University of Lisbon

Question

Asked 16th Oct, 2022

# How is absolute position determined in cosmology ?

How would we go about specifying the position of our solar system in the universe, let us say

to an intelligence residing in an unknown part of the universe (assuming for simplicity that we can neglect the sun's motion in our galaxy).

Are there any objects or "landmarks" in the universe that could be used as known points of reference that could be used to specify our location to other intelligent beings residing in a distant part of the universe ? I am thinking of an exact analogue of longitude and latitude for the earth's surface.

An obvious answer would be simply to specify the aspect of the sky (and all known data) as seen from earth or the sun. But would this really be helpful, even if this did specify uniquely our position ?

Relativistic considerations further complicate matters.

## Most recent answer

Ellis 1977 põe a hipótese dum black hole global nos antípodas. se assim fosse, a tua pergunta sobre o polo norte (Articaca anisotropica) tem a resposta -apenas global- na Antartida

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## All Answers (20)

University of Lisbon

GFR ELLIS 1977, Nature

pôe o black hole unico nos antipodas do universo destarte explicando a isotropia aparente apenas da milky way e grupolocal. as suas sinteses recentes nao mencionam tal tentativa. vâ na revista de comunicação e linguagens, vol 1

University of Cambridge

Clarence Lewis Protin I have been able to define a reference frame for absolute positions in space. The underlying model of the evolution of the universe is one in which the universe is finite with a space boundary.

You can see from this model that there will be a centre point of the universe and this will be located at that point in space where the CMB radiation is uniform in all directions. Using the velocity of the Milky way galaxy relative to the CMB rest frame at 552 km/sec and applying Hubble’s law, we get a position of the Milky Way galaxy at around 26 million light years from the centre of the universe.

This centre of the universe can then be used as a centre for Cartesian coordinates to define the x,y,z position of galaxies. I used this in a presentation on galaxy distribution:

Presentation Galaxy Distribution

Preprint Space Rest Frame (March 2022)

Conference Paper The Explanation for Dark Matter and Dark Energy

Richard

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Independent Scientific Consultant & Lecturer

Dear Clarence,

if you really want to - as you write - provide other intelligent beings with directions as to where within the universe our Milky Way may be found, I'd advise to provide them with pictorial images of our galaxy and its immediate surroundings (Andromeda etc.) as well as of our Local Group, supercluster etc. On yet larger scales, you may provide images pointing at where within the various filaments and voids (Laniakea etc.) we may be found. Such directions do not necessarily require an absolute spatial reference system of the kind that Richard suggests (please not that proposing an absolute center within a spatially finite cosmos is not uncontroversial; many scientists will be arguing that space has been expanding since the alleged Big Bang singularity and that thus no "center" of the universe can be identified). Some basic mapping of our "home address" was inscribed on one (or even both?) of the Voyager probes, I believe. Please also keep in mind that conveying information even one-way - let alone two-way communication - will be extremly slow (if you accept c [the speed of light] as an absolute upper limit to the velocity at which information can be transmitted).

What is the background to your question??

All the best,

Julius

University of Cambridge

If you don’t like the starting assumption of a finite universe with a boundary you could still use the CMB rest frame to help identify location. The observation that the CMB is anisotropic taken together with the expansion of space allows us to identify a CMB rest point where we know that the observed CMB will be isotropic . This identifies a unique reference point in space which is around 26 million light years away in a known direction.

Someone in another galaxy could do a similar observation and you have the basis of a reference system based only on observations of the CMB and the expansion of space.

Richard

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Universidade Aberta

Julius Riese Thank you for your answer. Yes, I had in mind what I had read about the Voyager probes including a certain mapping. The background for this question was actually problems in the philosophy of language. Many of our natural language utterances make sense only relative to the time and place and point-of-view of the speaker. If somebody says "It rained yesterday in Paris", then 'yesterday' depends on the speaker and his present time. 'Paris' only makes sense relative to human communities in a certain bounded region of space-time.

