
Imagine a moment just after the big bang two points in space. One point is 'us', the other point will eventually be a star near the edge of our observable universe.

Just after the big bang we and the star will be quite close (as the entire universe is small), but as the universe expands the points will obviously get further apart. The rate of expansion is such that after 13.8 billion years we and the star will be more than 40 billion light years apart.

That seems odd, because it implies a separation speed faster than the speed of light. The reason the light speed-limit can be broken is that c is only a limit in so-called 'inertial frames', ie frames where acceleration is not a factor and the case of a universe undergoing cosmological expansion is not an inertial frame.

It would take a longer post that I am willing to write to go into the details of inertial frames (covered by special relativity) and why the expanding universe isn't an inertial frame (covered by general relativity), but that's the gist of it. Google and Wikipedia are your friend for more.

An alternative explanation is that 'It just is, ok? Get over it.'
Furyan5
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10/18/2015 9:21:50 PM
Posted: 1 year ago
At 10/18/2015 8:16:47 PM, kp98 wrote:
Imagine a moment just after the big bang two points in space. One point is 'us', the other point will eventually be a star near the edge of our observable universe.

Just after the big bang we and the star will be quite close (as the entire universe is small), but as the universe expands the points will obviously get further apart. The rate of expansion is such that after 13.8 billion years we and the star will be more than 40 billion light years apart.

That seems odd, because it implies a separation speed faster than the speed of light. The reason the light speed-limit can be broken is that c is only a limit in so-called 'inertial frames', ie frames where acceleration is not a factor and the case of a universe undergoing cosmological expansion is not an inertial frame.

It would take a longer post that I am willing to write to go into the details of inertial frames (covered by special relativity) and why the expanding universe isn't an inertial frame (covered by general relativity), but that's the gist of it. Google and Wikipedia are your friend for more.

An alternative explanation is that 'It just is, ok? Get over it.'

One problem with your theory. We are not looking at where the star is now. We are looking at where the star was 40 billion years ago. 40 billion light years is not the edge of the known universe. It's the edge of the observable universe. I get that 2 objects can be 40 billion light years apart. What you can't seem to grasp is that we see those galaxies that are 40 billion light years away.

For us to see a galaxy 40 billion light years away, those galaxies must have existed 40 billion years ago. That is how long it would take for that light to reach us. I would agree with you that if we were traveling away from the galaxy it would take light longer to reach us but then galaxies in the opposite direction would seem closer. But i see no such scientific claim.

Anyway it's obvious I'm talking to the wrong person. But perhaps you know someone who can explain it.
TBR
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10/18/2015 9:26:40 PM
Posted: 1 year ago
At 10/18/2015 7:08:51 PM, Furyan5 wrote:
At 10/18/2015 6:55:27 PM, TBR wrote:
You are looking at light-years (distance) and implying age. That is not the case.

To my understanding, it takes light a year to travel one light year. So light from a star 45 billion light years away took 45 billion years to get here. That sun had to exist 45 billion years ago and is probably burnt out by now. How is it not the case?

OK. Try this. A is a star. B is our planet. -> is light.

Billions of years ago it looks like this
A-> B

Time passes, light is still heading from A to B, but the distance has "expanded"

A--> B

Keep going

A----> B

A------> B

A-------> B

A---------> B

A----------> B

A------------>B

A is much further from B than when the light started leaving A.
RuvDraba
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10/18/2015 9:40:43 PM
Posted: 1 year ago
At 10/18/2015 7:08:51 PM, Furyan5 wrote:
At 10/18/2015 6:55:27 PM, TBR wrote:
You are looking at light-years (distance) and implying age. That is not the case.
To my understanding, it takes light a year to travel one light year. So light from a star 45 billion light years away took 45 billion years to get here. That sun had to exist 45 billion years ago and is probably burnt out by now. How is it not the case?

Furyan, i realise other members have offered legitimate explanations, but informally: the universe is expanding faster than light.

