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Therefore, I wonder how it could be that our scientists claim that the expansion in space could increase the light from a far end galaxy.
Therefore, less photons get to our detector.
It is very clear to me that you fully support the BBT and protect whatever our scientists claim.
Get a piece of rubber sheeting, draw a picture of a galaxy on it.Stretch the rubber sheet.The picture gets bigger.
Let's also assume that based on the size of our light detector on earth (without the expansion impact) we should detect 10,000 photons from this far end galaxy.
Remember the following message:Let's also assume that based on the size of our light detector on earth (without the expansion impact) we should detect 10,000 photons from this far end galaxy.Now due to the expansion in the picture of the far end galaxy, we get in our detector only one photon instead of 10,000,000Therefore, with this ration, we should get 0.001 photon from the far end galaxy (instead of 10,000 photons without the expansion)Therefore, it is clearly that we can't detect this galaxy at all.
You have just worked out why we need big telescopes and long exposures to take these pictures.That's OK, we have big telescopes and take long exposures.Why do you see this as a problem?
However, the expansion in space should decrease the detected intensity of light from any far away galaxy.
Nobody cares about the intensity.That is not what defines the size of something.Does your house get smaller when it's only lit by the moon?If the source isn't bright enough to see properly then, as I said, you can use a bigger telescope, or a longer exposure time.
So, it is not the expansion in space activity that makes a further away galaxy to look as a bigger sized one, but it is due to the dark energy that is responsible for that activity.I hope that we all agree with that!!!
Do you understand that what the dark energy does is make the rate of expansion variable?
https://www.forbes.com/sites/startswithabang/2019/12/07/ask-ethan-do-ancient-galaxies-get-magnified-by-the-expanding-universe/#586dda7cb5fcIf we had an expanding Universe with nothing but matter in it, the angular scale would get progressively smaller in a quantitatively different fashion, but the farther away you looked, the same-sized object would always look smaller than a closer version of the same object."
they clearly claim that in an expanding Universe with nothing but matter in it, the same-sized object would always look smaller than a closer version of the same object."
Is there a possibility for expansion without dark energy?
If "what the dark energy does is make the rate of expansion variable" than why they claim that "in an expanding Universe with nothing but matter in it, the same-sized object would always look smaller than a closer version of the same object."
I really don't understand the logic.
QuoteQuote from: Dave Lev on Yesterday at 19:11:45Is there a possibility for expansion without dark energy?Yes.
Quote from: Dave Lev on Yesterday at 19:11:45Is there a possibility for expansion without dark energy?
Because a universe with only matter in it is different from a universe with matter and also dark energy.Like a pizza with cheese and ham is different from a pizza with only cheese.
Why in a universe with dark energy it s expected that - the farther away you looked, the same-sized object would look bigger than a closer version of the same object"
So please, try to explain this difference:
More distant things are older, so the images of them have had more time for the space to be stretched. So they are stretched out more, so they look bigger.Do you understand that?
All dark energy does is make those dotted worldlines curved. They'd be straight without dark energy. You'll notice that the curvature of those lines make almost no difference. The dark energy causes an event horizon to form (not in this picture, but I have others) that would not exist with inertial expansion.
https://www.forbes.com/sites/startswithabang/2019/12/07/ask-ethan-do-ancient-galaxies-get-magnified-by-the-expanding-universe/#586dda7cb5fcIf we had an expanding Universe with nothing but matter in it, the angular scale would get progressively smaller in a quantitatively different fashion, but the farther away you looked, the same-sized object would always look smaller than a closer version of the same object."So, they clearly claim that in an expanding Universe with nothing but matter in it, the same-sized object would always look smaller than a closer version of the same object."In all my explanations I have only focused on a Universe with nothing but matter in it.However, they also add the following:But what we actually have is a Universe filled with dark energy; the angular scale does something very different. The farther away you look, the same-sized object looks smaller and smaller, but only to a point. Beyond that point, that object will actually start to look bigger again."So, it is not the expansion in space activity that makes a further away galaxy to look as a bigger sized one, but it is due to the dark energy that is responsible for that activity.
So, they clearly claim that in an expanding Universe with nothing but matter in it, the same-sized object would always look smaller than a closer version of the same object.
But what we actually have is a Universe filled with dark energy; the angular scale does something very different. The farther away you look, the same-sized object looks smaller and smaller, but only to a point. Beyond that point, that object will actually start to look bigger again."