I was wondering if you could associate these utterances with any objective denotation (for instance refer objectively to a given point in space).

Even if we can solve this problem for a given cosmological theory, such as in the interesting answer provided by Richard Lewis , one can reiterate the problem for multiverse theory: how do we identify our universe uniquely ? Or in Penrose's cyclic cosmology, how do we uniquely define a given moment of time ?

In axiomatic set theory we cannot form the set of all elements which satisfy a certain property P. We can only form the set of all elements in a given set X which satisfy this property, { x in X : P(x)}. In the same way perhaps there are no absolute definitions for concrete physical entities, only definitions relative to a certain theory, point-of-view, domain, coordinate system, etc. Ultimately much of our linguistic discourse must be traced back to the frame of the sum-total of our current scientific understanding of the universe (with all its disagreements and different points of view !).

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Institute of Physics of the National Academy of Science of Ukraine

“

*How is absolute position determined in cosmology*?”- till now in no way. That is for a number of reasons, first of all – since in the mainstream cosmology real Matter’s spacetime is postulated in accordance with the standard GR - it is a 4D imaginary mathematically pseudo-Riemannian space, in imaginary space only some imaginary coordinates are possible, which cannot be observed by really completely real [mathematically] instruments.

Though what is in the standard Big Bang model, that Matter was created in some real mathematically 3D space point, looks as rational; that is another case that when this model addresses to the origin of Matter – what is really fundamental problem, in this case,

- because of in the mainstream sciences, including physics, all really fundamental phenomena/notions, first of all in this case “Matter”– and so everything in Matter, i.e. “particles”, “fields”, etc., “Consciousness”, “Space”, “Time”, “Energy”, are fundamentally completely transcendent/uncertain/irrational and so in every case, including in this one, when the mainstream addresses to some fundamental problem, the result completely obligatorily logically is nothing else than some transcendent fantastic mental constructions,

- and so the versions of the origin in the standard Big Bang model are really nothing else than some sets of fantastic claims about mystic “fields”, “fluctuations”, density and temperature “singularities”, etc.

- however the conjecture that Matter was created in a practically point in its space [further the inflation epoch expansion, etc.], again, looks as well rational since well rationally complies with observed now Matter [more see comments to an well informative Ethan Siegl article https://www.forbes.com/sites/startswithabang/2019/06/07/does-time-have-a-beginning/?sh=75fcc85f513b

in the SS post in https://www.researchgate.net/post/Is_the_Big_Bang_theory_falsifiable/32].

So – including having in mind that so Matter is some limited in space and time system – this thread question looks as is well rational, and now - since now there exist really scientifically rational Matter’s creation model, including the origin [see the Shevchenko-Tokarevsky’s informational physical model, paper https://www.researchgate.net/publication/355361749_The_informational_physical_model_and_fundamental_problems_in_physics , section “Cosmology”,

- where it is well rationally shown that Matter’s spacetime is the fundamentally absolute, fundamentally flat, and fundamentally real mathematically “Cartesian”, [5]4D spacetime with metrics (

*cτ,X,Y,Z,ct*), where the ultimate base of Matter – the [5]4D dense lattice of [5]4D binary reversible fundamental logical elements [FLE] is placed, and practically everything in Matter is determined by the logical construction and properties of FLEs,- including that Matter started in some concrete point in the 3D XYZ space above, relatively of which existent now [but observed as are in different time,

*ct*, points, etc.] cosmological objects exist/are observed,- it looks as that determination of the “origin point’s” coordinates – and so the cosmological objects’ coordinates in the coordinate system with (0,0,0,0) reference “origin point” is, in principal, possible.