I say 'informally' because this explanation isn't formally correct. Distance itself is a property of the universe, so what's actually happening is that the galaxies are getting further away, but aren't moving away. A common analogy is to think of ants on the surface of an expanding balloon. They start close enough to rub antennae, and their little legs cling to the rubber, but as the balloon expands, they become unable to touch one another... and ants further away on the surface of the balloon seem to be receding faster than ants closer -- because the rate of separation is 'apparent speed per distance', not simply 'distance per time'.

Nevertheless, if they tried to gallop around the balloon, they could still only do so at ant-speed.

This corresponds pretty closely to actual observations: the more distant the star, the faster it appears to be receding -- to the point where stars can appear to move away faster than the speed of light itself, even thought they couldn't traverse space itself at light-speed.

What this means is that eventually, distant stars and galaxies will move beyond our ability to actually see them ever... they'll vanish beyond our observable information-space, as though they'd never existed. This would be like ants trying to catch up with old friends, but unable to out-gallop the expansion of the balloon.

So the stars aren't 45 billion years old; light just takes longer to travel between points than once it did, when things were closer.

It's weird, but things very large and very small don't work like human-sized things on earth. Our myths and lived experiences don't predict them accurately. That's why we need objective data.

I hope that may help. :)
SM2
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10/19/2015 12:19:20 AM
Posted: 1 year ago
At 10/18/2015 9:21:50 PM, Furyan5 wrote:

One problem with your theory. We are not looking at where the star is now. We are looking at where the star was 40 billion years ago. 40 billion light years is not the edge of the known universe. It's the edge of the observable universe. I get that 2 objects can be 40 billion light years apart. What you can't seem to grasp is that we see those galaxies that are 40 billion light years away.

For us to see a galaxy 40 billion light years away, those galaxies must have existed 40 billion years ago. That is how long it would take for that light to reach us. I would agree with you that if we were traveling away from the galaxy it would take light longer to reach us but then galaxies in the opposite direction would seem closer. But i see no such scientific claim.

Anyway it's obvious I'm talking to the wrong person. But perhaps you know someone who can explain it.

I'll explain it. Imagine this:

____________________Galaxy A________________Galaxy B_______________________

Galaxy A emits light. If both galaxies are stationary, that looks like this:

____________________Galaxy A--------------------->Galaxy B_______________________

However, since the galaxies are moving, it actually looks like this:

__________Galaxy A_______________________Start-------------------------------->Galaxy B____________

The light, having been emitted from the point that galaxy A occupied at the time, continues from that point, and not from where galaxy A is now.

By the time that light reaches us, galaxy A is even further away.

Galaxy A_____________________________________________________________________________Start--------------------------------------->Galaxy B

We're not actually seeing 46.5 billion-year-old light; we're seeing 13.8 billion-year-old light and using relativity to calculate the current distance of its source (galaxy A).

Hope this helps.
dee-em
Posts: 6,486
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10/19/2015 12:44:13 AM
Posted: 1 year ago
At 10/18/2015 9:21:50 PM, Furyan5 wrote:

One problem with your theory. We are not looking at where the star is now. We are looking at where the star was 40 billion years ago.

No, you are still confusing distance with time. We can only see light which has been travelling for less than 13.8 billion years. That light was emitted by the galaxy when it was much closer to us than its current extrapolated distance. Space has expanded in the intervening time putting the galaxy much, much further away. Light emitted from that galaxy 'now' will never reach us.

40 billion light years is not the edge of the known universe. It's the edge of the observable universe. I get that 2 objects can be 40 billion light years apart.

It's actually closer to 46 billion light years.

What you can't seem to grasp is that we see those galaxies that are 40 billion light years away.

Yes, but we are only seeing the light which was emitted when they were much closer. We are not seeing the light which they emit in our 'now'. This is where your confusion stems from. The light from those galaxies has been travelling for less than 13.8 billion years. It can't be any longer given the age of the universe.

For us to see a galaxy 40 billion light years away, those galaxies must have existed 40 billion years ago.

