Expansion

Nov 16, 2019
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How do we know that the universe is expanding?
Redshift measurements, among others, and it's not just expanding, it's accelerating. Better question is why... currently we have no f-ing idea. My money is on something like anti-gravity or repulsive gravity.
 

rod

Oct 22, 2019
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Redshift measurements, among others, and it's not just expanding, it's accelerating. Better question is why... currently we have no f-ing idea. My money is on something like anti-gravity or repulsive gravity.
Hawkstein, the redshift used to explain the expanding universe depends upon the interpretation from the principle of equivalence. Do you have a specific particle experiment from labs studies that shows 3D space is expanding, and at what rate? Example, something by shooting particles around near c.
 
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Jan 22, 2020
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Relative sensory perspective. What perception would resemble IN an advanced dimensional particle, string , torus tube, energy, or other sub atomic mass entity, etc. with point data formed/forged in the various atomic/subatomic.depending on structural level, mass components we have named molecules, atoms, neutrons, protons, electrons, quarks, qualms, neutrinos, etc.,etc. Similar to sound recording on magnetic tape with dots and dashes but with enhancement. Some advanced computer/reality like the direction our tech seems progressing through.
 

rod

Oct 22, 2019
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Trying to find out if there is experimental verification of photons red-shifting as 3D space expands other than the interpretation based upon the principle of equivalence from GR, used since the 1930s or so based upon redshifts in galaxies based upon Edwin Hubble et al. Is there measurements showing New Horizons transmissions, redshift on their way to Earth? Is there particle accelerator experiments in labs that show photons redshift as they move along in the lab? Hawkstein said "Redshift measurements, among others..." The redshift interpretation is principle of equivalence, not direct, experimental verification, e.g. *others*.
 

rod

Oct 22, 2019
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This is a useful reference:

A good read here but there are some important caveats too. "Theoretical cosmologists developing models of the universe have drawn upon a small number of reasonable assumptions in their work. These workings have led to models in which the metric expansion of space is a likely feature of the universe.", also we have "More direct results of the expansion, such as change of redshift, distance, flux, angular position and the angular size of astronomical objects, have not been detected yet due to smallness of these effects. Change of the redshift or the flux could be observed by Square Kilometre Array or Extremely Large Telescope in the mid-2030s.[32]"

It seems a direct experimental test has not yet been conducted but different theoretical physics applied. That is okay, we have this in inflation, e.g. the inflaton particle, not observed in the universe today, neither are magnetic monopoles. At the moment it seems, in our solar system we do not have a direct measurement of photons doing their redshift as 3D space expands in the solar system or in labs here on Earth. I find this is not well documented in reports on the Big Bang model. The Copernican Principle is always interesting in cosmology. There is no direct test for this either, you may need to travel to M31 or M33 and view the universe from that reference point to test it :). It is a way of avoiding an unpleasant concept with philosophical implications concerning origins, that the Earth could still occupy a special place, even be at or near the center of an expanding universe. This cannot be tested and proved either.
 
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Feb 18, 2020
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rod

"My questions, what shows that space is static? Example, particle experiments, do these show 3D space is expanding, static, or contracting?"

You seem as though you might be able to correct me on this:

What if the Universe is static and it is our measuring rods which are getting smaller. Would a linear decrease in length (as measured in expansion) give rise to a cubed decrease in "size". I can see all sorts of issues arising from this. To me it is somehow connected with the Universe 'expanding' but galaxies staying the same "size".

Measuring rods which apply to the concept of 'space' but galaxies which have a 'real' 'size'.

Or am I just showing my ignorance?

Cat :)
 
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rod

Oct 22, 2019
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Cat, some interesting questions and thoughts. Concerning expanding or static 3D space, I am not aware of published reports using particle accelerators and experiments that show photons redshift during the experiment as 3D space expands, e.g. space.com reports or others like phys.org. From what I understand, the redshift interpretation of galaxies dating back to the time of Edwin Hubble et al, is based upon the Principle of Equivalence from Einstein GR. Seeing the redshift of photons during particle accelerator experiments would be very interesting, like observing the redshift in communications from New Horizons to Earth or telescope observations showing redshifted light while measuring and observing Galilean moon eclipse events at Jupiter. It was at Jupiter that astronomy first discovered the speed of light was finite and not infinitely fast during Galilean moon eclipse events observed in the 1670s.

If someone proposes that the universe is static in size but experimental measuring rods used today are getting smaller, that would need experimental verification. Cat you said "To me it is somehow connected with the Universe 'expanding' but galaxies staying the same "size".

This is a concern I have about the BB model. I find little reporting on galaxy size, i.e. angular size compared to redshift measurements. As galaxy redshifts increase, according to the cosmological interpretation, they are at greater distances from Earth, their angular sizes should decrease. I am not sure if this can be documented well though, for example galaxies and *objects* with large redshifts where z >=1.0. When it comes to the BB model, the origin of the CMBR is the cornerstone. Calculations for the cosmic fireball (first done by George Gamow and Ralph Alpher in late 1940s, reworked multiple times since then), indicate the redshift we see today is some 1,000 or more from its original wavelength or z>=1000 for the CMBR with temperature near 3K vs. the original temperature (50-51K for George Gamow and Ralph Alpher). Consider that telescopes show objects with z numbers only about 7-12 or so.
 
