| 1 Jeff Umbarger |
Big Bang Question | maandag 12 november 2001 0:36 |
| 2 V.Z.Nuri |
Re: Big Bang Question | maandag 12 november 2001 3:56 |
| 3 Jeff Umbarger |
Re: Big Bang Question | maandag 12 november 2001 6:01 |
| 4 AndroclesInFlorida |
Re: Big Bang Question | woensdag 14 november 2001 3:16 |
| 5 AndroclesInFlorida |
Re: Big Bang Question | woensdag 14 november 2001 7:09 |
| 6 Tom Roberts |
Re: Big Bang Question | woensdag 14 november 2001 19:22 |
| 7 Robert Karl Stonjek |
Re: Big Bang Question | woensdag 14 november 2001 20:34 |
Hello All, I'm sure this has been asked before, but I can't seem to find a similar posting. I'll start by stating the facts I believe to be true (and these can be refuted) and then I'll ask the questions based on those facts.
Facts:
1.) The universe is expanding - evidence by recessional redshifts and 3
degree CBR.
2.) The current *radius* of the universe is between 10 and 15 billion
light years.
3.) The farther we look in distance, the farther back in time we see.
If I look 15 billion light years to my left and see Galaxy A and then 15 billion light years to my right and see Galaxy B, then Galaxy A must be 30 billion light years from Galaxy B, right? However, because of the great distance I'm looking in to see these objects, they are very young when compared to the age of an expanding universe. Therefore these two galaxies must have been much closer together back 15 billion years ago as compared to today. However, they appear to be separated by 30 billion light years at the time I observed them.
Questions:
1.) How could two young galaxies appear on oppisite sides of the
universe when they should be right next to each other?
2.) Wouldn't observations like this indicate a steady-state universe vs.
an expanding one?
Thanks for any help on this.
- Jeff
Dear Jeff Umbarger:
| > |
Facts: 1.) The universe is expanding - evidence by recessional redshifts and 3 degree CBR. |
Which has been measured to be 9 degrees at some point in the "recent" past.
| > | 2.) The current *radius* of the universe is between 10 and 15 billion light years. |
'Visible' radius. What 'radius' is the CBR coming from?
| > |
3.) The farther we look in distance, the farther back in time we see.
If I look 15 billion light years to my left and see Galaxy A and then 15 billion light years to my right and see Galaxy B, then Galaxy A must be 30 billion light years from Galaxy B, right? However, because of the great distance I'm looking in to see these objects, they are very young when compared to the age of an expanding universe. Therefore these two galaxies must have been much closer together back 15 billion years ago as compared to today. However, they appear to be separated by 30 billion light years at the time I observed them.
Questions: |
If you live on the surface of a balloon, and you look far enough to the left, you will see the back of your head (assuming light also adheres to the balloon in its travel), similarly you can see galaxy A to your left and galaxy B to your right each at 15 billion light years. If we know the Universe popped 17 billion years ago, these two galaxies _might_ be only 4 billion light years apart, at the time the light you observed from them was emitted.
We don't know how long ago the Universe popped.
We don't know the relative velocity of these two galaxies, assuming we could even guess at the shape of the Universe, it might mean something to guess further.
| > | 2.) Wouldn't observations like this indicate a steady-state universe vs. an expanding one? |
CBR has been noted to be decreasing in energy with time. Increasing red shift with time (aka distance). Do either of those sound like there is no time variance... the definition of steady state?
Sorry if I come off being snide.
David A. Smith
Follow-up questions based on David Smith's response:
- Ok, so another assumption here, based on your response, is that space is curved and not flat, right?
- I understand how space *is* curved near massive objects, but the description of the balloon you gave below would indicate that the entire universe sits in a highly curved space. What's "curving" this space? I would not think that the universe is dense enough (that is; many massive galxies in a very compact space) to curve all of space. The effects of mass on curvature rapidly drop off with distance. Do you agree?
- Also, what if the universe is flat, Euclidian space. How, then, would we be able to explain galaxies a great distances from each other (30 billion light years) very close to the begining of the universe?