No. You confuse where those galaxies are 'now' with where they were when the light we are receiving now first was emitted by them. You need to grasp this point or no explanation given to you will make sense.

That is how long it would take for that light to reach us. I would agree with you that if we were traveling away from the galaxy it would take light longer to reach us but then galaxies in the opposite direction would seem closer. But i see no such scientific claim.

Galaxies are not travelling away from each other. The intervening space is stretching to give that appearance.

Anyway it's obvious I'm talking to the wrong person. But perhaps you know someone who can explain it.

See above. I hope it helped.
Furyan5
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10/19/2015 8:23:00 AM
Posted: 1 year ago
At 10/19/2015 12:19:20 AM, SM2 wrote:
At 10/18/2015 9:21:50 PM, Furyan5 wrote:

One problem with your theory. We are not looking at where the star is now. We are looking at where the star was 40 billion years ago. 40 billion light years is not the edge of the known universe. It's the edge of the observable universe. I get that 2 objects can be 40 billion light years apart. What you can't seem to grasp is that we see those galaxies that are 40 billion light years away.

For us to see a galaxy 40 billion light years away, those galaxies must have existed 40 billion years ago. That is how long it would take for that light to reach us. I would agree with you that if we were traveling away from the galaxy it would take light longer to reach us but then galaxies in the opposite direction would seem closer. But i see no such scientific claim.

Anyway it's obvious I'm talking to the wrong person. But perhaps you know someone who can explain it.

I'll explain it. Imagine this:

____________________Galaxy A________________Galaxy B_______________________

Galaxy A emits light. If both galaxies are stationary, that looks like this:

____________________Galaxy A--------------------->Galaxy B_______________________

However, since the galaxies are moving, it actually looks like this:

__________Galaxy A_______________________Start-------------------------------->Galaxy B____________

The light, having been emitted from the point that galaxy A occupied at the time, continues from that point, and not from where galaxy A is now.

By the time that light reaches us, galaxy A is even further away.

Galaxy A_____________________________________________________________________________Start--------------------------------------->Galaxy B

We're not actually seeing 46.5 billion-year-old light; we're seeing 13.8 billion-year-old light and using relativity to calculate the current distance of its source (galaxy A).

Hope this helps.

Then 46.5 is not the observable edge of the universe. It's the calculated edge of the universe.
kp98
Posts: 729
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10/19/2015 8:47:15 AM
Posted: 1 year ago
What you can't seem to grasp is that we see those galaxies that are 40 billion light years away.

I grasp it just fine, thank you. Maybe I didn't get what you were asking. I think the easiest answer is : what we see now is the light emitted by the most distant galaxies 13.8 billion years ago. In the 13.8 billion years since emiting that light the galaxy has moved even further out and it is 40 odd billion light years away today.

So the galaxy wasn't 40 billion light years away when it emited the light we see today. We will see the light it is emiting today (ie from 40 billion light years away) in 40 billion years time(personally, I can hardly wait), by which time it will be at an even more ginormous distance from us.
Furyan5
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10/19/2015 10:03:37 AM
Posted: 1 year ago
At 10/19/2015 8:47:15 AM, kp98 wrote:
What you can't seem to grasp is that we see those galaxies that are 40 billion light years away.

I grasp it just fine, thank you. Maybe I didn't get what you were asking. I think the easiest answer is : what we see now is the light emitted by the most distant galaxies 13.8 billion years ago. In the 13.8 billion years since emiting that light the galaxy has moved even further out and it is 40 odd billion light years away today.

So the galaxy wasn't 40 billion light years away when it emited the light we see today. We will see the light it is emiting today (ie from 40 billion light years away) in 40 billion years time(personally, I can hardly wait), by which time it will be at an even more ginormous distance from us.