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Mar 19, 2020
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All of this expansion and redshift talk reminds me that on a "local" level, galaxies are blueshifted.

I keep reading all these stories about how all galaxies are expanding away from each other, but this is clearly not true or we would not be seeing supercluster formation.

To be sure, our Local Group is blueshifted towards the Virgo supercluster, which itself is blueshifted towards something called the Great Attractor. I may have missed an Abel cluster in there, but the bottom line is that all these galaxies are merging, not expanding, and it appears that a great many of these galaxies are getting ready for a massive collision.

from wiki:

""Large-scale dynamics:

Since the late 1980s it has been apparent that not only the Local Group, but all matter out to a distance of at least 50 Mpc is experiencing a bulk flow on the order of 600 km/s in the direction of the Norma Cluster (Abell 3627).[11] Lynden-Bell et al. (1988) dubbed the cause of this the "Great Attractor". The Great Attractor is now understood to be the center of mass of an even larger structure of galaxy clusters, dubbed "Laniakea", which includes the Virgo Supercluster (including the Local Group) as well as the Hydra-Centaurus Supercluster, the Pavo-Indus Supercluster, and the Fornax Group. "" (end quote)


The redshift only comes into play when you are beyond a certain distance to the object you are looking at. If the universe is expanding, a great deal of it is also contracting into galactic superclusters. If one accepts the expansion, it seems like it must be superclusters that are expanding away from each other, with "local contractions" superimposed on this expansion. One might imagine this is why the universe appears to be a web-like structure with massive voids in between the webs, which are the galaxy clusters, etc. Or so it has been suggested.

It all seems a tad murky to me.
 
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Feb 18, 2020
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rod

When I wrote this:

"What if the Universe is static and it is our measuring rods which are getting smaller. Would a linear decrease in length (as measured in expansion) give rise to a cubed decrease in "size". "

I think what I was getting at is that I (probably wrongly) think of expansion as linear (away from me) whereas I should be thinking of it expanding away from me in all directions. Rather like when we have this oversimplified picture of a black hole as being flat (as on paper) whereas it 'should' be 3 or 4 or ? dimensional'

My apologies for making this sound stupidly simple but it is leading me to the point semantics play in this. Is it an 'unreal' 'comprehension' of expansion which allows our 'real' picture of a galaxy (as above) to differ from a 'theoretical' 'expansion'.

Have you come across General Semantics by Korzybsky?
His by-phrase was "The map is not the territory" and I suppose that I am trying to apply this expansion.

It works in the 'same' way that we 'know' what we 'actually' see when we look at something is not the 'real' collection of molecules jumping around. When we think we see an expanding Universe what is really 'beneath' the apparent expansion?

Sorry about the oversimplification in getting to the point (if, indeed, there is a point).

Cat :)
 
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rod

Oct 22, 2019
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"Have you come across General Semantics by Korzybsky?" Only since you posted this comment today :) I see a report at Wikipedia, https://en.wikipedia.org/wiki/General_semantics

I enjoy using telescopes to observe. I am not sure how the wiki description of General Semantics fits with Galileo observations of Jupiter's moons or Kepler's planetary laws that were used in the geocentric vs. heliocentric debates in astronomy. I routinely observe eclipse events at Jupiter or other enjoy views of other planets and conjunctions like the recent Mars and Jupiter close conjunction.
 
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rod

Oct 22, 2019
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Cat, the wiki report on General Semantics did catch my eye with this comment "Time binding: The human ability to pass information and knowledge from one generation to the next. Korzybski claimed this to be a unique capacity, separating people from animals. This distinctly human ability for one generation to start where a previous generation left off, is a consequence of the uniquely human ability to move to higher and higher levels of abstraction without limit. Animals may have multiple levels of abstraction, but their abstractions must stop at some finite upper limit; this is not so for humans: "

Seldom do I see this obvious and easily verifiable difference pointed out in evolutionary biology. When was the last time the monkeys made telescope observations of the Galilean moons and debated the difference between the geocentric universe vs. heliocentric universe?
 
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Feb 18, 2020
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rod
"I enjoy using telescopes to observe. I am not sure how the wiki description of General Semantics fits with Galileo observations of Jupiter's moons or Kepler's planetary laws that were used in the geocentric vs. heliocentric debates in astronomy."

I must be careful not to digress :) but I once enjoyed telescopic observation. At my advanced age I now prefer looking at the wonderful photographs such as of Io or Europa and relating those to the tiny dots of light I once saw (accompanying Ganymede and Calisto) through my 2 and a bit inch refractor.

