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Andrex wrote: So you have one angle with a degree and one known length for the each sides of the triangle. You don't need more to find the degrees for the two angles missing.
Andrex wrote:To find the length of the arc, scientist know that the brightest microwave background fluctuations (or "spots") on the arc would be about one degree across if the universe is "flat".
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Jorrie wrote:you (say sitting on the pole, but it does not matter where) can measure the radar distance to all three points and all three their bearing relative to you.
Jorrie wrote:To calculate the sum of the inside angles of my triangle is then easy and hence you know the curvature of "flatlander earth" - it could be positive, zero or positive, but you will know it.
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Andrex » December 20th, 2016, 4:52 pm wrote:VivianIf our eyes "capture" light from photons, then how can we say our eyes "produce" light? I would have thought the photons were producing the light that our eyes captured. I am perhaps over-simplifying?
You're right; it's not our eyes that "produces" light; our eyes have the ability to capture only a small part of electromagnetism which we call "light". It's "special" only to our eyes; not to electromagnetism. Photons don't "produce" light either; photons are the "particle part" of light; the other part is "ondulation". Both are the causes of electromagnetism and of that portion we "see" as light.
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Dave_Oblad » 21 Dec 2016, 09:04 wrote:I can't measure more than the one corner where I'm located. Radar or Not ;)
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You can then use your optical instruments to measure the sum of internal angles of my triangle.
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Andrex » 21 Dec 2016, 17:13 wrote:Do you mean that I can, but you cannot?
What is the difference between measuring from which ever angle of the triangle?
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MEASUREMENTS FROM WMAP
The WMAP spacecraft can measure the basic parameters of the Big Bang theory including the geometry of the universe. If the universe was flat, the brightest microwave background fluctuations (or "spots") would be about one degree across. If the universe was open, the spots would be less than one degree across. If the universe was closed, the brightest spots would be greater than one degree across.
Recent measurements (c. 2001) by a number of ground-based and balloon-based experiments, including MAT/TOCO, Boomerang, Maxima, and DASI, have shown that the brightest spots are about 1 degree across. Thus the universe was known to be flat to within about 15% accuracy prior to the WMAP results. WMAP has confirmed this result with very high accuracy and precision. We now know (as of 2013) that the universe is flat with only a 0.4% margin of error. This suggests that the Universe is infinite in extent; however, since the Universe has a finite age, we can only observe a finite volume of the Universe. All we can truly conclude is that the Universe is much larger than the volume we can directly observe.
The ‘critical density’ is the average density of matter required for the Universe to just halt its expansion. A Universe with the critical density is said to be flat
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Also, this analogous wall that "surrounds" us is much much "smaller" than the current size of the Visible Universe. That's kinda cool.
Also, I've said we exist in a 3D Universe that has a 4th dimension.
... and realize they are the same single one, but viewed in opposite directions from us.
This won't be easy, because the only way for them to be identical, is if they are on exactly the opposite sides of the Sphere.
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[quote="[url=http://sciencechatforum.com/viewtopic.php?p=312537#p312537]Andrex » 21 Dec 2016, 17:13[/url]"]
[quote="Andrex"]Paste in a piece of copied text...[/quote]
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Dave_Oblad » 22 Dec 2016, 11:11 wrote:I think I get you now. If I assume the wall to be perfectly radial but get a difference in distance from three points on the wall, then the difference must be due to 4D curvature?
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by Dave_Oblad » December 22nd, 2016, 4:49 am
But where would the event horizon be if we realize the size of the Universe was much smaller back then?
Could there be any features visible looking south (back in time) far enough that might be visible, regardless of the direction we choose to look? A bit like looking at the CMB through a Telescope for greater details.
by BurtJordaan on December 22nd, 2016, 5:43 am
but we are just trying to get our heads around the concept here. I hope this clears up some of the issues
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Andrex » 22 Dec 2016, 17:30 wrote:Dpar (particle horizon) seems to have "expanded" in a straight line since "time zero" wherever they might actually be.
So according to PLANCK composition of our universe (5% baryo-matter, 25% Dark matter and 70% of Dark energy (radiating)) it shouldn’t have an event horizon; no?
But in fact, PLANCK as calculated it at 67,15 km/s/Mpc so the radius, in reality, is even shorter than 13,7 bly. And that would be the radius of the “observable universe. Wouldn't it?
Furthermore, it seems that Dhor and R could merge in the future.???
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but later during cosmological constant dominance, it starts to slope upwards.
The %'s that you quoted are rough cut values.
The cosmological constant dominates and is equivalent to vacuum energy
But in fact, PLANCK as calculated it at 67,15 km/s/Mpc so the radius, in reality, is even shorter than 13,7 bly. And that would be the radius of the “observable universe. Wouldn't it?
Nope, the observable universe is the same as the particle horizon, presently around 46 Gly in radius.
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Andrex » 22 Dec 2016, 19:11 wrote:PLANK says that in 10Gly cosmological constant (Dark energy) will compose 93,4% of the universe. Does that mean that there won't be anymore "radiating" in the universe?
And vacuum energy doesn't "radiate"; right?
But the CMB is at 13,7 Gly in radius; and the more we could ever "observe" cannot be more than 380,000 light-years before that??? You're implying that we cannot observe all of "observable universe???
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Jorrie wrote:you can make selected remote measurements to determine if the flatland surface is curved or not. In the example it is positively curved, because you measure a larger triangle than what I do.
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Andrex » 22 Dec 2016, 19:11 wrote: You're implying that we cannot observe all of "observable universe???
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by BurtJordaan » December 22nd, 2016, 12:35 pm
And vacuum energy doesn't "radiate"; right?
Correct, but there will still be CMB radiation in 10 Gy time,
Various parts are lost from our view as time goes on, but that would need another post to explain.
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Andrex » 23 Dec 2016, 08:54 wrote:Burt wrote:Various parts are lost from our view as time goes on, but that would need another post to explain.
I guess you'll have to explain; because if parts are lost from our view, either it's not part of our observable universe anymore or it's not lost of our view.
As for the distance of CMB from us (its radius), PLANCK satellite made the picture we have by "capturing" photons that started 13,7 billions years ago; so the image of CMB we look at, today, cannot be farther than 13,7 light-years from us, because photons can't go faster than light-speed.
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by BurtJordaan on December 23rd, 2016, 5:38 am
Andrex, can you please give a link to the picture with the %'s, because the one you posted does not read very clearly.
“'observable universe' means the part of the universe that we could have received signals from before the emitters have moved over our cosmological horizon.”
“In fact, most galaxies that we still observe lie beyond the cosmological horizon today,”
and those photons stared out only 41 million ly from us; but that distance has expanded 1090 times
The photons (or rather light waves, because GR does not know or care about photons) moved steadily at 'c' against the local spacetime, but in the beginning the expanding space dragged light away from us at a pretty huge rate.”
“Only when the dominant matter density slowed the expansion down enough, could light start to make headway towards us”
“This can all be studied by LightCone 7's charts, without bothering about the math behind it.”
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Andrex wrote:I'll have to think about it; because it implies that "time" is not "distance" and vice versa. It even means that the "present" is not the center of all the "past" around it.
Andrex wrote:Are you asking me an “act of faith”? :-)
But it doesn't fit with your 41 million light-years starting point. (always with the premisse of a "traveling" photon, or lightwave, mind you)
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Remember "spatially flat" does not mean flat spacetime.
Only faith in GR and its solution that describes our universe extremely well
Or do you disagree that if we see the CMB redshifted by a factor 1090 ...
How much of this is fact? Only the redshift and the CMB characteristics that we directly measure
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