Am I mistaken in assuming that observable means some that can be seen now. Not something that will only be seen in 40 billion years from now? Considering that you and I will probably both be dead by then, its safe to say that the edge of the observable universe is in fact around 13 billion light years currently even if those galaxies are currently 40 billion light years away. At that distance they are not currently observable.
dee-em
Posts: 6,486
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10/19/2015 10:07:02 AM
Posted: 1 year ago
At 10/19/2015 8:47:15 AM, kp98 wrote:
What you can't seem to grasp is that we see those galaxies that are 40 billion light years away.

I grasp it just fine, thank you. Maybe I didn't get what you were asking. I think the easiest answer is : what we see now is the light emitted by the most distant galaxies 13.8 billion years ago. In the 13.8 billion years since emiting that light the galaxy has moved even further out and it is 40 odd billion light years away today.

So the galaxy wasn't 40 billion light years away when it emited the light we see today. We will see the light it is emiting today (ie from 40 billion light years away) in 40 billion years time(personally, I can hardly wait), by which time it will be at an even more ginormous distance from us.

Actually it will be far more than 40 billion years since space is still expanding between us. In fact, I seem to recall reading that galaxies now at that distance will emit light that may never reach us at all.
dee-em
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10/19/2015 10:12:50 AM
Posted: 1 year ago
At 10/19/2015 10:03:37 AM, Furyan5 wrote:
At 10/19/2015 8:47:15 AM, kp98 wrote:
What you can't seem to grasp is that we see those galaxies that are 40 billion light years away.

I grasp it just fine, thank you. Maybe I didn't get what you were asking. I think the easiest answer is : what we see now is the light emitted by the most distant galaxies 13.8 billion years ago. In the 13.8 billion years since emiting that light the galaxy has moved even further out and it is 40 odd billion light years away today.

So the galaxy wasn't 40 billion light years away when it emited the light we see today. We will see the light it is emiting today (ie from 40 billion light years away) in 40 billion years time(personally, I can hardly wait), by which time it will be at an even more ginormous distance from us.

Am I mistaken in assuming that observable means some that can be seen now. Not something that will only be seen in 40 billion years from now? Considering that you and I will probably both be dead by then, its safe to say that the edge of the observable universe is in fact around 13 billion light years currently even if those galaxies are currently 40 billion light years away. At that distance they are not currently observable.

There is no such thing as seeing anything now when large distances are involved. Even with our Sun, the light you see left the surface about 8 minutes ago. When looking into space you are always seeing the past, never the present.

Your term 'currently observable' is meaningless.
Furyan5
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10/19/2015 10:46:33 AM
Posted: 1 year ago
At 10/19/2015 10:12:50 AM, dee-em wrote:
At 10/19/2015 10:03:37 AM, Furyan5 wrote:
At 10/19/2015 8:47:15 AM, kp98 wrote:
What you can't seem to grasp is that we see those galaxies that are 40 billion light years away.

I grasp it just fine, thank you. Maybe I didn't get what you were asking. I think the easiest answer is : what we see now is the light emitted by the most distant galaxies 13.8 billion years ago. In the 13.8 billion years since emiting that light the galaxy has moved even further out and it is 40 odd billion light years away today.

So the galaxy wasn't 40 billion light years away when it emited the light we see today. We will see the light it is emiting today (ie from 40 billion light years away) in 40 billion years time(personally, I can hardly wait), by which time it will be at an even more ginormous distance from us.

Am I mistaken in assuming that observable means some that can be seen now. Not something that will only be seen in 40 billion years from now? Considering that you and I will probably both be dead by then, its safe to say that the edge of the observable universe is in fact around 13 billion light years currently even if those galaxies are currently 40 billion light years away. At that distance they are not currently observable.

There is no such thing as seeing anything now when large distances are involved. Even with our Sun, the light you see left the surface about 8 minutes ago. When looking into space you are always seeing the past, never the present.

Your term 'currently observable' is meaningless.

Lol if you actually read what I said it would help. Then you wouldn't look like an idiot for pointing out something I already said.
Furyan5
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10/19/2015 10:51:49 AM
Posted: 1 year ago
At 10/19/2015 10:07:02 AM, dee-em wrote:
At 10/19/2015 8:47:15 AM, kp98 wrote:
What you can't seem to grasp is that we see those galaxies that are 40 billion light years away.