Now, whilst I appreciate the part played by Jupiter's satellites in the expansion saga, I prefer the more philosophical topics relating to "our" Universe.

I was particularly interested in this which you posted:

"Cat you said "To me it is somehow connected with the Universe 'expanding' but galaxies staying the same "size".

This is a concern I have about the BB model. I find little reporting on galaxy size, i.e. angular size compared to redshift measurements." et seq

I have concerns also very much related to expansion.
If the Big Bang relies heavily (but not, of course, entirely) on running expansion backwards in time, how is it assumed to be linear or, in other words, how can it justifiably be extrapolated backwards to zero time ESPECIALLY when time is not supposed to be separate from spacetime? This is a particular hobbyhorse of mine. This seems to be the base of all sorts of 'silly' questions like What was before the BB? I rather favour a smooth transition to something like a "white hole" whatever that may be.

Sorry, just noticed more seems to have appeared in your previous post I thought I had read.
 
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Feb 18, 2020
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rod

"Seldom do I see this obvious and easily verifiable difference pointed out in evolutionary biology."

I would like to respond but do not want to go off topic (having once suffered a dire consequence).
Do you think it might fit into xenobiology?
 

rod

Oct 22, 2019
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Cat, I plan to leave biology alone here now. Thanks for the info though on General Semantics. I am glad to see you did enjoy the use of a telescope, even if it was perhaps a 60-mm size. I enjoy using my 90-mm refractor, about 3.6 inch size mirror and a 10-inch, Newtonian on a Dob mount. That system fully assembled is near 60 lbs of equipment and with the refractor too and eyepieces, I lug some 90 lbs or more for stargazing in my horse pastures. I am not old, over 65 but still in good shape :)
 
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Mar 22, 2020
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the uniquely human ability to move to higher and higher levels of abstraction without limit. Animals may have multiple levels of abstraction, but their abstractions must stop at some finite upper limit; this is not so for humans: "
This appears to be so. Animals may abstract, but their abstractions are germane only to their day-to-day existence. Hunans, however, do so about things that don't even exist.
 
Feb 18, 2020
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Yevaud
"This appears to be so. Animals may abstract, but their abstractions are germane only to their day-to-day existence. Hunans, however, do so about things that don't even exist."

If you wish to pursue this I suggest Xenobiology might be a suitable place where we could widen the question to include why only humans? I would be happy to join in.
Cat :)
 
Nov 20, 2019
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Trying to find out if there is experimental verification of photons red-shifting as 3D space expands other than the interpretation based upon the principle of equivalence from GR, used since the 1930s or so based upon redshifts in galaxies based upon Edwin Hubble et al. Is there measurements showing New Horizons transmissions, redshift on their way to Earth? Is there particle accelerator experiments in labs that show photons redshift as they move along in the lab? Hawkstein said "Redshift measurements, among others..." The redshift interpretation is principle of equivalence, not direct, experimental verification, e.g. *others*.
Hi rod, I can't understand the connection between the principle of equivalence and redshift, can you explain a bit more, please.

Also, is the redshift due to the expansion of space or a doppler shift or a bit of both?

Do I detect that you don't believe space is expanding, or are you merely pointing out that it's not proven?

Thanks:)

[redacted]
 
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Feb 18, 2020
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Hi David
Whilst waiting for Rod to reappear, you will find a vast amount if you search:
Principle of equivalence red shift.

On another matter, what is your view on objects appearing to remain the same size whilst the Universe is expanding? If everything expanded equally we would notice nothing and so not know the Universe was expanding. If our measuring rods expanded equally with the Universe then they could not measure the expansion. Problem?

Best wishes,
Cat :)
 
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Nov 20, 2019
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Hi David
Whilst waiting for Rod to reappear, you will find a vast amount if you search:
Principle of equivalence red shift.

On another matter, what is your view on objects appearing to remain the same size whilst the Universe is expanding? If everything expanded equally we would notice nothing and so not know the Universe was expanding. If our measuring rods expanded equally with the Universe then they could not measure the expansion. Problem?

Best wishes,
Cat :)
Hi Cat, in my post above, rather than post 7, I should have used a quote from rod in post 5, as below:

"Hawkstein, the redshift used to explain the expanding universe depends upon the interpretation from the principle of equivalence. Do you have a specific particle experiment from labs studies that shows 3D space is expanding, and at what rate? Example, something by shooting particles around near c."

It looks clearer to me from this post, that rod is suggesting the expansion of the universe was measured using gravitational redshift. I'm under the impression that the type of redshift used to measure expansion is that caused by the expansion or stretching of space, not the type which is caused by gravity.

That's why I asked him to explain a bit more. So my question to rod still stands.

It's also why I asked him - "is the redshift due to the expansion of space or a doppler shift or a bit of both?"

I did look up Principle of equivalence red shift as you suggested and discovered that what I referred to as redshift due to expansion of space is actually called 'cosmological redshift',

I'm still working on the second topic in your post :)
 
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