However the Matter’s topology at the expansion in the (1+3+1)D spacetime above till now isn’t known, whereas the spacetime is observed, because of the FLE lattice expansion only rather locally [seems in a ~ hundreds of parsecs region around Earth], and though in this region the absolute motion in the 3D space, say, of the Sun system, and the system’s absolute velocity can be measured – a couple of experiments see in https://www.researchgate.net/publication/259463954_Measurement_of_the_absolute_speed_is_possible],

- and after some experiment in this paper will be made, we will can to assign the absolute coordinates in some Earth local absolute coordinate system,

- without real knowledge of the topology of whole Matter [in the Ethan Siegl article above some arbitrary picture of Matter on a hyperspace of a hypertorus is shown] it is impossible to define corresponding coordinate system in some, well probably hyperspace that is embedded in the whole space Matter’s matter distribution, and to define the “absolutely absolute” [relating to the “origin point”] coordinates of cosmological objects, including of Earth.

Cheers

Independent Scientific Consultant & Lecturer

Dear Richard,

many thanks for clarifying that your "universal positioning system" based on the CMB works independently of assuming a spatially finite or infinite universe. That is very helpful and I shall keep your method in mind for future reference.

All the best,

Julius

Independent Scientific Consultant & Lecturer

Dear Clarence,

many thanks for your detailed response. I am not a philosopher of language, but I do share the quest for a truly universal reference frame for space, time and - consequentially - for space-time.

Let me try to respond to some of the other points you made:

I think Richard's, mine and other suggestions do point to the possibility of unambiguously identifying points in space and time within the part of the universe observable to us.

You mention multiverse theory and the problem of "uniquely identifying our own universe". I think this lies clearly beyond our current capacities and perhaps always will. Keep in mind that most multiverse theorists would argue that different universes "branch off" from each other (e.g., when the wave function collapses as in the Many Worlds interpretation of quantum mechanics) and that from this branching point forward, no communication or interaction between them is possible. It just wouldn't make sense to even attempt to look for possibilities of "locating" our universe then, because according to such theories, there is no "outer/external" space, in which these branching-off events would take place and resulting universe "bubbles" would be located.

I am not quite sure about cyclic cosmology. I do, however, think that a potential scenario would be that time is eternal and thus "has existed forever". This would allow for the possibility of defining discrete moments in time (along the time arrow). If however, time itself was conceptualised as cyclical (note that I am not talking about Big Bounce theories here!), things would be getting even more complicated than they already are... :-)

Let us keep up this fascinating conversation!

Best wishes,

Julius

University of Geneva

Suppose the universe were a perfect 2D sphere (expanding or not), then there would be no way to specify a point without fixing first a standard coordinate system, say as the GPS system does. But if no such standard exists, then there is no way to communicate our position, since all points on a perfect sphere are equivalent.

Now, as on earth, suppose the sphere is not uniform, irregular. Then it is possible to communicate our position by describing the probably unique features in the surrounding of the location (e.g. nearby galaxy relative positions). The intelligence receiving this information should then "geolocate" the position by building a map of the irregular sphere.

A remaining problem with this method is if the distance to the intelligence is too large then the local features (e.g. relative galaxy positions) may change too much during the message transfer to be recognizable.

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Institute of Physics of the National Academy of Science of Ukraine

“…

*Suppose the universe were a perfect 2D sphere (expanding or not), then there would be no way to specify a point without fixing first a standard coordinate system, say as the GPS system does. But if no such standard exists, then there is no way to communicate our position, since all points on a perfect sphere are equivalent*.……”- that really is inessential. Again - see the SS post above, if the Big Bang hypothesis is correct [and seems really is correct – see the SS post above], than there exist one “absolutely unique” point in Matter’s spacetime, which is the same in any coordinate systems. As, say, in the trivial 2D sphere case in the quote above - for those on the sphere, who “cannot” define their coordinates because of that all points on the sphere are equivalent, but know, nonetheless, that somewhere in 3D space there exists the unique point – the center of the corresponding 3D sphere/ball, and this point for them is known, that all the 3D space points, including on the 2D sphere, can be definitely concretely defined in any concrete coordinate system.