"dlzc@aol.com (formerly)" wrote:
| > | Dear Jeff Umbarger: |
| > > |
Facts: |
| > |
Which has been measured to be 9 degrees at some point in the "recent" past. |
| > > |
2.) The current *radius* of the universe is between 10 and 15 billion light years. |
| > |
'Visible' radius. What 'radius' is the CBR coming from? |
| > > |
3.) The farther we look in distance, the farther back in time we see. If I look 15 billion light years to my left and see Galaxy A and then 15 billion light years to my right and see Galaxy B, then Galaxy A must be 30 billion light years from Galaxy B, right? However, because of the great distance I'm looking in to see these objects, they are very young when compared to the age of an expanding universe. Therefore these two galaxies must have been much closer together back 15 billion years ago as compared to today. However, they appear to be separated by 30 billion light years at the time I observed them.
Questions: |
| > |
If you live on the surface of a balloon, and you look far enough to the left, you will see the back of your head (assuming light also adheres to the balloon in its travel), similarly you can see galaxy A to your left and galaxy B to your right each at 15 billion light years. If we know the Universe popped 17 billion years ago, these two galaxies _might_ be only 4 billion light years apart, at the time the light you observed from them was emitted. We don't know how long ago the Universe popped. We don't know the relative velocity of these two galaxies, assuming we could even guess at the shape of the Universe, it might mean something to guess further. |
| > > |
2.) Wouldn't observations like this indicate a steady-state universe vs. an expanding one? |
| > |
CBR has been noted to be decreasing in energy with time. Increasing red shift with time (aka distance). Do either of those sound like there is no time variance... the definition of steady state? Sorry if I come off being snide. David A. Smith |
"Jeff Umbarger"
| > |
Hello All, I'm sure this has been asked before, but I can't seem to find a similar posting. I'll start by stating the facts I believe to be true (and these can be refuted) and then I'll ask the questions based on those facts.
Facts: |
| > | 2.) The current *radius* of the universe is between 10 and 15 billion light years. |
| > | 3.) The farther we look in distance, the farther back in time we see. |
| > | If I look 15 billion light years to my left and see Galaxy A and then 15 billion light years to my right and see Galaxy B, then Galaxy A must be 30 billion light years from Galaxy B, right? |
| > |
However, because of the
great distance I'm looking in to see these objects, they are very young
when compared to the age of an expanding universe. Therefore these two
galaxies must have been much closer together back 15 billion years ago
as compared to today. However, they appear to be separated by 30 billion
light years at the time I observed them.
Questions: Thanks for any help on this. |
see http://members.home.net/androcles/tiredlight
and
http://members.home.net/androcles/dark2
"dlzc@aol.com (formerly)"
| > | Dear Jeff Umbarger: |
| > > |
Facts: |
| > |
Which has been measured to be 9 degrees at some point in the "recent" past. |
| > > | 2.) The current *radius* of the universe is between 10 and 15 billion light years. |
| > |
'Visible' radius. What 'radius' is the CBR coming from? |
| > > |
3.) The farther we look in distance, the farther back in time we see.
If I look 15 billion light years to my left and see Galaxy A and then 15 billion light years to my right and see Galaxy B, then Galaxy A must be 30 billion light years from Galaxy B, right? However, because of the great distance I'm looking in to see these objects, they are very young when compared to the age of an expanding universe. Therefore these two galaxies must have been much closer together back 15 billion years ago as compared to today. However, they appear to be separated by 30 billion light years at the time I observed them. Questions: 1.) How could two young galaxies appear on oppisite sides of the universe when they should be right next to each other? |
| > |
If you live on the surface of a balloon, and you look far enough to the left, you will see the back of your head (assuming light also adheres to the balloon in its travel), |
| > |
similarly you can see galaxy A to your left and
galaxy B to your right each at 15 billion light years. If we know the
Universe popped 17 billion years ago, these two galaxies _might_ be only 4
billion light years apart, at the time the light you observed from them was
emitted.
We don't know how long ago the Universe popped. We don't know the relative velocity of these two galaxies, assuming we could even guess at the shape of the Universe, it might mean something to guess further. |
| > > |
2.) Wouldn't observations like this indicate a steady-state universe vs. an expanding one? |
| > |
CBR has been noted to be decreasing in energy with time. |
| > | Increasing red shift with time (aka distance). Do either of those sound like there is no time variance... the definition of steady state? |
| > | Sorry if I come off being snide. |
Jeff Umbarger wrote:
| > |
Facts: 1.) The universe is expanding - evidence by recessional redshifts and 3 degree CBR. |
You need to keep more careful track of the distinction between facts and conclusions. The redshifts and CMBR observations are facts; that the universe is expanding is a conclusion. But that is the best conclusion presented so far which is in agreement with all the facts....