Therefore, why they insist that the dark energy is mandatory requested in order to make a further away galaxy to look as a bigger sized one
QuoteTherefore, why they insist that the dark energy is mandatory requested in order to make a further away galaxy to look as a bigger sized oneI see no such insistence in what you quoted. Ethan says something about a universe 'with nothing but matter in it', which, if you read, means without radiation and dark energy'. Without radiation, galaxies would not 'appear' as anything since there would be no light, so Ethan is technically wrong in how galaxies would 'appear' with nothing but matter.Anyway, I see no statement that this effect would not be true without dark energy, although he says the dark energy case makes the scaling 'very different', so I agree the hint is there. This seems to be self inconsistency since in his pictures just above that statement, every case has the universe smaller in the far past and thus similar sized objects would occupy a larger field of view. To quote him:"the same sized object, billions of years ago, took up a greater proportion of the Universe's scale than the same object does at later times." which is true of each diagram, meaning that really distant things look larger in all four of his cases, not just the accelerating one.What Ethan says (and means) is that things would scale in a 'quantitatively different manner', meaning we see something different than what we would expect without accelerated expansion, which is how we learned of the acceleration in the first place. Dark energy is one explanation for this acceleration, and not the only one.
My post said that if it appears bigger, we're seeing something when it was closer, not further away. I don't see Ethan claiming otherwise. I see him claiming that the further you look in time (not in space), there's a point after which older objects were actually closer and thus appear larger. This is entirely consistent with my post.
The science law is very clearhttps://www.answers.com/Q/Why_does_the_intensity_decrease_with_the_square_of_the_distance_from_a_point_sourceWhy does the intensity decrease with the square of the distance from a point source?Intensity of light is defined as energy per unit area. As we move away from the light point source, the area over which the energy of light distributes is generally spherical or hemispherical. The area of a sphere or hemisphere increases proportional to the square of radius, where the radius in this case is the distance from the point source. Thus Intensity of light, which is inversely proportional to area, decreases with the square of distance.
Thanks for the explanation about the dark energy, although in the article they don't say anything about "radiation".
But if your Universe is evolving in shape and size over time — which our expanding Universe consisting of radiation, matter, and dark energy most definitely is — you have to take that into account as well.
In any case, I would like to focus on your following explanation:
Well, I can agree that if a galaxy is closer, (not further away) than it should appear bigger.
However, I still don't understand why if it was closer 13BY ago, but due to the expansion its emitted photons of light had to cross very long distance (13BLY) than it also should appear bigger?
The science law is very clearhttps://www.answers.com/Q/Why_does_the_intensity_decrease_with_the_square_of_the_distance_from_a_point_sourceWhy does the intensity decrease with the square of the distance from a point source?
Intensity of light is defined as energy per unit area.
So, we must understand the total distance that the emitted photon of light from that galaxy had to cross over time.
Don't you agree that if the photon of light from this galaxy that 13 BY ago was located next to us, had to cross a distance of 13 BLY than it should appear much smaller today?
With regards to the space - time diagram that you have offered:This diagram represents only the observable universe of about 46BLY.
So, don't you agree that the space time diagram for a bigger universe (or even infinite Universe) should be quite different from this diagram?
QuoteSo, we must understand the total distance that the emitted photon of light from that galaxy had to cross over time.It is very dependent on how that distance is measured, so there's no meaningful answer to this without that definition. I defined the distance between here and where the light was emitted as proper distance in the comoving coordinate system (scaled for normal distance and time) as per my linked graph in post 396. The distance is marked off at the bottom of the chart. Where (or how long) the light traveled between here and there is irrelevant to the apparent size of the galaxy since the apparent size is not a function of either of those things, and where that galaxy is 'now' is also irrelevant since I'm not looking at light from where it is now, and yet it is on this that you choose to focus, having this naive intuition that we see things where they are now because that is a good approximation when you're looking at a tree.
I defined the distance between here and where the light was emitted as proper distance in the comoving coordinate system (scaled for normal distance and time) as per my linked graph in post 396.
QuoteQuoteDon't you agree that if the photon of light from this galaxy that 13 BY ago was located next to us, had to cross a distance of 13 BLY than it should appear much smaller today?You ignore the logic that shows this to result in a contradiction.
QuoteDon't you agree that if the photon of light from this galaxy that 13 BY ago was located next to us, had to cross a distance of 13 BLY than it should appear much smaller today?
QuoteHowever, I still don't understand why if it was closer 13BY ago, but due to the expansion its emitted photons of light had to cross very long distance (13BLY) than it also should appear bigger?The distance the light travels is pretty meaningless without an exact specification of how that distance is measured. Point is, that light was emitted from fairly close by, and the apparent size of the object can be directly computed from that without consideration of how much time it takes. When I compute the apparent size (in arseconds) of the moon, I don't need to worry about how long light takes to make the trip or if the moon has moved somewhere else while the light was getting here. It is simple trigonometry.
Point is, that light was emitted from fairly close by
and the apparent size of the object can be directly computed from that without consideration of how much time it takes.
When I compute the apparent size (in arseconds) of the moon, I don't need to worry about how long light takes to make the trip or if the moon has moved somewhere else while the light was getting here. It is simple trigonometry.