So, say, that

“…

*A remaining problem with this method is if the distance to the intelligence is too large then the local features (e.g. relative galaxy positions) may change too much during the message transfer to be recognizable*. ….”- really isn’t a problem, if some intelligence is intelligent enough to understand what is the Matter’s topology, it can define the absolute “Big Bang” point and designate for itself and for observed cosmological objects corresponding really unique – though, of course different, since in this case the sets of coordinates’ axes directions are arbitrary – coordinates; without any communication with other intelligences.

Cheers

University of Geneva

There is no centre in the Big Bang theory, where all space is homogeneous. The singularity at t=0 concerns the whole universe. It is like the 2D sphere positive curvature case, easier to visualize, where the whole sphere reduces at t=0 to a point in 3D space, there is no particular centre on the 2D sphere at t>0.

Institute of Physics of the National Academy of Science of Ukraine

Daniel Pfenniger

“…

*There is no centre in the Big Bang theory, where all space is homogeneous. The singularity at t=0 concerns the whole universe. It is like the 2D sphere positive curvature case, easier to visualize, where the whole sphere reduces at t=0 to a point in 3D space, there is no particular centre on the 2D sphere at t>0*….”- you seems commented the last SS post above on the first thread’s page too quickly, and didn’t read the post attentively enough. More see the two SS posts above, here only note that if Matter was created

**physically really****in one point in the space**– and that happened really without any “singularity”, though - then this point really cannot – and so doesn’t, disappear to anywhere. It remains in the space[time], where concrete system “Matter” was created in rather “homogeneous” form just after the inflation epoch, and further evolved into some other topology that is observed now by detecting photons; which [topology], again, really is unknown till now.And, again, as that is in the “perfect” 2D sphere positive curvature case in the SS post above - if some intelligence on the sphere understands that it is on an really 2D surface of 3D sphere with a radius

*r*, for it is possible to define the 3D – intelligence’s 2D spheres radius*r*, and where the center of both spheres is; if the radius was increasing, and was determined at*t>*0 – the particular centre on the 2D sphere at*t=*0 is the same as at*t>*0; nothing happens with this center when the 2D sphere expands.All that above is true for Matte’s

**observed**topology, nothing can happen with the unique “Matter’s start point” in the space. From that the mainstream cosmology isn’t able to define this real “centre point”, including when attempting to define it in the really fundamentally non-existent pseudo-Riemannian 4D space, by no means it follows that this point doesn’t exist.Cheers

University of London

"EARTH IS THE ANSWER!" [ for me ] .

This is the reason why classical Greek Philosophers defined this point! Considering PLATO'S "REPUBLIC"

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Universidade Aberta

I agree that (in standard cosmology) an absolute coordinate system would require an observable invariable structurally unique object in the universe.

I would also like to raise the following point:

A smooth manifold (such as the pseudo-Riemannian manifolds considered in cosmology) can be seen either an abstract structure (a topological space) locally homeomorphic to n-dimensional Euclidean space having smooth coordinate changes or a else as a subspace of m-dimensional Euclidean given locally by the zeros of a set of smooth functions. One also can require the metric to coincide with the induced metric of the ambient space. Does it make sense to consider space-time as an embedded submanifold in some higher- dimensional space ? Would this ambient space have physical meaning ?

University of Cambridge

Clarence Lewis Protin I think it is much simpler to think in terms of what is real and observable. This means three space dimensions. If you imagine a universe with all the matter removed then locally there will be no space curvature:

If you then imagine the entire universe as a finite spherical region you would expect there to be intrinsic space curvature which is flat in the radial direction from the centre and curved parallel to the spherical boundary. Then you can see that the cause of the expansion of space is the expansion at the boundary.

In this model there is no advantage in going up beyond three space dimensions. Time arises within this region of space because the medium of space supports wave propagation at speed c. There is a well defined absolute reference time which can be defined and synchronised everywhere.

It is still useful in this model to think of Spacetime because this provides a good way of representing Spacetime curvature when dealing with gravity.