I grasp it just fine, thank you. Maybe I didn't get what you were asking. I think the easiest answer is : what we see now is the light emitted by the most distant galaxies 13.8 billion years ago. In the 13.8 billion years since emiting that light the galaxy has moved even further out and it is 40 odd billion light years away today.

So the galaxy wasn't 40 billion light years away when it emited the light we see today. We will see the light it is emiting today (ie from 40 billion light years away) in 40 billion years time(personally, I can hardly wait), by which time it will be at an even more ginormous distance from us.

Actually it will be far more than 40 billion years since space is still expanding between us. In fact, I seem to recall reading that galaxies now at that distance will emit light that may never reach us at all.

Exactly. That light may never reach us. So how can they call it observable? When it is currently not observable, might never be observable and in my lifetime will definitely not be observable. They should alter the 46 billion light years to be the deductible edge of the galaxy. Instead of saying its the observable edge of the galaxy.
dee-em
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10/19/2015 10:57:20 AM
Posted: 1 year ago
At 10/19/2015 10:46:33 AM, Furyan5 wrote:
At 10/19/2015 10:12:50 AM, dee-em wrote:
At 10/19/2015 10:03:37 AM, Furyan5 wrote:
At 10/19/2015 8:47:15 AM, kp98 wrote:
What you can't seem to grasp is that we see those galaxies that are 40 billion light years away.

I grasp it just fine, thank you. Maybe I didn't get what you were asking. I think the easiest answer is : what we see now is the light emitted by the most distant galaxies 13.8 billion years ago. In the 13.8 billion years since emiting that light the galaxy has moved even further out and it is 40 odd billion light years away today.

So the galaxy wasn't 40 billion light years away when it emited the light we see today. We will see the light it is emiting today (ie from 40 billion light years away) in 40 billion years time(personally, I can hardly wait), by which time it will be at an even more ginormous distance from us.

Am I mistaken in assuming that observable means some that can be seen now. Not something that will only be seen in 40 billion years from now? Considering that you and I will probably both be dead by then, its safe to say that the edge of the observable universe is in fact around 13 billion light years currently even if those galaxies are currently 40 billion light years away. At that distance they are not currently observable.

There is no such thing as seeing anything now when large distances are involved. Even with our Sun, the light you see left the surface about 8 minutes ago. When looking into space you are always seeing the past, never the present.

Your term 'currently observable' is meaningless.

Lol if you actually read what I said it would help. Then you wouldn't look like an idiot for pointing out something I already said.

Sorry, but I fail to see where I echoed what you said. There is no such thing as 'currently observable' as you used it. We can only observe the past.
Furyan5
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10/19/2015 10:58:34 AM
Posted: 1 year ago
For those who are struggling to grasp the question... I'm not asking how galaxies can be 46 billion light years away from us. My question is how they can call those galaxies observable at that distance.
46 billion light years is the estimated outer limit of the OBSERVABLE universe as per most definitions on Google.
Not my definition!
Furyan5
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10/19/2015 11:08:07 AM
Posted: 1 year ago
At 10/19/2015 10:57:20 AM, dee-em wrote:
At 10/19/2015 10:46:33 AM, Furyan5 wrote:
At 10/19/2015 10:12:50 AM, dee-em wrote:
At 10/19/2015 10:03:37 AM, Furyan5 wrote:
At 10/19/2015 8:47:15 AM, kp98 wrote:
What you can't seem to grasp is that we see those galaxies that are 40 billion light years away.

I grasp it just fine, thank you. Maybe I didn't get what you were asking. I think the easiest answer is : what we see now is the light emitted by the most distant galaxies 13.8 billion years ago. In the 13.8 billion years since emiting that light the galaxy has moved even further out and it is 40 odd billion light years away today.