| > | 2.) The current *radius* of the universe is between 10 and 15 billion light years. |
Here's your crucial mistake -- the radius of the _VISIBLE_ universe be between 10 and 15 billion lightyears. We don't know what the radius of the entire universe is....
| > | 3.) The farther we look in distance, the farther back in time we see. |
Yes, as long as one uses the preferred "cosmological time" of the FRW manifolds.
| > | If I look 15 billion light years to my left and see Galaxy A and then 15 billion light years to my right and see Galaxy B, then Galaxy A must be 30 billion light years from Galaxy B, right? However, because of the great distance I'm looking in to see these objects, they are very young when compared to the age of an expanding universe. Therefore these two galaxies must have been much closer together back 15 billion years ago as compared to today. However, they appear to be separated by 30 billion light years at the time I observed them. |
Yes.
| > | 1.) How could two young galaxies appear on oppisite sides of the universe when they should be right next to each other? |
They are on opposite sides of the _VISIBLE_ universe, _TODAY_. Back when the light we see today was emitted from them, they were _THEN_ also on opposite sides of the _VISIBLE_ universe _BACK_THEN_. Back then they were much closer to earth (and to each other), but between emission and detection the expansion of the universe has caused the light to travel much longer paths. They were never "right next to each other" -- earth was always between them.
Note I am using the usual "cosmological" coordinates in FRW manifolds: time is measured everywhere along the geodesic paths of the dust particles (galaxies), and distance is measured along surfaces of constant time.
| > | 2.) Wouldn't observations like this indicate a steady-state universe vs. an expanding one? |
No. How can it be "steady state" if space is expanding?
Tom Roberts tjroberts@lucent.com
"Tom Roberts"
| > | Jeff Umbarger wrote: |
| > > |
Facts: 1.) The universe is expanding - evidence by recessional redshifts and 3 degree CBR. |
| > |
You need to keep more careful track of the distinction between facts and conclusions. The redshifts and CMBR observations are facts; that the universe is expanding is a conclusion. But that is the best conclusion presented so far which is in agreement with all the facts.... |
| > > |
2.) The current *radius* of the universe is between 10 and 15 billion light years. |
| > |
Here's your crucial mistake -- the radius of the _VISIBLE_ universe be between 10 and 15 billion lightyears. We don't know what the radius of the entire universe is.... |
| > > |
3.) The farther we look in distance, the farther back in time we see. |
| > |
Yes, as long as one uses the preferred "cosmological time" of the FRW manifolds. |
| > > |
If I look 15 billion light years to my left and see Galaxy A and then 15 billion light years to my right and see Galaxy B, then Galaxy A must be 30 billion light years from Galaxy B, right? However, because of the great distance I'm looking in to see these objects, they are very young when compared to the age of an expanding universe. Therefore these two galaxies must have been much closer together back 15 billion years ago as compared to today. However, they appear to be separated by 30 billion light years at the time I observed them. |
| > |
Yes. |
| > > |
1.) How could two young galaxies appear on oppisite sides of the universe when they should be right next to each other? |
| > |
They are on opposite sides of the _VISIBLE_ universe, _TODAY_. Back when the light we see today was emitted from them, they were _THEN_ also on opposite sides of the _VISIBLE_ universe _BACK_THEN_. Back then they were much closer to earth (and to each other), but between emission and detection the expansion of the universe has caused the light to travel much longer paths. They were never "right next to each other" -- earth was always between them. Note I am using the usual "cosmological" coordinates in FRW manifolds: time is measured everywhere along the geodesic paths of the dust particles (galaxies), and distance is measured along surfaces of constant time. |
| > > |
2.) Wouldn't observations like this indicate a steady-state universe vs. an expanding one? |
| > |
No. How can it be "steady state" if space is expanding? |
Tom, I've had my toes roasted several times for referring to 'expanding space'. As has been pointed out to me, it is not space that expands but *spacetime*. If you are telling me something different, ie expanding space, then I will have to comb through previous posts and challenge those who corrected me to explain why you say expanding space and they say expanding spacetime!!
Philosophically, expanding spacetime requires only a physics account, but expanding space is quite different because for space to expand, we must either know or make assumptions about the nature of free space. No assumptions of that kind are required for expanding spacetime which is really an expansion of a coordinate system.
Further, the ether has no effect (its existence or non existence) except when space expands. If space expands then the ether expands (becomes thinner) and may have real and measurable consequences (though I'm not an etherist and have not thought what these consequences/measurements might be).
Kind Regards,
Robert Karl Stonjek.
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