Richard

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Thales Group, UK

The gold plaque on the Pioneer and Voyager craft did this using pulsars as reference points:

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Independent Scientific Consultant & Lecturer

Yes, I agree that the two Pioneer plaques are a prime and well thought-through example of humans attempting to "geolocate" their galactic home to potential other sentient, intelligent and technologically advanced beings. Note that the pulsar map included on the two Pioneer plaques is also found on the cover of the two Voyager "Golden Records".

Institute of Physics of the National Academy of Science of Ukraine

“…

*I agree that (in standard cosmology) an absolute coordinate system would require an observable invariable structurally unique object in the universe*…”- really that is incorrect claim. Real Matter’s spacetime is the fundamentally absolute, fundamentally flat, and fundamentally “Cartesian”, [5]4D spacetime with metrics (

*cτ,X,Y,Z,ct*), and practically everything in Matter is determined by the logical construction and properties of FLEs, first of all the properties- the all identical in 4D space with metrics (

*cτ,X,Y,Z*) “sizes” of FLE,*lP*, and FLE “flip time”,*tP*, which are practically for sure equal to the Planck length and Planck time,*c=lP/tP*.At that really practically all/every material objects always constantly move in the 4D space above with 4D velocities that have identical absolute values be equal to

*c*,*c*[“**bold**” means 4D vector], photons move only in 3D XYZ space, and so move with 3D*. Most of other objects move in the***c***cτ-*dimension also, and so have “rest masses” in the 3D XYZ space; and so, if are impacted by some this 3D space momentums, move in the space with velocities that are lesser, by Pythagoras theorem, than c. At that in parallel simultaneously practically all/every objects move in the “true time”,*t*, for which it is convenient – while is fundamentally possible – to assign metrics “*ct*” in the whole metrics aboveIf a having rest mass object – particle, body, etc., [“T-particle”, “T-body”, etc.] is at the absolute rest in the absolute 3D space, and so moves only in the

*cτ-*dimension with the speed of light; and so to indicate in the absolute space some absolute*XYZ*point, there is no necessity in any some special concrete “invariable structurally unique object in the universe” – that can be any point in the 3D space; again, that can be anything and anywhere in the space that moves in the*cτ-*dimension with maximal, i.e. equal to*c*, speed, and if such object is observed [or the absolute velocity of an object is measured], its spatial point for sure can be basic point [used at assigning of a basic point] for some “absolute” reference frame and corresponding absolute coordinate system.That is another thing, that because of the action of extremely mighty Galileo-Poincaré relativity principle the absolute motion in the 3D space is till now experimentally non-observable, however that is possible – see https://www.researchgate.net/publication/259463954_Measurement_of_the_absolute_speed_is_possible, including in this case in this system the ““absolutely unique” Matter’s origin point” really can, in principle, have concrete coordinates (

*0,X,Y,Z,“-ct now”*).However that above, albeit is well applicable in the region ~ billion light years radius around Earth, is very essentially complicated by, first of all, two problems:

- that, despite of that because of the T-objects and “S-objects” [the last move only in 3D space, say, photons] motion above whole Matter is always on the 4D hyperplane, which constantly moves along the

*ct-*axis, for humans it is possible only to obtain information about the distant objects as they were in*ct*-points that are before the recent observer’s*ct*-position – say, practically Earth;- and that Matter rather probably really constantly expanding/expands, and so essentially changes its topology.

So these problems, first of all the topology problem, should be solved before attempts to find the “Matter’s origin point”.

Cheers

Universidade Aberta

Due to the complexity and non-linearity of the orbital mechanics of planetary systems I believe that data consisting in the number of large bodies orbiting a star together with their position, velocity, acceleration (relative to the star) and mass at a given moment might serve as a unique identifier (signature) relative to the entire universe. The time for which such an identifier will serve will depend on the accuracy of the measurements. Of course the speed of light limit and the vast size of the universe will cause such signatures to be of very transient value and limited practicality.

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