So the galaxy wasn't 40 billion light years away when it emited the light we see today. We will see the light it is emiting today (ie from 40 billion light years away) in 40 billion years time(personally, I can hardly wait), by which time it will be at an even more ginormous distance from us.

Am I mistaken in assuming that observable means some that can be seen now. Not something that will only be seen in 40 billion years from now? Considering that you and I will probably both be dead by then, its safe to say that the edge of the observable universe is in fact around 13 billion light years currently even if those galaxies are currently 40 billion light years away. At that distance they are not currently observable.

There is no such thing as seeing anything now when large distances are involved. Even with our Sun, the light you see left the surface about 8 minutes ago. When looking into space you are always seeing the past, never the present.

Your term 'currently observable' is meaningless.

Lol if you actually read what I said it would help. Then you wouldn't look like an idiot for pointing out something I already said.

Sorry, but I fail to see where I echoed what you said. There is no such thing as 'currently observable' as you used it. We can only observe the past.

Yes idiot. We currently view events which happened 13 billion years ago and it's taken that light 13 billion years to get here. Ie an even that is 13 billion years old and happened 13 billion years ago is CURRENTLY OBSERVABLE here.

Already covered.
dee-em
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10/19/2015 11:10:59 AM
Posted: 1 year ago
At 10/19/2015 10:51:49 AM, Furyan5 wrote:
At 10/19/2015 10:07:02 AM, dee-em wrote:
At 10/19/2015 8:47:15 AM, kp98 wrote:
What you can't seem to grasp is that we see those galaxies that are 40 billion light years away.

I grasp it just fine, thank you. Maybe I didn't get what you were asking. I think the easiest answer is : what we see now is the light emitted by the most distant galaxies 13.8 billion years ago. In the 13.8 billion years since emiting that light the galaxy has moved even further out and it is 40 odd billion light years away today.

So the galaxy wasn't 40 billion light years away when it emited the light we see today. We will see the light it is emiting today (ie from 40 billion light years away) in 40 billion years time(personally, I can hardly wait), by which time it will be at an even more ginormous distance from us.

Actually it will be far more than 40 billion years since space is still expanding between us. In fact, I seem to recall reading that galaxies now at that distance will emit light that may never reach us at all.

Exactly. That light may never reach us. So how can they call it observable?

It depends on how you define observable. As I understand it, if light from an object can reach us (even if it is from a long time in the past) then it is part of the observable universe. This is despite the fact that any light it emits right now might never reach us. Read this:

https://en.wikipedia.org...

This fact can be used to define a type of cosmic event horizon whose distance from us changes over time. For example, the current distance to this horizon is about 16 billion light years, meaning that a signal from an event happening at present can eventually reach us in the future if the event is less than 16 billion light years away, but the signal will never reach us if the event is more than 16 billion light years away.[11]

When it is currently not observable, might never be observable and in my lifetime will definitely not be observable.

But it is observable. You are seeing it as it was when it was much closer.

They should alter the 46 billion light years to be the deductible edge of the galaxy. Instead of saying its the observable edge of the galaxy.

See above.
dee-em
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10/19/2015 11:13:02 AM
Posted: 1 year ago
At 10/19/2015 11:08:07 AM, Furyan5 wrote:
At 10/19/2015 10:57:20 AM, dee-em wrote:
At 10/19/2015 10:46:33 AM, Furyan5 wrote:
At 10/19/2015 10:12:50 AM, dee-em wrote:
At 10/19/2015 10:03:37 AM, Furyan5 wrote:
At 10/19/2015 8:47:15 AM, kp98 wrote:
What you can't seem to grasp is that we see those galaxies that are 40 billion light years away.

I grasp it just fine, thank you. Maybe I didn't get what you were asking. I think the easiest answer is : what we see now is the light emitted by the most distant galaxies 13.8 billion years ago. In the 13.8 billion years since emiting that light the galaxy has moved even further out and it is 40 odd billion light years away today.

So the galaxy wasn't 40 billion light years away when it emited the light we see today. We will see the light it is emiting today (ie from 40 billion light years away) in 40 billion years time(personally, I can hardly wait), by which time it will be at an even more ginormous distance from us.

Am I mistaken in assuming that observable means some that can be seen now. Not something that will only be seen in 40 billion years from now? Considering that you and I will probably both be dead by then, its safe to say that the edge of the observable universe is in fact around 13 billion light years currently even if those galaxies are currently 40 billion light years away. At that distance they are not currently observable.

There is no such thing as seeing anything now when large distances are involved. Even with our Sun, the light you see left the surface about 8 minutes ago. When looking into space you are always seeing the past, never the present.

Your term 'currently observable' is meaningless.

Lol if you actually read what I said it would help. Then you wouldn't look like an idiot for pointing out something I already said.

Sorry, but I fail to see where I echoed what you said. There is no such thing as 'currently observable' as you used it. We can only observe the past.

Yes idiot. We currently view events which happened 13 billion years ago and it's taken that light 13 billion years to get here. Ie an even that is 13 billion years old and happened 13 billion years ago is CURRENTLY OBSERVABLE here.

Already covered.

If you are going to be rude, get stuffed. Work it out for yourself.
kp98
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10/19/2015 11:39:49 AM
Posted: 1 year ago
Consider a galaxy (call it Galaxy B) a little further away from us that the galaxy I was talking about before(Galaxy A).

The light from B will take a little longer to reach us that the light from A - say 14 billion years rather than 13.8. So the galaxy B must be currently invisible, because there has not been enought time for its light to reach us - however B's light will appear in another 0.2 billion years, (presumably rather faintly).

When galaxy B does appear, its actual distance at that time will be something more than the 40+ billion light years of galaxy A when A was visible, so at that time the 'observable universe' will be bigger then it is now, so as to include Galaxy B's current position.

Space is big. You just won't believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space. Douglas Adams.
dee-em
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10/19/2015 12:03:51 PM
Posted: 1 year ago
At 10/19/2015 10:03:37 AM, Furyan5 wrote:
At 10/19/2015 8:47:15 AM, kp98 wrote:
What you can't seem to grasp is that we see those galaxies that are 40 billion light years away.

I grasp it just fine, thank you. Maybe I didn't get what you were asking. I think the easiest answer is : what we see now is the light emitted by the most distant galaxies 13.8 billion years ago. In the 13.8 billion years since emiting that light the galaxy has moved even further out and it is 40 odd billion light years away today.

So the galaxy wasn't 40 billion light years away when it emited the light we see today. We will see the light it is emiting today (ie from 40 billion light years away) in 40 billion years time(personally, I can hardly wait), by which time it will be at an even more ginormous distance from us.

Am I mistaken in assuming that observable means some that can be seen now. Not something that will only be seen in 40 billion years from now? Considering that you and I will probably both be dead by then, its safe to say that the edge of the observable universe is in fact around 13 billion light years currently even if those galaxies are currently 40 billion light years away. At that distance they are not currently observable.

How interesting. Confirmation that you were using the term 'currently observable' exactly as I thought. Who is the idiot now?
dee-em
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10/19/2015 12:07:18 PM
Posted: 1 year ago
At 10/19/2015 11:39:49 AM, kp98 wrote:
Consider a galaxy (call it Galaxy B) a little further away from us that the galaxy I was talking about before(Galaxy A).

The light from B will take a little longer to reach us that the light from A - say 14 billion years rather than 13.8. So the galaxy B must be currently invisible, because there has not been enought time for its light to reach us - however B's light will appear in another 0.2 billion years, (presumably rather faintly).

When galaxy B does appear, its actual distance at that time will be something more than the 40+ billion light years of galaxy A when A was visible, so at that time the 'observable universe' will be bigger then it is now, so as to include Galaxy B's current position.

Yes, the radius of the observable universe is projected to grow to about 65 billion light years (from memory).

Space is big. You just won't believe how vastly, hugely, mind- bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space. Douglas Adams.